WO1995011716A1

WO1995011716A1 - Integrated end tidal carbon dioxide monitor and endotracheal tube

Info

Publication number: WO1995011716A1
Application number: PCT/US1994/012087
Authority: WO
Inventors: Steven Chang; Rodger Wine
Original assignee: The Regents Of The University Of California
Priority date: 1993-10-26
Filing date: 1994-10-19
Publication date: 1995-05-04

Abstract

This invention is an endotracheal tube (12) having an integrated carbon dioxide detector (10). The detector has a plurality of holes (48) through which carbon dioxide passes through. A strip of carbon dioxide sensitive paper (52) is placed over the holes and changes color when carbon dioxide is present, and thereby indicates proper placement of the endotracheal tube in the patient's trachea. The detector is covered by a transparent sleeve (54).

Description

INTEGRATED END TIDAL CARBON DIOXIDE MONITOR AND ENDOTRACHEAL TUBE

FIELD OF THE INVENTION

The present invention relates generally to endotracheal tubes, and more particularly to systems and "methods for ascertaining proper placement of endotracheal tubes in a patient.

BACKGROUND

Endotracheal (ET) tubes are devices which can be advanced into a patient's pharynx and trachea to establish an artificial air passageway, and, if necessary, a breathing apparatus can be engaged with the proximal end of the ET tube for directing oxygen through the ET tube and into the patient's lungs. Also, carbon dioxide (C0₂) from the patient's lungs passes back through the ET tube and out of the patient. Thus, use of an ET tube may be indicated to alleviate a variety of potentially life-threatening respiratory ailments.

Properly positioning an ET tube in a human patient is not without difficulties, because anatomic variations of the upper airway make it difficult to precisely locate the glottis. Consequently, because a human's respiratory tract is in fluid communication with his or her digestive tract, a tube which is advanced into a human patient through the patient's pharynx can be placed either into the trachea, or into the esophagus of the digestive tract . It happens that it is not always possible for medical personnel to ascertain whether they have indeed properly placed an ET tube in the trachea or have improperly placed the ET tube into the esophagus, despite the use of visual indications, stethoscopes, and other methods for determining whether ET intubation has been achieved. This is most unfortunate, because undetected improper ET tube positioning can quickly lead to brain damage and death.

Accordingly, it is crucial to rapidly and reliably ascertain whether an ET tube has been properly placed into the trachea, and not improperly positioned into the esophagus. To this end, infrared (IR) capnographic apparatus are available in many hospitals which present an indication of whether an ET tube has been properly positioned. Given the power consumption and bulkiness of IR capnographic apparatus, however, IR capnography is unsuitable for field use or other applications requiring ET tube intubation in patients who are at locations remote from hospitals.

Not surprisingly, several portable devices which are directly engageable with ET tubes have been introduced for ascertaining whether the ET tube has been properly positioned in a patient's trachea. One such device is disclosed in U.S. Patent No. 4,879,999 to Leiman et al . The Leiman et al. device includes a special housing having a C0₂ detector strip, and the housing is adapted to be engaged with a standard ET tube assembly. If the ET tube has been properly positioned, C0₂ from the patient's expired breath will quickly cause the detector strip to change color. Otherwise, the strip will not change color. U.S. Patent No. 4,691,701 to Williams similarly discloses a device having a specially-designed adaptor for engaging an ET tube assembly, and a C0₂ detector strip is mounted on the adaptor.

While effective for their intended purpose, both the

Williams and Leiman et al. adaptor devices have inherent disadvantages. Among these disadvantages is the necessity for the user to remember to actively engage the adaptor devices with a standard ET tube. Thus, if the user forgets to engage the adaptor, no indication of end- tidal C0₂ will be available. Also, requiring the user to actively engage an adaptor results in wasted time in detecting proper ET tube placement . Even a small time loss in detection is undesirable, particularly in circumstances wherein the savings of a few seconds can be crucial .

Also, adaptor devices require creating a potential site for unintended breathing circuit disconnection. Further, adaptor devices are relatively expensive, and they are bulky, which is a particularly significant drawback in the context of rescue vehicle use, given the limited storage space available in rescue vehicles. Additionally, many if not most adaptor devices occlude the ET tube lumen, and must consequently be disconnected in the event that pulmonary toilet maintenance (e.g., suctioning and lavage) must be performed.

Accordingly, it is an object of the present invention to provide a device for quickly determining whether an ET tube has been properly positioned. Another object of the present invention is to provide a portable, powerless device for determining whether an ET tube has been properly positioned. Still another object of the present invention is to provide a device for determining proper ET tube placement which does not require a user to manually engage the device with an ET tube system. Yet another object of the present invention is to provide a device for determining proper ET tube placement which is easy to use and cost-effective to manufacture.

SUMMARY OF THE INVENTION

A device is disclosed for providing visual indication of proper endotracheal (ET) tube placement in a patient. The ET tube can be associated with ancillary respiratory support systems. The device includes an ET tube which has a distal segment configured to be positioned in the trachea of a patient, and a unitarily constructed proximal segment. A hollow connector is coaxially attached to the proximal segment of the ET tube for establishing a pathway for fluid communication between the ET tube and the ancillary support systems.

In accordance with the present invention, the connector has an inside surface, an outside surface, and a plurality of holes are formed between the inside surface and the outside surface of the connector. A detector strip is positioned against the outside surface of the connector for covering at least some of the holes, and the detector strip changes color in the presence of a predetermined amount of carbon dioxide (C0₂) . To cover the detector strip, a transparent sleeve is surroundingly engaged with the outside surface of the connector, and the sleeve surrounds the detector strip.

Preferably, particularly for application in adult patients, the distal segment of the ET tube includes an inflatable cuff for establishing a fluid seal between the esophagus and lungs, and to facilitate positive pressure ventilation. In a presently preferred embodiment, the detector strip is a colorimetric strip that is impregnated with a material for changing color in the presence of C0₂. Advantageously, the detector strip is filter paper, and the material includes calcium hydroxide, glycerol, propylene glycol, and metacresol purple sodium salt.

In another aspect of the present invention, an improvement to an endotracheal (ET) tube apparatus is disclosed. The ET tube apparatus includes an ET tube with inflatable cuff for establishing a fluid seal between the esophagus and lungs, and for facilitating positive pressure ventilation. Also, the apparatus has an ancillary support system, and a hollow connector is engaged with the ET tube and the support system to establish a passageway for fluid communication therebetween. The connector has an outside wall and defines a lumen.

The improvement in accordance with the present invention includes a carbon dioxide (C0₂) detector which is positioned against the outside wall of the connector for providing visual indication when a predetermined amount of C0₂ gas is present inside the connector. The C0₂ detector is in fluid communication with the lumen of the connector but is not disposed in the passageway between the ET tube and the support system. A transparent cover is positioned over the C0₂ detector.

In still another aspect of the present invention, a portable powerless device is disclosed for quickly providing visual indication of proper endotracheal (ET) placement . The device includes an ET tube assembly that is configured for placement within a human trachea. At least a portion of the assembly has an inside wall, and outside wall, and is modified to have a plurality of holes radially extending from the inside wall to the outside wall on a proximal segment of the assembly. A detector is positioned against the outside wall of the assembly to cover the holes for changing color in response to a predetermined amount of carbon dioxide (C0₂) within the assembly.

In yet another aspect of the present invention, a method for ascertaining whether an endotracheal (ET) tube has been properly positioned in a patient is disclosed. The method of the present invention contemplates providing a single hollow ET connector and an ET tube. The ET tube has a distal segment which is configured for positioning within the patient and a proximal segment which is configured for engaging the ET connector. Together, the connector and ET tube establish an integrated ET tube assembly.

A plurality of holes is formed in the ET connector, and each hole establishes a passageway for fluid communication from the interior of the connector to the exterior of the connector. In accordance with the method of the present invention, a detector strip is positioned against the exterior of the connector to cover at least some of the holes, and the detector strip changes color when a predetermined amount of carbon dioxide (C0₂) is present inside the connector.

With this arrangement, the ET tube is positioned in the patient, and the detector strip can visually be observed to ascertain whether the ET tube has been properly positioned.

The details of the present invention, both as to its construction and operation, can best be understood in reference to the accompanying drawings, in which like numerals refer to like parts, and which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of the endotracheal device of the present invention; and

Figure 2 is a cross-sectional view of the endotracheal device of the present invention, as seen along the line 2-2 in Figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to Figure 1, a device for ascertaining whether an endotracheal (ET) tube has been properly positioned in a patient is shown, generally designated 10. As shown, the device 10 includes an elongated, flexible, hollow ET tube 12 which, as shown, has continuous cylindrical inside and outside surfaces 12a, 12b. Preferably, the ET tube 12 is a standard endotracheal tube such as the single-use endotracheal device marketed by Mallinckrodt, Inc. under the trade name Hi-Lo^R Tracheal Tube.

In accordance with industry standards, most standard endotracheal devices, including the above-mentioned Mallinckrodt device, include an ET tube such as the tube 12 and a standard so-called "15mm" ET connector, such as an ET connector 14 shown in Figure 1, for operably engaging the ET tube 12 with an ancillary support system 16. As shown in Figure 1, the ET connector 14 is attached to a hollow system line 18, and the line 18 is in turn attached to the support system 16. Thereby, the support system 16 is placed in fluid communication with the lumen of the ET tube 12. As will be appreciated by the skilled artisan, the support system 16 can be any well-known device for providing respiration support, e.g., oxygenation, suction, lavage, etc. to the patient in whom the ET tube 12 is to be positioned. Together, the ET tube 12 and ET connector 14 establish an ET tube assembly which is preferably made of a biocompatible plastic material.

Figure 1 also shows that the ET tube 12 has a distal segment 20 which terminates in an open distal end 22. As shown in Figure 1, the open distal end 22 is bevelled relative to the long axis of the ET tube 12, and an opening 23 can be formed in the ET tube 12 opposite the open distal end 22. An inflatable cuff 24 is positioned in a surrounding relationship with the distal segment 20, and a cuff line 26 connects the interior of the cuff 24 with a cuff connector 28. In turn, the cuff connector 28 can be engaged with a source of inflating fluid (not shown) for inflating the cuff 24. As is well-known in the art, the purpose of inflating the cuff 24 is to establish a fluid seal between the lungs and the esophagus, and to permit positive pressure ventilation.

It is to be understood that the cuff line 28 can extend through the lumen of the ET tube 12 to the cuff 24. Alternatively, the cuff line 26 can be connected to a small lumen (not shown) that is formed in a wall 30 of the ET tube 12 during the extrusion manufacturing process. In such an embodiment, the small lumen would be in fluid communication with the interior of the cuff 24 to establish a pathway for fluid communication between the lumen of the cuff line 26 and the cuff 24.

In cross-reference to Figures 1 and 2, the ET connector 14 is preferably configured as a standard rigid hollow cylindrical ET tube connector. More specifically, as shown best in Figure 2, the ET connector 14 has a distal segment 32 which is closely received in a unitarily constructed proximal segment 34 of the ET tube 12, and is held within a main lumen 36 of the ET tube 12 in an interference fit. Although not ordinarily done, the ET connector 14 can also be bonded or otherwise fastened to the ET tube 12. Preferably, the inner diameter "ID" of the main lumen 36 of the ET tube 12 is between about seven to nine millimeters (7-9 mm) .

Further, the ET connector 14 has a proximal segment 38 which terminates in a proximal flange 40, and, as shown, the flange 40 protrudes radially outwardly relative to the longitudinal axis of the ET connector 14. The proximal segment 38 of the ET connector 14 has a configuration well-known in the art for permitting the segment 38 to be quickly manually engaged with the support system 16. More specifically, the proximal segment 38 of the ET connector 14 is cylindrical, rigid, and has an inside diameter "D" that is appropriate for establishing an interference fit with the particular ET tube 12 being used, and an outside diameter "OD" of fifteen millimeters (15 mm) .

As discussed above and as shown in Figure 2, the ET connector 14 has a cylindrical inside surface 42 defining a lumen 44, and a cylindrical outside surface 46. The lumen 44 of the ET connector 14 is in fluid communication with the lumen 36 of the ET tube 12 and is coaxial with the lumen 36 of the ET tube 12. Ordinarily, the ET tube 12 with ET connector 14 attached thereto is provided to medical personnel as a complete assembly, with the ET connector 14 being manually detachable from the ET tube 12.

In accordance with the present invention, the ET assembly described above is modified to include a plurality of perforations, i.e., cylindrical holes 48, which are formed in the ET connector 14. Each hole 48 extends radially outwardly from the inside surface 42 to the outside surface 46 of the ET connector 14 and the axis of each hole is perpendicular to the axis of the ET connector 14. Thus, each hole 48 establishes a pathway for fluid communication from the lumen 44 of the ET connector 14 to the outside surface 46 of the ET connector 14. Preferably, the diameter "d" of each hole is equal to between about one to three millimeters (1-3 mm) .

The holes 48 can be formed during the manufacturing process in the matrix shown, or some other suitably- configured matrix. Alternatively, the holes 48 can be formed in the ET connector 14 after manufacturing by appropriately perforating the ET connector 14. Figure 2 shows that the ET connector 14 has a distal end 50, and in one presently preferred embodiment, the holes 48 matrix extends from the distal end 50 to near the flange 40.

Figure 2 additionally shows that a detector 52 is positioned in fluid communication with the lumen 44 of the ET connector 14 through at least some of the holes

48. Preferably, the detector 52 is a strip of filter paper having a width "w" equal to about five millimeters

(5mm) , and the filter paper is wrapped around the outside surface 46 of the ET connector 14 to cover all of the holes 48. Thus, the detector 52 is positioned outside the lumen 44 of the ET connector 14. If desired, the detector 52 can be solvent bonded to the ET connector 14.

As intended by the present invention, the detector 52 is a colorimetric device which provides visual indication of the presence of carbon dioxide (C0₂) above a predetermined level inside the lumen 44 of the ET connector 14. By so providing such an indication, the detector 52 aids the user in ascertaining whether the ET tube 12 has been properly positioned in a patient's trachea.

To this end, the detector 52 is a strip of filter paper which is impregnated with a material that quickly changes color when the C0₂ level inside the lumen 44 exceeds a predetermined level . In one presently preferred embodiment, the material includes calcium hydroxide, glycerol, propylene glycol, and metacresol purple sodium salt. Consequently, in the preferred embodiment, when the detector 52 is not in the presence of high levels of C0₂, i.e., the levels of C0₂ in a person's expired breath, the detector 52 is purple. It is to be understood that other suitable materials which change color in the presence of C0₂ can be used, including but not limited to the materials disclosed in U.S. Patent Nos. 4,691,701 to Williams and 4,879,999 to Leiman et al . , both of which are incorporated herein by reference.

Further, Figure 2 shows that a transparent, preferably polyvinylchloride (PVC) cylindrical sleeve 54 surrounds and covers the detector 52. A small chamber 55 is established between the sleeve 54 and the detector 52, to facilitate C0₂ flow through the detector 52 and thereby aid in end-tidal C0₂ detection.

Accordingly, the sleeve 54 has an inside diameter equal to or slightly larger than the diameter of the ET tube 12. If desired, the sleeve 54 can be bonded to the ET tube 12. To establish a fluid seal such that substantially no fluid escapes from inside the endotracheal device 10 except through the main lumens 36, 44, the sleeve 54 preferably abuts the flange 40 of the ET connector 14 and covers the proximal about ten millimeters (10mm) of the proximal segment 34 of the ET tube 12.

In the operation of the endotracheal device 10, reference is made to Figures 1 and 2. The distal segment 20 of the ET tube 12 is positioned into a patient (not shown) , and the cuff 24 is inflated as appropriate for ventilation. The user of the endotracheal device 10 observes the detector 52.

When the patient expires air, and the detector 52 immediately changes to a color that indicates the presence of C0₂ in the lumens 36, 44 of the ET tube 12 and

ET connector 14, e.g., in the preferred embodiment, from purple to yellow, then the ET tube 12 has been properly positioned in the patient's trachea. After the patient has expired, oxygenated air from the system 16 is directed into the patient through the ET tube 12, which causes the detector 52 to change color back to purple. The user may continuously monitor the above-described cyclic color change of the detector 52, to continuously monitor end-tidal C0₂.

On the other hand, if the detector 52 does not rapidly change to a color that indicates the presence of C0₂ in the lumens 36, 44 of the ET tube 12 and ET connector 14, then the ET tube 12 may have been improperly positioned in the patient's esophagus, and further evaluation of ET tube placement is necessary.

Accordingly, the skilled artisan will appreciate that the endotracheal device 10 is a lightweight, powerless device which can be used to establish a pathway for fluid communication through a patient's pharynx and trachea to permit oxygenation and ventilation. Also, the device 10 quickly, simply, and reliably provides visual indication of end-tidal C0₂ as an indicator of proper ET tube 12 placement, without requiring the user to connect and disconnect adapters, thereby saving crucial seconds in ascertaining proper placement while ensuring continuous end-tidal C0₂ monitoring. Further, the endotracheal device 10 does not create an unwanted site of potential fluid leakage or breathing circuit disconnection from the endotracheal device 10. Moreover, because the endotracheal device 10 does not require the use of specialized adapters, it is relatively less bulky and less expensive than adaptor-based devices. Also, the endotracheal device 10 continuously and passively monitors for end-tidal C0₂, and it permits activation of the support system 16 without requiring the endotracheal device 10 to be disconnected from specialized adapters or removed from the patient . While the particular integrated end tidal carbon dioxide monitor and endotracheal tube as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims.

Claims

WHAT IS CLAIMED IS:

A device for providing visual indication of proper endotracheal (ET) tube placement in a patient, the ET tube being associable with an ancillary support system, comprising: an ET tube having a distal segment configured to be positioned in the trachea of a patient, the ET tube also having a unitarily constructed proximal segment; a hollow connector coaxially attached to the proximal segment of the ET tube for establishing a pathway for fluid communication between the ET tube and the ancillary support system, wherein the connector has an inside surface, an outside surface, and a plurality of holes therebetween; a detector strip positioned against the outside surface of the connector for covering at least some of the holes, wherein the detector strip changes color in the presence of a predetermined amount of carbon dioxide (C0₂) ; and a transparent sleeve surroundingly engaged with the outside surface of the connector - for covering the detector strip.

2. The device of Claim 1, wherein the distal segment of the ET tube includes an inflatable cuff .

3. The device of Claim 2, wherein the detector strip is impregnated with a material for changing color in the presence of C0₂.

4. The device of Claim 3 , wherein the detector strip is filter paper, and the material includes calcium hydroxide, glycerol, propylene glycol, and metacresol purple sodium salt .

5. In an endotracheal (ET) tube apparatus having an ET tube with inflatable cuff, an ancillary support system, and a hollow connector engaged with the ET tube and the support system to establish a passageway for fluid communication therebetween, wherein the connector has an outside surface and defines a lumen, an improvement comprising: a carbon dioxide (C0₂) detector positioned against the outside surface of the connector for providing visual indication when a predetermined amount of C0₂ gas is present inside the connector, wherein the C0₂ detector is in fluid communication with the lumen of the connector but is not disposed in the passageway between the ET tube and the support system; and a transparent cover positioned over the C0₂ detector.

6. The improved apparatus of Claim 5, wherein the connector is formed with a plurality of holes, each extending between the lumen of the connector and the outside surface of the connector for establishing fluid communication between the lumen and the C0₂ detector.

7. The improved apparatus of Claim 6, wherein the detector is impregnated with a material for changing color in the presence of C0₂.

8. The improved apparatus of Claim 7, wherein the detector is filter paper, and the material includes calcium hydroxide, glycerol, propylene glycol, and metacresol purple sodium salt .

9. A portable powerless device for quickly providing visual indication of proper endotracheal (ET) placement, comprising: an ET tube assembly configured for positioning within a human trachea, wherein at least a portion of the assembly has an inside surface, an outside surface, and is modified to have a plurality of holes radially extending from the inside surface to the outside surface on a proximal segment of the assembly; and a detector positioned against the outside surface of the assembly to cover the holes for changing color in response to a predetermined amount of carbon dioxide (C0₂) within the assembly.

10. The device of Claim 9, wherein the ET tube assembly comprises an ET tube and a hollow connector substantially configured as a standard fifteen millimeter (15mm) ET tube connector for engaging the ET tube with a standard ancillary support system, wherein users of the device in the field do not have to manually engage the connector with the ET tube.

11. The device of Claim 10, wherein the ET tube includes an inflatable cuff.

12. The device of Claim 11, wherein the detector is a detector strip made of filter paper and the detector strip is impregnated with calcium hydroxide, glycerol, propylene glycol, and metacresol purple sodium salt for changing color in the presence of C0₂, and the device further comprises a transparent sleeve closely positioned around the connector for covering the detector strip.

13. The device of Claim 12, wherein the connector has a proximal segment terminating in an outwardly- protruding flange, the holes are formed in the proximal segment, and the transparent sleeve abuts the flange of the connector.

14. A method for ascertaining whether an endotracheal (ET) tube has been properly positioned in a patient, comprising the steps of:

(a) providing a single hollow ET connector and an ET tube having a distal segment advanceable into the patient and a proximal segment configured for engaging the ET connector, wherein the connector and ET tube together establish an integrated ET tube assembly;

(b) forming a plurality of holes in the ET connector, each hole establishing a passageway for fluid communication from the interior of the connector to the exterior of the connector;

(c) positioning a detector strip against the exterior of the connector to cover at least some of the holes, such that the detector strip changes color when a predetermined amount of carbon dioxide (C0₂) is present inside the connector;

(d) advancing the ET tube into the patient; and

(e) observing the detector strip for end-tidal C0₂.

15. The method of Claim 14, further comprising the step of providing a transparent sleeve to cover the detector strip.

16. The method of Claim 15, wherein the provided ET tube includes an inflatable cuff.