WO1999065552A1

WO1999065552A1 - Device and method for intubation and an endotracheal tube therefor

Info

Publication number: WO1999065552A1
Application number: PCT/IL1999/000334
Authority: WO
Inventors: Aharon Abramovitch; Yuli Lozinski
Original assignee: Alcor Medical Instruments Ltd.
Priority date: 1998-06-17
Filing date: 1999-06-17
Publication date: 1999-12-23
Also published as: IL124963A0; AU4388199A

Abstract

An intubation device (1) utilizing an endotracheal tube (2) is presented. The device (1) comprises at least one temperature sensor (T1, T2, T3) located at a distal end (2A) of the endotracheal tube (2), which is intended for insertion into the patient's trachea opening, and a processor unit (8) located at opposite end of the tube (2). The sensor (T1, T2, T3) is capable of generating a temperature response to air circulation in the vicinity of the sensor (T1, T2, T3). The processor unit (8) receives this temperature sensor (T1, T2, T3) and analyzes it to generate data representative of a relative location of the distal end (2A) of the endotracheal tube (2) relative to the trachea opening. This data can be used for guiding a movement of the distal end (2A) of the endotracheal tube (2) into the trachea opening.

Description

Device and Method for Intubation and an Endotracheal Tube Therefor

FIELD OF THE INVENTION

This invention is generally in the field of an intubation technique, and relates to a device and method aimed at improving the intubation technique, and an endotracheal tube used therein.

BACKGROUND OF THE INVENTION

The intubation technique provides for supplying air or oxygen-enriched air into the lungs of a patient through an endotracheal tube during emergency situations and particularly for anesthesia purposes. The introduction of an endotracheal tube into the trachea opening is usually carried out by employing a laryngoscope (and its variations) for enabling visual control of the trachea opening, for example such as described in PCT/IL96/00191 by the inventor of the present application. Sometimes the introduction of an endotracheal tube is performed "blindly", based solely on the experience and intuition of a clinician. However, even a highly experienced clinician may face difficulty in quickly orienting the endotracheal tube to its proper location. Anatomically difficult intubation often occurs in the following cases: recessive mandible, large tongue, narrow oral cavity, short necked, obese patients, larynx displacements, prominent and maldeveloped teeth, short rigid epiglottis, etc. The intubation has to be performed quickly and smoothly, especially in neck-and brain-injured patients, as well as in open-heart surgery patients, where the use of premedication myorelaxent drugs is limited. A delay in inserting the endotracheal tube (i.e., starting the intubation process) may be critical for the patient, while improper placement of the endotracheal tube could cause damage to the vocal cords, esophagus or tracheal mucous. The existing methods and devices do not prevent complications such as the incorrect insertion of the endotracheal tube into the esophagus or into the main right bronchus, damage to vocal cords, etc.

Various techniques aimed at facilitating the proper placement of an endotracheal tube have been developed, disclosed for example in U.S. Patents Nos. 4,672,960; 5,487,731 and 5,885,248. U.S. Patent No. 4,672,960 discloses a technique based on the use of a mechanical means, namely a flexible guide having a part thereof that obliterates the esophagus thereby preventing the insertion of the endotracheal tube thereto and allowing its insertion into the trachea. Needless to say that the insertion of such a mechanical means obliterating the esophagus is complicated and may harm the patient. U.S. Patents 5,487,731 and 5,885,248 disclose a technique utilizing a pressure changing source, such as a volume changing device, connected to an endotracheal tube and to an appropriate transducer. By detecting the existence of occlusion of the tip and its absence, the system determines whether the tip is in the esophagus or in the trachea, respectively. Such a system is bulky, due to the need for a chamber of a volume changing device.

SUMMARY OF THE INVENTION

There is accordingly a need in the art to facilitate the correct application of an endotracheal tube to patients, by providing a novel device and method for intubation. It is a major feature of the present invention to provide such a device that enables quick and proper insertion of the endotracheal tube into the patient's trachea opening.

It is a further feature of the present invention to provide such a device that can easily be used with a conventional endotracheal tube.

It is a still further feature of the present invention to provide such a device that has a simple and inexpensive construction thereby enabling it to be disposable.

It is a still further feature of the present invention to provide a device capable of controlling the entire intubation process. The main idea of the present invention is based on the following. It is known that a temperature sensor (thermistor) is capable of generating a temperature response to air circulation in its vicinity. This temperature response is indicative of the temperature changes caused by the air circulation. Hence, by locating at least one such sensor at a distal end of the endotracheal tube, the temperature response generated by the sensor can be used for guiding a movement of the distal end within the patient's oral cavity towards the trachea opening. Indeed, even weak air circulation in the oral cavity is definitely associated with the trachea and not with the esophagus. It is also known that the air circulation in the oral cavity is defined by the inspiration and expiration airflow. Consequently, the air circulation at the trachea opening is higher than at deeper regions thereof. By detecting changes in the temperature response during a progressive movement of the distal end of the tube inside the trachea, a proper position of the tube inside the trachea can be established. Owing to the fact that most of the commercially available thermistors are inexpensive, an endotracheal tube using such a kind of sensor may be disposable.

There is thus provided according to one aspect of the present invention, an intubation device utilizing an endotracheal tube to be inserted into the patient's trachea opening, the device comprising: (a) at least one temperature sensor located at a distal end of the endotracheal tube, the sensor generating a temperature response to air circulation in the vicinity thereof;

(b) a processor unit coupled to said at least one temperature sensor so as to be responsive to the temperature response for analyzing it and generating data representative of a relative location of the distal end of the endotracheal tube relative to the trachea opening; and

(c) an indicator coupled to the processor unit for receiving said data and generating an indication signal which can be used for guiding a movement of the distal end of the endotracheal tube into the trachea opening. Preferably, the indicator comprises an audio transceiver capable of transmitting different audio indication signals depending on different relative locations of the distal end relative to the trachea opening. Preferably, three temperature sensors are used, being mounted on a support ring in a spaced-apart relationship along its circumference so as to form three tops of an equilateral triangle. The indication signal corresponding to substantially equal values of the temperature response produced by these three sensors is indicative of that the distal end of the tube is aligned with a central region of the trachea opening. If two temperature sensors are used, they are located substantially at opposite sides of the distal end of the endotracheal tube.

A single temperature sensor may be used, being located substantially at a central region of the distal end. In this case, the indication signal corresponding to a maximal value of the temperature response is indicative of that the temperature sensor is aligned with a central region of the trachea opening. Preferably, such a single temperature sensor is mounted on a tip of the conventionally used guiding device (mandrin), which is sufficiently flexible to repeat the form of the endotracheal tube and is sufficiently rigid to slightly force its movement downward into the trachea. According to another aspect of the present invention, there is provided an endotracheal tube comprising at least one temperature sensor accommodated at its distal end, the sensor being capable of generating a temperature response to air circulation in the vicinity of the sensor which is indicative of a relative location of the distal end relative to the patient's trachea opening, and can therefore be used for guiding a movement of the endotracheal tube into the trachea opening.

According to yet another aspect of the present invention, there is provided a method for intubation utilizing an endotracheal tube, the method comprising the steps of: (i) providing at least one temperature sensor located at a distal end of said endotracheal tube intended for insertion into the patient's trachea opening, the sensor being capable of generating a temperature response to air circulation in the vicinity of the sensor; (ii) whilst moving the distal end of the endotracheal tube towards the trachea opening, detecting analyzing said temperature response to determine a relative location of the distal end of the tube relative to the trachea opening ; (iii) generating an indication signal indicative of the relative location of the distal end; and (iv) manipulating the distal end of the tube in accordance with the indication signals for guiding a movement of the distal end of the tube into the trachea opening.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. la is a schematic illustration of the main components of intubation devices constructed according to one embodiment of the present invention; Figs, lb and lc illustrate two different embodiments of an endotracheal tube suitable to be used in the device of Fig. 1 ;

Fig. 2 is a schematic block diagram of the main functional elements of the device of Fig. 1; 5 Fig. 3 is a flow chart of the main steps of a method according to the invention;

Figs. 4 and 5 are schematic illustrations of two more embodiments of an intubation device of the present invention; and

Fig. 6 is a schematic illustration of yet another embodiment of the invention.

o DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to Fig. la, there is illustrated an intubation device 1 constructed according to one embodiment of the invention. Such an intubation device is applied to patients with spontaneous breathing and for anesthesia purposes. The device 1 typically comprises an endotracheal tube 2, which is made of a flexible material5 (typically silicone) and is equipped with an inflating assembly, generally at 4, for inflating/deflating a portion 5 of the tube 2. The construction and operation of the assembly 4 do not form part of the present invention and therefore need not be specifically described, except to note that it is used for fixing the position of the tube upon properly locating it inside the patient's trachea. A distal end 2 A of the0 tube 2, which is intended for insertion into the trachea opening, is usually cut at an angle of approximately 45° for facilitating the sliding movement of the tube into the trachea. The distal end 2A thus has an elliptical cross section.

It should, however, be noted that, generally, the provision of such an elliptical end is optional. The tubes with a distal end having a circular cross section5 may also be employed. These tubes may posses a soft distal tip.

The device 1 comprises a pair of temperature sensors (thermistors) Ti and T , for example of a kind made of semiconductor covered by glass or other material certified for use with human tissues. The thermistors Ti and T₂ are mounted on a support arrangement 6 inserted into the tube 2 and are accommodated at opposite sides of the end 2A. The support arrangement 6 is made of a flexible (e.g., plastic) material, and is designed like a so-called "three-leg frame", formed by three elongated flexible pins Pi, P₂ and P3 and three ring-like members - a lower ring Ri mounted at the distal ends of the pins, an intermediate ring R₂ and an upper ring R₃. The diameter of the support arrangement 6 is substantially equal to the inner diameter of the tube 2. The upper ring R₃ is designed such as to circumferentially engage the end 2B of the tube 2, thereby preventing the movement of the support arrangement 6 through the tube 2.

Further provided is a processor unit 8 which is coupled to the thermistors Ti and T₂ through wires (not shown) passing through either two pins of the support arrangement 6. The entire device 1 is operated by switching a button 10 on the processor unit 8. Also shown on the processor unit 8 is a transceiver 11 transmitting output audio signals in a manner described more specifically further below. It should be noted that the processor 8 may be a stand-alone unit coupled to the thermistors through wires, or wireless in which case an appropriate additional transceiver is provided.

Figs, lb and lc illustrate endotracheal tubes 102 and 202, having somewhat different constructions as compared to the tube 2 and being suitable to be used in the device 1. Same reference numbers are used for identifying those components which are common in the tubes 2, 102 and 202.

In the tube 102, three thermistors Ti, T₂ and T₃ are provided being mounted on the lower ring Ri of the support arrangement 6 in a spaced-apart manner so as to form the tops of an equilateral triangle. The provision of three thermistors is associated with the fact that the trachea opening is actually shaped like a triangle, two sides of which being formed by the vocal cords.

In the tube 202, the pair of thermistors Ti and T₂ are attached directly to the distal end 2A of the tube, thereby eliminating the use of any support arrangement. The thermistors Ti and T₂ are coupled to the processor unit (not shown here) through wires Wi and W₂, respectively, attached to the inner surface of the tube by any suitable means. Turning now to Fig. 2, the main functional elements of the device 1 are more specifically illustrated in a way of a block diagram. As shown, the processor unit 8 comprises analog-to-digital utilities 12A and 12B coupled to the thermistors Ti and T₂, respectively, and a programming means 14. The programming means 14, in response to the actuation of the switch button 10, operates a power source (not shown) to supply voltage to thermistors Ti and T₂. The programming means 14 utilizes a suitable model for analyzing signals coming from thermistors Ti and T₂ and generating data representative thereof which is transmitted to the audio transceiver 11 producing audio indication signals. Each of the thermistors Ti and T₂ generates a temperature response to air circulation in its vicinity. This temperature response is indicative of temperature changes caused by the air circulation. The air circulation in the patient's oral cavity is defined by the difference between the inspiration and expiration airflow. The air circulation increases with the approaching to the trachea opening, and reaches its maximal level at the trachea opening. Thus, on the one hand, the temperature response of each thermistor is maximal at the trachea opening, and, on the other hand, the temperature response of both thermistors is substantially the same when the distal end 2A of the tube 2 is aligned with the central region of the trachea opening. Additionally, the air circulation increases along the trachea from its deeper regions to its opening. Accordingly, the temperature response of the thermistors would decrease whilst moving downward inside the trachea.

The operation of the device 1 will now be described with reference to Fig. 3. Prior to the use of the device 1 for intubation purposes, two calibration procedures are sequentially carried out, one in a neutral environment, e.g., within a package containing the device 1, (step 20) and the other in the patient's oral cavity (step 22). To this end, the device 1 (i.e., its processor unit 8) is actuated (by pressing the switch button 10), and the model utilized in the programming means 14 is optimized ("tuned") so as to ensure that the temperature response of both thermistors is the same. This is associated with the fact that practically the temperature response in the same medium varies from thermistor to thermistor. Then, the clinician (i.e., an authorized person) starts the intubation process by switching on the device 1 and moving the distal end 2A of the tube 2 towards the pharynx (step 24). At this stage, the clinician has to find the proper location for the distal end 2A, namely the trachea opening. As indicated above, due to even weak breathing of the patient, the air circulation in the vicinity of the trachea opening is higher than that of the vicinity of the esophagus. Accordingly, the temperature in the vicinity of the trachea opening is higher than that of the vicinity of the esophagus. Owing to the fact that the thermistors Ti and T₂ are located at the opposite sides of the distal end 2A, the existence of the difference in the temperatures is indicative of the situation when one thermistor is closer to the trachea opening than the other one. In other words, the end 2A is not exactly aligned with the trachea opening, and should therefore be slightly repositioned.

The programming means 14 is operated by suitable software so as to generate different signals depending on the different values of the temperature difference between the two thermistors Ti and T₂. Consequently, the audio signals generated in response to the data coming from the programming means 14 are different, being of different levels identified by the clinician to realize how to manipulate the distal end 2A. For example, four different audio levels are provided differing in amplitude and frequency. In this case, the one with maximum amplitude and frequency corresponds to the relative location of the distal end being aligned with the trachea opening. Upon identifying such an audio signal, the clinician inserts the distal end into the trachea opening. It is understood, that the clinician waits for the moment of opening the epiglottis, which is defined by the air circulation towards and out of the trachea.

Thus, by manipulating the tube 2, the clinician orients the distal end 2A such that the temperature at both thermistors is the same and at a maximal value, i.e., t^(raax i« t^(max) ₂ (steps 26). This means that the distal end 2 A is aligned with the center of the trachea opening, and, therefore, the clinician can proceed with the intubation process by moving the distal end downwardly into the trachea (step 28). As indicated above, the temperature response is higher at the opening of the trachea than in a deeper region thereof. In other words, the air circulation at the trachea opening is stronger than in the deeper regions. Whilst deepening the distal end 2A of the tube into the trachea, the temperature response decreases. Hence, by controlling the temperature response changes during the downward movement of the distal end up to a preset minimal value (step 30), the extreme position of this end inside the trachea can be detected. At this moment, the insertion of the tube 2 is complete, and its position inside the trachea is fixed by inflating the portion 5 of the tube (step 32). At this stage, the support arrangement 6 may actually be removed from the tube 2, and the end 2B of the tube 2 may be coupled to the air or oxygen-enriched air supply means (a ventilation machine) in a conventional manner.

Reference is now made to Fig. 4 illustrating an intubation device 100 having a somewhat different construction as compared to the device 1. To facilitate understanding, the same reference numbers are used for identifying those components which are common in the devices 1 and 100. In the device 100, a single thermistor T is used being mounted on a tip-end 106A of a pin-like support arrangement 106. This support arrangement 106 may be that conventionally used for guiding the flexible tube 2 into the trachea opening. Such a guiding device, called "mandrin", is typically sufficiently flexible to repeat the form of the tube 2 and sufficiently rigid to slightly force its movement downward. Due to the rigidity of the device 106, its tip end 106A may be maintained at the center of the distal end 2A of the tube 2. The maximal temperature response would thus be provided when the thermistor T is aligned with the central region of the trachea opening. Fig. 5 illustrates yet another example of the intubation device 200, which is intended for both the intubation and functional pulmunologic diagnostics. For this purpose, the device 200 is provided with the pair of thermistors Ti and T₂ supported as described above with reference to Fig. la, and a tube-like probe 204 inserted into the endotracheal tube 2 so as to have inlaid ability to be moved through the bronchial tree segments by the gradual projection of its distal end 204A. An additional thermistor T3 is attached to the distal end 204A, and, when in the operative position of the device 200 (inserted into the trachea), it approaches the branches of the bronchial tree and can enter the patient's lung. The thermistor T3 provides the temperature response to the air circulation in its vicinity, and would indicate the abnormal operation, if any, of certain segments of the patient's terminal bronchial tree, including small segments.

It should be understood that according to circumstances of the environment, the thermistors may also be operated in the mode of conventive heat transfer detection. To this end, they are heated up to a preset temperature prior to the intubation process, and then their temperature changes (i.e., cooling) affected by the air circulation are controlled in the above-described manner. Generally speaking, the temperature response of the thermistors is always indicative of the temperature changes caused by the air circulation.

It should also be noted that the device according to the invention may be used in situations when the patient's breathing is not detectable. To operate the device in such a case, a clinician (i.e., an authorized person) has just to induce an artificial breathing.

It is understood that the commercially available thermistors are very cheap devices, and therefore the entire endotracheal tube equipped with such thermistors could be disposable.

Fig. 6 illustrates a device 300 constructed according to another embodiment of the invention that serves for controlling the circulation of the supplied air or oxygen-enriched air from a ventilation machine 301 into an endotracheal tube 302. In other words, this device controls the operation of the ventilation machine during the entire intubation process. The device 300 comprises a pipe-like adapter 303 coupled to a processor unit (by wires or wireless), which is not specifically shown here. The pipe-like adapter 303 connects the tube 302 to the pipe of the ventilation machine 301. As shown, a pair of thermistors Ti and T₂ (or more than two thermistors) is accommodated at a butt-end 303A of the adapter 303 at its opposite sides, and is coupled to the processor unit through wires (not shown here). The temperature response of the thermistors is indicative of the differences in the laminar airflow. Such a device actually presents a backing control block for the real time control of the parameters of the in- and outflow of air or oxygen-enriched air between the endotracheal tube 302 and the ventilation machine 301.

Those skilled in the art will appreciate that various modifications and changes can be applied to the preferred embodiments of the invention as hereinbefore exemplified without departing from its scope defined in and by the appended claims.

Claims

CLAIMS:

1. An intubation device utilizing an endotracheal tube to be inserted into the patient's trachea opening, the device comprising:

(a) at least one temperature sensor located at a distal end of the endotracheal tube, the sensor generating a temperature response to air circulation in the vicinity thereof;

(c) an indicator coupled to the processor unit for receiving said data and generating an indication signal which can be used for guiding a movement of the distal end of the endotracheal tube into the trachea opening.

2. The device according to Claim 1, wherein the indicator comprises an audio transceiver capable of transmitting different audio indication signals depending on different relative locations of the distal end relative to the trachea opening.

3. The device according to Claim 1, wherein the processor unit is coupled to the temperature sensor through wires passing inside the endotracheal tube.

4. The device according to Claim 1, wherein said at least one temperature sensor is located substantially at a central region of the distal end.

5. The device according to Claim 4, wherein the indication signal corresponding to a maximal value of the temperature response is indicative of that the temperature sensor is aligned with a central region of the trachea opening.

6. The device according to Claim 1, and also comprising an additional temperature sensor coupled to said processor, the two sensors being located substantially at opposite sides of the distal end of endotracheal tube.

7. The device according to Claim 1, and also comprising two additional temperature sensors coupled to said processor, the three sensors are located in a spaced-apart relationship along circumference of the distal end of the tube so as to form three tops of an equilateral triangle.

8. The device according to Claim 6, wherein the indication signal corresponding to substantially equal values of the temperature response produced by the two sensors is indicative of that the distal end of the tube is aligned with a central region of the trachea opening.

9. The device according to Claim 7, wherein the indication signal corresponding to substantially equal values of the temperature response produced by the three sensors is indicative of that the distal end of the tube is aligned with a central region of the trachea opening.

10. The device according to Claim 1, wherein said at least one temperature sensor is supported on an elongated support arrangement insertable into the endotracheal tube.

11. The device according to Claim 10, wherein said support arrangement comprises:

- at least two elongated flexible pins, at least one of them carrying said at least one temperature sensor at its distal end; and

- a ring-like member attached to distal ends of said at least two pins, the ring-like member having a diameter substantially equal to an inner diameter of the endotracheal tube.

12. The device according to Claim 11, wherein said support arrangement has a fixing means for fixing the position of the support arrangement inside the tube such as to prevent its sliding movement through the tube.

13. The device according to Claim 12, wherein said fixing means comprises an upper ring-like member attached to opposite ends of said at least two elongated flexible pins and being capable of circumferentially engaging the opposite end of the endotracheal tube, when in an extreme position of the support arrangement inserted into the endotracheal tube.

14. The device according to Claim 1, and also comprising an elongated thin probe for inserting into the endotracheal tube and an additional temperature sensor mounted on a distal end of the probe for generating a temperature response to air circulation in the vicinity thereof, the distal end of the probe being slidable towards and into the trachea bifurcation.

15. An endotracheal tube comprising at least one temperature sensor

5 accommodated at its distal end, the sensor being capable of generating a temperature response to air circulation in the vicinity of the sensor which is indicative of a relative location of the distal end relative to the patient's trachea opening, and can therefore be used for guiding a movement of the endotracheal tube into the trachea opening. ╬╣o

16. The tube according to Claim 15, wherein said at least one temperature sensor is located substantially at a central region of the distal end.

17. The tube according to Claim 16, wherein a maximal value of the temperature response is indicative of that the temperature sensor is aligned with a central region of the trachea opening.

15 18. The tube according to Claim 15, and also comprising an additional temperature sensor capable of generating a temperature response to air circulation in the vicinity thereof, wherein the two temperature sensors are located substantially at opposite sides of the distal end of the tube, changes between the temperature response generated by the two sensors being indicative of the relative

20 location of the distal end relative to a central region of the trachea opening.

19. The device according to Claim 15, and also comprising two additional temperature sensors coupled to said processor, the three sensors are located in a spaced-apart relationship along circumference of the distal end of the tube so as to form three tops of an equilateral triangle.

25 20. The tube according to Claim 18, wherein substantially equal values of the temperature response produced by the two sensors is indicative of that the distal end of the tube is aligned with a central region of the trachea opening.

21. The device according to Claim 19, wherein the indication signal corresponding to substantially equal values of the temperature response produced by the three sensors is indicative of that the distal end of the tube is aligned with a central region of the trachea opening.

22. A device for real time control of a process of intubation utilizing an endotracheal tube coupled to a ventilation machine supplying air or oxygen-enriched air to the endotracheal tube, the device comprising:

- a pipe-like adapter whose one end is connectable to an end of the endotracheal tube and an the other end is connectable to an outlet of the ventilation machine;

- at least one temperature sensor located at either end of the adapter, the temperature sensor being capable of providing a temperature response to air circulation in the vicinity of the sensor; and

- a processor unit coupled to said at least one temperature sensor for detecting and analyzing said temperature response and generating data representative thereof.

23. A method for intubation utilizing an endotracheal tube, the method comprising the steps of:

(i) providing at least one temperature sensor located at a distal end of said endotracheal tube intended for insertion into the patient's trachea opening, the temperature sensor being capable of generating a temperature response to air circulation in the vicinity of the sensor; (n) whilst moving the distal end of the endotracheal tube towards the trachea opening, detecting and analyzing said temperature response to determine a relative location of the distal end of the tube relative to the trachea opening; (iii) generating an indication signal indicative of the relative location; and (iv) manipulating the distal end of the tube in accordance with the indication signals for guiding a movement of the distal end of the tube into the trachea opening.

24. The method according to Claim 23, wherein said at least one temperature sensor is located substantially at a central region of the distal end of the tube.

25. The method according to Claim 23, wherein the indication signal corresponding to a maximal value of the temperature response is indicative of that the temperature sensor is aligned with a central region of the trachea opening.

26. The method according to Claim 23, and also comprising the steps of: - providing an additional temperature sensor capable of generating a temperature response to air circulation in the vicinity thereof, and locating the two sensors substantially at opposite sides of the distal end of the endotracheal tube;

- whilst moving the distal end of the endotracheal tube towards the trachea opening, detecting and analyzing the temperature response of the additional sensor to detect changes in the temperature response generated by the two sensors and determine said relative location of the distal end of the tube relative to the trachea opening.

27. The method according to Claim 23, and also comprising the steps of:

- providing two additional temperature sensors each capable of generating a temperature response to air circulation in the vicinity thereof, and locating the three sensors in a spaced-apart relationship along circumference of the distal end of the tube so as to form three tops of an equilateral triangle;

- whilst moving the distal end of the endotracheal tube towards the trachea opening, detecting and analyzing the temperature response of the two additional sensor to detect changes in the temperature response generated by the three sensors and determine said relative location of the distal end of the tube relative to the trachea opening.

28. The method according to Claim 24, wherein the indication signal corresponding to substantially equal values of the temperature response produced by the two sensors is indicative of that the distal end of the tube is aligned with a central region of the trachea opening.

29. The method according to Claim 25, wherein the indication signal corresponding to substantially equal values of the temperature response produced by the three sensors is indicative of that the distal end of the tube is aligned with a central region of the trachea opening.