JPH0531192A - Tracheal tube - Google Patents

Abstract

PURPOSE:To prevent various disorders associated with a rise in an internal pressure of a pressure cuff and bag accurately by holding a transmission coefficient of nitrous oxide gas in a pressure cuff and a pilot balloon within different specified ranged to check a rise in the internal pressure of the pressure cuff and bag by the transmission of a narcotic gas with a handy construction. CONSTITUTION:A transmission coefficient of nitrous oxide gas of a pressure cuff 6 is 1X10<-10> to 5X10<-10>ml(STP).cm/cm<2>.seccmHg. The transmission coefficients of the nitrous oxide gases of a pipe and a balloon 9 are 30X10<-10> to 75X10<-10>ml(STP).cm/cm<2>.sec.cmHg. As a result, the nitrous oxide gas in an atmosphere enters into the pressure cuff 6 and an internal pressure of the pressure cuff tends to rise, the nitrous oxide gas is diffused and discharged from a pilot balloon 9. This achieves higher handleability thereby ensuring the strength of the pilot balloon sufficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endotracheal tube used for general anesthesia during surgery, artificial respiration control after surgery, and long-term respiration control.

[0002]

2. Description of the Related Art As shown in FIG.
Is inserted into the trachea 43 of the patient 42 and through the check valve 41 at the rear of the pilot balloon 44, the cuff 4 at the tip is
5 is inflated by pressurization of air using a syringe or the like and is fixed in the trachea 43 so as to seal the trachea, and through a connector 46 and a flexible tube 47 attached to the base thereof, an anesthesia machine or a respirator not shown. Used by connecting to etc.

When anesthesia is performed with laughing gas using such a circuit, laughing gas (N ₂ O) has a very strong permeability and diffusion, and is initially absorbed into the human body for anesthesia. . However, when the laughing gas eventually reaches a saturated state in the human body tissue, it comes to reversely permeate from the tracheal wall into the trachea, and in addition to the laughing gas in the atmosphere, the laughing gas that leaches out, It penetrates into the cuff 45 formed of a flexible vinyl chloride resin thin film. This is because laughing gas is easier to permeate the resin film forming the cuff than the air component. As a result, the internal pressure of the cuff increases.

Further, it has been reported that the cuff that fixes the endotracheal tube inside the trachea and seals the trachea causes various obstacles to the trachea and the like as the internal pressure thereof increases. Specifically, on the tracheal surface, the epidermis is protected by the mucous membrane, and when laughing gas penetrates into the cuff to increase the intracuff pressure as described above, ischemia, ulcers, and perforation of capillaries occur. , Cartilage fracture of the trachea, mucosal formation inhibition, etc. In particular, inhibition of mucous membrane formation seriously damages the vocal cords and trachea.

As a method for solving such a problem,
Either reduce the laughing gas permeability of the cuff itself, or separately provide a hollow body made of a laughing gas permeable material that communicates with the cuff on the outer peripheral surface of the tube body, and laugh through the membrane of this hollow body. It has been proposed to diffuse air gas.
(Japanese Patent Publication No. 01-28587).

However, in the above, when the film of the cuff is made of a conventional material such as polyvinyl chloride resin or silicone resin, the film has to be made thick, and the rigidity of the cuff becomes large, so that the cuff becomes large. When it contracts, a rigid fold may be generated, which may damage the trachea, vocal cords, etc. when the endotracheal tube is intubated.

Further, there is a limit in terms of materials and manufacturing technology in reducing the laughing gas permeability of the cuff itself, and it is impossible to manufacture a cuff that does not allow laughing gas to pass through at all. The pressure inside the cuff rises.

Further, in the above, providing the hollow body separately causes the structure to be complicated.

Further, in the above, the cuff has a high laughing gas permeability (7.66 × 10 ^-9 ml · cm / cm ² · sec · cmHg or more).
Therefore, the hollow body needs more laughing gas permeability,
Therefore, the volume of the hollow body must be increased or the film thickness of the hollow body must be made extremely thin.

When the volume of the hollow body is increased, the hollow body obstructs the face and is an obstacle when the endotracheal tube is inserted into the mouth of the patient.

Further, if the thickness of the hollow body is made thin, the strength of the hollow body becomes insufficient, so that the hollow body is easily damaged, and it is inconvenient and dangerous to handle.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an endotracheal tube which has a simple structure and which can more surely prevent the harmful effects caused by the increase of the internal pressure of the cuff.

[0013]

The above objects are achieved by the present invention described in (1) to (6) below.

(1) A tube body having a main lumen, and provided along the longitudinal direction of the tube body,
A side lumen extending at least near the tip of the tube body, and an inflatable / contractible cuff provided near the tip of the tube body to surround the outer peripheral surface of the tube body and communicating with the side lumen; It has a pilot balloon that communicates with the side lumen and confirms the expansion / contraction state of the cuff, and has a laughing gas permeability coefficient of 1 × 10 ^{−10 to} 5 × 10 ⁻¹⁰ ml (STP) · cm / cm ² · s
ec · cmHg, wherein the laughing gas permeation coefficient of the pilot balloon is 30 × 10 ⁻¹⁰ ml (STP) · cm / cm ² · sec · cmHg or more.

(2) The pilot balloon has a laughing gas permeability coefficient of 30 × 10 ⁻¹⁰ to 75 × 10 ⁻¹⁰ ml (STP) · cm.
The endotracheal tube according to (1) above, which has a pressure of / cm ² · sec · cmHg.

(3) The ratio of the laughing gas permeability coefficient of the cuff to the laughing gas permeability coefficient of the pilot balloon is
The endotracheal tube according to (1) or (2) above, which is 1:15 or more.

(4) The ratio of the inflated volume of the cuff to the inflated volume of the pilot balloon is 1: 0.1.
The endotracheal tube according to any one of (1) to (3) above, wherein the endotracheal tube is 1: 1.

(5) Effective surface area of the cuff when inflated,
The endotracheal tube according to any one of (1) to (4), wherein the ratio of the effective surface area of the pilot balloon when inflated is 1: 0.3 to 1: 1.

(6) The endotracheal tube according to any one of (1) to (5) above, wherein the cuff is made of a film made of a soft fluororesin or a mixture of a soft fluororesin and a thermoplastic resin.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The endotracheal tube of the present invention will now be described in detail with reference to the preferred embodiments shown in the accompanying drawings.

FIG. 1 is a perspective view showing a structural example of the endotracheal tube of the present invention, and FIG. 2 is an enlarged vertical sectional view of a cuff portion of the endotracheal tube shown in FIG.

As shown in these figures, an endotracheal tube 1 is provided along a tube body 2 having a main lumen 3 and a longitudinal direction of the tube body 2, and extends to at least the vicinity of the tip of the tube body 2. The side lumen 5, the cuff 6, which is provided near the tip of the tube body 2 so as to surround the outer peripheral surface of the tube body 2 and communicates with one end of the side lumen 5, and the side lumen 5. It has a pilot balloon 9 in communication with the end to check if the cuff 6 is inflated.

The tube body 2 is made of a flexible material and has a main lumen 3 penetrating from a tip end to a base end for introducing anesthetic gas, oxygen gas and the like. The tip 4 of the tube body 2 is, as shown in FIG.
It is shaped like a smooth bevel for easy insertion into the body. Further, a connector 12 for connecting to the breathing circuit is attached to the other end.

As the constituent material of the tube body 2, soft polyvinyl chloride resin, polyurethane, silicone rubber or the like is preferably used.

The inner wall forming the tube body 2 has a structure shown in FIG.
As shown in, a side lumen 5 thinner than the main lumen 3 is provided along the longitudinal direction of the tube body 2. The side lumen 5 is an inflation lumen for feeding gas into the cuff 6 described later, and is closed in the vicinity of the beveled tip 4 as shown in FIG.

Further, the side lumen 5 communicates with the internal space of the cuff 6 through a side hole (communication hole) 11 formed in the outer surface of the tube wall of the tube body 2 in the cuff 6.

As shown in FIG. 1, the side lumen 5 communicates with the inflation tube 8 at a position near the base end through a notch 7 formed on the outer surface of the tube wall of the tube body 2. .

The inflation tube 8 and the side lumen 5 are connected by, for example, inserting a preheated mandrel into the side lumen 5, and removing the mandrel and inserting the inflation tube 8 into the side lumen 5 at the same time. It is carried out by a method of fixing with a solvent or an adhesive.

The tube body 2 is preferably provided with an X-ray opaque line over the entire length of the tube body 2 in the longitudinal direction. This is because the position of the tube body 2 can be easily confirmed by X-ray contrast.

A cuff 6 capable of expanding and contracting is provided near the tip of the tube main body 2 so as to surround the outer peripheral surface thereof in an annular shape.

The cuff 6 is covered with a film formed in a tubular shape in advance on the outer circumference of the tube body 2 so as to cover the side hole 11, and both ends of the cuff 6 are adhered to the outer circumference of the tube body 2 with an adhesive or a solvent. By adhering or fusing with heat, high frequency, or the like, they are airtightly fixed and attached.

At the rear end of the inflation tube 8, an inflatable and defensible pilot balloon 9 for recognizing the degree of inflation and deflation of the cuff 6 is installed so as to communicate with the inside of the tube 8. .

Further, on the rear end side of the pilot balloon 9, a check valve 10 having a function of allowing the gas to flow into the pilot balloon 9 but preventing the gas from flowing out from the inflated pilot balloon 9 is provided. is set up. When a syringe or the like is connected to the check valve 10 and a gas such as air is pressed in, the gas is stored in the pilot balloon 9,
The inflation tube 8 is fed into the cuff 6 through the side lumen 5 and the side hole 11, and the cuff 6 is inflated.

As will be described later, the pilot balloon 9 is excellent in laughing gas permeability, so that even if laughing gas enters the cuff 6 and the cuff internal pressure tends to rise, this laughing gas Gas can be diffused and discharged from the pilot balloon 9 to suppress an increase in the cuff internal pressure.

The endotracheal tube 1 of the present invention is characterized by the gas permeability and size of the cuff 6 and pilot balloon 9.

The laughing gas permeability coefficient of the cuff 6 is 1 × 10.
^{-10 to} 5 × 10 ^-10 ml (STP) ・ cm / cm ²・ sec ・ cmHg,
Preferably 1 × 10 ^{−10 to} 3 × 10 ⁻¹⁰ ml (STP) · cm / cm ² ·
sec · cmHg, more preferably 1 × 10 ⁻¹⁰ to 2 ×
It is 10 ⁻¹⁰ ml (STP) · cm / cm ² · sec · cmHg. 1 x 10
To obtain a cuff 6 of less than ^-10 ml (STP) · cm / cm ² · sec · cmHg, the rigidity of the cuff 6 becomes large, and 5 × 10 ⁻⁵ ml (STP) ·
If it exceeds cm / cm ² · sec · cmHg, it is necessary to increase the size of the pilot balloon 9 or reduce its film thickness in order to obtain a sufficient laughing gas discharge capability.

The laughing gas permeability coefficient of the pilot balloon 9 is 30 × 10 ^-10 ml (STP) · cm / cm ² · sec · cmHg or more, preferably 30 × 10 ^-10 to 75 × 10 ^-10 ml. (ST
P) · cm / cm ² · sec · cmHg, more preferably 50 ×
It is 10 ⁻¹⁰ to 75 × 10 ⁻¹⁰ ml (STP) · cm / cm ² · sec · cmHg. If it is less than 30 × 10 ⁻¹⁰ ml (STP) · cm / cm ² · sec · cmHg, the size of the pilot balloon 9 must be increased in order to sufficiently obtain the laughing gas discharging ability of the pilot balloon. Because it will disappear. Also, 75
The pilot balloon 9 having a thickness of more than × 10 ^-10 ml (STP) · cm / cm ² · sec · cmHg has a thin film thickness and is insufficient in strength depending on the material.
It is not suitable as a pilot balloon 9 for supplying gas to the.

The ratio of the laughing gas permeability of the cuff 6 to the laughing gas permeability of the pilot balloon 9 is 1:15.
It is preferably not less than 1, more preferably 1:25 or more. This is because if the ratio is less than 1:15, the size of the pilot balloon 9 must be increased in order to obtain a sufficient laughing gas discharge capability of the pilot balloon 9.

If the size of the pilot balloon 9 is too large, it will be inconvenient to handle the endotracheal tube 1 during storage, transportation, use, disposal, etc. If the size of the pilot balloon 9 is too small, the laughing gas discharge capacity will be reduced. Is insufficient. Therefore, the size of the pilot balloon 9 is preferably in the following range in relation to the size of the cuff 6.

That is, the ratio between the inflated volume of the cuff 6 and the inflated volume of the pilot balloon 9 is 1: 0.1.
Is preferably 1: 1 and more preferably 1:
It is 0.4 to 1: 1.

The ratio of the effective surface area of the cuff 6 when inflated to the effective surface area of the pilot balloon 9 when inflated is
It is preferably 1: 0.1 to 1: 1 and more preferably 1: 0.5 to 1: 1.

The constituent material of the film of the cuff 6 may be a conventionally used material such as polyvinyl chloride, silicone, polyurethane, etc., but the laughing gas permeation coefficient as described above can be easily obtained. A soft fluororesin or a mixture of a soft fluororesin and a thermoplastic resin is preferable in that it can be produced.

The soft fluororesin is a resin having the characteristics of the fluororesin and flexibility, and specifically, a resin having the flexibility of the fluororubber and the melt moldability of the fluororesin. is there. Examples of such a resin include a polymer having fluororubber as a backbone and a crystalline fluororesin grafted thereto, or a block polymer of fluororubber and a crystalline fluororesin.

Specifically, in the case of a polymer having a fluororubber as a backbone and a crystalline fluororesin grafted thereto,
A crystalline polymer (side chain) containing at least one fluorine-containing monomer was graft-polymerized onto a fluorine-containing elastic copolymer (main chain) containing a peroxy group in the molecule and having a glass transition temperature of room temperature or lower. Polymers are preferred.

The fluorine-containing elastic copolymer (trunk polymer) as the main chain has a peroxy group of 0.02 to 0.2% by weight, and has a glass transition in order to have sufficient flexibility. A fluoroelastomer having a temperature (Tg) of not higher than room temperature is preferably used as a base, and when particularly high flexibility is to be obtained, it is preferable to select an appropriate composition and composition ratio thereof. For example, vinylidene fluoride (VDF) and hexafluoropropylene (HF
P), terpolymer of VDF and HFP and tetrafluoroethylene (TFE), copolymer of VDF and chlorotrifluoroethylene (CTFE), T
Many conventionally known fluorine-based elastomers such as copolymers of FE and propylene, copolymers of TFE and fluorine-containing vinyl ether, and copolymers of hydrocarbon diene compounds and fluorine-containing monomers. Can be used.

Examples of the crystalline polymer (crystalline fluororesin) containing at least one side chain fluorine-containing monomer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, Examples thereof include a copolymer of TFE and ethylene, a copolymer of CTFE and ethylene, and a copolymer of TFE and fluorine-containing vinyl ether.

The graft copolymer is prepared, for example, by adding a reducing agent and further a metal ion to the trunk polymer latex and, in the presence of these reducing agents, adding to the trunk polymer latex containing a peroxy group, for example, about 20 to 50 ° C. It is produced by graft polymerization by adding a crystalline fluororesin at a low temperature.

As the reducing agent, for example, sodium hydrogen sulfite, sodium sulfite, sodium thiosulfate, sodium persulfate and the like can be used, and as the metal salt, for example,
Salts containing ferric ion, cobalt ion, and copper ion, that is, ferric chloride, cobalt chloride, copper chloride and the like can be used. The amount of these used is determined from the total amount of unsaturated peroxide copolymerized with the charged trunk polymer, and is usually 0.
A reducing agent in an amount of about 5 to 10 times is preferably used.

In the block polymer of fluororubber and crystalline fluororesin, the elastomeric segment is vinylidene fluoride / hexafluoropropylene or pentafluoropropylene / tetrafluoroethylene (molar ratio 1
5 to 90: 5 to 5: 0 to 35) polymer, or perfluoro (C1 to C3 alkyl vinyl ether) / tetrafluoroethylene, vinylidene fluoride (molar ratio 15 to
75: 0 to 85: 0 to 85) polymer and the non-elastomer segment is vinylidene fluoride / tetrafluoroethylene (molar ratio 0 to 100: 0 to 100) polymer, or ethylene / tetrafluoroethylene / hexafluoropropylene, 3, 3, 3 / trifluoroacetic propylene-1,2-trifluoromethyl / 3, 3, 3-preparative Ori hexafluoropropylene -1 or ethylene / perfluoro (C ₁ -C ₃ alkyl vinyl ether) (molar ratio 40
-60: 60-40: 0-30) and the like are preferably used.

The thermoplastic resin used in the mixture of the soft fluororesin and the thermoplastic resin (hereinafter simply referred to as the mixture) includes polyurethane, nylon, polyester, polypropylene, polyethylene, polyolefin elastomer, ethylene-vinyl acetate copolymer. Polymer (EV
A), polystyrene, polybutadiene, or a mixture of any of these is used.

Such a soft fluororesin or mixture has good moldability because it can be molded by heating and melting.
A stable cuff 6 can be manufactured.

The film thickness of the cuff 6 when inflated, particularly the film thickness of the soft fluororesin or the mixture, is 0.1.
Approximately 0.5 mm, particularly 0.1 to 0.2 mm is preferable.

On the other hand, the constituent material of the film of the pilot balloon 9 is not particularly limited, and examples thereof include soft polyvinyl chloride, polyurethane, polyethylene, polypropylene, polyester, EVA, silicone and the like, or a mixture of any of these. Can be mentioned.

The film thickness of the pilot balloon 9 when inflated is preferably about 0.1 to 0.5 mm, particularly preferably about 0.1 to 0.3 mm.

[0055]

EXAMPLES Next, specific examples of the present invention will be described. (Examples 1 to 3) Using a soft polyvinyl chloride resin (containing 100 parts by weight of polyvinyl chloride and 110 parts by weight of a plasticizer (DOP)), an inner diameter of 8 mm, an outer diameter of 11 mm, and a wall thickness of 1.5 mm
Then, a main body tube having a side lumen for inflation having a diameter of 0.3 mm within its wall thickness was produced by extrusion molding. The tip of the main body tube was cut obliquely with respect to the axial direction, and the tip was placed in a heating mold to form a rounded tip. Furthermore, a communication hole with the cuff is provided near the tip of the side lumen, and a mounting hole for the inflation tube is made on the rear end side.The mounting hole is equipped with a check valve at the rear end, and a pilot balloon is provided on the way. The inflation tube having the above was inserted and fixed airtightly.

A tube having an outer diameter of 8.6 mm and a wall thickness of 0.3 mm was prepared using a soft fluororesin (trade name: Cefralsoft G880R, Shore A80, manufactured by Central Glass Co., Ltd.).

Then, the above-mentioned soft fluororesin tube is put into a metal mold whose inner surface has a shape when the cuff is at maximum expansion, one end is closed, and hot air is blown from the other end to melt the tube, After the resin was brought into close contact with the inner surface of the mold, it was cooled to produce a cuff. The characteristics of the cuff are shown in Table 1 below. The thickness of the cuff when inflated is 0.054 to 0.202 mm.
And the numerical values in Table 1 are averages thereof.

As the pilot balloon, a resin obtained by kneading polyvinyl chloride (PVC): polyurethane (PV) at a ratio of 45:55 was used, and three kinds shown in the following Table 1 were prepared in the same manner as the cuff. The PVC in the pilot balloon contains 110 parts by weight of the plasticizer DOP per 100 parts by weight of polyvinyl chloride. Also,
The thickness of the pilot balloon when inflated is 0.084-
It is 0.149 mm, and the numerical value in Table 1 is the average thereof.

Comparative Example 1 A cuff was made of the same material as the pilot balloons of Examples 1 to 3, and the pilot balloon was made of soft polyvinyl chloride (containing 100 parts by weight of polyvinyl chloride and 60 parts by weight of a plasticizer DOP). The endotracheal tubes similar to those in Examples 1 to 3 except for the preparation were prepared.

The thickness of the cuff when inflated is 0.079-
0.160 mm, the thickness of the pilot balloon when inflated is 0.173 to 0.190 mm, and the numerical values in Table 1 are averages thereof.

(Comparative Example 2) As a pilot balloon,
Endotracheal tubes similar to those in Examples 1 to 3 were produced except that the same one as in Comparative Example 1 was used.

The gas permeability coefficient of the cuff and pilot balloon was measured by using a gas permeability measuring device (K-315N type manufactured by Rika Seiki Kogyo Co., Ltd.) as a test device.
The measurement gas was laughing gas (N ₂ O), the measurement method was the pressure method (low vacuum method), the gas pressure was 760 mmHg, and the measurement temperature was 23 ° C.

As the sample used for the measurement, a press film prepared from each roll sheet and cut out by 39 mmφ was used.

[0064]

[Table 1]

<Experiment> Using the experimental apparatus shown in FIG. 4, the intracuff pressures of the endotracheal tubes of Examples 1 to 3 and Comparative Examples 1 and 2 were monitored.

In FIG. 4, 20 is a thermostat (37 ° C.), 21 is a flask, 22 is water, 23 is a syringe (volume 20 ml),
Reference numeral 24 is a flow meter, 25 is a pressure gauge, and 26 is a recorder.

The measurement time was 180 minutes, and the gas used was a mixed gas of laughing gas: oxygen gas = 2: 1.

The maximum cuff pressure value during the measurement is shown in Table 2 below, and the relationship between the contact time of the laughing gas / oxygen mixed gas and the cuff pressure is shown in the graph of FIG. The data for Examples 1 to 3 are almost the same, and are shown overlapping in FIG.

[0069]

[Table 2]

As shown in the graph of FIG. 5, in each of Examples 1 to 3 of the present invention, the rise of the cuff internal pressure is effectively prevented.

[0071]

According to the endotracheal tube of the present invention, with a simple structure, it is possible to suppress an increase in the internal pressure of the cuff due to the permeation of the anesthetic gas, and more surely prevent various adverse effects associated with the increase in the internal pressure of the cuff. it can.

Particularly, since it is not necessary to increase the volume of the pilot balloon or make the pilot balloon thin, the handling is good, the strength of the pilot balloon is sufficiently secured, and the inflation and deflation of the cuff is prevented. Suitable for use as a balloon for confirmation.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration example of an endotracheal tube of the present invention.

FIG. 2 is an enlarged vertical sectional view of a cuff portion of the endotracheal tube shown in FIG.

FIG. 3 is a schematic view showing a usage state of an endotracheal tube.

FIG. 4 is a side view schematically showing an experimental device for confirming the effect of the present invention.

FIG. 5 is a graph showing the relationship between the contact time of the laughing gas / oxygen mixed gas and the cuff internal pressure in the example.

[Explanation of symbols]

1 endotracheal tube 2 tube body 3 main lumens 4 tip 5 side lumens 6 cuffs 7 Notch 8 inflation tubes 9 pilot balloon 10 Check valve 11 side hole 12 connectors 20 constant temperature bath 21 flasks 22 water 23 syringes 24 flow meter 25 pressure gauge 26 recorder 40 endotracheal tube 41 Check valve 42 patients 43 trachea 44 pilot balloon 45 cuff 46 connector 47 serpentine

Claims (6)

[Claims] 1. A tube main body having a main lumen, a side lumen provided along the longitudinal direction of the tube main body, the side lumen extending at least near the distal end of the tube main body, and a tube near the distal end of the tube main body. The cuff is provided so as to surround the outer peripheral surface of the main body, and has an inflatable / contractible cuff that communicates with the side lumen, and a pilot balloon that communicates with the side lumen and that confirms an inflated / contracted state of the cuff. Laughing gas permeability coefficient of 1 × 10 ^{-10 to} 5 × 10
^-10 ml (STP) · cm / cm ² · sec · cmHg, and the pilot balloon has a laughing gas permeability coefficient of 30 × 1.
Endotracheal tube, characterized in that at ^{0 -10 ml (STP) · cm} / cm 2 · sec · cmHg or more. Wherein laughing gas permeability coefficient of the pilot balloon ^{30 × 10 -1 0 ~75 × 10} -10 ml (STP) · cm / cm 2
-The endotracheal tube according to claim 1, which is sec-cmHg. 3. The ratio of the laughing gas permeability coefficient of the cuff to the laughing gas permeability coefficient of the pilot balloon is 1: 1.
The endotracheal tube according to claim 1 or 2, which is 5 or more. 4. The ratio of the inflated volume of the cuff to the inflated volume of the pilot balloon is 1: 0.1.
The endotracheal tube according to any one of claims 1 to 3, which is 1: 1. 5. The ratio of the effective surface area of the cuff when inflated and the effective surface area of the pilot balloon when inflated is:
The endotracheal tube according to any one of claims 1 to 4, which is 1: 0.3 to 1: 1. 6. The endotracheal tube according to claim 1, wherein the cuff is formed of a film made of a soft fluororesin or a mixture of a soft fluororesin and a thermoplastic resin.