WO1993013707A1 - Fiberoptic blood pressure and oxygenation sensor - Google Patents

Fiberoptic blood pressure and oxygenation sensor Download PDF

Info

Publication number
WO1993013707A1
WO1993013707A1 PCT/US1993/000715 US9300715W WO9313707A1 WO 1993013707 A1 WO1993013707 A1 WO 1993013707A1 US 9300715 W US9300715 W US 9300715W WO 9313707 A1 WO9313707 A1 WO 9313707A1
Authority
WO
WIPO (PCT)
Prior art keywords
blood
optical fiber
sensor according
light
catheter
Prior art date
Application number
PCT/US1993/000715
Other languages
French (fr)
Inventor
Marek T. Wlodarczyk
Charles D. Anderson
Daniel L. Vokovich
Original Assignee
Fiberoptic Sensor Technologies, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fiberoptic Sensor Technologies, Inc. filed Critical Fiberoptic Sensor Technologies, Inc.
Publication of WO1993013707A1 publication Critical patent/WO1993013707A1/en

Links

Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Measuring for diagnostic purposes; Identification of persons
    • A61B5/145Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A61B5/1459Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters invasive, e.g. introduced into the body by a catheter
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Measuring for diagnostic purposes; Identification of persons
    • A61B5/02Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/021Measuring pressure in heart or blood vessels
    • A61B5/0215Measuring pressure in heart or blood vessels by means inserted into the body
    • A61B5/02154Measuring pressure in heart or blood vessels by means inserted into the body by optical transmission

Definitions

  • This invention is related to a system for patient care and particularly to a sensor incorporating a catheter which can be inserted transcutaneously within a blood vessel for 5 measuring blood pressure and oxygen saturation.
  • the shape and spacing of the diaphragm from the fiber end affects the intensity of returned light which is calibrated to provide a pressure measurement.
  • Fiberoptic pressure sensor of the type described in FST's previously issued patents and pending application posses a number of fundamental advantages over the previously used approach of invasive blood pressure measurement which comprises the use of a catheter lumen communicating with a remote site within the body which is connected to an external fluid column type pressure measuring device.
  • These systems posses inherent disadvantages that arise from mechanically coupling a blood pressure wave through a fluid column embedded within a catheter, to an external transducer. Both the mechanical compliance and the damping losses of the fluid column, the catheter material, and the transducer membrane result in broad resonance artifacts, typically occurring at frequencies in the vicinity of 10 to 20 Hertz, and limit high frequency response.
  • any extensions of the catheter link used, for example, for a bed ridden patient often result in impedance mismatching between tubing and connectors which can create additional resonance peaks.
  • significant blood pressure wave spectral components lie near the resonance frequencies of column sensors, some frequencies will be amplified relative to others, producing a distorted waveform. Waveform distortion is also produced by bubbles trapped in the fluid column.
  • these types of pressure sensors suffer the disadvantage that distortions are caused by patient or catheter movement. Motion produces a shift in fluid column position which adds baseline or low frequency artifacts to the pressure waveform. It is for these reasons that direct pressure sensing at the tip of a catheter is becoming a preferred approach in clinical settings for pressure measurement and is gaining wider acceptance in such applications.
  • blood oxygen saturation is defined as the fraction of oxygen bound to all available hemoglobin as compared to total oxygen binding capacity.
  • Various approaches toward blood oxygen saturation evaluation are presently available.
  • One type of clinical laboratory measuring device requires that blood samples be withdrawn from the body, and then transferred into the device.
  • Such devices typically employ gas chromatography or use other methods such as optical spectroscopy.
  • optical spectroscopy In the latter approach, a blood absorption spectrum is obtained over a continuous range of optical wavelengths. The extinction coefficients at the various wavelength can be used to determine the concentration of various blood species of clinical interest.
  • continuous spectrum measurement produces the greatest amount of information, its unsuitability for use in clinical settings for real time analysis limits it applicability.
  • the cost of light sources and associated electronics required for such analysis are of concern.
  • the catheter In the design of catheter type sensing system for blood vessel access, a number of design considerations must be addressed. Most significantly, the catheter must have a small diameter so as to permit access to small caliper blood vessels and further to prevent occlusion of blood flow through the vessel where measurements are being taken. Cost of the catheter of the system is another important consideration, particularly where catheters are designed for single use application to prevent the spread of infection between patients or to medical personnel. Also significant is the cost associated with the sensing head of the sensor to which the catheter is connected which is designed for long term use. In that regard, is preferable to reduce the number of individual light sources and photodetectors used in the sensing head to inject light signals into the catheter and receive reflected back signals. An underlying consideration of paramount significance is the accuracy and reliability of the sensors which must be assured in that the devices are employed in critical patient care settings.
  • This invention relates to a novel fiberoptic sensor for simultaneous measurement of blood pressure and oxygen saturation.
  • the sensor of this invention uses optical fibers exclusively for measurement.
  • the sensor of this invention further provides an efficient and cost effective measuring system through the use of light sources which provide outputs which are shared between the pressure and oxygen saturation measuring fibers. By reducing the number of light emitters, the stability of optical signals is enhanced and a smaller sized and less complex sensing head is possible as compared with systems utilizing a greater number of independent elements.
  • the sensor of this invention also permits synchronizing outputs of the oxygen saturation fiber with that of the pressure measuring fiber, or visa versa. Such synchronous detection may be used to enhance measurement accuracy to provide additional information of clinical use.
  • This invention further encompasses a sensor for oxygen saturation measurement based on the evanescent effect, which is believed to be relatively insensitive to hematocrit. And finally, this invention relates to sensors having sensing tips which are designed to inherently reduce the susceptibility to vessel wall effects.
  • Figure 1 is pictorial view of the sensor in accordance with this invention.
  • Figure 2 is a optical spectrum showing absorption extinction coefficients for reduced hemoglobin and oxy- hemoglobin.
  • Figure 3 is a schematic diagram of a sensor according to a first embodiment of this invention showing components of the sensing head and used with an oxygen sensing system incorporating a single optical fiber;
  • Figure 4 is a schematic diagram of a sensor according to an alternate embodiment of this invention shown with the oxygen sensing system incorporating two optical fibers;
  • Figure 5 is a cross-sectional view through a sensing tip in accordance with an embodiment of this invention employing a chamber for blood light absorption having a planar light reflective surface.
  • Figure 6 is a partial cross-sectional view through a sensing tip similar to that shown in Figure 5 but shown having a concave reflective surface.
  • Figure 7 is a partial cross-sectional view through a sensing tip according to an alternate embodiment of this invention based on back scatter measurement;
  • Figure 8 is a partial cross-sectional view through a sensing tip according to an embodiment of this invention based on an evanescence measurement.
  • Figure 9 is a partial cross-sectional view through a sensing tip according to an alternate embodiment of this invention based on a modified evanescence measurement in which the optical fiber cross section is perturbed.
  • a sensor in accordance with this invention is shown in pictorial fashion in Figure 1 and is designated there by reference number 10.
  • Sensor 10 generally comprises catheter assembly 11 and sensor head 13.
  • Catheter assembly 11 is adapted for introduction into human patient blood vessels.
  • Catheter assembly 11 includes a sensing tip 12 which will be described in detail later in this description.
  • Catheter assembly 11 includes fiber optic couplers 14 and 16 which are provided for connection to optical fiber within the catheter for pressure and oxygen saturation measurement.
  • a lumen is provided with connector 18 for enabling a known fluid pressure to be applied at sensing tip 12 for purposes of calibrating the pressure sensing features of the sensor.
  • An optical fiber coupler 18 is provided as a termination for the optical fibers within the catheter which are provided for the transmission of light signals for both pressure and oxygenation sensing, as is described in more detail below.
  • the catheter assembly incorporates a catheter outer covering or sheath 20 made of a material which reduces thrombolytic (clot forming) activity and would be made, for example, of a polymer which binds to heparin.
  • FIG. 2 provides a spectrum showing the extinction coefficients for absorption of reduced hemoglobin shown as curve 22, and oxy-hemoglobin shown as curve 23 at various light wavelengths. At around 800 nm, the two spectrum curves overlap or define a "crossover point".
  • the extinction coefficients at that wavelength are the same for both reduced hemoglobin and oxy-hemoglobin.
  • This characteristic is significant in that the extinction coefficient of light signals at that wavelength can be used as a measure of other parameters, for example hematocrit. For many sensor designs, and especially those relying on light absorption, hematocrit will strongly influence the extinction coefficient. Accordingly, by using a wavelength of around 800 nm, absorption of that signal can be used to calibrate the system for changes in hematocrit. It is also significant to note that at wavelengths below the crossover point, oxy- hemoglobin absorbs more than reduced hemoglobin, and the opposite occurs at wavelength above the crossover point. FIG.
  • FIG. 3 illustrates in pictorial fashion a configuration for a sensor system 10 in accordance with this invention.
  • the sensing head 13 is shown incorporating three discrete light sources, preferably in the form of LEDs or semiconductor lasers designated by references numbers 32, 34, and 36.
  • Sensing head 13 also includes three photodetectors designated by reference numbers 38, 40 and 42.
  • the lines connecting the various elements in FIG. 3 with direction arrowheads represent light paths which may be provided by sections of optical fibers.
  • a single optical fiber 44 is provided for pressure sensing.
  • sensor system 10 for pressure detection is identical to FST's sensing systems as described in the prior referenced patents in which a deformable diaphragm is employed to modulate the intensity of a returned light signal along fiber 44.
  • Sensor system 10 also preferably incorporates a dual wavelength referencing system as described in FST's previously issued U. S. Patent No. 4,924,870. That patent describes a system in which a reflective coating is deposited on the end of optical fiber 44 which reflects light below a threshold cutoff wavelength, while transmitting light having a greater wavelength. The intensity of the two returned back light signals are ratioed as a means of reducing sensitivity of the pressure sensing system to differences in fiber characteristics, and the effects of fiber bending and other signal noise.
  • LED 32 is selected to emit light at a wavelength of about 810 nm which is inputted into optical fiber 44 and is fully reflected at the dielectric filter (not shown) at the end of the fiber and thus provides a reference or calibration signal.
  • LED 34 emits light at a wavelength of 940 nm which is transmitted through the dielectric filter and is modulated by the deformable diaphragm.
  • Light which is returned along optical fiber 44 is coupled to photodetector 38.
  • photodetector 38 receives signals reflected back along optical fiber 44 relating both to the calibration signal emitted by LED 32 and the pressure measuring signal emitted by LED 34.
  • optical fiber 46 which is provided for oxygen saturation measurement. All three LED's 32, 34, and 36 are coupled into optical fiber 46. LED 36 emits light at about 660 nm. Accordingly, light signals having wavelengths of 660, 810 and 940 nm are sent along optical fiber 46. With reference to FIG. 2, it can be seen that these wavelengths include the crossover point of the curves 22 and 23, and wavelengths above and below the crossover point . Light returned along optical fiber 46 is received by photodetector 42.
  • reference photodetector 40 is coupled to each of LED's 32, 34, and 36 and is provided for the purposes of evaluating the output intensity of each of the LED's. Photodetector 40 is used in calibrating the returned back signals so that the system can comprehend changes in output which are attributable to the specific characteristics of an individual LED or changes which occur during its operating life span, or in response to temperature changes, driving current, etc.
  • an optical fiber can be initially formed from plural strands which are fused at a point along their length to one end, thus providing a branching fiber.
  • so called “mixing balls” or other known fiber coupling techniques could be used.
  • the sensing head 13 would incorporate a timing mechanism designated as CPU 48 for sequentially firing LED's 32, 34, and 36. Readings from photodetectors 38 and 42 would be synchronized so that the returned back signals at the various wavelengths can be discriminated.
  • This synchronous demodulation technique avoids the requirement of providing wavelength selective optical filters, as a means of discriminating the signals returned along fibers 44 and 46 at the various wavelengths.
  • the ability to provide simultaneous measurement of oxygen saturation and blood pressure at the sensing tip 12 of the sensor is believed to provide a number of significant attributes.
  • the orientation of red blood cells tends to change in response to the pressure difference between diastolic and systolic blood pressures. These orientation changes are known to change the light scattering effect of the blood.
  • red blood cells tend to become oriented in a stacked-together fashion at the high pressure point of the pressure wave and become more randomly oriented in the lower pressure regions.
  • oxygen saturation measurements relying upon traditional absorption extinction coefficient measurement, are sensitive to scattering, such devices are subject to inaccuracy if they are sensitive to the pressure dependent effects of scattering which occur during a single blood pressure wave.
  • blood vessel walls, especially arteries tend to move or pulse in response to the pressure wave. This characteristic also can produce light attenuation changes as the wall moves relative to the sensor.
  • FIG. 4 is a pictorial view of a sensor system 50 in accordance with this invention which has many elements common with the prior embodiment but differs from that shown in FIG. 3 in that the oxygen saturation detection employs two separate fibers 52 and 54.
  • -Fiber 52 is used to conduct light signals to sensing tip 12, whereas a separate fiber 54 is provided only for the returned signal.
  • This configuration may be advantageous in some applications since it would be possible to custom tailor fibers 52 and 54 in consideration of their roles.
  • the diameter of optical fiber 54 could be greater than that of fiber 52 for the purposes of increasing light gathering capability.
  • optical fiber 54, shown in FIG. 4 is directly connected to photodetector 42 and does not have to be branched which results in a reduction in signal strength.
  • FIGS. 5 through 8 various alternative designs for sensing tip 12 are shown. As shown in FIG. 5, sensing tip 12 is connected to catheter sheath 20 through an interfitting connector, or alternately bonding or other joining techniques could be used.
  • Pressure sensing optical fiber 44 terminates adjacent to deformable diaphragm 58.
  • the pressure sensing features of sensing tip 12 are fully described in applicant's issued U. S. Patents mentioned previously.
  • One difference, however, of tip 12 with respect to previous designs of applicant is the provision of a protective cap 60 terminating the sensing tip having pressure sensing openings 62.
  • Cap 60 is provided to protect pressure diaphragm 58, especially from loading effects caused by contact with structures in the body. Cap 60 also aids in minimizing the sinitic effect of blood flow striking the diaphragm
  • sensing tip 12 comprise a notched or recessed area within the side of tip.
  • Sensing tip 12 incorporates a dual fiber oxygen saturation measuring approach as described in connection with FIG. 4.
  • Spaced from the terminations of both fibers 52 and 54 is a mirror 66.
  • Light emitted from fiber 52 passes through blood in the area of recess 64.
  • the reflective surface of mirror 66 returns some of this signal in the direction of return fiber 54 which is transmitted to photodetector 42.
  • the absorption extinction coefficient associated with the transmission of light through the blood in the area of recess 64 is used as a means for measuring oxygen saturation.
  • hematocrit affects the scattering of light passing through the area of recess 64
  • an independent measure of hematocrit is provided through transmission of light at the wavelength of 810 nm as explained previously.
  • Apertures for the transmission of blood such as heparin or the withdrawal of fluid can be provided within sensing tip 12 or within catheter sheath 20 at a location near the sensing tip.
  • FIG. 6 illustrates a sensing tip 67 according to an alternate embodiment of the invention.
  • the device is identical to sensing tip 12 described above except that reflective surface 68 is concave. This configuration increases the returned light signal strength. In all other respects, sensing tip 67 operates like tip 12.
  • FIG. 7 illustrates a portion of sensing tip 70 in accordance with a alternate embodiment of this invention. Since sensing tip 70 incorporates many of the elements of sensing tip 12, these elements are identified by like reference numbers. Sensing tip 70 provides oxygen saturation measurement through the effect of evaluating back scatter radiation. In this case, light is emitted through fiber 52 in a field area provided by recess 72. Back scatter radiation is received by return optical fiber 54. Extinction coefficient curves similar to that attributable to absorption, shown in FIG. 2, also exist for the back scatter operational mode. As in the prior embodiments, recess 72 prevents blood vessel walls from directly confronting the fibers, thus reducing the likelihood of affecting oxygen saturation measurement.
  • FIGS. 8 and 9 A second class of sensing tip designs according to this invention are shown in FIGS. 8 and 9, and employ an evanescent principle for examining the interaction of light of known wavelengths with erythrocytes.
  • evanescent effect light is propagated along an optical fiber which has a polished outer surface region 81 exposed to blood. Since blood contains erythrocytes which absorb light of various wavelengths in a characteristic fashion, a fraction of the energy transmitted along the fiber tends to leak from the fiber into the absorber. The fraction of the light of a given wavelength which leaves the fiber is related to the absorption characteristics of the blood.
  • the principal advantage of employing the evanescence phenomenon is that it is not subject to scattering error since it does not rely on light propagating through blood.
  • sensing tip 80 is shown employing a single optical fiber 46 for oxygen saturation measurement.
  • the terminal end of the fiber 46 is coated with a reflective film 82.
  • the original fiber thickness is reduced by slightly polishing away a few microns to facilitate strong interaction between the evanescent field and blood cells.
  • the sensitivity of the sensor can be increased through increasing the length of region 81 and recess 84.
  • sensing tip 88 like that of FIG. 8, employs a single fiber 46 for oxygen saturation measurement terminated by reflective film 82.
  • Sensing tip 88 employs a modified evanescent transmission coupling effect where a geometry perturbation is applied to the fiber core. A local thinning or tapering of the core enhances sensitivity to oxygen concentration changes.
  • the core is perturbed as shown in FIG. 9 by milling away a portion of its diameter. Other core perturbations could be provided, such as removing wedge shaped slices or generating special surface roughness features.
  • the essence of sensing tip 88 is a local change in the cross-sectional shape of the fiber core along its length.

Abstract

A fiberoptic based sensor (10) for patient care use. The sensor includes a catheter (11) placed transcutaneously into a blood vessel which is connected to an external measuring head. A sensing tip (12) of the catheter includes a pressure sensing element (58) and an oxygen saturation measuring element (64). Features of the invention include novel tip designs, measuring head features, and approaches for enhancing measurement through correlation of the saturation and pressure readings.

Description

>
FIBEROPTIC BLOOD PRESSURE AND OXYGENATION SENSOR
BACKGROUND OF THE INVENTION This invention is related to a system for patient care and particularly to a sensor incorporating a catheter which can be inserted transcutaneously within a blood vessel for 5 measuring blood pressure and oxygen saturation.
In a variety of critical care situations it is desirable to continuously monitor blood pressure and oxygen saturation at remote sites within the body, for example in cardiac arteries. The present applicant. Fiberoptic Sensor
10 Technologies, Inc. (FST) has been in the forefront of development of fiberoptic based invasive pressure sensing devices. Such devices are described in a number of U.S. Patents previously issued to FST, including U. S. Patents 4,711,246 and 4,924,870 and pending U.S. patent application
15 serial no. 748,082, filed on August 21, 1991, which are hereby incorporated by reference. Briefly, the systems described in the above referenced documents employ a catheter having a deformable diaphragm positioned near the distal end of an optical fiber. Deformation of the
20 diaphragm in response to fluid pressure applied to its outside surface by the blood changes its shape and
* proximity to the end of the optical fiber. A light signal ft injected into the proximal end of the optical fiber exits
- the distal end of the fiber and is reflected to return
25 along the fiber by the deformable diaphragm. The shape and spacing of the diaphragm from the fiber end affects the intensity of returned light which is calibrated to provide a pressure measurement.
Fiberoptic pressure sensor of the type described in FST's previously issued patents and pending application posses a number of fundamental advantages over the previously used approach of invasive blood pressure measurement which comprises the use of a catheter lumen communicating with a remote site within the body which is connected to an external fluid column type pressure measuring device. These systems posses inherent disadvantages that arise from mechanically coupling a blood pressure wave through a fluid column embedded within a catheter, to an external transducer. Both the mechanical compliance and the damping losses of the fluid column, the catheter material, and the transducer membrane result in broad resonance artifacts, typically occurring at frequencies in the vicinity of 10 to 20 Hertz, and limit high frequency response. Moreover, any extensions of the catheter link used, for example, for a bed ridden patient, often result in impedance mismatching between tubing and connectors which can create additional resonance peaks. Since significant blood pressure wave spectral components lie near the resonance frequencies of column sensors, some frequencies will be amplified relative to others, producing a distorted waveform. Waveform distortion is also produced by bubbles trapped in the fluid column. In addition, these types of pressure sensors suffer the disadvantage that distortions are caused by patient or catheter movement. Motion produces a shift in fluid column position which adds baseline or low frequency artifacts to the pressure waveform. It is for these reasons that direct pressure sensing at the tip of a catheter is becoming a preferred approach in clinical settings for pressure measurement and is gaining wider acceptance in such applications. I n addition to blood pressure monitoring, clinicians are often interested in evaluating other blood parameters. Most significant in many patient care settings is the monitoring of blood oxygen saturation which is defined as the fraction of oxygen bound to all available hemoglobin as compared to total oxygen binding capacity. Various approaches toward blood oxygen saturation evaluation are presently available. One type of clinical laboratory measuring device requires that blood samples be withdrawn from the body, and then transferred into the device. Such devices typically employ gas chromatography or use other methods such as optical spectroscopy. In the latter approach, a blood absorption spectrum is obtained over a continuous range of optical wavelengths. The extinction coefficients at the various wavelength can be used to determine the concentration of various blood species of clinical interest. Although continuous spectrum measurement produces the greatest amount of information, its unsuitability for use in clinical settings for real time analysis limits it applicability. Moreover, the cost of light sources and associated electronics required for such analysis are of concern.
As a compromise compared to continuous spectrum evaluation, there are presently available a number of fiberoptic based oxygen saturation sensors which are based on evaluating absorption extinction coefficients at a number of discrete wavelengths; for example, three wavelengths. The absorption extinction coefficients at these wavelengths are used to determine the concentration of oxyhemoglobin, which is the state of hemoglobin bound with oxygen. Absorption extinction coefficients are highly affected by hematocrit (the concentration of erythrocytes in the blood) . Therefore, another wavelength source is used to measure hematocrit which is considered in deriving an oxygen saturation value. Although such devices using a limited number of discrete wavelengths are not capable of resolving many significant blood component species, they do provide clinically useful information. Despite the existence of technology concerning fiberoptic pressure sensing and fiberoptic oxygen saturation measurement, such systems have heretofore not been combined in a single commercially viable sensor. The prior art teachings do, however, disclose the use of a fiberoptic based oxygen saturation measuring system employed in a catheter which also provides a lumen for fluid column pressure measurement. However, such a sensor posses the disadvantages previously discussed related to fluid column type pressure measurement. In addition to those shortcomings, such a combined sensor according to the prior art does not provide the ability to synchronize the measurement of oxygen saturation with the pressure reading. Other systems according to the prior art attempt to provide pressure measurement along with other measurements, such as blood gasses or oxygen saturation using optical fibers. However, these systems have disadvantages of cost, reliability and limited accuracy. Simultaneous accurate measurement at the tip of a catheter of both oxygen saturation and pressure would offer unique physiological information not available today with existing instrumentation. In view of these factors, there is a current need in medicine to provide a sensing system providing such simultaneous measurement. Presently available invasive fiberoptic oxygen saturation sensors are often subject to erroneous readings when the sensing tip is positioned to abut the walls of a blood vessel. To avoid misinterpreting readings taken in this condition, special data reduction algorithms must be applied or special procedures must be followed, complicating measurement. Even when the catheter is correctly placed, some catheters are affected by the movement of blood vessels, especially arteries in response to the blood pressure wave. It is therefore desirable to provide a sensor which is inherently not subject to such vessel wall effects. In the design of catheter type sensing system for blood vessel access, a number of design considerations must be addressed. Most significantly, the catheter must have a small diameter so as to permit access to small caliper blood vessels and further to prevent occlusion of blood flow through the vessel where measurements are being taken. Cost of the catheter of the system is another important consideration, particularly where catheters are designed for single use application to prevent the spread of infection between patients or to medical personnel. Also significant is the cost associated with the sensing head of the sensor to which the catheter is connected which is designed for long term use. In that regard, is preferable to reduce the number of individual light sources and photodetectors used in the sensing head to inject light signals into the catheter and receive reflected back signals. An underlying consideration of paramount significance is the accuracy and reliability of the sensors which must be assured in that the devices are employed in critical patient care settings.
This invention relates to a novel fiberoptic sensor for simultaneous measurement of blood pressure and oxygen saturation. The sensor of this invention uses optical fibers exclusively for measurement. The sensor of this invention further provides an efficient and cost effective measuring system through the use of light sources which provide outputs which are shared between the pressure and oxygen saturation measuring fibers. By reducing the number of light emitters, the stability of optical signals is enhanced and a smaller sized and less complex sensing head is possible as compared with systems utilizing a greater number of independent elements.
The sensor of this invention also permits synchronizing outputs of the oxygen saturation fiber with that of the pressure measuring fiber, or visa versa. Such synchronous detection may be used to enhance measurement accuracy to provide additional information of clinical use. This invention further encompasses a sensor for oxygen saturation measurement based on the evanescent effect, which is believed to be relatively insensitive to hematocrit. And finally, this invention relates to sensors having sensing tips which are designed to inherently reduce the susceptibility to vessel wall effects.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is pictorial view of the sensor in accordance with this invention;
Figure 2 is a optical spectrum showing absorption extinction coefficients for reduced hemoglobin and oxy- hemoglobin.
Figure 3 is a schematic diagram of a sensor according to a first embodiment of this invention showing components of the sensing head and used with an oxygen sensing system incorporating a single optical fiber; Figure 4 is a schematic diagram of a sensor according to an alternate embodiment of this invention shown with the oxygen sensing system incorporating two optical fibers;
Figure 5 is a cross-sectional view through a sensing tip in accordance with an embodiment of this invention employing a chamber for blood light absorption having a planar light reflective surface.
Figure 6 is a partial cross-sectional view through a sensing tip similar to that shown in Figure 5 but shown having a concave reflective surface. Figure 7 is a partial cross-sectional view through a sensing tip according to an alternate embodiment of this invention based on back scatter measurement; and
Figure 8 is a partial cross-sectional view through a sensing tip according to an embodiment of this invention based on an evanescence measurement.
Figure 9 is a partial cross-sectional view through a sensing tip according to an alternate embodiment of this invention based on a modified evanescence measurement in which the optical fiber cross section is perturbed.
DETAILED DESCRIPTION OF THE INVENTION A sensor in accordance with this invention is shown in pictorial fashion in Figure 1 and is designated there by reference number 10. Sensor 10 generally comprises catheter assembly 11 and sensor head 13. Catheter assembly 11 is adapted for introduction into human patient blood vessels. Catheter assembly 11 includes a sensing tip 12 which will be described in detail later in this description. Catheter assembly 11 includes fiber optic couplers 14 and 16 which are provided for connection to optical fiber within the catheter for pressure and oxygen saturation measurement. A lumen is provided with connector 18 for enabling a known fluid pressure to be applied at sensing tip 12 for purposes of calibrating the pressure sensing features of the sensor.
An optical fiber coupler 18 is provided as a termination for the optical fibers within the catheter which are provided for the transmission of light signals for both pressure and oxygenation sensing, as is described in more detail below. The catheter assembly incorporates a catheter outer covering or sheath 20 made of a material which reduces thrombolytic (clot forming) activity and would be made, for example, of a polymer which binds to heparin. Now with reference to FIG. 2, the general approach of providing oxygen saturation measurement provided by sensor 10 will be described. FIG. 2 provides a spectrum showing the extinction coefficients for absorption of reduced hemoglobin shown as curve 22, and oxy-hemoglobin shown as curve 23 at various light wavelengths. At around 800 nm, the two spectrum curves overlap or define a "crossover point". Therefore, the extinction coefficients at that wavelength are the same for both reduced hemoglobin and oxy-hemoglobin. This characteristic is significant in that the extinction coefficient of light signals at that wavelength can be used as a measure of other parameters, for example hematocrit. For many sensor designs, and especially those relying on light absorption, hematocrit will strongly influence the extinction coefficient. Accordingly, by using a wavelength of around 800 nm, absorption of that signal can be used to calibrate the system for changes in hematocrit. It is also significant to note that at wavelengths below the crossover point, oxy- hemoglobin absorbs more than reduced hemoglobin, and the opposite occurs at wavelength above the crossover point. FIG. 2 designates several additional discrete wavelengths, namely, 660 nm and 940 nm which are employed for oxygen sensing systems in accordance with this invention. FIG. 3 illustrates in pictorial fashion a configuration for a sensor system 10 in accordance with this invention. The sensing head 13 is shown incorporating three discrete light sources, preferably in the form of LEDs or semiconductor lasers designated by references numbers 32, 34, and 36. Sensing head 13 also includes three photodetectors designated by reference numbers 38, 40 and 42. The lines connecting the various elements in FIG. 3 with direction arrowheads represent light paths which may be provided by sections of optical fibers. A single optical fiber 44 is provided for pressure sensing. The approach incorporated in sensor system 10 for pressure detection is identical to FST's sensing systems as described in the prior referenced patents in which a deformable diaphragm is employed to modulate the intensity of a returned light signal along fiber 44. Sensor system 10 also preferably incorporates a dual wavelength referencing system as described in FST's previously issued U. S. Patent No. 4,924,870. That patent describes a system in which a reflective coating is deposited on the end of optical fiber 44 which reflects light below a threshold cutoff wavelength, while transmitting light having a greater wavelength. The intensity of the two returned back light signals are ratioed as a means of reducing sensitivity of the pressure sensing system to differences in fiber characteristics, and the effects of fiber bending and other signal noise.
In the system shown in FIG. 3, LED 32 is selected to emit light at a wavelength of about 810 nm which is inputted into optical fiber 44 and is fully reflected at the dielectric filter (not shown) at the end of the fiber and thus provides a reference or calibration signal. LED 34 emits light at a wavelength of 940 nm which is transmitted through the dielectric filter and is modulated by the deformable diaphragm. Light which is returned along optical fiber 44 is coupled to photodetector 38. Through the network of fiber connections shown in FIG. 3, photodetector 38 receives signals reflected back along optical fiber 44 relating both to the calibration signal emitted by LED 32 and the pressure measuring signal emitted by LED 34. Sensor system 10 shown in FIG. 3 further incorporates a second optical fiber 46 which is provided for oxygen saturation measurement. All three LED's 32, 34, and 36 are coupled into optical fiber 46. LED 36 emits light at about 660 nm. Accordingly, light signals having wavelengths of 660, 810 and 940 nm are sent along optical fiber 46. With reference to FIG. 2, it can be seen that these wavelengths include the crossover point of the curves 22 and 23, and wavelengths above and below the crossover point . Light returned along optical fiber 46 is received by photodetector 42. Since the absorption relationship between oxygenated and reduced hemoglobin reverses at the crossover point, evaluating the absorption of light at the wavelengths of 660 and 940 nm provides a so called "push/pull effect" in which ratioing of those returned signals increases sensitivity. In sensing head 13, reference photodetector 40 is coupled to each of LED's 32, 34, and 36 and is provided for the purposes of evaluating the output intensity of each of the LED's. Photodetector 40 is used in calibrating the returned back signals so that the system can comprehend changes in output which are attributable to the specific characteristics of an individual LED or changes which occur during its operating life span, or in response to temperature changes, driving current, etc. The optical fiber pathways shown in FIG. 3 can be provided through various branching techniques known in the optical fiber art. For example, an optical fiber can be initially formed from plural strands which are fused at a point along their length to one end, thus providing a branching fiber. In addition, so called "mixing balls" or other known fiber coupling techniques could be used. In apreferredmode of operation of the system shown in FIG. 3, the sensing head 13 would incorporate a timing mechanism designated as CPU 48 for sequentially firing LED's 32, 34, and 36. Readings from photodetectors 38 and 42 would be synchronized so that the returned back signals at the various wavelengths can be discriminated. This synchronous demodulation technique avoids the requirement of providing wavelength selective optical filters, as a means of discriminating the signals returned along fibers 44 and 46 at the various wavelengths. The ability to provide simultaneous measurement of oxygen saturation and blood pressure at the sensing tip 12 of the sensor is believed to provide a number of significant attributes. For example, it is known that the orientation of red blood cells tends to change in response to the pressure difference between diastolic and systolic blood pressures. These orientation changes are known to change the light scattering effect of the blood. In particular, it is known that red blood cells tend to become oriented in a stacked-together fashion at the high pressure point of the pressure wave and become more randomly oriented in the lower pressure regions. Since oxygen saturation measurements, relying upon traditional absorption extinction coefficient measurement, are sensitive to scattering, such devices are subject to inaccuracy if they are sensitive to the pressure dependent effects of scattering which occur during a single blood pressure wave. In addition to scattering changes, blood vessel walls, especially arteries, tend to move or pulse in response to the pressure wave. This characteristic also can produce light attenuation changes as the wall moves relative to the sensor.
The simultaneous pressure and oxygen saturation measurement achievable by this invention would allow oxygen saturation measurements to be taken at a segment of the period of the pulse waveform such that light scattering tendencies of the blood will tend to be the same from one pulse to the next. In addition, observing absorption changes in measuring oxygen saturation in response to the pressure wave may also enable hematocrit to be evaluated without reference to a crossover wavelength, thus enabling a reduction in wavelengths used or enabling other blood species to be evaluated using a given number of available wavelengths. FIG. 4 is a pictorial view of a sensor system 50 in accordance with this invention which has many elements common with the prior embodiment but differs from that shown in FIG. 3 in that the oxygen saturation detection employs two separate fibers 52 and 54. -Fiber 52 is used to conduct light signals to sensing tip 12, whereas a separate fiber 54 is provided only for the returned signal. This configuration may be advantageous in some applications since it would be possible to custom tailor fibers 52 and 54 in consideration of their roles. For example, the diameter of optical fiber 54 could be greater than that of fiber 52 for the purposes of increasing light gathering capability. It is also significant to note that optical fiber 54, shown in FIG. 4, is directly connected to photodetector 42 and does not have to be branched which results in a reduction in signal strength. Now with reference to FIGS. 5 through 8, various alternative designs for sensing tip 12 are shown. As shown in FIG. 5, sensing tip 12 is connected to catheter sheath 20 through an interfitting connector, or alternately bonding or other joining techniques could be used. Pressure sensing optical fiber 44 terminates adjacent to deformable diaphragm 58. The pressure sensing features of sensing tip 12 are fully described in applicant's issued U. S. Patents mentioned previously. One difference, however, of tip 12 with respect to previous designs of applicant is the provision of a protective cap 60 terminating the sensing tip having pressure sensing openings 62. Cap 60 is provided to protect pressure diaphragm 58, especially from loading effects caused by contact with structures in the body. Cap 60 also aids in minimizing the sinitic effect of blood flow striking the diaphragm
The oxygen sensing features of sensing tip 12 comprise a notched or recessed area within the side of tip. Sensing tip 12 incorporates a dual fiber oxygen saturation measuring approach as described in connection with FIG. 4. Spaced from the terminations of both fibers 52 and 54 is a mirror 66. Light emitted from fiber 52 passes through blood in the area of recess 64. The reflective surface of mirror 66 returns some of this signal in the direction of return fiber 54 which is transmitted to photodetector 42. As described previously, the absorption extinction coefficient associated with the transmission of light through the blood in the area of recess 64 is used as a means for measuring oxygen saturation. Since hematocrit affects the scattering of light passing through the area of recess 64, an independent measure of hematocrit is provided through transmission of light at the wavelength of 810 nm as explained previously. Apertures for the transmission of blood such as heparin or the withdrawal of fluid can be provided within sensing tip 12 or within catheter sheath 20 at a location near the sensing tip. By providing recess 64 having a depth (as measured from the outer surface of sheath 20 toward its longitudinal center axis) of at least two millimeters, it is believed possible to substantially reduce or eliminate the tendency for erroneous readings to be created when a blood vessel wall interferes with the transmission of light in the area of recess 64.
FIG. 6 illustrates a sensing tip 67 according to an alternate embodiment of the invention. The device is identical to sensing tip 12 described above except that reflective surface 68 is concave. This configuration increases the returned light signal strength. In all other respects, sensing tip 67 operates like tip 12.
FIG. 7 illustrates a portion of sensing tip 70 in accordance with a alternate embodiment of this invention. Since sensing tip 70 incorporates many of the elements of sensing tip 12, these elements are identified by like reference numbers. Sensing tip 70 provides oxygen saturation measurement through the effect of evaluating back scatter radiation. In this case, light is emitted through fiber 52 in a field area provided by recess 72. Back scatter radiation is received by return optical fiber 54. Extinction coefficient curves similar to that attributable to absorption, shown in FIG. 2, also exist for the back scatter operational mode. As in the prior embodiments, recess 72 prevents blood vessel walls from directly confronting the fibers, thus reducing the likelihood of affecting oxygen saturation measurement.
A second class of sensing tip designs according to this invention are shown in FIGS. 8 and 9, and employ an evanescent principle for examining the interaction of light of known wavelengths with erythrocytes. In employing the evanescent effect, light is propagated along an optical fiber which has a polished outer surface region 81 exposed to blood. Since blood contains erythrocytes which absorb light of various wavelengths in a characteristic fashion, a fraction of the energy transmitted along the fiber tends to leak from the fiber into the absorber. The fraction of the light of a given wavelength which leaves the fiber is related to the absorption characteristics of the blood. The principal advantage of employing the evanescence phenomenon is that it is not subject to scattering error since it does not rely on light propagating through blood. Therefore, it is possible that a sensor relying on evanescence may not require a third discrete wavelength or other signal reduction for the purpose of calibrating for scattering differences due to hematocrit. In FIG. 8, sensing tip 80 is shown employing a single optical fiber 46 for oxygen saturation measurement. The terminal end of the fiber 46 is coated with a reflective film 82. Within recess 84, the original fiber thickness is reduced by slightly polishing away a few microns to facilitate strong interaction between the evanescent field and blood cells. The sensitivity of the sensor can be increased through increasing the length of region 81 and recess 84.
In FIG. 9, sensing tip 88, like that of FIG. 8, employs a single fiber 46 for oxygen saturation measurement terminated by reflective film 82. Sensing tip 88, however. employs a modified evanescent transmission coupling effect where a geometry perturbation is applied to the fiber core. A local thinning or tapering of the core enhances sensitivity to oxygen concentration changes. The core is perturbed as shown in FIG. 9 by milling away a portion of its diameter. Other core perturbations could be provided, such as removing wedge shaped slices or generating special surface roughness features. The essence of sensing tip 88 is a local change in the cross-sectional shape of the fiber core along its length.
While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible of modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.

Claims

IN THE CI-AIMS
1. A sensor for in vivo evaluation of blood pressure and blood oxygen saturation of a patient, comprising: a catheter having a distal end for introduction within patient blood vessels and a proximal end, said catheter having at least a first optical fiber means for blood pressure sensing and a second optical fiber means separate from said first optical fiber means for blood oxygen saturation measurement, a sensing tip affixed to said catheter distal end having pressure sensing means for modulating a light signal sent along said first optical fiber means, said sensing tip further having means for causing said blood to interact with a light signal sent along said second optical fiber means, and a sensing head coupled to said catheter proximal end for injecting light signals into said first and second optical fiber means and for receiving light signals returned along said first and second optical fiber means thereby enabling said blood pressure and blood oxygen saturation evaluation said sensing head having at least a first light source coupled into both said first and second optical fiber means.
2. A sensor according to Claim 1 wherein said pressure sensing means comprises a deformable diagram positioned adjacent the distal end of said first optical fiber means and exposed to said blood whereby said diagram is deformed in response to blood pressure, and said diagram modulating the intensity of a light signal sent along said first optical fiber means.
3. A sensor according to Claim 1 wherein said catheter further comprises a lumen for calibrating said pressure sensing means by allowing a known pressure of a fluid to act on said pressure sensing means.
4. A sensor according to Claim 1 wherein said means for causing said blood to interact with a light signal along said second optical fiber means comprises a chamber filled with blood positioned adjacent the distal end of said second optical fiber means.
5. A sensor according to Claim 4 wherein said chamber defines a reflective surface for reflecting light signals emitting from said second optical fiber means after passing through said blood back into said second optical fiber means.
6. A sensor according to Claim 5 wherein said reflective surface is planer.
7. A sensor according to Claim 5 wherein said reflective surface is concave.
8. A sensor according to Claim 1 wherein said means for causing said light to interact with said blood comprises a region adjacent the terminal end of said second fiber means wherein light is launched into the blood and back scattered light is recoupled into said second fiber means.
9. A sensor according to Claim 1 wherein said means for causing said blood to interact with a light signal comprises a surface along a section of a fiber of said second optical fiber means exposed to said blood wherein light traveling along said fiber interacts with blood through an evanescence effect.
10. A sensor assembly according to Claim 9 wherein a reflective surface is positioned at the terminal end of said second optical fiber means whereby said inputted light signal crosses past said fiber section and is thereafter reflected back along said second optical fiber means.
11. A sensor according to Claim 9 wherein said second of said fiber comprises a polished length of the outer surface of said fiber in direct contact with said blood.
12. A sensor according to Claim 9 wherein said section of said fiber comprises a perturbation of the cross sectional configuration of said fiber.
13. A sensor according to Claim 12 wherein said perturbation comprises a local reduction in the cross sectional area of said fiber.
14. A sensor according to Claim 1 wherein said sensor tip defines a recess adjacent said terminal end defining said chamber and including a termination of said second optical fiber means which is displaced at least 2 millimeters from the outer surface of said catheter toward the longitudinal center axis of said catheter tip.
15. A sensor according to Claim 1 wherein said second optical fiber means comprises a single optical fiber for transmitting both an inputted and returned light signals.
16. A sensor according to Claim 1 wherein said second optical fiber means comprises a pair of optical fibers with a first fiber for transmitting an inputted light signal and a second fiber for transmitting a returned light signal.
17. A sensor according to Claim 1 wherein light from said first light coupled into said first optical means is reflected at a reflective surface at the distal end of said first optical means for serving as a reference signal for blood pressure measurement.
18. A sensor assembly according to Claim 17 wherein at least one of said first and said second fiber means comprise a fiber core having a main section within said catheter and a branching portion within said sensing head optically coupled to said first light source.
19. A sensor according to Claim 1 wherein said sensing head comprises a second light source coupled to both said first and second optical fiber means.
20. A sensor according to Claim 19 wherein both said first and said second fiber means comprise a fiber core having a main section within said catheter and separate branching portions within said sensing head optically coupled to said first and second light sources.
21. A sensor according to Claim 1 wherein said light signal returned along said first optical fiber means enable a blood pressure waveform to be measured and said sensing head gates signals received along said second fiber means in response to said waveform to evaluate blood oxygen concentration during a prescribed segment of the period of said waveform.
22. A sensor for in vivo evaluation of blood pressure and blood oxygen saturation of a patient, comprising: a catheter having a distal end for introduction within patient blood vessels and a proximal end, said catheter having a sensing tip having blood pressure sensing means and blood oxygen sensing means, said blood pressure sensing means enabling a blood pressure waveform responsive to a heartbeat to be measured, and . a sensing head coupled to said proximal end of said catheter which gates signals received from said blood oxygen sensing means in response to said waveform to evaluate blood oxygen concentration during a prescribed segment of the period of said waveform.
23. A sensor according to claim 22 wherein said pressure sensing means comprises a deformable diagram positioned adjacent the distal end of a first optical fiber means extending between said catheter distal and proximal ends and exposed to said blood whereby said diagram is deformed in response to blood pressure, and said diagram modulating the intensity of a light signal sent along said first optical fiber means.
24. A sensor according to Claim 23 wherein said blood oxygen sensing means comprising a second optical fiber means for causing light inputted into said second optical fiber means to be modulated in response to blood oxygen content.
PCT/US1993/000715 1992-01-21 1993-01-21 Fiberoptic blood pressure and oxygenation sensor WO1993013707A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US07/823,143 US5280786A (en) 1992-01-21 1992-01-21 Fiberoptic blood pressure and oxygenation sensor
US07/823,143 1992-01-21

Publications (1)

Publication Number Publication Date
WO1993013707A1 true WO1993013707A1 (en) 1993-07-22

Family

ID=25237920

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1993/000715 WO1993013707A1 (en) 1992-01-21 1993-01-21 Fiberoptic blood pressure and oxygenation sensor

Country Status (3)

Country Link
US (1) US5280786A (en)
EP (1) EP0576670A1 (en)
WO (1) WO1993013707A1 (en)

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2308888B (en) * 1995-12-28 2000-08-02 British Aerospace Pressure measuring device
WO2012058716A1 (en) * 2010-11-02 2012-05-10 Edith Cowan University An optical sensor for measuring a property of a fluid
WO2013074084A1 (en) * 2011-11-15 2013-05-23 Empire Technology Development Llc Integrated optical sensor
WO2015013646A1 (en) * 2013-07-26 2015-01-29 Boston Scientific Scimed, Inc. Ffr sensor head design that minimizes stress induced pressure offsets
US9429713B2 (en) 2014-04-17 2016-08-30 Boston Scientific Scimed, Inc. Self-cleaning optical connector
US9775523B2 (en) 2013-10-14 2017-10-03 Boston Scientific Scimed, Inc. Pressure sensing guidewire and methods for calculating fractional flow reserve
US9782129B2 (en) 2014-08-01 2017-10-10 Boston Scientific Scimed, Inc. Pressure sensing guidewires
US9795307B2 (en) 2014-12-05 2017-10-24 Boston Scientific Scimed, Inc. Pressure sensing guidewires
US10028666B2 (en) 2013-03-15 2018-07-24 Boston Scientific Scimed, Inc. Pressure sensing guidewire
US10278594B2 (en) 2014-06-04 2019-05-07 Boston Scientific Scimed, Inc. Pressure sensing guidewire systems with reduced pressure offsets
US10499820B2 (en) 2013-05-22 2019-12-10 Boston Scientific Scimed, Inc. Pressure sensing guidewire systems including an optical connector cable
US10582860B2 (en) 2012-08-27 2020-03-10 Boston Scientific Scimed, Inc. Pressure-sensing medical devices and medical device systems
US10702162B2 (en) 2010-11-09 2020-07-07 Opsens Inc. Guidewire with internal pressure sensor
US10835182B2 (en) 2013-08-14 2020-11-17 Boston Scientific Scimed, Inc. Medical device systems including an optical fiber with a tapered core
US10932679B2 (en) 2014-03-18 2021-03-02 Boston Scientific Scimed, Inc. Pressure sensing guidewires and methods of use
US11058307B2 (en) 2016-02-23 2021-07-13 Boston Scientific Scimed, Inc. Pressure sensing guidewire systems including an optical connector cable
US11311196B2 (en) 2018-02-23 2022-04-26 Boston Scientific Scimed, Inc. Methods for assessing a vessel with sequential physiological measurements
US11559213B2 (en) 2018-04-06 2023-01-24 Boston Scientific Scimed, Inc. Medical device with pressure sensor
US11564581B2 (en) 2017-08-03 2023-01-31 Boston Scientific Scimed, Inc. Methods for assessing fractional flow reserve
US11666232B2 (en) 2018-04-18 2023-06-06 Boston Scientific Scimed, Inc. Methods for assessing a vessel with sequential physiological measurements
US11850073B2 (en) 2018-03-23 2023-12-26 Boston Scientific Scimed, Inc. Medical device with pressure sensor

Families Citing this family (98)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5422478A (en) * 1992-04-17 1995-06-06 Fiberoptic Sensor Technologies, Inc. Fiberoptic pressure sensor having drift correction means for insitu calibration
US5810741A (en) * 1992-11-05 1998-09-22 Synectics Medical Ab Method of measuring respiration and respiratory effort using plural catheters
US5477860A (en) * 1992-11-05 1995-12-26 Synectics Medical, Inc. Catheter for measuring respiration and respiratory effort
US5438985A (en) * 1993-01-25 1995-08-08 Synectics Medical, Incorporated Ambulatory recording of the presence and activity of substances in gastro-intestinal compartments
US5657759A (en) * 1993-05-13 1997-08-19 Synectics Medical, Incorporated Measurement of gastric emptying and gastrointestinal output
US5551425A (en) * 1993-05-13 1996-09-03 Synectics Medical, Inc. Potential difference and perfusion pressure catheter
US5477854A (en) * 1993-09-16 1995-12-26 Synectics Medical, Inc. System and method to monitor gastrointestinal Helicobacter pylori infection
US5507289A (en) * 1993-09-16 1996-04-16 Synectics Medical, Inc. System and method to diagnose bacterial growth
US5479935A (en) * 1993-10-21 1996-01-02 Synectics Medical, Inc. Ambulatory reflux monitoring system
US5833625A (en) * 1993-10-21 1998-11-10 Synectics Medical Ab Ambulatory reflux monitoring system
US5654539A (en) * 1995-08-17 1997-08-05 Vasamedics L.L.C. Laser doppler optical sensor for use on a monitoring probe
US5701905A (en) * 1995-11-13 1997-12-30 Localmed, Inc. Guide catheter with sensing element
AU4634799A (en) * 1998-07-04 2000-01-24 Whitland Research Limited Non-invasive measurement of blood analytes
NL1009565C2 (en) * 1998-07-06 2000-01-10 Academisch Ziekenhuis Utrecht Catheter system and a catheter to be used therein.
US6144444A (en) * 1998-11-06 2000-11-07 Medtronic Avecor Cardiovascular, Inc. Apparatus and method to determine blood parameters
US20090027659A1 (en) * 1999-06-18 2009-01-29 Sambra Sensors Ab Measuring system for measuring a physical parameter influencing a sensor element
SE514745C2 (en) * 1999-06-18 2001-04-09 Samba Sensors Ab Method and apparatus for bending compensation in intensity-based optical measurement systems
US20060009740A1 (en) * 2001-08-28 2006-01-12 Michael Higgins Multiple lumen catheter having a soft tip
US6650799B2 (en) 2001-09-18 2003-11-18 Hampton University Apparatus for and methods of sensing evanescent events in a fluid field
US8996090B2 (en) * 2002-06-03 2015-03-31 Exostat Medical, Inc. Noninvasive detection of a physiologic parameter within a body tissue of a patient
US6999809B2 (en) * 2002-07-16 2006-02-14 Edwards Lifesciences Corporation Central venous catheter having a soft tip and fiber optics
US7029467B2 (en) * 2002-07-16 2006-04-18 Edwards Lifesciences Corporation Multiple lumen catheter having a soft tip
US20040263857A1 (en) * 2003-06-24 2004-12-30 Basavanhally Nagesh R. Fiber-optic gauge having one or more side-mounted sensors
US8784336B2 (en) 2005-08-24 2014-07-22 C. R. Bard, Inc. Stylet apparatuses and methods of manufacture
JP2009507569A (en) * 2005-09-13 2009-02-26 エドワーズ ライフサイエンシーズ コーポレイション Continuous spectroscopic measurement of total hemoglobin
US20070197888A1 (en) * 2006-02-21 2007-08-23 Physical Logic Ag Blood Oxygenation Sensor
US7519407B2 (en) * 2006-02-21 2009-04-14 Physical Logic Ag Optical sensing catheter system
US20070201031A1 (en) * 2006-02-28 2007-08-30 Physical Logic Ag Optical Blood Pressure and Velocity Sensor
US8388546B2 (en) 2006-10-23 2013-03-05 Bard Access Systems, Inc. Method of locating the tip of a central venous catheter
US7794407B2 (en) 2006-10-23 2010-09-14 Bard Access Systems, Inc. Method of locating the tip of a central venous catheter
US10449330B2 (en) 2007-11-26 2019-10-22 C. R. Bard, Inc. Magnetic element-equipped needle assemblies
US8849382B2 (en) 2007-11-26 2014-09-30 C. R. Bard, Inc. Apparatus and display methods relating to intravascular placement of a catheter
US10751509B2 (en) 2007-11-26 2020-08-25 C. R. Bard, Inc. Iconic representations for guidance of an indwelling medical device
US8781555B2 (en) 2007-11-26 2014-07-15 C. R. Bard, Inc. System for placement of a catheter including a signal-generating stylet
US9649048B2 (en) * 2007-11-26 2017-05-16 C. R. Bard, Inc. Systems and methods for breaching a sterile field for intravascular placement of a catheter
US10524691B2 (en) 2007-11-26 2020-01-07 C. R. Bard, Inc. Needle assembly including an aligned magnetic element
CN103750858B (en) 2007-11-26 2017-04-12 C·R·巴德股份有限公司 Integrated system for intravascular placement of a catheter
US9521961B2 (en) 2007-11-26 2016-12-20 C. R. Bard, Inc. Systems and methods for guiding a medical instrument
US8478382B2 (en) 2008-02-11 2013-07-02 C. R. Bard, Inc. Systems and methods for positioning a catheter
US20090326390A1 (en) * 2008-06-30 2009-12-31 Andres Belalcazar Pressure and Oxygen Saturation Monitoring Devices and Systems
WO2010022370A1 (en) * 2008-08-22 2010-02-25 C.R. Bard, Inc. Catheter assembly including ecg sensor and magnetic assemblies
RU2478338C2 (en) 2008-09-11 2013-04-10 Эсист Медикал Системз, Инк. Device and method of physiological sensor delivery
US8437833B2 (en) 2008-10-07 2013-05-07 Bard Access Systems, Inc. Percutaneous magnetic gastrostomy
US20100114063A1 (en) * 2008-11-04 2010-05-06 Angiodynamics, Inc. Catheter injection monitoring device
RU2691318C2 (en) 2009-06-12 2019-06-11 Бард Аксесс Системс, Инк. Method for positioning catheter end
US9125578B2 (en) 2009-06-12 2015-09-08 Bard Access Systems, Inc. Apparatus and method for catheter navigation and tip location
US9532724B2 (en) 2009-06-12 2017-01-03 Bard Access Systems, Inc. Apparatus and method for catheter navigation using endovascular energy mapping
EP2464407A4 (en) 2009-08-10 2014-04-02 Bard Access Systems Inc Devices and methods for endovascular electrography
AU2010300677B2 (en) 2009-09-29 2014-09-04 C.R. Bard, Inc. Stylets for use with apparatus for intravascular placement of a catheter
US11103213B2 (en) * 2009-10-08 2021-08-31 C. R. Bard, Inc. Spacers for use with an ultrasound probe
US8771289B2 (en) * 2009-12-21 2014-07-08 Acist Medical Systems, Inc. Thrombus removal device and system
US20120316419A1 (en) 2010-02-18 2012-12-13 Eric Chevalier Multimodal catheter
WO2011150358A1 (en) 2010-05-28 2011-12-01 C.R. Bard, Inc. Insertion guidance system for needles and medical components
WO2011150376A1 (en) 2010-05-28 2011-12-01 C.R. Bard, Inc. Apparatus for use with needle insertion guidance system
CN103228219B (en) 2010-08-09 2016-04-27 C·R·巴德股份有限公司 For support and the covered structure of ultrasound probe head
KR101856267B1 (en) 2010-08-20 2018-05-09 씨. 알. 바드, 인크. Reconfirmation of ecg-assisted catheter tip placement
US8753292B2 (en) * 2010-10-01 2014-06-17 Angiodynamics, Inc. Method for locating a catheter tip using audio detection
WO2012058461A1 (en) 2010-10-29 2012-05-03 C.R.Bard, Inc. Bioimpedance-assisted placement of a medical device
EP2706908B1 (en) 2011-05-11 2019-07-10 Acist Medical Systems, Inc. Intravascular sensing system
WO2013006817A1 (en) 2011-07-06 2013-01-10 C.R. Bard, Inc. Needle length determination and calibration for insertion guidance system
USD724745S1 (en) 2011-08-09 2015-03-17 C. R. Bard, Inc. Cap for an ultrasound probe
USD699359S1 (en) 2011-08-09 2014-02-11 C. R. Bard, Inc. Ultrasound probe head
US9211107B2 (en) 2011-11-07 2015-12-15 C. R. Bard, Inc. Ruggedized ultrasound hydrogel insert
US8663116B2 (en) 2012-01-11 2014-03-04 Angiodynamics, Inc. Methods, assemblies, and devices for positioning a catheter tip using an ultrasonic imaging system
WO2013184625A2 (en) * 2012-06-05 2013-12-12 Siemens Healthcare Diagnostics Inc. Serum sample quality determination
EP2861153A4 (en) 2012-06-15 2016-10-19 Bard Inc C R Apparatus and methods for detection of a removable cap on an ultrasound probe
US9241641B2 (en) * 2012-07-20 2016-01-26 Acist Medical Systems, Inc. Fiber optic sensor assembly for sensor delivery device
JP2016506270A (en) * 2012-12-21 2016-03-03 デイビッド アンダーソン, Multi-sensor device
US10188831B2 (en) 2013-03-14 2019-01-29 Angiodynamics, Inc. Systems and methods for catheter tip placement using ECG
WO2015009970A1 (en) 2013-07-18 2015-01-22 Erythron Llc Spectroscopic measurements with parallel array detector
US10130269B2 (en) 2013-11-14 2018-11-20 Medtronic Vascular, Inc Dual lumen catheter for providing a vascular pressure measurement
US9877660B2 (en) 2013-11-14 2018-01-30 Medtronic Vascular Galway Systems and methods for determining fractional flow reserve without adenosine or other pharmalogical agent
US9913585B2 (en) 2014-01-15 2018-03-13 Medtronic Vascular, Inc. Catheter for providing vascular pressure measurements
EP3073910B1 (en) 2014-02-06 2020-07-15 C.R. Bard, Inc. Systems for guidance and placement of an intravascular device
US20150338338A1 (en) 2014-02-28 2015-11-26 Erythron, Llc Method and Apparatus for Determining Markers of Health by Analysis of Blood
US20150282734A1 (en) 2014-04-08 2015-10-08 Timothy Schweikert Medical device placement system and a method for its use
US10244951B2 (en) 2014-06-10 2019-04-02 Acist Medical Systems, Inc. Physiological sensor delivery device and method
US10973418B2 (en) 2014-06-16 2021-04-13 Medtronic Vascular, Inc. Microcatheter sensor design for minimizing profile and impact of wire strain on sensor
US10201284B2 (en) 2014-06-16 2019-02-12 Medtronic Vascular Inc. Pressure measuring catheter having reduced error from bending stresses
US11330989B2 (en) 2014-06-16 2022-05-17 Medtronic Vascular, Inc. Microcatheter sensor design for mounting sensor to minimize induced strain
US10194812B2 (en) 2014-12-12 2019-02-05 Medtronic Vascular, Inc. System and method of integrating a fractional flow reserve device with a conventional hemodynamic monitoring system
US10973584B2 (en) 2015-01-19 2021-04-13 Bard Access Systems, Inc. Device and method for vascular access
WO2016168090A1 (en) * 2015-04-14 2016-10-20 Nueon, Inc. Method and apparatus for determining markers of health by analysis of blood
WO2016210325A1 (en) 2015-06-26 2016-12-29 C.R. Bard, Inc. Connector interface for ecg-based catheter positioning system
JP6582129B2 (en) * 2015-09-04 2019-09-25 ボストン サイエンティフィック サイムド,インコーポレイテッドBoston Scientific Scimed,Inc. Medical device and pressure sensing guidewire
US11000207B2 (en) 2016-01-29 2021-05-11 C. R. Bard, Inc. Multiple coil system for tracking a medical device
WO2017165403A1 (en) 2016-03-21 2017-09-28 Nueon Inc. Porous mesh spectrometry methods and apparatus
US11272850B2 (en) 2016-08-09 2022-03-15 Medtronic Vascular, Inc. Catheter and method for calculating fractional flow reserve
WO2018085699A1 (en) 2016-11-04 2018-05-11 Nueon Inc. Combination blood lancet and analyzer
US11330994B2 (en) 2017-03-08 2022-05-17 Medtronic Vascular, Inc. Reduced profile FFR catheter
US10646122B2 (en) 2017-04-28 2020-05-12 Medtronic Vascular, Inc. FFR catheter with covered distal pressure sensor and method of manufacture
US11219741B2 (en) 2017-08-09 2022-01-11 Medtronic Vascular, Inc. Collapsible catheter and method for calculating fractional flow reserve
US11235124B2 (en) 2017-08-09 2022-02-01 Medtronic Vascular, Inc. Collapsible catheter and method for calculating fractional flow reserve
JP2021521943A (en) 2018-04-20 2021-08-30 アシスト・メディカル・システムズ,インコーポレイテッド Evaluation of blood vessels
US11185244B2 (en) 2018-08-13 2021-11-30 Medtronic Vascular, Inc. FFR catheter with suspended pressure sensor
WO2020081373A1 (en) 2018-10-16 2020-04-23 Bard Access Systems, Inc. Safety-equipped connection systems and methods thereof for establishing electrical connections
US11596317B2 (en) 2018-10-31 2023-03-07 Acist Medical Systems, Inc. Fluid pressure sensor protection
CN217525118U (en) * 2020-09-25 2022-10-04 巴德阿克塞斯系统股份有限公司 Medical instrument system for inserting a medical instrument into a patient

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3814081A (en) * 1971-04-02 1974-06-04 Olympus Optical Co Optical measuring catheter
US4803992A (en) * 1980-10-28 1989-02-14 Lemelson Jerome H Electro-optical instruments and methods for producing same
US4854321A (en) * 1986-06-18 1989-08-08 Medex, Inc. Integrated optic system for monitoring blood gases
US4934369A (en) * 1987-01-30 1990-06-19 Minnesota Mining And Manufacturing Company Intravascular blood parameter measurement system

Family Cites Families (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3866599A (en) * 1972-01-21 1975-02-18 Univ Washington Fiberoptic catheter
AU463065B2 (en) * 1972-02-01 1975-07-17 Oximetrix Inc. Oximeter and method
USRE31873F1 (en) * 1976-09-08 1988-11-15 Venous catheter device
US4114604A (en) * 1976-10-18 1978-09-19 Shaw Robert F Catheter oximeter apparatus and method
US4201222A (en) * 1977-08-31 1980-05-06 Thomas Haase Method and apparatus for in vivo measurement of blood gas partial pressures, blood pressure and blood pulse
US4416285A (en) * 1978-11-29 1983-11-22 Oximetrix, Inc. Improved optical catheter and method for making same
US4600015A (en) * 1980-10-28 1986-07-15 Antec Systems Limited Patient monitoring apparatus and method
US4623248A (en) * 1983-02-16 1986-11-18 Abbott Laboratories Apparatus and method for determining oxygen saturation levels with increased accuracy
US4622974A (en) * 1984-03-07 1986-11-18 University Of Tennessee Research Corporation Apparatus and method for in-vivo measurements of chemical concentrations
US4690492A (en) * 1984-09-04 1987-09-01 Oximetrix, Inc. Optical coupling
US4684245A (en) * 1985-10-28 1987-08-04 Oximetrix, Inc. Electro-optical coupler for catheter oximeter
US4730622A (en) * 1986-07-01 1988-03-15 Cordis Corporation Pressure and oxygen saturation catheter
US4727730A (en) * 1986-07-10 1988-03-01 Medex, Inc. Integrated optic system for monitoring blood pressure
US5012809A (en) * 1986-10-10 1991-05-07 Shulze John E Fiber optic catheter system with fluorometric sensor and integral flexure compensation
US5046497A (en) * 1986-11-14 1991-09-10 Millar Instruments, Inc. Structure for coupling a guidewire and a catheter
US4776340A (en) * 1987-03-23 1988-10-11 Spectramed, Inc. Hematocrit measurement by differential optical geometry in a short-term diagnostic cardiovascular catheter, and application to correction of blood-oxygen measurement
EP0336985B1 (en) * 1988-04-09 1993-01-27 Hewlett-Packard GmbH Method for manufacturing an optical probe
EP0336984B1 (en) * 1988-04-09 1990-12-27 Hewlett-Packard GmbH Measuring probe
JPH0257239A (en) * 1988-08-23 1990-02-27 Terumo Corp Probe for optical sensor
US5048524A (en) * 1989-03-03 1991-09-17 Camino Laboratories, Inc. Blood parameter measurement

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3814081A (en) * 1971-04-02 1974-06-04 Olympus Optical Co Optical measuring catheter
US4803992A (en) * 1980-10-28 1989-02-14 Lemelson Jerome H Electro-optical instruments and methods for producing same
US4854321A (en) * 1986-06-18 1989-08-08 Medex, Inc. Integrated optic system for monitoring blood gases
US4934369A (en) * 1987-01-30 1990-06-19 Minnesota Mining And Manufacturing Company Intravascular blood parameter measurement system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0576670A4 *

Cited By (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2308888B (en) * 1995-12-28 2000-08-02 British Aerospace Pressure measuring device
WO2012058716A1 (en) * 2010-11-02 2012-05-10 Edith Cowan University An optical sensor for measuring a property of a fluid
US10702162B2 (en) 2010-11-09 2020-07-07 Opsens Inc. Guidewire with internal pressure sensor
US11786130B2 (en) 2010-11-09 2023-10-17 Opsens Inc. Guidewire with internal pressure sensor
US10750949B2 (en) 2010-11-09 2020-08-25 Opsens Inc. Guidewire with internal pressure sensor
WO2013074084A1 (en) * 2011-11-15 2013-05-23 Empire Technology Development Llc Integrated optical sensor
US8958071B2 (en) 2011-11-15 2015-02-17 Empire Technology Development Llc Integrated optical sensor
US10582860B2 (en) 2012-08-27 2020-03-10 Boston Scientific Scimed, Inc. Pressure-sensing medical devices and medical device systems
US10028666B2 (en) 2013-03-15 2018-07-24 Boston Scientific Scimed, Inc. Pressure sensing guidewire
US10499820B2 (en) 2013-05-22 2019-12-10 Boston Scientific Scimed, Inc. Pressure sensing guidewire systems including an optical connector cable
WO2015013646A1 (en) * 2013-07-26 2015-01-29 Boston Scientific Scimed, Inc. Ffr sensor head design that minimizes stress induced pressure offsets
US11076765B2 (en) 2013-07-26 2021-08-03 Boston Scientific Scimed, Inc. FFR sensor head design that minimizes stress induced pressure offsets
JP2016530919A (en) * 2013-07-26 2016-10-06 ボストン サイエンティフィック サイムド,インコーポレイテッドBoston Scientific Scimed,Inc. FFR sensor head design to minimize stress-induced pressure offset
US10835182B2 (en) 2013-08-14 2020-11-17 Boston Scientific Scimed, Inc. Medical device systems including an optical fiber with a tapered core
US10499817B2 (en) 2013-10-14 2019-12-10 Boston Scientific Scimed, Inc. Pressure sensing guidewire and methods for calculating fractional flow reserve
US9775523B2 (en) 2013-10-14 2017-10-03 Boston Scientific Scimed, Inc. Pressure sensing guidewire and methods for calculating fractional flow reserve
US10932679B2 (en) 2014-03-18 2021-03-02 Boston Scientific Scimed, Inc. Pressure sensing guidewires and methods of use
US9563023B2 (en) 2014-04-17 2017-02-07 Boston Scientific Scimed, Inc. Self-cleaning optical connector
US9429713B2 (en) 2014-04-17 2016-08-30 Boston Scientific Scimed, Inc. Self-cleaning optical connector
US10278594B2 (en) 2014-06-04 2019-05-07 Boston Scientific Scimed, Inc. Pressure sensing guidewire systems with reduced pressure offsets
US9782129B2 (en) 2014-08-01 2017-10-10 Boston Scientific Scimed, Inc. Pressure sensing guidewires
US9795307B2 (en) 2014-12-05 2017-10-24 Boston Scientific Scimed, Inc. Pressure sensing guidewires
US11058307B2 (en) 2016-02-23 2021-07-13 Boston Scientific Scimed, Inc. Pressure sensing guidewire systems including an optical connector cable
US11564581B2 (en) 2017-08-03 2023-01-31 Boston Scientific Scimed, Inc. Methods for assessing fractional flow reserve
US11311196B2 (en) 2018-02-23 2022-04-26 Boston Scientific Scimed, Inc. Methods for assessing a vessel with sequential physiological measurements
US11850073B2 (en) 2018-03-23 2023-12-26 Boston Scientific Scimed, Inc. Medical device with pressure sensor
US11559213B2 (en) 2018-04-06 2023-01-24 Boston Scientific Scimed, Inc. Medical device with pressure sensor
US11666232B2 (en) 2018-04-18 2023-06-06 Boston Scientific Scimed, Inc. Methods for assessing a vessel with sequential physiological measurements

Also Published As

Publication number Publication date
US5280786A (en) 1994-01-25
EP0576670A1 (en) 1994-01-05
EP0576670A4 (en) 1994-03-30

Similar Documents

Publication Publication Date Title
US5280786A (en) Fiberoptic blood pressure and oxygenation sensor
Mignani et al. Biomedical sensors using optical fibres
CA1282251C (en) Optical fiber transducer driving and measuring circuit and method for using same
CA2441017C (en) Method and apparatus for improving the accuracy of noninvasive hematocrit measurements
US5427114A (en) Dual pressure sensing catheter
JP7366059B2 (en) Sensor for measuring fluid flow
US6041247A (en) Non-invasive optical measuring sensor and measuring method
US20080200784A1 (en) Method and device for measuring parameters of cardiac function
Mignani et al. In-vivo biomedical monitoring by fiber-optic systems
JPH05506171A (en) Infrared and near-infrared testing of blood components
US20060161055A1 (en) Probe design
US20120288230A1 (en) Non-Reflective Optical Connections in Laser-Based Photoplethysmography
Takatini et al. A miniature hybrid reflection type optical sensor for measurement of hemoglobin content and oxygen saturation of whole blood
US20070203414A1 (en) Optical Sensing Catheter System
WO2007096874A2 (en) Blood oxygenation sensor
US7508999B2 (en) Fiber optic sensor device for measuring chromophoric compounds in biological fluid
US6339714B1 (en) Apparatus and method for measuring concentrations of a dye in a living organism
Mignani et al. Fibre-optic sensors in health care
GB2308888A (en) Blood pressure measuring device
US5383453A (en) Method for manufacturing an optical probe
CN112168181B (en) Brain tissue blood oxygen saturation detection device and preparation method thereof
EP2706915A2 (en) Anti-reflective launch optics in laser-based photoplethysmography
JPS6235451Y2 (en)
Baldini et al. Advances in fiber optic sensors for in vivo monitoring
Anderson et al. Fiber optic sensor for simultaneous oxygen saturation and blood pressure measurement

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): JP

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE

WWE Wipo information: entry into national phase

Ref document number: 1993904659

Country of ref document: EP

WWP Wipo information: published in national office

Ref document number: 1993904659

Country of ref document: EP

WWW Wipo information: withdrawn in national office

Ref document number: 1993904659

Country of ref document: EP