CA1187946A - Pressure monitoring method and apparatus - Google Patents
Pressure monitoring method and apparatusInfo
- Publication number
- CA1187946A CA1187946A CA000402584A CA402584A CA1187946A CA 1187946 A CA1187946 A CA 1187946A CA 000402584 A CA000402584 A CA 000402584A CA 402584 A CA402584 A CA 402584A CA 1187946 A CA1187946 A CA 1187946A
- Authority
- CA
- Canada
- Prior art keywords
- housing
- pressure
- sensor
- diaphragm
- tubing
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/004—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by the use of counterbalancing forces
- G01L11/006—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by the use of counterbalancing forces hydraulic or pneumatic counterbalancing forces
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/03—Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs
- A61B5/031—Intracranial pressure
Abstract
PRESSURE MONITORING METHOD AND APPARATUS
ABSTRACT
An apparatus which measures and monitors the pressure within a human body includes a pressure sensor having a housing closed by a pressure sensitive diaphragm to define a plenum, an exhaust tube mounted within the plenum which terminates adjacent the inner surface of the diaphragm, And tubes which transmit a substantially constant flow of gas into the plenum and which withdraw gas from the exhaust tube to a location remote from the body. Changes in pressure within the body cause the diaphragm to alternately close and open the end of the exhaust tube, thereby resulting in an increase or decrease in the pressure within the plenum until an equilibrium pressure is reached. A source of gas pressure is provided, as well as a means for providing a substantially uniform flow rate and means for measuring the pressure within the tube that transmits the gas flow to the sensor. The flow rates to and from the sensor are compared, and the flow of gas to the sensor is cut off if the flow rates are unequal, a condition indicative of a leak in the sensor or in the tubing that transmits the gas to and from the sensors.
ABSTRACT
An apparatus which measures and monitors the pressure within a human body includes a pressure sensor having a housing closed by a pressure sensitive diaphragm to define a plenum, an exhaust tube mounted within the plenum which terminates adjacent the inner surface of the diaphragm, And tubes which transmit a substantially constant flow of gas into the plenum and which withdraw gas from the exhaust tube to a location remote from the body. Changes in pressure within the body cause the diaphragm to alternately close and open the end of the exhaust tube, thereby resulting in an increase or decrease in the pressure within the plenum until an equilibrium pressure is reached. A source of gas pressure is provided, as well as a means for providing a substantially uniform flow rate and means for measuring the pressure within the tube that transmits the gas flow to the sensor. The flow rates to and from the sensor are compared, and the flow of gas to the sensor is cut off if the flow rates are unequal, a condition indicative of a leak in the sensor or in the tubing that transmits the gas to and from the sensors.
Description
7~
BAC~GROUND OF TIIE INVENTION
The need to mon.itor and measure gas and liquid pressures has led to the development of a variety of pressure trans-ducing methods. The monitorin~ and measurincJ of pressurcs at reMote or inaccessible site~ is usually accomplisl1ec1 by one of the two ~ollowing methods.
(1~ The pressure is transmitted tllrough a pipe or tube to a centrally placed transducer or gauge, or ~ 2) ~ remote transducer probe is employed which sends lo a converted signal to a centxal recordiny instrumentO
The use of the first method requires a fluid connection to the pressure medium being measured. This is not desirable when the fluic3 column can cause the escape of noxious chemi-cals, be an avenue ~or infcctious agents, or be a site for obstruction by ohjects, blood clots, or other protein materials.
The use o~ the second method which employs a remote transducer probe is also not without dlsadvan~a~es. I'ho mvst commonly used remote transducer probes are usually nlcchanical to elcctrlca.].-transducers W}liCh convert the movc-merlt of a surface or diaphragm into an electricctl signal.
Such ~ransducers when reduced to the sizes of 5 mm. or less ,x}libit too much baseline drift and temperature instability to mak.e accurate rneasurements at small pressure changes (lmm llg) over long periods of time, such as weelcs.
rhere is a special need for a simple, inexpensive, compact and accura-te apparatus which is suitable for moni-torinc3 pressures within the body of living animals for 1~ cl.inic31 ancl medical research purposes; e.g=, the measuring of intracranial pressure.
SUMM~RY OF THE PRESENT INVENTION
It is ~n object of the present invention to di.sclose a novel pressure monitoring and measuring apparatus and method.
l.5 It is a further object to provide arl apparatus an(l mcthod for monitorincJ and measuring pressures at :remote ~it~s.
It is a still further object to provide a simple, inexpensive, compact and accurate apparatus :Eor monitoring
BAC~GROUND OF TIIE INVENTION
The need to mon.itor and measure gas and liquid pressures has led to the development of a variety of pressure trans-ducing methods. The monitorin~ and measurincJ of pressurcs at reMote or inaccessible site~ is usually accomplisl1ec1 by one of the two ~ollowing methods.
(1~ The pressure is transmitted tllrough a pipe or tube to a centrally placed transducer or gauge, or ~ 2) ~ remote transducer probe is employed which sends lo a converted signal to a centxal recordiny instrumentO
The use of the first method requires a fluid connection to the pressure medium being measured. This is not desirable when the fluic3 column can cause the escape of noxious chemi-cals, be an avenue ~or infcctious agents, or be a site for obstruction by ohjects, blood clots, or other protein materials.
The use o~ the second method which employs a remote transducer probe is also not without dlsadvan~a~es. I'ho mvst commonly used remote transducer probes are usually nlcchanical to elcctrlca.].-transducers W}liCh convert the movc-merlt of a surface or diaphragm into an electricctl signal.
Such ~ransducers when reduced to the sizes of 5 mm. or less ,x}libit too much baseline drift and temperature instability to mak.e accurate rneasurements at small pressure changes (lmm llg) over long periods of time, such as weelcs.
rhere is a special need for a simple, inexpensive, compact and accura-te apparatus which is suitable for moni-torinc3 pressures within the body of living animals for 1~ cl.inic31 ancl medical research purposes; e.g=, the measuring of intracranial pressure.
SUMM~RY OF THE PRESENT INVENTION
It is ~n object of the present invention to di.sclose a novel pressure monitoring and measuring apparatus and method.
l.5 It is a further object to provide arl apparatus an(l mcthod for monitorincJ and measuring pressures at :remote ~it~s.
It is a still further object to provide a simple, inexpensive, compact and accurate apparatus :Eor monitoring
2() pressures lnside the bodi.es of human and animal patients and subjects.
:r t is another ob ject of the invention to provide an apparatus and method enabling the monitoring and measuring o.E pressure in remote and small spaces which maintains an accuracy of at least lmm ~Ig for prolongecl periods.
The apparatus of the present invention includes a pressure source which supplies fluid under pressure; a pressure sensor including a cup-shaped l-ousin(3, having an inlet, an outlet, a pressure sensitive diaphragm closing thc mouth of the housing to form a plenum and an exhaust tul)e having one end connected to the outlet and the other end cxtel~ding into the plenum and terminating adjacent the underside of the pressure sensitive diaphragm; tubing con-necting the pressure source to the inlet of the pressurc ;ellsor; means ins~1ri1lcJ a uniform fluid flow; and mcans For eas11ri1lg thc pressure in the ple1lt11n.
In the preferrecl practice of the present inven~ion, thc prcssure source supplies a fluid, preferably a gas at a pressure which iS at least twice the maximum pressure to b-m~asurec1 and the mec1ns insuring a un:iforrn flow i5 a res~ric-tion w11ich impedes the fluicl flow sufficiently to provide a rclatively uniform, constant flow. The impedance o the restriction significantly exceeds the combined impcda~ccs o~
the inle-t and the exhaust tube so that the pressure drop in the ir-let is negligibly small. The measuring means which can be a gau~e or a transducer remotely reads the pressure Lll tl1e plenum of the pressure sensor.
i~hcn the pressure outsicle the diaphragm of the prcssure sensor exceeds the pressure inside the plenum, the diap1-rdgrn is pressed ~gaillSt the opening of the exhaust tube and bloc~s the outflow of fluicl. The fluid continues t:o flow throucJh the inlet and increases thc pressure i1l ~he plcr1ur11 ur1til it slightly exceeds the pressure outsic1e sensed by ~he .~0 diaphracJm. The diaphragrn then moves outwclrdly to unblock thc cx11aust tube which causes a drop`in t~he pressure in thc plenum until it equals the outside pressure. rhe impedallce of the exhaust tube is less than that oE the restriction which a]~ows the pressure in the plenum to decrease. 111C
describecl cycle repeats and by repeating main-tains the pressure in the plenum of the pressure sensor very close to the pressure sensed by the diaphragm.
lhe pressure in the plenum is read by the remote prcs-sure measuring means with only a slight error due to the pressure drop in the inlet tube. This error is renclered insi~nificanLly small by increasing the impeclance of the restriction so as to allow only very slow fluid flows. 13y adjusting the resistance created by the restriction, it is also possib~e to adjust the rate of filling when the e~ternal pressure increases, thereby affectincJ the response time of the pressure measuring means.
_~ _ The ef.Eective internal surface area of the di.aphragm and its external surface area which is in contac~ with or senses outside pressure are approximately equal because the exnaust tube outlet preferably contac-ts no more than 30% of 5 the internal surface of the diaphragm at any time.
The apparatus ancl method of the presenl: invention provicde for an inexpensive, accurate measuring and monitoring oE pressure and are particularly useful in monitoring pres-sure in a variety of medical applications ineluding intra-cranial, intrathoracic, intracardiac, gastrointestinal,intravesicular, (urinary bladder) and similar pressures.
In addition to the above mentioned ob jects, other objects and advanta~es of the present inventi.on will be apparent to those skilled in the art from the description ].5 which follows.
BRIFF DESCRIPTION GF DRAWINGS
In the drawings:
~ i~. 1 is a schematic view of one emb.odiment of the apparatus of the present invention implant~d in the ~rain of 2() a :Living human to monitor intracranial pressure;
~`ig. 2 is an enlarged side elevational view, partly in section, of the pressure sensor seen in Fi~ure 1, Fig. 3 is a bottom view of the pressure sensor of Fi.g.
2 with a portion thereof broken away for illustration;
Fig. 4 is a bottom view of an alternative embodimellt of a pressure sensor, with a portion thereof broken away for illustration;
Fig. 5 is a cross-sectional view of the pressure sensor of Fig. 4 taken along the lines 5-5 of Fig. 4.
PREFERRED EMBODIMENT OF THE INVENTION
In Fig. 1, is shown an embodiment of tile pressure ~onitoring apparatus of the present invention particularly adap-ted eor measuxing intracranial pressure. ~s seen therein the apparatus, which is generally re~errecl to as 10, incl~cles ~7~ ~
a pressure sensor ll, a fluid pressure source 12, which is preferably a pump, and tubing 13 which connects the senso ll to the pressure source 12. Located interme~iate the len~th of the tubing 13 between the se~sor ll and -the pressure source 12 is a pressure measuring means l~ which can be a gauge or an electrical transducer. Positionecl along the tubing 13 between the pressure measuring device 14 and -the pressure source 12 is a restriction R or other means of insuring uniform flow such as a tubing clamp or a valve.
The restriction R provides an impedance to the flow of fluid from -the fluid pressure source 12 to the pressure sensor ll thus providing a relatively constant fluid flow. A second length of tubing 15 can be seen in Fig. l leading from the pressure sensor ll to a sealed variable volume vessel 16 which can be of the piston--type shown or a bellows or the l;ke. The vessel 16 is operatively connectecl to the pres-sure source 12 by a third length of tubing 17.
~ s seen in Flg. l, the piston 18 of the sealed variable volume vessel 16 has a rocl 19 which :is connected at its free 2() elld 20 to a cord 21 which passes ovcr a ~ulley 22 ancl is connected at lts free end 23 to a wei'g}lt ~4. Positionetl intermecliate the length of the rod l9 is a finger 25. The finger 25 extends between two make and break switches 2G and 27 which are located in an electrical circuit 28 whicil connec-ts the pressure source 12 air pump to an electrical source 29. As seen in the drawing the switches 26 and 27 are both closed.
As seen in Fig. l, the pressure sensor 11 is implanted in the brain of a human between the dura D and -the skull S
so that it can measure and monitor intracranial pressure.
The tubing 13 and the tubing 15 lead from the pressure sensor ll through an opening O in the skull S to the outside.
Turning now to Fig. 2, it can be seen that the pressure sensor ll includes a cup-shaped housing 30 having an open mouth 31, an inlet 32 and an outlet 33. The open mouth 31 of the housincJ 30 is closed by a flexible, lnelastic dia~
phr~gm 34 to form a plenum 35. The diaphragm 3~ is prefer-~7~6 ably permanently glued in place. The outlet 33 communica~es a-t one end with the tubing 15 and at the other with an exhaust tube 36 which extends into the plenum 35 of the sensor 11 and terminates just short of the underside of the cliaphragm 34. The exact distance between the end of the exhaust tube 36 and the underside of the diaphrac3m 34 will depend upon the inelasticity and flexibility of the diaphragm, the pressure beiny measured and the desired sensitivity of the sensor. As seen only in Fig. 3, the exhaust ~ube 36 is centrally loca~ed within the plenum 35.
The embodiment shown in the drawiny is particularly adaptecl for use in measuring pressure in medical applications where the rupture of the diaphra~m of the indwelling sensor could allow fluid or air to escape into the body and where the described range of measurement includes negative pressures.
The connection of tubing 15 and the tubing 17 to the charnbe~r of the variable volume vessel 16 provides a closed fluid system which limits the quantity of 1uid which carl be introcluced through a leak in the indwelling sensor 11.
Further, the suction force applied to the vessel 16 by the cord 21, pulley 22 and weight 24 mai~tains.a negative pressllre in the vessel 16. This provides a stable negative pressure reference which enables the measurement of negative pressure. The negative pressure in the vessel also minimizes the likelihood of air leakage outwards in the event of rupture of the diaphragm 34. It will be appreciated that other means of providing the negative pressure may be used, e.g., the cord 21, pulley 22 and weight 2~ could be replaced by a spring.
~n additional safety feature of the embodiment illus-trated is provided by the combination of the finger 25 and the switches 26 and 27 of the electrical circuit 28. The movement of the piston 18 beyond prescribed limits which might occur due to leaks anywhere in the system will cause -the finger 25 to open a switch 26 or 27, turn off -the fluid pressure source 12 and alert the operator.
When intended for medical applicatiol1s/ all exposed portions of the pressure sensor ll and the tubing 13 and 15 axc made of a biocompatible plastic material such as silicone elastomer or polyurethane.
In a preferred embodiment for medical use, the housin(;
30 :is molded of a suitable plastic material and is about l centimeter in diameter and about 2.5 mms deep. The dia-phragm 34 is fabricated of a flexi~le but inelastic biocom-patible plastic about .25 mm 1hick and the exhaust tube 3G
ex-tends to w.ithin .l0 mms of 1he underside of the diaphragm 34. The material, thickness and inelasticity of the dia-phragm to be used will depend, or course~ upon the intended use of the apparatus and the pressure to be measurecl.
To verify the accuracy of the minia-tur:ized embodiment of the apparatus l0, a pressure sensor ll, similar to that descxibed above, was implanted in a dog's brain alons with a conventional mechanical~to elec-trical transc1ucer in a m~l1r1er similar to that illustrated in Fiq. l. In order to insllrc un:iform low the value o the resistance was set usincJ a tubing screw clamp so that the time (70% response) was 1('s5 than 0.3 seconds. (The base line error ~^~as about 0.5 rnrns Hg.) The pressure source, a tanJc of oxygen, was set to deliver oxygen at 500 mms Hg. The dog was then su~jected to manuevers which altered its intracranial pressure and the pressure measurements were made. The experimental results revealed that the apparatus of the present invention yielded the same results as the conventional unit during steady states and slow changes. Moreover, the apparatus of the present invention was superior in that it tracked fast changes durinq the injection of saline into the ventricles of the brain while the conventional transducer unit was unable to record such fast changes. Oscillographic traces were used to verify the results.
Further experimentation revealed that the apparatus was accurate up to 200 mms of Hg and that the base line drift over four weeks did not show any change of pressure exceedinq 0.2 mm ilg.
7~
It will be apparent to those skilled in the art that although the pressure monitoring apparatus and method of the present invention have been described primarily in connection with the measuring of intracranial pressure, the invention is not so limited. The lnvention may be used in a varicty of medical applications irscluding intracardiac, gastro-intestinal, intravesicular, and other applications where a simple, inexpensive, compact and accurate nleans to measure and monitor pressure can be used to advanta(3e.
In non-medical applications satisfactory results may be obtainable with an apparatus that does no-t include the variable pressure vessel 16, the cord 21, the pulley 22, the weight 24 and the electrical circuit 28~ Such an apparatus might comprise the sensor ll, the pressure source 12, the lS tubiny 13, the resistance R, the pressure measuring means l4 and the tubing 15 with all the named components connected as shown in Fig. l except that the tubing 15 would exhaust to the outside.
~l1 alternative e~odiment for a pressure sensor capable of being used in the apparatus lO is shown generally at ~l in ~'ig. ~. The pressure sensor 41 also in¢ludes a cup-shaped housin~ 42 formed as a circular disc of plastic having a circular open mouth 43 formed in one surface thereof surrounded by a peripheral annular face 44. A
flexible diaphragm 46 is secured by glue or other adhesive or by sonic welding, as desired, to the peripheral face 44 of the housing. ~ portion of the diaphragm 46 is shown broken away in Fig. 4 to illustrate the structure of the pressure sensor under the diaphragm. This structure includes a circular exhaust tube 47 centr~lly mounted in the mouth 43 and terminating~-at a position adjacent the inner side of the diaphragm 46--in an annular face which surrounds the open bore 48 of the exhaust tube. As shown in FigO 5, the annular face of the exhaust tube is formed substantially coplanar with the peripheral face 44 of the housing. ~ thin-walled metal outlet pipe sn has its inner bore in communication with the bore ~3 of the exhaust tube and extends outwardly _9_ throucJh the outer wall of the housing 42 and is connec-ted to plastic tubing 51 corresponding to the tube 15 shown in Fig.
l. ~n inlet pipe 53, also formed of a thin-walled metal pipe9 extends through the outer wall of -~he housing 42 such tha-t its bore is in communicatlon with the plenum 43, witll the outer end of the inlet pipe 53 being connected to plastic tubill~ 54 corresponding to the tubing 13 shown in ~ig. I.
The outlet pipe 50 and the inlet pipe 53 are preferably mounted closely ~djacent to one another at approximately the same elevation in -the outer wa~l of the housirlg 42 to minimize the space taken up by the pipes and by the tubirlg connected to them.
As best shown in Fig. 5, the outlet pipe 50 passes through the plenum 43 and the wall of the exhaust tube 47 to lS the bore 48 of the exhaust tube. This outlet arrangement may be compared to the outlet 33 formed as a channel in the housing 30, as shown in Fi~. 2. The pressure sellsor str~lcture of Fiys. 4 and 5 has the advantage over ti-le structure shown in FicJs. 2 and 3 of havlng a thlnner top wall por~Lon 56 o~
2() the sensor housincJ since the outlet for t~le sensor ~1 doe.s not have to be formed as a channel th`rouc~h the housing. As is illustrated in Fig. 5, the top wall 56 oE the sensor 41 need only be thick enough to provide structural strength and integrity. For example, the height of -the pressure sensor ~1, i.~., the distance from the outer surface of the diaphragm 46 to the surface of the top wall 56 of the housing, may be in the range of 1.5 mm., to thereby minimize the space within the patient that is occupled hy the sensor. The sensor structure 41 also has the advantage of allowing the plastic tubes 51 and S4 to extend from the sensor in closely spaced, parallel relation. The inlet and outlet pipes 53 and 50 are preferably located at a position in the wall of the sensor housing above the bottom of the mouth of the housing such that the top wall of the sensor housing can be made as thin as desired.
The housing of the pressure sensor 41 is formed of similar materials to the pressure sensor 11: biocompatible plastic materials such as silicone or polyurethane; and similar matcrials are used or the diaphragm 46 and the tubing 51 and 54. A stiffer diaphragm (less elastic) may be provided, iE desired, by molding a nylon mesh within the material of the diaphragm.
Those skilled in the art will appreciatc that the novcl mechanical desiyn of the pressure sensor of the present invention provides an inherent and automatic servo-control.
The sensor with its diaphragm which alternately opens and closes the exhaust -tube automatically maintains the pressure on -the plenum side of the diaphragm nearly equal to the pressure outside in the medium being tested and provides a simple, inexpensive and reliable means for measuring and monitoring pressure.
It will be readily apparent to those skilled in the art that a number of changes and modifica-tions can be made wi-thout depaxting from the spirit of the present invention.
For example, although the diaphragm is shown as glued in place closing the mouth of the sensor housing, it might be more advantageoùs in some applications to removably affiY.
the diaphragm to the housiny by usin~ a retaininy collar or similar means. Therefore, it is intehded-that the invention not be limi-ted by any of the foregoing descriptlon but only by the clairns which follow.
:r t is another ob ject of the invention to provide an apparatus and method enabling the monitoring and measuring o.E pressure in remote and small spaces which maintains an accuracy of at least lmm ~Ig for prolongecl periods.
The apparatus of the present invention includes a pressure source which supplies fluid under pressure; a pressure sensor including a cup-shaped l-ousin(3, having an inlet, an outlet, a pressure sensitive diaphragm closing thc mouth of the housing to form a plenum and an exhaust tul)e having one end connected to the outlet and the other end cxtel~ding into the plenum and terminating adjacent the underside of the pressure sensitive diaphragm; tubing con-necting the pressure source to the inlet of the pressurc ;ellsor; means ins~1ri1lcJ a uniform fluid flow; and mcans For eas11ri1lg thc pressure in the ple1lt11n.
In the preferrecl practice of the present inven~ion, thc prcssure source supplies a fluid, preferably a gas at a pressure which iS at least twice the maximum pressure to b-m~asurec1 and the mec1ns insuring a un:iforrn flow i5 a res~ric-tion w11ich impedes the fluicl flow sufficiently to provide a rclatively uniform, constant flow. The impedance o the restriction significantly exceeds the combined impcda~ccs o~
the inle-t and the exhaust tube so that the pressure drop in the ir-let is negligibly small. The measuring means which can be a gau~e or a transducer remotely reads the pressure Lll tl1e plenum of the pressure sensor.
i~hcn the pressure outsicle the diaphragm of the prcssure sensor exceeds the pressure inside the plenum, the diap1-rdgrn is pressed ~gaillSt the opening of the exhaust tube and bloc~s the outflow of fluicl. The fluid continues t:o flow throucJh the inlet and increases thc pressure i1l ~he plcr1ur11 ur1til it slightly exceeds the pressure outsic1e sensed by ~he .~0 diaphracJm. The diaphragrn then moves outwclrdly to unblock thc cx11aust tube which causes a drop`in t~he pressure in thc plenum until it equals the outside pressure. rhe impedallce of the exhaust tube is less than that oE the restriction which a]~ows the pressure in the plenum to decrease. 111C
describecl cycle repeats and by repeating main-tains the pressure in the plenum of the pressure sensor very close to the pressure sensed by the diaphragm.
lhe pressure in the plenum is read by the remote prcs-sure measuring means with only a slight error due to the pressure drop in the inlet tube. This error is renclered insi~nificanLly small by increasing the impeclance of the restriction so as to allow only very slow fluid flows. 13y adjusting the resistance created by the restriction, it is also possib~e to adjust the rate of filling when the e~ternal pressure increases, thereby affectincJ the response time of the pressure measuring means.
_~ _ The ef.Eective internal surface area of the di.aphragm and its external surface area which is in contac~ with or senses outside pressure are approximately equal because the exnaust tube outlet preferably contac-ts no more than 30% of 5 the internal surface of the diaphragm at any time.
The apparatus ancl method of the presenl: invention provicde for an inexpensive, accurate measuring and monitoring oE pressure and are particularly useful in monitoring pres-sure in a variety of medical applications ineluding intra-cranial, intrathoracic, intracardiac, gastrointestinal,intravesicular, (urinary bladder) and similar pressures.
In addition to the above mentioned ob jects, other objects and advanta~es of the present inventi.on will be apparent to those skilled in the art from the description ].5 which follows.
BRIFF DESCRIPTION GF DRAWINGS
In the drawings:
~ i~. 1 is a schematic view of one emb.odiment of the apparatus of the present invention implant~d in the ~rain of 2() a :Living human to monitor intracranial pressure;
~`ig. 2 is an enlarged side elevational view, partly in section, of the pressure sensor seen in Fi~ure 1, Fig. 3 is a bottom view of the pressure sensor of Fi.g.
2 with a portion thereof broken away for illustration;
Fig. 4 is a bottom view of an alternative embodimellt of a pressure sensor, with a portion thereof broken away for illustration;
Fig. 5 is a cross-sectional view of the pressure sensor of Fig. 4 taken along the lines 5-5 of Fig. 4.
PREFERRED EMBODIMENT OF THE INVENTION
In Fig. 1, is shown an embodiment of tile pressure ~onitoring apparatus of the present invention particularly adap-ted eor measuxing intracranial pressure. ~s seen therein the apparatus, which is generally re~errecl to as 10, incl~cles ~7~ ~
a pressure sensor ll, a fluid pressure source 12, which is preferably a pump, and tubing 13 which connects the senso ll to the pressure source 12. Located interme~iate the len~th of the tubing 13 between the se~sor ll and -the pressure source 12 is a pressure measuring means l~ which can be a gauge or an electrical transducer. Positionecl along the tubing 13 between the pressure measuring device 14 and -the pressure source 12 is a restriction R or other means of insuring uniform flow such as a tubing clamp or a valve.
The restriction R provides an impedance to the flow of fluid from -the fluid pressure source 12 to the pressure sensor ll thus providing a relatively constant fluid flow. A second length of tubing 15 can be seen in Fig. l leading from the pressure sensor ll to a sealed variable volume vessel 16 which can be of the piston--type shown or a bellows or the l;ke. The vessel 16 is operatively connectecl to the pres-sure source 12 by a third length of tubing 17.
~ s seen in Flg. l, the piston 18 of the sealed variable volume vessel 16 has a rocl 19 which :is connected at its free 2() elld 20 to a cord 21 which passes ovcr a ~ulley 22 ancl is connected at lts free end 23 to a wei'g}lt ~4. Positionetl intermecliate the length of the rod l9 is a finger 25. The finger 25 extends between two make and break switches 2G and 27 which are located in an electrical circuit 28 whicil connec-ts the pressure source 12 air pump to an electrical source 29. As seen in the drawing the switches 26 and 27 are both closed.
As seen in Fig. l, the pressure sensor 11 is implanted in the brain of a human between the dura D and -the skull S
so that it can measure and monitor intracranial pressure.
The tubing 13 and the tubing 15 lead from the pressure sensor ll through an opening O in the skull S to the outside.
Turning now to Fig. 2, it can be seen that the pressure sensor ll includes a cup-shaped housing 30 having an open mouth 31, an inlet 32 and an outlet 33. The open mouth 31 of the housincJ 30 is closed by a flexible, lnelastic dia~
phr~gm 34 to form a plenum 35. The diaphragm 3~ is prefer-~7~6 ably permanently glued in place. The outlet 33 communica~es a-t one end with the tubing 15 and at the other with an exhaust tube 36 which extends into the plenum 35 of the sensor 11 and terminates just short of the underside of the cliaphragm 34. The exact distance between the end of the exhaust tube 36 and the underside of the diaphrac3m 34 will depend upon the inelasticity and flexibility of the diaphragm, the pressure beiny measured and the desired sensitivity of the sensor. As seen only in Fig. 3, the exhaust ~ube 36 is centrally loca~ed within the plenum 35.
The embodiment shown in the drawiny is particularly adaptecl for use in measuring pressure in medical applications where the rupture of the diaphra~m of the indwelling sensor could allow fluid or air to escape into the body and where the described range of measurement includes negative pressures.
The connection of tubing 15 and the tubing 17 to the charnbe~r of the variable volume vessel 16 provides a closed fluid system which limits the quantity of 1uid which carl be introcluced through a leak in the indwelling sensor 11.
Further, the suction force applied to the vessel 16 by the cord 21, pulley 22 and weight 24 mai~tains.a negative pressllre in the vessel 16. This provides a stable negative pressure reference which enables the measurement of negative pressure. The negative pressure in the vessel also minimizes the likelihood of air leakage outwards in the event of rupture of the diaphragm 34. It will be appreciated that other means of providing the negative pressure may be used, e.g., the cord 21, pulley 22 and weight 2~ could be replaced by a spring.
~n additional safety feature of the embodiment illus-trated is provided by the combination of the finger 25 and the switches 26 and 27 of the electrical circuit 28. The movement of the piston 18 beyond prescribed limits which might occur due to leaks anywhere in the system will cause -the finger 25 to open a switch 26 or 27, turn off -the fluid pressure source 12 and alert the operator.
When intended for medical applicatiol1s/ all exposed portions of the pressure sensor ll and the tubing 13 and 15 axc made of a biocompatible plastic material such as silicone elastomer or polyurethane.
In a preferred embodiment for medical use, the housin(;
30 :is molded of a suitable plastic material and is about l centimeter in diameter and about 2.5 mms deep. The dia-phragm 34 is fabricated of a flexi~le but inelastic biocom-patible plastic about .25 mm 1hick and the exhaust tube 3G
ex-tends to w.ithin .l0 mms of 1he underside of the diaphragm 34. The material, thickness and inelasticity of the dia-phragm to be used will depend, or course~ upon the intended use of the apparatus and the pressure to be measurecl.
To verify the accuracy of the minia-tur:ized embodiment of the apparatus l0, a pressure sensor ll, similar to that descxibed above, was implanted in a dog's brain alons with a conventional mechanical~to elec-trical transc1ucer in a m~l1r1er similar to that illustrated in Fiq. l. In order to insllrc un:iform low the value o the resistance was set usincJ a tubing screw clamp so that the time (70% response) was 1('s5 than 0.3 seconds. (The base line error ~^~as about 0.5 rnrns Hg.) The pressure source, a tanJc of oxygen, was set to deliver oxygen at 500 mms Hg. The dog was then su~jected to manuevers which altered its intracranial pressure and the pressure measurements were made. The experimental results revealed that the apparatus of the present invention yielded the same results as the conventional unit during steady states and slow changes. Moreover, the apparatus of the present invention was superior in that it tracked fast changes durinq the injection of saline into the ventricles of the brain while the conventional transducer unit was unable to record such fast changes. Oscillographic traces were used to verify the results.
Further experimentation revealed that the apparatus was accurate up to 200 mms of Hg and that the base line drift over four weeks did not show any change of pressure exceedinq 0.2 mm ilg.
7~
It will be apparent to those skilled in the art that although the pressure monitoring apparatus and method of the present invention have been described primarily in connection with the measuring of intracranial pressure, the invention is not so limited. The lnvention may be used in a varicty of medical applications irscluding intracardiac, gastro-intestinal, intravesicular, and other applications where a simple, inexpensive, compact and accurate nleans to measure and monitor pressure can be used to advanta(3e.
In non-medical applications satisfactory results may be obtainable with an apparatus that does no-t include the variable pressure vessel 16, the cord 21, the pulley 22, the weight 24 and the electrical circuit 28~ Such an apparatus might comprise the sensor ll, the pressure source 12, the lS tubiny 13, the resistance R, the pressure measuring means l4 and the tubing 15 with all the named components connected as shown in Fig. l except that the tubing 15 would exhaust to the outside.
~l1 alternative e~odiment for a pressure sensor capable of being used in the apparatus lO is shown generally at ~l in ~'ig. ~. The pressure sensor 41 also in¢ludes a cup-shaped housin~ 42 formed as a circular disc of plastic having a circular open mouth 43 formed in one surface thereof surrounded by a peripheral annular face 44. A
flexible diaphragm 46 is secured by glue or other adhesive or by sonic welding, as desired, to the peripheral face 44 of the housing. ~ portion of the diaphragm 46 is shown broken away in Fig. 4 to illustrate the structure of the pressure sensor under the diaphragm. This structure includes a circular exhaust tube 47 centr~lly mounted in the mouth 43 and terminating~-at a position adjacent the inner side of the diaphragm 46--in an annular face which surrounds the open bore 48 of the exhaust tube. As shown in FigO 5, the annular face of the exhaust tube is formed substantially coplanar with the peripheral face 44 of the housing. ~ thin-walled metal outlet pipe sn has its inner bore in communication with the bore ~3 of the exhaust tube and extends outwardly _9_ throucJh the outer wall of the housing 42 and is connec-ted to plastic tubing 51 corresponding to the tube 15 shown in Fig.
l. ~n inlet pipe 53, also formed of a thin-walled metal pipe9 extends through the outer wall of -~he housing 42 such tha-t its bore is in communicatlon with the plenum 43, witll the outer end of the inlet pipe 53 being connected to plastic tubill~ 54 corresponding to the tubing 13 shown in ~ig. I.
The outlet pipe 50 and the inlet pipe 53 are preferably mounted closely ~djacent to one another at approximately the same elevation in -the outer wa~l of the housirlg 42 to minimize the space taken up by the pipes and by the tubirlg connected to them.
As best shown in Fig. 5, the outlet pipe 50 passes through the plenum 43 and the wall of the exhaust tube 47 to lS the bore 48 of the exhaust tube. This outlet arrangement may be compared to the outlet 33 formed as a channel in the housing 30, as shown in Fi~. 2. The pressure sellsor str~lcture of Fiys. 4 and 5 has the advantage over ti-le structure shown in FicJs. 2 and 3 of havlng a thlnner top wall por~Lon 56 o~
2() the sensor housincJ since the outlet for t~le sensor ~1 doe.s not have to be formed as a channel th`rouc~h the housing. As is illustrated in Fig. 5, the top wall 56 oE the sensor 41 need only be thick enough to provide structural strength and integrity. For example, the height of -the pressure sensor ~1, i.~., the distance from the outer surface of the diaphragm 46 to the surface of the top wall 56 of the housing, may be in the range of 1.5 mm., to thereby minimize the space within the patient that is occupled hy the sensor. The sensor structure 41 also has the advantage of allowing the plastic tubes 51 and S4 to extend from the sensor in closely spaced, parallel relation. The inlet and outlet pipes 53 and 50 are preferably located at a position in the wall of the sensor housing above the bottom of the mouth of the housing such that the top wall of the sensor housing can be made as thin as desired.
The housing of the pressure sensor 41 is formed of similar materials to the pressure sensor 11: biocompatible plastic materials such as silicone or polyurethane; and similar matcrials are used or the diaphragm 46 and the tubing 51 and 54. A stiffer diaphragm (less elastic) may be provided, iE desired, by molding a nylon mesh within the material of the diaphragm.
Those skilled in the art will appreciatc that the novcl mechanical desiyn of the pressure sensor of the present invention provides an inherent and automatic servo-control.
The sensor with its diaphragm which alternately opens and closes the exhaust -tube automatically maintains the pressure on -the plenum side of the diaphragm nearly equal to the pressure outside in the medium being tested and provides a simple, inexpensive and reliable means for measuring and monitoring pressure.
It will be readily apparent to those skilled in the art that a number of changes and modifica-tions can be made wi-thout depaxting from the spirit of the present invention.
For example, although the diaphragm is shown as glued in place closing the mouth of the sensor housing, it might be more advantageoùs in some applications to removably affiY.
the diaphragm to the housiny by usin~ a retaininy collar or similar means. Therefore, it is intehded-that the invention not be limi-ted by any of the foregoing descriptlon but only by the clairns which follow.
Claims (13)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Pressure monitoring apparatus comprising:
(a) a fluid pressure pump supplying gas under pressure;
(b) a pressure sensor including:
(1) a cup shaped housing having an open mouth and having an inlet and an outlet formed therein;
(2) a flexible diaphragm sealed over the open mouth of the housing to define a plenum between the walls of the mouth in the housing and the diaphragm, and wherein the inlet formed in the housing is in communication with the plenum;
(3) an exhaust tube centrally mounted in the housing within the plenum with an end thereof termi-nating adjacent the inner side of the diaphragm and connected to be in communication with the outlet from the housing;
(c) tubing connecting the pump to the inlet in the sensor housing to supply gas under pressure to the inlet and also connecting the outlet in the sensor housing to the pump to form a closed system;
(d) a flow restriction connected in the tubing between the pump and the inlet to the sensor housing so that the flow to the sensor is substantially uniform; and (e) means for measuring pressure connected to measure the pressure in the tubing between the flow restriction and the inlet to the sensor housing, whereby changes in ambient pressure at the pressure sensor will result in movement of the diaphragm to alternately open and close the exhaust tube to automatically maintain the pressure within the plenum approximately equal to the ambient pressure, and whereby the means for measuring pressure in the tubing will measure a pressure which is approximately equal to the pressure within the plenum.
(a) a fluid pressure pump supplying gas under pressure;
(b) a pressure sensor including:
(1) a cup shaped housing having an open mouth and having an inlet and an outlet formed therein;
(2) a flexible diaphragm sealed over the open mouth of the housing to define a plenum between the walls of the mouth in the housing and the diaphragm, and wherein the inlet formed in the housing is in communication with the plenum;
(3) an exhaust tube centrally mounted in the housing within the plenum with an end thereof termi-nating adjacent the inner side of the diaphragm and connected to be in communication with the outlet from the housing;
(c) tubing connecting the pump to the inlet in the sensor housing to supply gas under pressure to the inlet and also connecting the outlet in the sensor housing to the pump to form a closed system;
(d) a flow restriction connected in the tubing between the pump and the inlet to the sensor housing so that the flow to the sensor is substantially uniform; and (e) means for measuring pressure connected to measure the pressure in the tubing between the flow restriction and the inlet to the sensor housing, whereby changes in ambient pressure at the pressure sensor will result in movement of the diaphragm to alternately open and close the exhaust tube to automatically maintain the pressure within the plenum approximately equal to the ambient pressure, and whereby the means for measuring pressure in the tubing will measure a pressure which is approximately equal to the pressure within the plenum.
2. The pressure monitoring apparatus of Claim 1 in which the pressure pump supplies gas at a pressure at least twice the maximum pressure to be measured by the means for measuring pressure.
3. The pressure monitoring apparatus of Claim 1 including means connected to the tubing returning gas from the sensor to the pump for providing a stable negative pressure reference in the tubing which enables the measure-ment of negative pressure at the pressure sensor.
4. The pressure monitoring apparatus of Claim 1 including a sealed vessel connected in the tubing between the outlet of the sensor housing and the pump and means for maintaining a negative pressure in the sealed vessel, whereby negative ambient pressures can be sensed by the pressure sensor and whereby, if a leak develops in the pressure sensor, the gas supplied to the sensor will tend to be withdrawn into the vessel rather than leaking out of the sensor.
5. The pressure monitoring apparatus of Claim 4 wherein the means for maintaining a negative pressure in the sealed vessel includes a piston slideably engaging the walls of the vessel in substantially pressure tight relationship and a weight operatively connected to the piston to provide a constant force pulling on the piston to tend to draw the piston in a direction to enlarge the internal volume of the sealed vessel.
6. The pressure monitoring apparatus of Claim 5 including a pair of electrical switches operatively connected to said piston and connected in an electrical circuit supplying electrical power to drive the pump, the switches being arranged such that movement of the piston beyond preselected limits of either increased or decreased volume of the sealed vessel will cause one or the other of the switches to be opened to cut-off electrical power to the pump and thereby shut off the flow of gas to the pressure sensor, whereby the pressure monitoring apparatus will automatically shut down if a leak of gas supplied to or withdrawn from the sensor occurs.
7. The pressure monitoring apparatus of Claim 1 wherein the housing of the pressure sensor is formed of plastic having a circular open mouth formed therein to define a cup shape, the exhaust tube is formed integrally with the housing and extends upwardly from the bottom surface of the mouth of the housing at the center thereof and has a surface area adjacent the diaphragm which is not more than 30% of the area of the mouth of the housing covered by the diaphragm, and wherein the outlet in the housing includes a channel formed in the housing extending from the end of the exhaust tube adjacent the diaphragm and to the surface of the housing for connection to the tubing connected to the pump, and wherein the inlet is formed as a hole in the wall of the housing which terminates in the plenum and which is connected to the tubing leading from the pump, and wherein the points of connection of the tubing to the inlet and the outlet are adjacent to one another.
8. The pressure monitoring apparatus of Claim 1 wherein the pressure sensor housing is formed as a circular plastic disc having a circular open mouth formed in one surface of the housing which is surrounded by a peripheral annular face, and wherein the diaphragm is sealed to the surface of the peripheral annular face to cover the mouth of the housing and define the plenum between the diaphragm and the interior walls of the mouth of the housing, wherein the exhaust tube is formed integrally with the housing, extends upwardly from the center of the housing to terminate at a position adjacent the inner side of the diaphragm, and has a circular bore therein, and wherein an outlet pipe formed of metal extends through the wall of the exhaust tube into communication with the bore within the exhaust tube and also extends through the walls of the housing to the outside thereof and is connected to the tubing leading to the pressure pump, and wherein the inlet includes an inlet pipe formed of metal extending through the wall of the housing from a position outside of the housing into the plenum.
within the housing, the portion of the inlet pipe outside of the housing being connected to the tubing leading from the pressure pump, the inlet and outlet pipes being mounted closely adjacent to one another to minimize the space taken up by the pipes and by the tubing connected to them, and the inlet and outlet pipes being located at a position in the wall of the sensor housing above the bottom of the mouth of the housing such that the thickness of the top wall of the housing can be minimized.
within the housing, the portion of the inlet pipe outside of the housing being connected to the tubing leading from the pressure pump, the inlet and outlet pipes being mounted closely adjacent to one another to minimize the space taken up by the pipes and by the tubing connected to them, and the inlet and outlet pipes being located at a position in the wall of the sensor housing above the bottom of the mouth of the housing such that the thickness of the top wall of the housing can be minimized.
9. The pressure monitoring apparatus of Claim 7 or 8 wherein the pressure sensor housing is formed of a material selected from the group consisting of silicone and polyurethane.
10. The pressure sensor of Claim 8 wherein the height of the sensor from the surface of the diaphragm to the top surface of the housing is approximately 1.5 mm.
11. The pressure sensor of Claim 1 wherein the exhaust tube terminates just short of the diaphragm whereby gas can flow from the plenum into the exhaust tube when the pressure on either side of the diaphragm is approximately equal.
12. A pressure sensor adapted for implantation in a human body comprising:
(a) a cup-shaped housing formed as a circular plastic disc having a circular open mouth formed in one surface which is surrounded by a peripheral annular face;
(b) a pressure sensitive diaphragm sealed to the surfaces of the peripheral annular face to close the open mouth of the housing to define a plenum between the diaphragm and the interior walls of the mouth in the housing;
(c) an exhaust tube formed integrally with the housing and extending upwardly from the center of the plenum within the housing to terminate at a position adjacent to the inner side of the diaphragm, the exhaust tube having a circular bore therein;
(d) An outlet from the sensor including an outlet pipe formed of metal extending through the walls of the exhaust tube into communication with the bore within the exhaust tube and also extending through the walls of the housing to the outside thereof where it is adapted to be connected to external tubing;
(e) an inlet for the housing including an inlet pipe formed of metal extending through the wall of the housing from a position outside the housing into the plenum within the housing, the portion of the inlet pipe outside of the housing being adapted to be connected to external tubing, the inlet and outlet pipes being mounted closely adjacent to one another to minimize the space taken up by the pipes and by the tubing to be connected to them, and the inlet and outlet pipes being located at a position in the wall of the sensor housing above the bottom of the mouth of the housing such that the thickness of the top wall of the housing can be minimized.
(a) a cup-shaped housing formed as a circular plastic disc having a circular open mouth formed in one surface which is surrounded by a peripheral annular face;
(b) a pressure sensitive diaphragm sealed to the surfaces of the peripheral annular face to close the open mouth of the housing to define a plenum between the diaphragm and the interior walls of the mouth in the housing;
(c) an exhaust tube formed integrally with the housing and extending upwardly from the center of the plenum within the housing to terminate at a position adjacent to the inner side of the diaphragm, the exhaust tube having a circular bore therein;
(d) An outlet from the sensor including an outlet pipe formed of metal extending through the walls of the exhaust tube into communication with the bore within the exhaust tube and also extending through the walls of the housing to the outside thereof where it is adapted to be connected to external tubing;
(e) an inlet for the housing including an inlet pipe formed of metal extending through the wall of the housing from a position outside the housing into the plenum within the housing, the portion of the inlet pipe outside of the housing being adapted to be connected to external tubing, the inlet and outlet pipes being mounted closely adjacent to one another to minimize the space taken up by the pipes and by the tubing to be connected to them, and the inlet and outlet pipes being located at a position in the wall of the sensor housing above the bottom of the mouth of the housing such that the thickness of the top wall of the housing can be minimized.
13. The sensor of claim 12 wherein the pressure sensor housing is formed of a material selected from the group consisting of silicone and polyurethane.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US262,381 | 1981-05-11 | ||
| US06/262,381 US4393878A (en) | 1980-11-28 | 1981-05-11 | Pressure monitoring method and apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1187946A true CA1187946A (en) | 1985-05-28 |
Family
ID=22997257
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000402584A Expired CA1187946A (en) | 1981-05-11 | 1982-05-10 | Pressure monitoring method and apparatus |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4393878A (en) |
| EP (1) | EP0078312B1 (en) |
| JP (1) | JPS58500693A (en) |
| CA (1) | CA1187946A (en) |
| DE (1) | DE3278233D1 (en) |
| WO (1) | WO1982003976A1 (en) |
Families Citing this family (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4441357A (en) * | 1982-03-04 | 1984-04-10 | Meadox Instruments, Inc. | Pressure monitoring and leak detection method and apparatus |
| FR2579092B1 (en) * | 1985-03-22 | 1989-06-16 | Univ Toulouse | IMPLANTABLE INTRACRANIAL PRESSURE SENSOR |
| US4625553A (en) * | 1985-04-12 | 1986-12-02 | Dresser Industries, Inc. | System to determine the level and weight of liquid in a tank or the like |
| US4676255A (en) * | 1985-07-03 | 1987-06-30 | Cosman Eric R | Telemetric in-vivo calibration method and apparatus using a negative pressure applicator |
| US4677985A (en) * | 1985-08-12 | 1987-07-07 | Bro William J | Apparatus and method for determining intracranial pressure and local cerebral blood flow |
| CA1296928C (en) * | 1986-05-28 | 1992-03-10 | Baxter International Inc. | Oscillometric blood pressure monitoring technique which utilizes a temporal artery of its subject |
| GB8626601D0 (en) * | 1986-11-07 | 1986-12-10 | Pa Consulting Services | Testing apparatus |
| US4967764A (en) * | 1988-10-24 | 1990-11-06 | The United States Of America As Represented By The Department Of Health And Human Services | Pressure sensor element to measure contact stress |
| US5125408A (en) * | 1988-10-24 | 1992-06-30 | The United States Of America As Represented By The Of The Department Of Health And Human Services | Pressure sensor element and method to measure contact stress |
| PL169488B1 (en) * | 1992-11-30 | 1996-07-31 | Przed Wielobranzowe Med Froz S | Pneumatic intracranial pressure sensor |
| SE9302183D0 (en) * | 1993-06-23 | 1993-06-23 | Radi Medical Systems Ab | APPARATUS AND METHOD FOR VIVO MONITORING OF PHYSIOLOGICAL PRESSURES |
| JPH10248815A (en) * | 1997-01-13 | 1998-09-22 | Suugan Kk | Probe for measuring epidural pressure and elasticity of brain parenchyma |
| US6731976B2 (en) | 1997-09-03 | 2004-05-04 | Medtronic, Inc. | Device and method to measure and communicate body parameters |
| US6673023B2 (en) | 2001-03-23 | 2004-01-06 | Stryker Puerto Rico Limited | Micro-invasive breast biopsy device |
| US20020138091A1 (en) * | 2001-03-23 | 2002-09-26 | Devonrex, Inc. | Micro-invasive nucleotomy device and method |
| US20020138021A1 (en) * | 2001-03-23 | 2002-09-26 | Devonrex, Inc. | Micro-invasive tissue removal device |
| DE10357353B4 (en) * | 2003-12-09 | 2016-06-09 | Robert Bosch Gmbh | Device for testing at least one pressure sensor |
| US7520862B2 (en) * | 2004-02-03 | 2009-04-21 | Neuro Diagnostic Devices, Inc. | Cerebral spinal fluid shunt evaluation system |
| US20080214951A1 (en) * | 2004-02-03 | 2008-09-04 | Neuro Diagnostic Devices, Inc. | Cerebrospinal Fluid Evaluation Systems |
| US20070163604A1 (en) * | 2006-01-13 | 2007-07-19 | Olympus Medical Systems Corp. | Leak test method for medical procedure via natural orifice |
| SE534020C2 (en) * | 2009-08-11 | 2011-04-05 | Oilquick Ab | Utility bracket with hydraulic controlled locking function |
| US8477040B2 (en) * | 2011-01-26 | 2013-07-02 | Joseph D Jatcko | Method and apparatus for testing the integrity of a tank |
| WO2013143361A1 (en) * | 2012-03-27 | 2013-10-03 | 苏州达维生物医药有限公司 | System and method for monitoring bladder and abdominal pressures, and bladder function recovery system |
| CN104352233A (en) * | 2014-12-05 | 2015-02-18 | 苏州景昱医疗器械有限公司 | Probe contact of intracranial pressure monitoring system and probe provided with probe contact |
| CN104398251A (en) * | 2014-12-05 | 2015-03-11 | 苏州景昱医疗器械有限公司 | Intracranial pressure monitoring system probe and calibrating method thereof |
| CN106343998B (en) * | 2016-09-28 | 2023-03-21 | 苏州景昱医疗器械有限公司 | Sealing structure and test system of probe |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2831478A (en) * | 1955-04-30 | 1958-04-22 | Uddenberg Goran Olof | Apparatuses for observing and measuring of pressures within organs of the human body |
| US3099262A (en) * | 1962-06-21 | 1963-07-30 | Du Pont | Physiologic fluid pressure sensing head |
| US3299882A (en) * | 1963-10-25 | 1967-01-24 | Du Pont | Physiologic fluid pressure sensor mount |
| NO125760B (en) * | 1971-02-17 | 1972-10-30 | Sentralinst For Ind Forskning | |
| BE793608A (en) * | 1972-01-11 | 1973-05-02 | Apv Co Ltd | IMPROVEMENTS MADE TO DEVICES FOR DETECTING THE PRESSURE OF A LIQUID IN A CONTAINER |
| US3811429A (en) * | 1972-09-25 | 1974-05-21 | Nasa | Arterial pulse wave pressure transducer |
| US3831588A (en) * | 1972-10-16 | 1974-08-27 | Device Res Inc | Pressure sensing device |
| US4003141A (en) * | 1975-04-01 | 1977-01-18 | New Research And Development Lab., Inc. | Intracranial pressure monitoring device |
| US4206762A (en) * | 1976-06-21 | 1980-06-10 | Cosman Eric R | Telemetric differential pressure sensing method |
| US4206761A (en) * | 1976-06-21 | 1980-06-10 | Cosman Eric R | Pressure-balanced telemetric pressure sensing method |
| JPS5932136B2 (en) * | 1976-08-27 | 1984-08-07 | 株式会社医療工学研究所 | Brain pressure measuring device |
| FR2384482A1 (en) * | 1977-03-25 | 1978-10-20 | Anvar | Sensor for monitoring intracranial pressure - has gas capsule with membrane contacting skull outer membrane to control pressure transducer |
| US4128013A (en) * | 1977-07-08 | 1978-12-05 | Perry Joseph A | Pressure transducer |
| US4185641A (en) * | 1978-08-23 | 1980-01-29 | Hewlett-Packard Company | Pressure dome |
| CH645721A5 (en) * | 1980-09-24 | 1984-10-15 | Metabo Sa Construction D App S | DEVICE FOR MEASURING PRESSURE IN POOR ACCESIBLE LOCATIONS, ESPECIALLY FOR MEDICAL ART. |
-
1981
- 1981-05-11 US US06/262,381 patent/US4393878A/en not_active Expired - Lifetime
-
1982
- 1982-05-10 CA CA000402584A patent/CA1187946A/en not_active Expired
- 1982-05-11 JP JP57501830A patent/JPS58500693A/en active Granted
- 1982-05-11 DE DE8282901823T patent/DE3278233D1/en not_active Expired
- 1982-05-11 WO PCT/US1982/000625 patent/WO1982003976A1/en active IP Right Grant
- 1982-05-11 EP EP82901823A patent/EP0078312B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3278233D1 (en) | 1988-04-21 |
| JPH0566126B2 (en) | 1993-09-21 |
| WO1982003976A1 (en) | 1982-11-25 |
| EP0078312A4 (en) | 1983-10-06 |
| EP0078312A1 (en) | 1983-05-11 |
| EP0078312B1 (en) | 1988-03-16 |
| JPS58500693A (en) | 1983-05-06 |
| US4393878A (en) | 1983-07-19 |
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