Tracheal ventilating device

Details Tracheal ventilating device Tracheal ventilating device

2002-11-15

2004-10-12

Bennett, Henry (Department: 3743)

Surgery

Respiratory method or device

Respiratory gas supply means enters mouth or tracheotomy...

C128S207150, C128S207160, C604S103060, C604S103070, C604S103080

Reexamination Certificate

active

06802317

ABSTRACT:

The present invention relates to a tracheal ventilating device, especially a tracheal tube or tracheal cannula which obturates the trachea as hermetically as possible for ventilating a patient, the device comprising a cuffed balloon which blocks the trachea below the glottis and through which a ventilating cannula is passed, the cuffed balloon when filled or inflated and freely unfolded without any limitation, being larger than when placed in the trachea in an inflated state, and being made from a soft flexible foil material.
In a tracheal tube of such a type as is known from DE 196 38 935, it is suggested that a foil-like, extremely expandable material should be used for the cuffed balloon, the material closely nestling on the trachea or the local structures of the subglottic larynx. To optimize the tamponade of the subglottic space, it is recommended that the cuffed balloon should be pre-formed in accordance with the morphology of the space to be filled. An undesired draped fold is thereby to be avoided. It is to be ensured that the foil closely rests on the trachea so that no secretion passes from the pharyngeal space into the lung, if possible. A microaspiration of secretion beyond the cuffed balloon is thereby reduced considerably.
Secretion which passes into the distal trachea-bronchial system is the reason for the development of most of the ventilation-associated pneumonias.
In the tracheal tube suggested in DE 196 38 935, the cuffed balloon is elastically expanded while being inflated, and closely nestles on the wall of the trachea without any draped fold. When the filling pressure of the cuffed balloon exceeds the blood flow pressure of the vascular bed supplying the film of the mucous membrane, serious structural lesions of the epithelium might ensue. Above all with patients intubated for a long period of time, the filling pressure prevailing in the cuffed balloon should be kept at a level which is as low as possible and does not impair mucosal perfusion. By contrast, if the filling pressure is chosen such that it is too low, this might lead to a leakage of bacterially contamined pharyngeal secretion beyond the cuffed balloon, resulting in a contamination and infection of pulmonary tissue.
It has therefore been suggested for long-term intubation that use should be made of cuffed balloons which unfold at a moderate filling pressure in the trachea without the cuff coat itself having to be expanded. The diameter of the freely unfolded cuffed balloon is here greater than that of the trachea to be closed. The residual amount of the cuff coat is turned into folds during the tracheal blockage of the cuff. On the other hand, however, it has been found that such cuffs have a high permeability to pharyngeal secretion, which means an increased risk of pneunomia. The leakage of secretion of said cuffed balloons is in the range of milliliters per second, which even corresponds to a macroaspiration in quantitative terms.
Therefore, it must be assumed that conventional cuffed balloons cause most of the pneumonias frequently observed in patients who are ventilated for a long period of time (incidence: 10% to 80%, depending on the respective patient).
It is the object of the present invention to improve a tracheal tube of the above-mentioned type in such a manner that a patient can be intubated as gently as possible at low pressures over a long period of time and that the risk of infection is low.
According to the invention this object is achieved with a tracheal tube of the above-mentioned type which is characterized in that the draped fold of the cuffed balloon rests on the trachea and is designed in such a way that the loop formed at the dead end of a fold has a small diameter which inhibits the free flow of secretion through the loop of the fold.
The sealing capacity of the cuff can thus be improved considerably; the risk of ventilation-associated pneumonia is reduced accordingly.
Surprisingly enough, the flow of secretion can be influenced by a specific design of the cuff folding in the area of the loop of the fold, i.e. at the base of the fold. While in the prior art it has so far been assumed that cuffed balloons with a draped fold cannot rest on the trachea in a sufficiently tight manner because of the low filling pressure, the invention shows a method of inhibiting the flow of secretion, the method being employed in the area of the loop of the fold. When the diameter of the loop is sufficiently small at the base of the fold, the free flow of secretion through the loop is inhibited. When the cuff is blocked, the resultant loops at the deep end of the fold can be reduced with respect to their diameter, for instance by selecting the material or the foil thickness, in such a manner that the flow of secretion is decelerated or, ideally, stopped altogether.
This is surprising because leakage has always been regarded as a problem of pressure. A constructional change in the draped fold has so far not been considered yet.
Preferably, the loop is given a capillary size. This will then result in adequate adhesion forces of the secretion on the loop and in a sufficient viscosity-dependent resistance of the secretion to reduce the flow of secretion. The flow rate in the capillary-sized loop is then smaller than the theoretically possible rate without adhesion or viscosity forces, so that a smaller amount of secretion will flow therethrough in the course of time. In an optimum case the diameter of the loop is made so small that the flow of secretion is stopped altogether.
The diameter of the loop may be less than 0.1 or 0.05 mm in an especially advantageous development. At a value below 0.1 mm a certain inhibition of the flow rate of the secretion through the loop can already be observed. At a loop diameter of less than 0.05 mm, the flow of secretion is further decelerated and almost stopped.
Advantageously, the wall thickness of the foil material can be chosen to be so small that the inner radius of the developing loops is reduced at physiologically tolerated filling pressures to such an extent that the free flow of secretion is prevented. The more flexible and thinner the material is, the smaller is the diameter of the loop.
The wall thicknesses of conventional cuffed balloons predominantly range from 0.06 to 0.1 mm.
It is suggested that the wall thickness of the foil should be slightly smaller than or equal to 0.02 mm. When the cuffed balloon is made from such a foil, the flow of secretion through the loop will already be inhibited at a standard filling pressure.
In a variant of the invention, the wall thickness of the foil is approximately 0.01 to 0.005 mm. In the case of a wall thickness ranging from 0.01 to 0.005 mm, a soft flexible foil will already inhibit the flow of secretion in a satisfactory manner and the stasis thereof will be achieved in the area of the base of the fold, respectively.
Foils of presently available materials having wall thicknesses of less than 0.005 mm are not sufficiently tear-resistant for the cuffed balloon which is designed according to the invention. If suitable and sufficiently resistant materials are available, foil thicknesses below 0.005 mm should be aimed at for achieving optimum sealing characteristics.
According to a preferred embodiment the foil material of the cuffed balloon may e.g. consist of polyethylene teraphthalate (PETP), low-density polyethylene (LDPE), polyvinyl chloride (PVC) or polyurethane (PU). These materials are body-tolerated and, when being processed into correspondingly thin walls, are especially suited for forming a hermetically obturating draped fold. Copolymer admixtures for modifying the characteristics of the material are possible (e.g. LDPE-EVA).
The cuffed balloon possibly consists of a material which adheres to itself and the adhesion of which helps to reduce the clear diameter of a loop at the base of the fold.
In a variant of the invention, the wall thickness of the foil may be thinner in the area of the draped fold than in the fold-free area directly adjacent to the tracheal mucous membrane. Folds are preferably fo

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