CN1374137A

CN1374137A - Tracheal catheter position detecting method

Info

Publication number: CN1374137A
Application number: CN 01105630
Authority: CN
Inventors: 潘卫江
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-03-08
Filing date: 2001-03-08
Publication date: 2002-10-16

Abstract

The present invention is one kind of tracheal catheter position detecting method and one kind of relevant tracheal catheter. The tracheal catheter has small magnet embedded to the wall. One tracheal catheter position detector, comprising Hall sensor probe, operation amplifier, A/D converter and microprocessor, is used to detect the magnetic field generated by the small magnet and locates the small magnet and thus the tracheal catheter based on the change in magnetic field strength. By means of the small magnets on tracheal catheter, the present invention can judge whether the tracheal catheter is inserted in tracheal or in esophagus and whether the inserted depth is altered.

Description

A kind of tracheal catheter position detecting method

The present invention relates to a kind of medical detection method, particularly a kind of method that the position of endotracheal tube is detected.The invention still further relates to a kind of endotracheal tube that is used for this method.

Medically, when being the artificial respiration, endotracheal tube connects a breather line of patient's trachea and respirator, and its end inserts in the patient's trachea, and the other end links to each other with respirator.Existing endotracheal tube is generally by tube wall, and tube chamber and air bag three parts are formed.It is the first step that practices artificial respiration that endotracheal tube is inserted trachea, and the intubate quality has influence on patient's life security.Associated, there are three problems at present clinically: the one, how to judge that endotracheal tube is inserted in the trachea or has entered into esophagus, the 2nd, how to judge tube insertion depth, the 3rd, how to judge that endotracheal tube is in endotracheal displacement.For first problem, the method of judging clinically mainly contains at present: China-Japan Friendship Hospital's journal total the 40th phase of in November, 1997 the 317th page of end-tidal CO2 detection method that goes up introduction, " foreign medical science " anesthesia is gone up the chemical reagent paper variable color method of introducing with the 307th page of recovery fascicle the 5th phase of July in 1996, the acoustic reflection method of U.S. Anesthesiolopy magazine total the 92nd phase 1293-1299 page or leaf introduction in 2000, the airbag aeration method of U.S. Anesthesiology magazine total the 88th phase 898-902 page or leaf introduction in 1998.There is inconvenient operation in end-tidal CO2 detection method, the deficiency that cost is high; Chemistry reagent paper variable color method is subject to the influence of ambient temperature and humidity; Acoustic reflection method practicality is relatively poor; Airbag aeration method accuracy is not high.For second and the 3rd problem, still do not see solution at present.

The objective of the invention is by the position of endotracheal tube in trachea detected, solve and how to judge that endotracheal tube is inserted in the trachea or has entered into esophagus, how to judge the degree of depth that endotracheal tube inserts, how to judge conduit in problems such as endotracheal displacements, to improve the safety of endotracheal tube intubate.

For achieving the above object, the present invention at first improves the endotracheal tube that generally uses at present, embeds small magnet on its front end tube wall, in order to produce magnetic field.Secondly pop one's head in Hall element, operational amplifier, A/D converter (ADC), microprocessor has constituted the tracheal catheter position checkout gear, detects in order to the magnetic field that small magnet is produced.

According to electromagnetic theory, magnetic field intensity with square speed that the is directly proportional decay of distance, therefore, along with the increase of probe with the distance of Magnetic Field Source, the magnetic field intensity that Magnetic Field Source produces can sharply weaken, if measure the variable quantity that the variable quantity of magnetic field intensity can be measured both space lengths.Hall element is a kind of Sensitive Apparatus that can be transformed into magnetic field intensity voltage, can know corresponding magnitude of field intensity by the voltage swing of measuring Hall element output.Like this, just can know space length between Hall element and the Magnetic Field Source according to the voltage swing of measuring Hall element output.When Magnetic Field Source is a small magnet on the said endotracheal tube, Hall element is fixed on pars cervicalis tracheae top on the skin of glottis the time, change in voltage by Hall element output can be known the variation of the space length between small magnet and the glottis, thereby small magnet and endotracheal tube are made the location.The design of assay method is as follows:

During intubate, small magnet along with the motion of endotracheal tube near Hall element probe, the Hall element probe detection to magnetic field intensity will strengthen gradually or reduce, be to strengthen or reduce relevant with the relative polarity of Magnet and Hall element probe placement.In the time of under small magnet is popped one's head in by Hall element, it is maximum or minimum that the magnetic field intensity that detects reaches.If this maximum or the minima magnetic field intensity when not having small magnet to exist is compared, both differences can think then that greater than certain preset threshold value endotracheal tube is inserted in the trachea, if less than this threshold value then think and be inserted in the esophagus.Further, embed a small magnet, passed through glottis, can judge that then insertion depth is enough as long as detect this small magnet so if on the endotracheal tube wall, equal the place of the degree of depth of needs insertion.Wanting to detect endotracheal tube has not displacement in trachea, can pop one's head in by mobile Hall element above trachea, finds out the maximum or minimum place of magnetic field intensity, then promptly is place, small magnet place below this point.If fixing Hall element probe herein, later detected magnetic field intensity change and send displacement when surpassing certain threshold value and report to the police.

The said tracheal catheter position detecting method of the present invention, the characteristic of utilizing magnetic field intensity to be directly proportional with space length and to decay, can locate small magnet by the variation that detects magnetic field, because small magnet can be embedded on the certain position of endotracheal tube, thereby the position of endotracheal tube has also promptly been known in the position of having known small magnet, through clinical trial, can produce a desired effect.

Below in conjunction with accompanying drawing most preferred embodiment is elaborated.

Fig. 1 is the structural representation of endotracheal tube most preferred embodiment of the present invention.

Fig. 2 is the circuit diagram of tracheal catheter position checkout gear most preferred embodiment of the present invention.

Fig. 3 is the system block diagram of most preferred embodiment of the present invention.

Fig. 4-the 8th, the program flow diagram of the microprocessor in the tracheal catheter position checkout gear of the present invention.

Endotracheal tube among Fig. 1 is by tube chamber (1), and tube wall (6), and air bag (3) composition are to be embedded with on the tube wall small magnet (2) and (4) with the present generally difference of the endotracheal tube of use, and they can be made with high performance magnetic material, for example nd-fe-b magnet.The size of small magnet decides according to the diameter and the pipe thickness of conduit, guarantee under the enough situations of magnetic field intensity the smaller the better.Small magnet height in this example is 1.5mm, and diameter is 3.0mm.Small magnet requires decision in supravasal quantity and position distribution by detecting.For example, Magnet (4) is positioned on the conduit antetheca between air bag (3) and the head end (5), can detect endotracheal tube head end (5) and whether enter glottis, thereby can judge early that endotracheal tube is inserted in the trachea or is inserted in the esophagus; Magnet (2) is positioned on the conduit antetheca behind the air bag, can detect the degree of depth and the monitoring endotracheal tube that endotracheal tube inserts and be shifted in trachea.

UGN3503A is adopted in Hall element among Fig. 2 (41) and (42), when supply voltage is 5.0V, output voltage is not about 2.5V when having external magnetic field to exist, when magnetic field intensity changes in 0-900G (Gauss) scope, because the sensitivity of UGN3505A is 1.3mV/G, so the UGN3503A output voltage will be on the basis of 2.5V increases or reduces with the ratio of 1.3mV/G.For improving sensitivity, interference such as reduce that temperature is floated, among the figure with two UGN3503A polar phase replicates probe of the Hall element in the composition diagram 3 (40) together, output voltage enters among the three computing instrumentation amplifier AD620 (53) with differential form with electric bridge (51), send into after 500 times among the built-in A/D converter ADC (62) of microprocessor (61) through amplifying, the changes of magnetic field of 1G can produce the change in voltage of 0.65V at this moment, and the voltage that promptly enters ADC (62) is 1.85V or 3.15V.Convert the digital quantity of nominal magnetic field intensity after program in the microprocessor is measured the voltage analog of sending into to, and on liquid crystal (70), show by display routine.

Fig. 3-8 is in order to illustrate whole testing process:

Glottis (2) is the section start of trachea (9), and glottis (2) has tangible sign at the cervical region body surface, and promptly thyroid cartilage (6) can be touched with hands.During measurement Hall element popped one's head in (40) be fixed on thyroid cartilage (6) and locate, microprocessor (60) in the tracheal catheter position checkout gear (7) carries out 10 times earlier and detects after powering on, there is not the small magnet effect this moment, what measure is magnetic field intensity in the air, and the meansigma methods of getting these 10 measured values is as the reference value.The front end of endotracheal tube when intubate begins (1) moves closer to glottis (2), is subjected to the effect of small magnet (5), and Hall element probe (40) detected magnetic field intensity increases gradually.Locate at thyroid cartilage (6), skin surface generally is no more than 1.0cm to inner surface of trachea, and when small magnet (5) passed through glottis (2), Hall element probe (40) detected magnetic field intensity had been compared significant change with reference value, can reach more than the 0.8V after measured.Preestablish a threshold value, for example 0.5V with this change of magnetic field strength value and threshold, surpasses the threshold value buzzer warning if change, and judges that then small magnet (5) has entered glottis (2).If after this continue to insert conduit, hear again when reporting to the police and to judge that small magnet (4) has also entered glottis (2).It is generally acknowledged clinically air bag (3) on the endotracheal tube enter glottis after catheter depth enough, and after small magnet (4) is positioned at air bag (3), may command insertion depth in view of the above.

When endotracheal tube inserts esophagus (11), because the diameter of adult's trachea is generally 1.5-2.0cm, esophagus is positioned at the trachea back, add the soft tissue (12) between trachea and the esophagus, detected magnetic field intensity when this moment, Hall element probe (40) detected magnetic field intensity will be in endotracheal tube be inserted in trachea is compared with reference value, and both is poor, changing value does not occur reporting to the police less than threshold value less than 0.1V after measured.Same when continuing to insert, when small magnet (4) can not occur reporting to the police during by glottis yet, thereby can judge that conduit inserts in the esophagus.Fig. 5 is the program flow diagram of this process.

After inserting trachea, endotracheal tube also can position again, method is as follows: move Hall element probe (40) at cervical region, show two values on the liquid crystal, one is the field strength values of detected this point, maximum or minima in another magnetic field intensity that is in the moving process to be surveyed, in the program shown in Figure 4, when increasing to certain maximum gradually, the continuous measurement value diminishes gradually again, or increase gradually again when being varied down to certain minima gradually, this turning point is an extreme value from mathematics, might be maximum or the minima in the whole measured value, buzzer is reported to the police at this value place, the operator is by comparing the show value of this moment, can find magnetic field intensity be maximum or minimum a bit, this point is following over against small magnet, as long as measure Hall element probe (40) is promptly known endotracheal tube to the distance of thyroid cartilage (6) insertion depth.Further, in magnetic field intensity is fixedly Hall element probe (40) of maximum or smallest point place, and select 10 average value measured of this moment to be worth by the button (92) among Fig. 2 as reference, if after this between endotracheal tube (1) and the trachea (9) obvious displacement is arranged, can report to the police when the change of magnetic field strength that then detects surpasses threshold value, thereby can monitor the endotracheal tube slippage.

Above said threshold value be a predefined value, it and measured's tracheal diameter, factors such as skin and subcutaneous tissue thickness are relevant.The size of threshold value influences the accuracy of detection sensitivity and judgement.Generally according to clinical substantive test data, set a threshold constant when start, later on if desired, can adjust by the button (91) of Fig. 2 according to measured's situation, Fig. 6 is the flow chart of the subprogram that the control threshold value is adjusted in the microprocessor.

Above said reference value define three kinds of methods, a kind of is to adopt the method for measuring and remaining unchanged after the start, another kind be by button (92) with the meansigma methods of certain 10 measured value constantly as with reference to value and remain unchanged, both can use flowcharting shown in Figure 7.The third method is applicable to the situation when the slow variation in magnetic field is apparent in view in the air, available subprogram shown in Figure 8 is determined reference value with adaptive method, if the maximum in this method between successive 10 measured values changes less than certain threshold value, then the meansigma methods with these 10 measured values is worth as reference, so the reference value that this method is determined is a dynamic value.Can select by the button among Fig. 2 (93).

Claims

1 one kinds of endotracheal tubes, by tube wall, tube chamber and air bag are formed, and it is characterized in that, are embedded with small magnet on the tube wall.

2 according to the said endotracheal tube of claim 1, it is characterized in that, a small magnet is only arranged and on the conduit antetheca between air bag and the conduit head end, or a small magnet is only arranged and is positioned on the conduit antetheca after the air bag.

3 according to the said endotracheal tube of claim 1, it is characterized in that, two small magnets are only arranged, and wherein a small magnet is on the conduit antetheca between air bag and the conduit head end, and another small magnet is positioned on the air bag conduit antetheca afterwards.

4 one kinds of methods that detect tracheal catheter position, this method is by claim 1, said endotracheal tube and pop one's head in 2 or 3 by Hall element, operational amplifier, A/D converter, the tracheal catheter position checkout gear that microprocessor constitutes is realized, it is characterized in that microprocessor execution following steps:

When a) if the said endotracheal tube of claim 1 is inserted into, by being fixed in the Hall element probe on measured's cervical region thyroid cartilage place skin, detected magnetic field intensity is after the A/D converter conversion, compare with reference value, if both difference is greater than threshold value, buzzer sends warning, show that endotracheal tube is inserted in the trachea, if both differences are less than threshold value, buzzer is not reported to the police, and shows that trachea has been inserted in the esophagus; After if the small magnet on the said endotracheal tube is positioned at air bag, reports to the police and represent that also the endotracheal tube insertion depth is enough.

B) after the endotracheal tube in the right requirement 1 has inserted trachea, move Hall element when probe at the skin place above the pars cervicalis tracheae along the trachea y direction, liquid crystal illustrates maximum and the minima in all measured values in the measured value of this point and the moving process, when increasing to certain maximum gradually, the continuous measurement value diminishes gradually again, or increase gradually again when being varied down to certain minima gradually, then at this maximum place or minima place buzzer warning, show that this some below is over against small magnet.

C) when requiring the endotracheal tube in 1, right inserted trachea, after the Hall element probe has found the position at small magnet place, fixedly Hall element is popped one's head on the corresponding skin of this point, pass through button, the measured value of selecting this moment is as the reference value, after this if the magnetic field intensity that detects and the difference of reference value are greater than threshold value, and buzzer warning represents that displacement has taken place endotracheal tube in trachea.

Said tracheal catheter position checkout gear is characterized in that in 5 claim 4, and an operation sequence is controlled determining of reference value according to the selection of button in the microprocessor.

Said tracheal catheter position checkout gear is characterized in that in 6 claim 4, and an operation sequence is controlled determining of threshold value according to the selection of button in the microprocessor.