US3616796A - Humidified respiratory tube and method - Google Patents

Abstract

A SYSTEM FOR HUMIDIFYING AND DELIVERING GASES SUCH AS AIR OR OXYGEN TO A PATIENT FROM RESPIRATOR, ANESTHESIA MACHINE OR OXYGEN OUTLET. THE SYSTEM INCLUDES A COMPOSITE TUBE FORMED FROM AN INNER WATER PERMEABLE TUBE THROUGH WHICH THE GAS FLOWS AND AN OUTER TUBE WHICH SURROUNDS THE INNER TUBE TO DEFINE A JACKET ABOUT THE INNER TUBE. WARM WATER IS CAUSED TO FLOW THROUGH THE JACKET AND

PERMEATES THE INNER TUBE SO THAT THE WATER IS EXPOSED AND ABSORBED BY THE AIR STREAM. THE OUTLET FROM THE INNER TUBNE IS DIRECTED TO THE PATIENT WHO RECEIVES THE HUMIDIFIED, CONDITION GAS.

Description

NW3 R. R. JACKSON HUMIDIFIED RESPIRATORY TUBE AND METHOD Filed June 30, 1969 TO lll- PATIENT RESPIRATOR FIG! / Ill/l INVENTOR RICHARD R. JACKSON ATTORNEYS United States Patent 3,616,796 HUMIDIFIED RESPIRATORY TUBE AND METHOD Richard Robert Jackson, 8 Trinity Road, Marblehead, Mass. 01945 Filed June 30, 1969, Ser. No. 837,397 Int. Cl. A62b 7/02 U.S. Cl. 128212 Claims ABSTRACT OF THE DISCLOSURE A system for humidifying and delivering gases such as air or oxygen to a patient from a respirator, anesthesia machine or oxygen outlet. The system includes a composite tube formed from an inner water permeable tube through which the gas flows and an outer tube which surrounds the inner tube to define a jacket about the inner tube. Warm water is caused to flow through the jacket and permeates the inner tube so that the water is exposed and absorbed by the air stream. The outlet from the inner tube is directed to the patient who receives the humidified, conditioned gas.

SUMMARY OF THE INVENTION My invention relates to the humidification of air or other gases and more particularly to respiratory systems, and an improved system for delivering moist, conditioned air to a patient.

In treating patients it is necessary frequently to promote or induce breathing by delivering air to the patient through a tube which may direct the air or oxygen into a hood or tent or face mask placed about the patients head or directly into the patients trachea or nasal passage by an endotracheal tube or nasal catheter. In order to avoid discomfort and possible danger to the patient, the air must be sufliciently moist to insure that the patients airway, nose, throat, windpipe, and lungs does not become dry. Accordingly, a number of arrangements have been proposed and employed in the prior art to humidity the air directed to the patient.

One of the more common systems employs an atomizer or nebulizer which disperses, mechanically, the water into tiny droplets and then combines the tiny droplets with the air stream directed to the patient. These systems present some difiiculties in that it is difiicult to control accurately the temperature of the conditioned air delivered to the patient. Additionally, some of the water droplets may tend to condense or become attracted to the Walls of the delivery tube thus reducing the moisture content of the air delivered to the patient and obstructing the tube, particularly in its lower portions.

Another technique employed is to inject heated water vapor into the air stream before it is delivered to the patient. The vaporizing devices employed in this technique, as well as the devices employed to nebulize the water, have enlarged air chambers which are filled with a volume of compressible air. When used to treat patients having stiff or hardened lungs these devices may present some difficulties resulting from the necessity of delivering air or other gas to the patient under high pressures in order to ventilate or force feed his lungs. A portion of the volume of gas to be delivered remains stored and compressed in the enlarged chamber thus making this volume unavailable to the patient for expansion of his lungs.

My invention overcomes the foregoing difficulties of the prior techniques. The invention employs few mechanical parts and does not need a separate nebulizer or vaporizer. The simplicity of the device enhances both its reliability and its cost of manufacture.

Among the features of my invention is that the water is not forced or pumped into the air stream as in the prior devices but is picked up or absorbed naturally and continuously into the air as it flows toward the patient. The temperature of the air is increased continuously as it flows toward the patient to increase the amount of water which may be absorbed. By the time the air reaches the patient, it is at or near saturation and is at body temperature for the patients comfort. Additionally, the invention avoids the generation of any surging characteristics in the air flow.

Also among the advantages of the instant invention is that there is little likelihood of its malfunction. For example, in prior devices, if the vaporizer or nebulizer fails to inject the required amount of water into the air stream, the air directed to the patient will tend to become dry quickly with consequent, rapid drying of the patients airway. In contrast, even in the event of failure of the few mechanical elements present in the invention, the air flowing to the patient will still be humidified.

The invention employs a respirator tube leading from the respirator to the patient and the tube has a pair of passageways separated by a water permeable wall, the passageways extending along the full length of the tube. One of the passageways is connected to the respirator to deliver the air along that passageway to the patient. Warm water is caused to flow in the other passageway, preferably along a flow direction opposite to that of the air flow. The water permeates the wall and is absorbed by the air flowing toward the patient. The opposite direction of flow of the heated water enhances delivery of the air to the patient at his body temperature. The water is caused to flow by a system which, in the event of failure of the pump, maintains the water in contact with the permeable wall so that the flowing air will continue to absorb the water from the wall and deliver humidified air to the patient.

It is among the objects of my invention to provide a respiratory delivery system of simple construction and operation.

It is another object of my invention to provide a respiration delivery system which eliminates the requirement for separate mechanisms to vaporize or nebulize the water and to combine the water with the air.

Also among the objects of my invention is to provide a respiration delivery system which is less prone to malfunction and which reduces the likelihood of discomfort or danger to the patient.

A further object of the invention is to provide a respiration delivery system which is effective to humidify the air directed to the patient even in the event of mechanical failure of the system.

An additional object of the invention is to provide a respiration delivery system which insures a stable flow rate of air and accurate control of air temperature.

These and other objects and advantages of the instant invention will be understood more fully from the following detailed description, with reference to the accompanying drawings wherein:

FIG. 1 is a somewhat schematic view of the invention as incorporated into a respiratory system;

FIG. 2 is a sectional view of one end of the humidifying tube;

FIG. 3 is a cross sectional view of the tube as seen from the plane 33 of FIG. 2.

As shown in the drawings, the system includes a respirator 10 of conventional design to provide a constant flow of air under a light but positive pressure for the patients use. The outlet 12 of the respirator 10 is connected, as described below, to a composite delivery tube, indicated generally by the reference character 14. The delivery tube 14 is formed from an outer tube 16 and an inner tube 18. The outer tube 16 may consist of a length 3 of conventional flexible respirator tubing, formed from a water impermeable material such as a polyvinyl. The inner tube 18 is formed from a material which may be permeated readily by water such as, for example, cellophane. Seamless cellophane tubing, which has been found to be satisfactory, is available commercially from Edward Week and Company in Brooklyn, N.Y. The inner and outer tubes 18, 16 thus cooperate to define passageways 20, 22 which are separated along the length of the delivery tube 14 by the wall of the inner, water-permeable tube 18.

The inner and outer tubes 18, 16 are secured and sealed at their ends by the fittings 24, 24. The fittings 24, 24 preferably are of identical construction but for ease of explanation the fitting shown at the right end of the tube 14 in FIG. 1, and its component parts, will be designated with a prime mark when appropriate.

Each of the fittings 24, 24 has a tubular end 26 which fits snugly within the sealing ring 25 in the end of the outer tube 16. The cellophane inner tube 18 protrudes outwardly beyond the free end 28 of its fittings Z4 and is draped about the free end 28 as shown at 32. The ends of the cellophane inner tube 18 are secured to the fittings 24 by a connector plug 30 which is press-fitted into the outer end 28 of the fitting 24. The draped end 32 of the inner tube 18 may be secured further to the fitting 24 by wrapping a length of adhesive tape about the outer end 28 of the fitting 24.

Fittings 24, 24 include integrally formed ports 36, 36 which are defined by tubular projections 38, 38 to which conventional rubber hoses may be secured. Thus, the passageway of the delivery tube has an inlet and outlet port defined by the tubular ends 28, 28 and the passageway 22 also has an inlet and outlet at its opposite ends at the tubes 38, 38. In assembling the apparatus for operation, the inlet connector plug 30 is connected to the respirator 10 which, during operation, will cause air to flow through the inner tube 18 toward and out of the tube 28'. The passageway 22 defined between the inner tube 18 and outer tube 16 is connected to the water circuit so that the water will flow in the opposite direction to that of the air flow through the passageway 20. To this end, the port 38' is employed as an inlet to the passageway 22 so that water may flow over and about the permeable inner tube 18 toward and out of the outlet port 36. The outlet port 36 is connected, as by a conventional rubber tube 40, to an inlet of a pump 42. The pump 42 preferably includes an integral heating element to heat and maintain the water at a selected temperature. Pumps of this type are employed with frequency for a wide variety of medical purposes and are available commercially from Gorman-Rupp Industries, Inc. of Bellville, Ohio. The outlet of the pump 42 is connected, by a rubber tube 44, to a free reservoir 46 and another rubber hose 48 is immersed in the water of the reservoir and is connected to the inlet tube 38' of the fitting 24' to complete the water circuit.

In operating the system, the reservoir 46 is filled with water and the passageway 22 and hose 48 preferably are primed and filled with water. As the pump 42 operates to draw the water from the passageway 22, the pressure within the passageway 22 and rubber hose 48 will be reduced so that the atmospheric pressure acting on the water in the reservoir 46 will cause water to flow through the rubber hose 48 and into the passageway 22. It should be noted that, although the foregoing arrangement is preferred, a pump could be employed to force the water directly into the inlet of the passageway 22 instead of employing the siphoning action described. The siphoning action, however, is desirable in that it precludes the possibility of water being pumped into the inner tube 18 and toward the patient in the unlikely event that the inner tube 18 ruptures or begins to leak. In the preferred siphoning arrangement, should the inner tube leak, the slight positive pressure within the passageway 22, which is greater than the static pressure within the passageway 4 20, would cause some of the air in the tube 18 to flow into the passageway 20 which precludes any water from reaching the patient.

It is important, for the comfort of the patient, that the humidified air be delivered to him at a temperature that is as close to body temperature as is reasonably possible and that this temperature be relatively invariable and constant. Although the more broad aspects of the invention may be practiced by flowing the water along the same direction as the air flow (toward the patient), I have found that when the water flow is reversed the temperature of the humidified air exiting from the inner tube 18 is more easily controlled, may be maintained at a constant level and is less prone to fluctuate. For example, the temperature of the water entering the inlet port 38' should be substantially equal to the body temperature of the patient. As the water flows through the passageway 22, it will heat the air flowing in the opposite direction to increase the air temperature gradually as it flows toward the patient. The heat exchange causes the water temperature to be lowered as it flows along the paassageway 22 while the temperature of the air is raised gradually as it flows toward the patient and is presented to the surrounding water jacket at a continually increasing temperature. When the air reaches the portion of the passageway 20 adjacent the water inlet port 36', it will have been raised gradually to a uniform temperature equal to that at the inlet port 38 and the patients body temperature.

It should be noted that the heating element of the pump 42 should be calibrated so that it heats the water to a temperature that is slightly above the body temperature of the patient to compensate for any heat loss from the water between the pump and the inlet port 36'. In some instances it may be desirable to employ a supplemental thermostatically controlled heating element about the reservoir to maintain the water at the desired temperature before it is introduced into the delivery tube 14.

The figures show a modification of the preferred embodiment in which the permeable inner tube 18 is surrounded and rigidified by a wire mesh jacket 50. The Wire mesh jacket 50 serves as a reinforcing element in the event that the respirator 10 is operated improperly so that the pressure in the tube 18 becomes excessive and ruptures the tube 18. If desired, an inner mesh tube 52 may be provided Within the tube 18 for further support. Although not strictly necessary, the reinforcing mesh is desirable when the inner tube 18 is formed from a material which might rupture. The substitution of other, more durable, water-permeable material may eliminate the desirability of providing such reinforcement.

It should be understood that the foregoing description is intended merely to be illustrative of my invention and that other embodiments and modifications thereof will be apparent to those skilled in the art without departing from its spirit. For example, although cellophane has been suggested as a preferred material for the inner tube 18, other materials displaying similar properties of water permeability and durability may be employed. Additionally, the embodiment disclosed relates to a flexible delivery tube although, in some instances it may be desired to provide a rigid unit. It should be noted further that although the invention has been described as being embodied in a respiratory system it may be employed in other environments in which it is desired to humidify gases.

Having thus described my invention, what I desire to claim and secure by Letters Patent is:

1. A method of delivering gas to a patient from a respirator comprising:

passing said gas from said respirator along one of two separate, coextensive conduits defined in part by a water-permeable wall, and in intimate contact with said wall;

causing water to flow continuously, in a direction opposite to the flow of said gas and in intimate contact 6 with the other side of said water-permeable wall in the passage within said inner tube before said gas whereby said water may permeate said wall and be passes through the exit of said inner tube; and absorbed continuously by said gas as it passes along means for maintaining the temperature of said Water said conduit; and introduced to said one of said passages at a level heating said water before it is introduced into said equal to the body temperature of the patient,

conduit. 4. A system as defined in claim 3 wherein said ea s 2. A method as defined in claim 1 wherein said step for directing said stream of water within said other of said of causing said water to flow comprises: passages comprises:

pumping water from one end of said conduit out Of pumping means connected to the outlet of said other said conduit and into a reservoir; and 10 passage to draw water from said other passage; siphoning Water from said reservoir into the other end means communicating th o tlet of aid pum .t a

of said conduit to maintain a reduced static pressure reservoir exposed to atmospheric pressure; and of the water within said conduit. siphoning means having one end immersed in said res- 3. A respiratory system comprising: ervoir and the other end thereof connected to the a respirator adapted to generate a gas stream deliverinlet end of said other passage, whereby the water able to a patient at an uptake stat on; within said conduit may be maintained at a reduced an outer tube having inlet and outlet means; static pressure. an inner tube disposed within and extending along said 5. A system as defined in claim 4 further comprising: outer tube, said inner tube having inlet and outlet means for introducing heat to said water while said Water means and being formed from a water-permeable is disposed externally of said other passage whereby the material, said tubes defining a central passage and an temperature of the Water entering the inlet of said other annular passage, said passages being defined and sep- Passagfi y be Controlled and whereby a temperature gradient may be established along the coextensive length arated by said water-permeable tube, each end of of said passages.

said passage terminating in an inlet and an outlet,

said inlet and outlet ends of each of said passages References Cit d being disposed at opposite ends from the inlet and UNITED STATES PATENTS outlet of the other of said passages; means connecting said respirator to the inlet end of one 2,650,709 9/1953 Rosenak et a1 210 321 of said passages to cause gas to flow along that pas- 2,675,349 4/1954 Saroff et 210-321 sage toward and out of said exit of said passage; 2812762 11/1957 Jordan et a] 128-191 3,442,389 5/1969 Mendelson 2lO32l means for introducing a stream of Water into the inlet of the other of said passages and to cause said water RICHARD A, GAUDET, Primary Examiner to flow toward the outlet 0t said other passage 111 a G F. DUNNE, Assistant Examiner direction opposlte to the direction of flow of said gas, whereby water flowing within said other passage 30 US. Cl. X.R. may permeate said inner tube and humidify the gas 261153

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