WO1997014464A1

WO1997014464A1 - Pediatric endotracheal apparatus

Info

Publication number: WO1997014464A1
Application number: PCT/US1996/016739
Authority: WO
Inventors: Joel C. Colburn; James M. Davenport
Original assignee: Nellcor Puritan Bennett Incorporated
Priority date: 1995-10-20
Filing date: 1996-10-18
Publication date: 1997-04-24
Also published as: AU7456096A

Abstract

Apparatus for cooperating with an endotracheal tube (10) or face mask when used on a pediatric or neonate patient, to limit excessive rebreathing of expired air and to assure the safe placement of the tube (10), the apparatus including a colorimetric carbon dioxide indicator (20) for sensing that the tube (10) has been placed in the trachea rather than the esophagus. The apparatus further includes a housing (21) for the indicator (20) which housing (21) includes a port (25), a ventilation port (22) and an internal space where the indicator (20) is mounted. The volume of the housing internal space is selected to limit the deadspace volume of the device to less than 10 cubic centimeters to thus avoid excessive rebreathing of expired air by the patient, while at the same time avoiding an undesirably high airflow resistance in the system.

Description

PEDIATRIC E DOTRACHEAL APPARATUS

Background of the Invention

Field Q£ the invention The present invention relates to improved medical apparatus for detecting a patient's exhaled gas constituents, most often carbon dioxide, especially for a pediatric or neonate patient . The invention is particularly useful for assuring proper placement of an endotracheal tube, and for use with a face mask designed to test for the continued presence of metabolism. Still more particularly, the present invention comprises an improved housing for a gaseous element detector to be used in conjunction with an endotracheal tube or face mask for the purposes described.

Description of the Prior Art

The need for, and practice of, endotracheal intubation into the trachea of a patient is well-known. Such intubation is performed when it is found that normal ventilation of the patient's lungs may be impaired. Failure to artificially ventilate an apneic patient rapidly could result in serious brain damage or death.

In general, the endotracheal tube which is used to provide ventilation is a flexible tube which defines an internal respiration lumen so that once the tube has had its distal end placed within the trachea of the patient, a bidirectional breathing path is established through the respiratory lumen. In the case of interruption of the respiratory process, a resuscitator bag can be attached to the proximal end of the endotracheal tube, which end extends external to the patient . One of the long recognized disadvantages of the use of an endotracheal tube is that an accidental misplacement of the tube into the esophagus can in itself cause death and disability if not quickly detected. In the prior art, a primary means of detecting accidental esophageal intubation has been utilizing a gaseous element detector connected within the air flow path of the respiring patient.

U.S. Patent Nos. 4,728,499; 4,879,999; and 4,994,117 are examples of prior art devices which utilize a carbon dioxide detector to ensure proper placement of the endotracheal tube. The general concept of detecting the presence of carbon dioxide is a successful safety measure to detect esophageal intubation. Carbon dioxide, a product of metabolism, is normally present in exhaled air in approximately a 5% concentration, but is only minutely present in esophageal gas. Thus, if an approximately 5% concentration of carbon dioxide is detected in air exhaled from the endotracheal tube, the tube is not misplaced in the esophagus. In preferred embodiments of this safety device, a colorimetric carbon dioxide detector is used to enable the personnel responsible for placing the endotracheal tube to have a rapid visual indication of the presence of carbon dioxide.

Colorimetric carbon dioxide detectors and various housings for the detectors, which are generally connected at or near the proximal end of the endotracheal tube, are fully described in the prior art, including the above-cited United States patents. One problem that remains with regard to the detection of proper placement of an endotracheal tube relates to the use of the tube and the above-described detection safety device on a neonate or pediatric patient. In general, such indicator housings cannot properly be used on pediatric patients because the housings have a high deadspace volume which results in the infant rebreathing too much expired air, a highly undesirable and dangerous situation. It is apparent that problems related to the size of a pediatric or neonate patient also may occur in applications with a mask rather than an endotracheal tube for sensing metabolism.

The present invention involves a design for a pediatric endotracheal device or face mask device including a gaseous element detector. The basis of the present invention is the recognition that the excess deadspace volume found in adult devices, which can result in the undesirable rebreathing of expired air, cannot be solved simply by shrinking the dimensions of the endotracheal tube, or mask, and the housing (including input/output parts) for the gaseous element detector, which dimensions relate to the deadspace volume of a device. When the adult devices are simply scaled down to have a suitably low deadspace volume, the usual result is a high increase in the flow resistance to the patient's breathing. Thus simply changing the deadspace volume is likely to only change from one breathing problem where previously expired air is again inhaled, to another breathing problem involving a difficulty of moving the breath through the endotracheal tube, or mask and the gaseous element detector housing into the patient's lungs against the force of high flow resistance, an obviously undesirable result. In the apparatus of this invention, it has been found that for pediatric patients it is necessary not only to make an adjustment in the deadspace volume of the housing, but it is necessary to make an adjustment which will also prevent an excess of air flow resistance, such resistance usually measured in centimeters of H₂0. More specifically, it has been found through experimentation that a deadspace volume in the housing of less than ten cubic centimeters is desirable for neonate and pediatric patients. In fact, for one kilogram patients it is desirable to have a deadspace volume for the housing below five cubic centimeters. It has also been found that for a deadspace volume limitation of less than ten cubic centimeters an air flow resistance of less than five centimeters of H2O at a flow rate of 11.5 liters per minute is acceptable. It is the relationship between the deadspace volume and the flow of resistance of a device with a gaseous element detector that forms the basis of the present invention .

Brief Description of the Drawings

Other objects of the present invention and many of the attendant advantages of the present invention will be readily appreciated as they become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof, and wherein:

Fig. 1 is a perspective view of a carbon dioxide detector housing incorporating the elements of the present invention; b

Fig. 2 is a drawing showing a pediatric endotracheal tube, the gaseous element detector of Fig. 1, and an adapter for connecting the proximal end of the tube to the port of the detector; Fig. 3 is another perspective view of the apparatus of Fig. 1 including a portion of the detector housing shown in an exploded view.

Detailed Description of the Preferred Embodiments Fig. 1 shows a perspective view of detector 20 including a gaseous element detector housing 21 having a female port 25. Another port 22 is shown attached to housing 21, which port 22 has an inner diameter 24 and which port 22 may be connected to a ventilation circuit such as a manual resuscitation bag, an anesthesia machine or a mechanical ventilator, for example. As shown, housing 21 includes a top surface having a transparent portion 27 through which a device such as a colorimetric carbon dioxide detector can be seen.

Fig. 2 discloses a tube 10 intended to be representative of an endotracheal tube with an internal diameter reduced for use with a pediatric or neonate patient. Also shown is gaseous element or carbon dioxide detector 20 and port 25. An adapter 15 is shown in position to connect the proximal end of tube 10 to port 25. Fig. 3 is an exploded perspective view of detector 20 including housing 21 having port 25 and ventilator port 22. In Fig. 3, a portion of housing 21 has been exploded to show the apparatus of the present invention for mounting a colorimetric carbon dioxide or other gaseous element detector. Within housing 21, to minimize shunt and provide a specific gas pathway, a wall 31 is placed between the path of outside gas which enters via port 22 and into housing 21. The gas flows over detector 36 mounted in housing 21. Expired gas flows from port 25, through a filter 33, over a top surface of detector 36, above wall 31 and through port 22. This dispersion of the expired air has been found to be useful.

Also shown within housing 21 is a detector mounting surface 32. Filter 33, formed from a material such as polypropylene, is placed on surface 32. A detector mounting plate 34 is then placed on top of filter 33. A pair of detector mounting guides 35 are mounted on opposite ends of plate 34. Detector 36, which in this preferred embodiment is a colorimetric carbon dioxide detector of a type fully described in the above prior art patents, includes a pair of notches 37 allowing for simplifying placement of detector 36 on plate 34.

Also shown is a lid 38 including a circumferential indented flange 41. Flange 41 includes a pair of female notches 39 for mating with male guides 35 on plate 34.

From Fig. 3 it can be seen that the use of the male guides 35 on plate 34 in conjunction with notches 37 and female notches 39 provides for a rapid assembly of a detector such as detector 36. Further, the indented flange 41 on lid 38 is designed to provide a friction fit with the internal wall of housing 21, to optionally further provide for a rapid replacement of carbon dioxide detector 36, if desired, and rapid assembly of carbon dioxide detector 20.

When viewing the figures of the drawing, it is seen how port 25 is fitted onto adapter 15 into endotracheal tube 10 at its proximal end, and how expired air will flow through the respiratory lumen defined by tube 10 from a properly placed distal end of the tube in the patient's trachea through the respiratory lumen and through port 25, detector housing 21 and ventilator port 22. It thus becomes apparent that the overall deadspace volume is directly related to the volume within detector device 20.

As stated above, an attempt to use an adult endotracheal system of on a neonate or pediatric patient would result in a device which has excess deadspace volume. This excess deadspace volume is undesirable in that it will result in expired air remaining within the deadspace volume to be rebreathed by the patient. It has been found that this undesirable effect of excess deadspace volume cannot be overcome by simply decreasing the volume within the endotracheal tube and the detector housing. This simple decrease in volume has been shown to result in an undesirably high air flow resistance which itself could make introducing air to the patient so difficult for the patient as to be dangerous .

For the present invention, it has been found that an adjustment to the deadspace volume in housing 21 can provide not only an acceptable deadspace volume which prevents excessive rebreathing of expired air, but will also allow for a sufficiently low air flow resistance to enable normal breathing by the pediatric or neonate patient, when the invention is applied to an endotracheal tube or a face mask.

Thus, the internal volume of detector housing 21 of the present invention is selected to provide a deadspace volume limitation of less than ten cubic centimeters, preferably less than eight cubic centimeters, more preferably less than five cubic centimeters, optionally less than four cubic centimeters, and most preferably less than three cubic centimeters. For such a deadspace limitation it has been found that a desirable air flow resistance is less than five centimeters of H₂0 at a flow rate of 11.5 liters per minute. Thus, the dimensions of the systems utilizing the present invention can be selected to give the desired combination of a deadspace volume of less than ten, eight, five, four or three cubic centimeters with an air flow resistance at a flow rate of 11.5 liters per minute which resistance is less than five centimeters of H2O.

In the case of one kilogram patients, it has been found that it is desirable to have a deadspace limitation of less than five cubic centimeters. In this instance, the internal diameter 24 of port 22 is adjusted to provide an air flow resistance at a flow rate of 11.5 liters per minute which is less than three centimeters of H₂0.

Further modifications and alternative embodiments of the apparatus of this invention will be apparent to those of skill in the art, particularly in view of this disclosure. Accordingly, the above description is to be construed as illustrative of only the preferred embodiments of the apparatus of this invention and that various changes may be made without departing from the spirit and scope of this invention as defined in the claims hereto attached.

Claims

What is claimed is:

1. In endotracheal apparatus including a tube defining a respiration lumen, the tube having a first end for insertion into a trachea within a patient and a second end for extending external to the patient, the improved safety apparatus comprising: a housing defining an internal volume of space and including first port means for connection to said tube second end, and second port means connecting said internal space to an external supply of gas; indicator means mounted within said housing for detecting and visually indicating the presence of a gaseous element in expired air from the patient; and said housing internal volume of space being sized for limiting rebreathing of expired air from said space to an amount less than 10 cubic centimeters.

2. The apparatus of claim 1 in which: said housing internal volume of space is sized for providing an airflow resistance of less than 5 centimeters of H₂0 at a flow rate of 11.5 liters per minute.

3. The apparatus of claim 2 in which said indicator means for detecting comprises a colorimetric carbon dioxide indicator.

4. Pediatric endotracheal apparatus comprising: a tube defining an internal respiration lumen and having a distal end for intubation into the trachea of a patient and a proximal end extending external to the patient; a housing having a port for connection to said respiration lumen at said proximal end of said tube and an additional port, said housing and said ports defining an internal deadspace volume of less than 10 cubic centimeters; said housing including said ports being sized to cooperate to provide an airflow resistance of less than 5 centimeters of H₂0 at a flow rate of 11.5 liters per minute; and means for mounting at least one colorimetric carbon dioxide indicator in said housing for sensing the presence of carbon dioxide in the breath of the patient.

5. The apparatus of claim 4 in which said means for mounting includes: an indicator receiving plate including at least a pair of male mount guides, and a transparent indicator cover plate having a flange sized to fit within said housing, said flange including at least a pair of female mount guides for mating with said receiving plate male connectors.

6. The apparatus of claim 4 in which said deadspace volume is less than 5 cubic centimeters, for endotracheal intubation in a patient weighing approximately one kilogram.

7. The apparatus of claim 6 in which said port internal diameter is sized to cooperate with said deadspace volume for providing an airflow resistance of less than 3 centimeters of H₂0 at a flow rate of 11.5 liters per minute.

8. A carbon dioxide detector, comprising: a housing having a port adapted for connection to an endotracheal tube, and an additional port, said housing and said ports defining an internal deadspace volume of less than ten cubic centimeters: said housing including said ports being sized to cooperate to provide an airflow resistance of less than five centimeters of H₂0 at a flow rate of 11.5 liters per minute; and means for mounting at least one colorimetric carbon dioxide indicator in said housing for sensing the present of carbon dioxide in the breath of a patient.