AN AIR RESERVOIR

Abstract: An air reservoir (4) intended for regulating the pressure in the sealing cuff of a respiration catheter has a wall consisting of an elastic membrane (3). The reservoir also functions as a pressure gauge, the elastic membrane when inflated being caused to contact a semitransparent plate (2) which is firmly connected with a rigid part (1) of the reservoir. At contact between the membrane and the plate, indicator rings on the membrane become visible through the semitransparent plate.

Description: An air reservoir The invention concerns an air reservoir of the type stated in the introductory portion of claim 1. Endotracheal tubes for insertion through the mouth, the nose or implanted in the neck (oro-naso and tracheostomy tubes) are usually provided with an inflatable cuff for sealing against the tracheal wall. The efficiency of the sealing is determined by the magnitude of the cuff pressure against the tracheal wall since the inflated cuff does not seal off pressures exceeding the pressure of the cuff against the wall. The air pressure in the cuff deter- mines the pressure against the tracheal wall. The pressure of the cuff against the tracheal wall can be controlled and regulated only if the cuff has a sufficiently large diameter to make contact with the tracheal wall without any stretching of the sheet material of the cuff, i.e. the cuff must be lying folded on the tracheal wall. If this demand is met, the pressure in the cuff is identical with its pressure on the wall. If the pressure of the cuff against the tracheal wall is considerably higher than 30 cm H 2 0 the blood supply to the mucosa is occluded, and this causes damage in the form of superficial or deeper ulcerations after some time. This damage is prevented in that the sealing cuff, lying folded on the wall, is kept inflated from an outer pressure sour- ce with a constant, regulated pressure of 20 to 30 cm H„0. The sealing cuff has the additional function of preventing liquid (blood, saliva, vomit) from flowing past the cuff down into the lungs. It has been found that this function is accomplished when the pressure of the sealing cuff against the tracheal wall is at least 20 to 30 cm H 2 0. Spontaneous changes in the diameter of the trachea, changes in the catheter position and the diffusion of cer¬ tain anaesthetic gases through the wall of the sealing cuff may cause considerable changes in the pressure in the sealing cuff if the inflation pressure is not controlled and regulated. A reservoir of the present type is capable of maintaining the pressure within the stated pressure range in the seal¬ ing cuff of a respiration catheter as the reservoir com¬ pensates for the rise and fall in pressure that might occur in the sealing cuff. The object of the invention is to provide a reservoir of the present type which has means for indicating the magni¬ tude of the pressure in the reservoir. This object is obtained in that the reservoir is con- structed as stated in the characterizing portion of claim 1 since, in this structure, the externally observable size of the engagement face between the membrane and the plate depends upon and is thus a measure of the pressure in the reservoir. The feature stated in claim 2 protects the reservoir against diffusion through the membrane and consequent changes in pressure. The embodiment defined in claim 3 makes it possible to relate the size of the engagement face to predetermined values indicated by the markings. An embodiment of the air reservoir is shown schematically in the drawing, partly in longitudinal section, fig. 1 partly seen from above, fig. 2, and will be described more fully below with reference to the drawing. In the drawing, 1 is a circular, inelastic container, the " edge of an elastic, diffusionproof membrane 3 being fastened along the bottom edge of said container. The container has as supply tube 6 for filling with air and a cut-off valve 7. Through an opening 5, the air supply tube communicates with a reservoir 4 formed by the elastic mem¬ brane 3 and the bottom of the container 1. The reservoir communicates with the sealing cuff of an endotracheal tube (not shown) via a supply tube 8. The container 1 is cover¬ ed by a lid 2, whose underside has such a roughness that the cover is semitransparent. The upper side of the mem¬ brane 3 is wetted with a thin liquid layer, e.g. silicone oil, and is imprinted with one or more marker or indicator rings 9. • When the reservoir 4 is filled with air, the elastic mem¬ brane 3 is stretched and consequently brought into contact with the underside of the lid. The liquid is hereby caused to fill the small cavaties in the rough underside of the layer so that the lid will be transparent, and one or more indicator rings 9 are visiable through the semitransparent lid and thereby indicate the air pressure in the reservoir. . * ,- The lid does not have to be flat, as shown in fig. 1, but may be outwardly vaulted, which increases the volume of the reservoir and increases the distances between the in- dicator rings compared with a flat lid at the same pressure, so that also the pressure reading will be more precise. Other modifications to the details of the shown and described reservoir are possible within the scope of the invention.

Claims: P a t e n t C l a i m s 1. An air reservoir for control of the pressure in the sealing cuff of a respiration catheter, having a wall con¬ sisting of an elastic membrane whose edges are connected with a rigid part of the reservoir, c h a r a c t e r ¬ i z e in that this rigid part is firmly connected with a semitransparent plate so arranged with respect to the membrane that the outer side of the membrane is pressed into engagement with the plate by the pressure in the reservoir, and that a thin liquid layer is provided on the outer side of the membrane, said liquid layer changing the optical properties of the plate from semitransparent to transparent when the membrane engages the plate. 2. A reservoir according to claim 1, c h a r a c t e r ¬ i z e d in that the membrane is diffusionproof. 3. A reservoir according to claim 1 or 2, c h a r a c ¬ t e r i z e d in that the reservoir is equipped with one or more markings which indicate the size of the pressure upon engagement between the membrane and the plate. 4. A reservoir according to claim 3, c h a r a c t e r ¬ i z e d in that the marking or markings are ring-shaped. 5. A reservoir according to any of claims 1-4, c h a r a c t e r i z e d in that the plate is outwardly vaulted.

Inventors: LOMHOLT VAGN NIELS FINSEN, LOMHOLT, VAGN, NIELS, FINSEN
Applicants: LOMHOLT VAGN NIELS FINSEN, LOMHOLT, VAGN, NIELS, FINSEN
Application year: 1991
Main classification: A61M16
IPC codes: A61M16