Apparatus for monitoring bronchial electrocardiogram and cardiac pacing

Abstract: An intrabronchial catheter (1) has an inflatable balloon (2) with the bronchial ECG lead electrodes (4a, 4b, 4c, 4d). Upon inserting the intrabronchial catheter into the trachea or bronchus of a human body, air is supplied to the balloon (2) so that the balloon is stably retained in the trachea or bronchus, thereby bringing the bronchial ECG lead electrodes (4a, 4b, 4c, 4d) in close contact with the internal wall surface of the trachea or bronchus so as to effectively monitor bronchial electrocardiogram.

Description: This invention relates generally to a bronchial electrocardiogram monitoring apparatus and more particularly to an intrabronchial catheter for use in such apparatus. An electrocardiogram is essential to diagnose possible heart disorders such as arrhythmia and ischemia. There are commonly known body-surface electrocardiography as the most popular electrocardiography widely practiced at present, transesophageal lead electrocardiography capable of precisely diagnosing the cardiac function, intracardiac lead electrocardiography, and intrabronchial electrocardiography. As known, in the body-surface electrocardiography, electrocardiographic (ECG) lead electrodes are located at icanatomically prescribed locations (usually, twelve regions) on the surface of the human body in order to detect an ECG lead current generated by the heart. This medical method is convenient because it can be easily effected by merely attaching the ECG lead electrodes to the surface of the human body. However, since the ECG lead electrodes are positioned at the locations far from the heart, the ECG lead current cannot sufficiently be detected. Particularly, this medical method is not applicable for searching for a location causing cardiac insufficiency. The transesophageal lead electrocardiography is effected by inserting a catheter provided at its leading end portion with ECG lead electrodes into the esophagus through the oral cavity or nasal cavity and bringing the lead electrodes into contact with the internal surface of the esophagus so as to detect the ECG lead current. This medical method enjoys an advantage in that the lead electrodes can be positioned near the heart, especially, the posterior wall of the left atrium of the heart, thereby obtaining more reliable cardiac information compared with the aforenoted the body-surface electrocardiography. However, this medical method demands skill in inserting the catheter into the esophagus and attaching the lead electrodes to the internal wall of the esophagus. Accordingly, this medical method cannot easily be practiced. On the other hand, the intracardiac lead electrocardiography uses a catheter with ECG lead electrodes which is introduced into the heart through thick blood vessels and secured onto the internal wall of the heart in order to directly pick up a lead current. Thus, this is looked on as a medical method capable of obtaining most precise cardiac information. However, this medical method entails a disadvantage such that it cannot easily be effected since it requires remarkably high-level surgical skill for inserting the catheter with the lead electrodes into the heart while applying the X-ray to the human body to secure the lead electrodes onto the anatomically prescribed locations in the heart with a high accuracy. Intrabronchial electrocardiography is similar to the transesophageal lead electrocardiography, but a catheter with ECG lead electrodes is inserted into the trachea or bronchus instead of the esophagus to detect the ECG lead current from the trachea or bronchus. This medical method is effected by positioning the ECG lead electrodes mounted on the leading end portion of the catheter at the bifurcation or the internal surface of at least one of the left and right bronchi in order to detect the ECG lead current near the heart. This intrabronchial electrocardiography also suffers a disadvantage that, though the X-ray irradiation is used in inserting the lead electrodes into the trachea and bronchus, the lead electrodes disposed on the leading end portion of the catheter cannot easily be secured in position on the anatomically prescribed locations in the trachea or bronchus. The fact of the matter is that the catheter can be inserted into the trachea with relative ease because the trachea is hollow at all times, whereas the work of stably positioning the lead electrodes at the optimum locations in the trachea or bronchus often becomes much harder and more time-consuming, and besides, possibly entails the risk of causing a patient pain. Under these circumstances, this medical method is of little use clinically. As noted above, various medical methods for obtaining an electrocardiogram have been so far proposed and applied practically, but as is also apparent from the foregoing, the body-surface electrocardiography makes it impossible to obtain precise cardiac information for diagnosing possible heart disorders, and the transesophageal electrocardiography, intracardiac electrocardiography and intrabronchial electrocardiography disadvantageously call for high-level surgical skill and specific medical equipment and the work of inserting the lead electrodes which consumes much time and labour. However, a need has been earnestly felt for easy and reliable electrocardiography capable of obtaining precise cardiac information for making a diagnosis of heart disorders such as arrhythmia. In the light of the present circumstances, the inventors of this invention have studied intrabronchial electrocardiography and have eventually developed an improved intrabronchial electrocardiography capable of being practiced easily and reliably. As described above, the intrabronchial electrocardiography suffers from the defect that the lead electrodes cannot easily and stably be positioned at the anatomically prescribed locations in the trachea or bronchus. Particularly, the lead electrodes should be kept in close contact with the internal surface of the trachea or bronchus in order to provide a precise electrocardiogram, whereas the conventional intrabronchial electrocardiography has not employed means for stably retaining the lead electrodes at the suitable locations on the internal surface of the trachea or bronchus for effectively picking up the ECG lead current. Moreover, it is inadmissible to dislocate the lead electrodes in the trachea or bronchus, and thus, there has been a great need for a safe, reliable and handy intrabronchial catheter which can be suitably applied for intrabronchial electrocardiography and has ECG lead electrodes capable of being secured reliably onto the anatomically prescribed locations in the trachea or bronchus. To overcome the drawbacks of the conventional apparatus for monitoring bronchial electrocardiogram applicable for intrabronchial electrocardiography, an apparatus can be used capable of stably and reliably monitoring bronchial electrocardiogram with a high accuracy, which has a structure capable of securely and easily retaining ECG lead electrodes at anatomically prescribed locations in the trachea or bronchus, and effectively detecting an ECG lead current. An object of this invention is to provide an apparatus for obtaining a bronchial electrocardiogram, which is applicable not only for intrabronchial electrocardiography, but also for atrial pacing so as to obtain various cardiac information for diagnosing possible heart disorders such as supraventricular tachyarrhythmia and distinguishing supraventricular tachyarrhythmia from ventricular tachycardia while effecting the atrial pacing. To attain the aforementioned objects, according to this invention, a bronchial electrocardiogram apparatus comprising an elastic intrabronchial catheter to be inserted into the trachea or bronchus, the catheter being provided at the leading end portion thereof with at least one inflatable balloon, which is inflatable with air when the catheter has been inserted into the trachea or bronchus; and bronchial ECG lead electrodes mounted on the balloon and connectable, in use, to an electrocardiograph, a pair of the bronchial ECG lead electrodes being for detecting an ECG lead current, (as disclosed in US-A-4383534) is characterised in that another pair of the ECG lead electrodes is adapted to be used for cardiac pacing. In the apparatus according to the invention an air tube may be arranged along the intrabronchial catheter and have a leading end connected to the balloon and a tail end connected to an air pump so as to supply air to the balloon, thereby inflating the balloon. The bronchial ECG lead electrodes may be connected to respective lead wires extending out of the intrabronchial catheter so as to be connected to an electrocardiograph. When inserting the intrabronchial catheter into the trachea or bronchus, the balloon is first kept in its deflated state until the leading end of the intrabronchial catheter arrives at the trachea or bronchus. When the leading end of the catheter reaches a prescribed position in the trachea or bronchus, the balloon is inflated by being supplied with air through the air tube, thereby bringing the bronchial ECG lead electrodes in close contact with the internal wall of the trachea or brochus to effectively pick up an ECG lead current for an electrocardiogram. The invention is described below by way of example with reference to the accompanying drawings, in which; Figure 1 is a partially sectioned side view showing one a bronchial electrocardiogram apparatus; Figure 2 is an explanatory diagram of the apparatus in use; Figure 3 is an enlarged view showing an embodiment of the invention having four ECG lead electrodes mounted in line on one peripheral side of a balloon; Figure 4 is an enlarged view showing another embodiment having four ECG lead electrodes wherein two of these electrodes are mounted on one peripheral side of a balloon and wherein the other two electrodes are attached to the front surface of the balloon. Figure 5 is an enlarged view showing yet another embodiment having four ECG lead electrodes mounted on the other peripheral side of a balloon; Figure 6 is a partially sectioned side view showing a further embodiment having an auxiliary balloon; and, Figure 7 is an enlarged view showing the principal portion of Figure 6. An apparatus for monitoring bronchial electrocardiogram and of the kind to which this invention is applicable is shown in Figures 1 and 2 and basically comprises an intrabronchial catheter 1 to be inserted into the trachea of bronchus, and an inflatable balloon 2 disposed around the outer periphery at the leading end portion of the intrabronchial catheter 1, an air tube 3 for supplying air to the balloon 2 therethrough, and bronchial ECG lead electrodes 4a and 4b mounted on the balloon 2. The intrabronchial catheter 1 is made from an elastic material such as synthetic resins. A tube to be inserted into the trachea T for the purpose of general anesthesia or artificial respiration may be substituted for the intrabronchial catheter 1. Therefore, the catheter 1 is provided at the tail end portion thereof with a connector 5 of a kind which is generally utilized in an air supply tube connected to an artificial respirator. The balloon 2 mounted on the leading end portion of the catheter 1 is made of a thin membrane of synthetic resin or rubber, and shaped as a bag enveloping the leading end portion of the catheter 1. The balloon 2 assumes a deflated state in its normal condition and is inflated by being supplied with air when the catheter 1 is completely inserted into the trachea as illustrated in Figure 2. The balloon 2 mounted on the catheter 1 has a function of not only fixedly retaining the leading end portion of the catheter 1 at a prescribed location in the trachea T, but also preventing the air introduced into the lungs through the outside periphery of the catheter 1 from leaking out. Therefore, the balloon 2 is designed so that the outer surface thereof comes into tight contact with the internal wall surface of the trachea or bronchus when inflated with a supply of air. The air tube 3 enters inside the catheter 1 from the middle portion of the catheter and extends toward the leading end portion of the catheter along the internal surface of the catheter. Where the air tube 3 reaches the balloon 2, the air tube 3 pierces the wall of the catheter to be connected to the balloon. The air tube 3 is provided at the tail end thereof with a check valve 6 through which it is connected to an air pump 7 so as to supply the air to the balloon 2. Though the air pump 7 fundamentally serves to supply the air to the balloon 2, it may possess a function of releasing the air in the balloon 2 by force to deflate the balloon. Bronchial ECG lead electrodes 4a and 4b are secured on the surface of the balloon 2 at prescribed intervals. The ECG lead electrodes are connected to respective lead wires 8 extending along the internal wall surface of the catheter 1 in the same manner as the air tube 3. The tail ends of the ECG lead electrodes have external terminals 9a and 9b connected to a not-shown electrocardiograph. The locations at which the bronchial ECG lead electrodes 4a and 4b are attached to the balloon 2 are variously determined in accordance with the material of the balloon. In a case of using the balloon of non-conductive material such as rubber, the ECG lead electrodes may be attached to the outside of the membrane of the balloon. However, the ECG lead electrodes may be arbitrarily disposed on either side of the membrane of the balloon. In either case, the ECG lead electrodes must be secured so as not to fall away from the balloon when inserting the catheter into the trachea. Therefore, it is preferable to partially bury each electrode in the membrane of the balloon so as to expose a part of the electrode outside to ensure an electrical connection of the electrode to the internal wall surface of the trachea. The aforementioned intrabronchial catheter 1 is applied practically in performing general anesthesia or inserted into the trachea T through the oral cavity or nasal cavity as illustrated in Figure 2. The intrabronchial catheter 1 is introduced until the leading end thereof reaches the bifurcation Y of the trachea in the same way as a tube for general anesthesia. The bronchial ECG lead electrodes can easily be inserted into the trachea and located at the anatomically prescribed position on the bifurcation Y of the trachea by a person who has some experience of practicing medicine. When the leading end of the catheter reaches the anatomically prescribed location on the bifurcation Y of the trachea, air is supplied to the balloon 2 through the air tube 3 to inflate the balloon. As mentioned above, the balloon 2 is inflated with air in the trachea, thereby bringing the outer surface of the balloon into tight contact with the internal wall surface of the trachea. Consequently, the ECG lead electrodes 4a and 4b are stably fixed in close contact with the internal wall surface of the trachea, to thereby enable the ECG lead current to be detected through the lead wires 8. When removing the catheter 1 from the trachea, the air in the balloon 2 is released through the air tube 3 by operating the air pump, thereby deflating the balloon. As illustrated, the catheter 1 has the connector 5 at the tail end thereof to enable use of common tube for general anesthesia or artificial respiration and as the catheter 1, but the connector 5 is by no means necessary to this invention. Furthermore, the balloon 2 will be provided with a plurality of ECG lead electrodes arranged on the membrane of the balloon at intervals. Also, when using the plurality of ECG lead electrodes, the electrodes must fundamentally be disposed in pairs, but the number of the electrodes should not be understood as limitative. Figures 3 to 5 illustrate embodiments of catheters according to the invention each having additional bronchial ECG lead electrodes 4c and 4d on the balloon 2. These catheters can be applied for not only obtaining a bronchial electrocardiogram, but also effecting cardiac pacing. In the embodiment shown in Figure 3, four bronchial ECG lead electrodes 4a, 4b, 4c and 4d are arranged on the left side portion of the membrane of the balloon 2 in line in the lengthwise direction of the catheter. It is possible to use the pair of ECG lead electrodes 4a and 4c used for obtaining an electrocardiogram, and the pair of ECG lead electrodes 4b and 4d for cardiac pacing. The two pairs of ECG lead electrodes are arranged in line alternatively at regular intervals so as to ensure a sufficient distance between the paired electrodes for effectively detecting the ECG lead current. Thus, when practicing cardiac pacing, the ECG lead electrodes sufficiently separated can be applied to detect a faint pacing current, and therefore, a patient will little feel an unpleasant sensation such as a cauterized feeling. The ECG lead electrodes arranged in line in this embodiment are separated by a distance of about 20 mm so as to leave a distance of 40 mm between the electrodes 4a-4c and 4b-4d which are substantially paired off. In the embodiment shown in Figure 4, two bronchial ECG lead electrodes 4a and 4b are attached to the peripheral side surface of the balloon 2, and another set of two bronchial ECG lead electrodes 4c and 4d are attached to the front surface of the balloon. The embodiment shown in Figure 5 has four bronchial ECG lead electrodes 4a, 4b, 4c and 4d arranged in line on the right side surface of the balloon 2. These embodiments having the different arrangements of the ECG lead electrodes might be expected to change the electrocardiogram. But, the inventors experimentally produced some intrabronchial catheters based on these embodiments for ascertaining the cardiac pacing performance, but the difference among them was not noticeable even on careful observation. As was touched on earlier, the bronchial ECG lead electrodes can easily be inserted into the trachea and located at the anatomically prescribed position on the bifurcation Y of the trachea by a person skilled in practicing medicine. However, if the inflated balloon 2 slightly deviates from the prescribed position on the bifurcation Y, thereby separating the ECG lead electrodes from the anatomically prescribed locations in the trachea or bronchus, the electrocardiogram is not affected too much. Next, a modified embodiment of the apparatus for obtaining a bronchial electrocardiogram according to this invention will be described with reference to Figure 6 and Figure 7. The apparatus in this embodiment has an auxiliary balloon 11 for supporting the intrabronchial catheter 1 in addition to the balloon 2 with the ECG lead electrodes 12a and 12b. The auxiliary balloon 11 is disposed spaced from the primary balloon 2 at the leading end portion of the catheter 1 by a suitable distance. The auxiliary balloon 11 is connected to an air tube 13 which extends along the internal surface of the catheter 1 in the same manner as the air tube 3 connected to the primary balloon 2. Similarly to the air tube 3 with the check valve 6, the air tube 13 is also provided at the tail end thereof with a check valve 14 through which the air tube 13 is connected to an air pump. By selectively operating the air pumps, the balloons 2 and 11 can be optionally inflated or deflated. The ECG lead electrodes 12a and 12b in this embodiment are connected to external terminals 9a and 9b through lead wires 8 extending along the internal surface of the catheter 1. The ECG lead electrodes 12a and 12b are disposed one on either side of the outer surface of the balloon 2, and can be used as electrodes for electrocardiogram or cardiac pacing. In the illustrated embodiment, reference numeral 17 denotes vent holes formed in the leading end portion 1a of the catheter 1 between the balloons 2 and 11. The intrabronchial catheter 1 in this embodiment is inserted into the trachea until the balloon 2 reaches the bifurcation Y of the trachea, and thereafter, both the balloons 2 and 11 are inflated by being supplied with air through the respective air tubes. The balloon 2 may be inserted into the right or left bronchus B1 or B2. In Figure 7, the balloon 2 is inserted into the left bronchus B2 and inflated with air, thereby bringing the ECG lead electrodes 12a and 12b into close contact with the internal wall surface of the bronchus. The vent holes 17 serves as paths for permitting air to flow into the right bronchus B1 therethrough. The intrabronchial catheter 1 in this embodiment is inserted across the bifurcation Y of the bronchus B2 so that the ECG lead electrodes 12a and 12b can be brought further close to the heart. Therefore, precise cardiac measurement or cardiac pacing can be effected with ease. To facilitate the insertion of the intrabronchial catheter into the trachea and further into the bronchus having a smaller inner diameter than the trachea, it is desirable to made the balloon 2 smaller in diameter when being inflated than the inflated balloon 11, and the part 1a of the intrabronchial catheter between the balloons 2 and 11 may preferably be made rather small in diameter. As is described above, the apparatus according to this invention was fundamentally developed for the purpose of monitoring bronchial electrocardiogram for diagnosing the cardiac function, and can be effectively applied to transbronchial atrial pacing which is effected by inserting the intrabronchial catheter into the bronchus near the atrium of the heart in the manner identical to transesophageal atrial pacing which is effected by inserting pacing electrodes into the esophagus. When practicing the transbronchial atrial pacing by using the apparatus according to this invention, the connection of the bronchial ECG lead electrodes mounted on the balloon in this invention may be switched from an electrocardiograph to a pacing device for imparting electrical stimulation to the heart. However, since the atrial pacing which is generally effected while monitoring the cardiac function requires plural sets of the bronchial ECG lead electrodes, namely, at least four ECG lead electrodes are necessary. Also, the ECG lead electrodes are required to be arranged at regular intervals as described above. In this respect, the apparatus of this invention has a rational structure capable of arranging the ECG lead electrodes at regular intervals on the surface of the balloon by alternatively positioning the ECG lead electrodes in pairs, thereby to automatically position the bronchial ECG lead electrodes on the anatomically prescribed locations on the inernal surface of the trachea or bronchus. As is apparent from the description given in detail above, according to this invention, by inserting the intra-bronchial catheter into the trachea or bronchus and supplying air to the balloon through the air tube to inflate the balloon in the trachea or bronchus, the bronchial ECG lead electrodes can easily be secured stably in close contact with the internal wall surface of the trachea or bronchus. Besides, by releasing the air from the inflated balloon, the ECG lead electrodes can safely be pulled out from the trachea or bronchus with ease. Thus, the present invention enables the intra-bronchial catheter of this invention to be easily inserted into the trachea or bronchus and the bronchial ECG lead electrodes to be reliably positioned the anatomically prescribed locations in the trachea or bronchus near the heart, and proves advantageous in obtaining a bronchial electrocardiogram. Since the bronchial ECG lead electrodes can be secured close to an atrium of the heart, the apparatus of this invention can be efficiently used for not only detecting an ECG lead current for an electrocardiogram, but also effecting atrial pacing. Furthermore, since the intrabronchial catheter of this invention can be used as a tube for general anesthesia or artificial respiration, it is convenient from the standpoint of medical treatment to effect the general anesthesia or artificial respiration while observing an electrocardiogram. As described above, since the apparatus for monitoring bronchial electrocardiogram according to this invention can be effectually applied for not only intrabronchial electrocardiography, but also atrial pacing, various cardiac information for diagnosing possible heart disorders such as supraventricular tachyarrhythmia and distinguishing supraventricular tachyarrhythmia from ventricular tachycardia can be reliably obtained with ease.

Claims: A bronchial electrocardiogram apparatus comprising an elastic intrabronchial catheter (1) to be inserted into the trachea or bronchus, the catheter (1) being provided at the leading end portion thereof with at least one inflatable balloon (2), which is inflatable with air when the catheter has been inserted into the trachea or bronchus; and bronchial ECG lead electrodes (4a,4b,4c,4d) mounted on the balloon and connectable, in use, to an electrocardiograph, a pair of the bronchial ECG lead electrodes (4a,4c) being for detecting an ECG lead current; characterised in that another pair of the ECG lead electrodes (4b,4d) is adapted to be used for cardiac pacing. An apparatus according to claim 1, in which the bronchial ECG lead electrodes (4a,4b,4c,4d) are arranged at prescribed intervals. An apparatus according to claim 1 or claim 2, in which the balloon (2) is connected to an air tube (3) through which air can be supplied to inflate the balloon. An apparatus according to claim 3, in which the air tube (3) is connected to an air pump (7) for supplying air to the balloon (2). An apparatus according to claim 4, in which the air tube (3) is connected to the air pump (7) through a check valve (6). An apparatus according to any one of the preceding claims, in which the catheter (1) is provided with a connector (5) to be connected to an air supply tube of an artificial respirator. An apparatus according to any one of the preceding claims, in which the ECG lead electrodes (4a,4b,4c,4d) are connected to respective lead wires (8) which extend along an internal wall surface of said catheter (1) and are connected to external terminals (9a,9b). Apparatus according to any one of the preceding claims, in which the bronchial ECG lead electrodes (4a,4b,4c,4d) are arranged in line in the longitudinal direction of the catheter. An apparatus according to any one of claims 1 to 7, in which the catheter (1) has a peripheral side surface on which one pair of the ECG lead electrodes (4a,4b) are mounted and a front surface on which said another pair of the ECG lead electrodes (4c,4d) are mounted. An apparatus according to any one of the preceding claims, in which an auxiliary balloon (11) is disposed on the catheter (1) spaced from the balloon (2). An apparatus according to claim 10, in which the catheter (1) has one or more vent holes (17) formed between the balloons (2,11).

Inventors: KAJIWARA NAGAO, WATANABE TAKAYOSHI, KAJIWARA, NAGAO, WATANABE, TAKAYOSHI
Applicants: KAJIWARA NAGAO, WATANABE TAKAYOSHI, KAJIWARA, NAGAO, WATANABE, TAKAYOSHI
Application year: 1992
Main classification: A61B5
IPC codes: A61B5, A61M25