Surgery – Respiratory method or device – Respiratory gas supply means enters mouth or tracheotomy...
Reexamination Certificate
2002-05-15
2003-11-18
Dawson, Glenn K. (Department: 3761)
Surgery
Respiratory method or device
Respiratory gas supply means enters mouth or tracheotomy...
C604S099020, C128S207150
Reexamination Certificate
active
06647984
ABSTRACT:
The present invention relates to apparatus for controlling cuff pressure in an endotracheal tube.
Endotracheal tubes are well known. In use, an endotracheal tube is inserted through the mouth of a subject into the trachea for facilitating ventilating of the subject from a ventilator or other suitable ventilating medium source. Typically, an endotracheal tube terminates at one end in a coupling for coupling the tube to a supply tube which supplies the ventilating medium source. A inflatable cuff is provided at the other end of the endotracheal tube and extends around the tube so that on inflating of the cuff the endotracheal tube is secured in the trachea of the subject and leak passed of the ventilating medium into the mouth of the subject is avoided during the inrspiratory phase of each breathing cycle. A communicating tube is provided on the endotracheal tube for communicating with the cuff and for facilitating inflating of the cuff. Typically, the communicating tube extends along the side of the endotracheal tube, and ideally, forms an integral part therewith. Typically, the cuff is manually inflated by a syringe to a pressure which is adequate for retaining the endotracheal tube in the trachea and also for preventing leak passed of the ventilating medium. However, care is required in order to avoid over-inflating the cuff, which could lead to injury and trauma, and in particular, to damage of the vocal cords of the subject.
Due to pressure variation of the ventilating medium during a breathing cycle, for example, the pressure variation as a breathing cycle transitions between the inspiratory phase and the expiratory phase, and indeed, over a series of breathing cycles, it is difficult to achieve an adequate degree of sealing of the endotracheal tube between the cuff and the trachea for all such pressure variations to avoid leakage of the ventilating medium into the mouth of the subject.
Additionally, in order to facilitate manual inflating of the cuff by a syringe which can deliver a relatively large volume of air at a relatively low pressure, it is necessary in general to form the cuff from a relatively highly compliant material, for example, a latex material which will inflate at relatively low pressures. However, latex materials suffer from a number of disadvantages. Firstly, latex materials cause allergies in many people, secondly, latex materials tend to be permeable to some of the anaesthetic gases, such as nitrous oxide which can permeate into the cuff. Since the latex material is a highly compliant material, as the nitrous oxide permeates into the cuff the cuff further inflates, and this can cause trauma and indeed, serious injurious effects to the subject.
A further problem with known endotracheal tubes, and in particular, endotracheal tubes which are adapted for manually inflating with a syringe, or indeed, are adapted for inflating by a compressed air source is that a check valve is required in the communicating tube to the cuff for maintaining the cuff inflated after it has been disconnected from the syringe or compressed air source.
Attempts to overcome these problems associated with endotracheal tubes have been made. In particular, attempts have been made to provide apparatus for varying the cuff pressure as the pressure of the ventilating medium varies, in other words to provide high cuff pressure during the inspiratory phase of each breathing cycle and low cuff pressure during the expiratory phase. In general, such apparatus require that the cuff be inflated from an external source, typically an external compressed air source, such as a compressed air source available in a hospital. This, thus requires that the endotracheal tube as well as being connected to a ventilator must also be connected to a separate compressed air source, and in the absence of such a compressed air source the endotracheal tube must be connected to a large pressurised gas cylinder, or alternatively the endotracheal tube cannot be used. A valving system which generally includes solenoid operated valves and a pressure regulating system are also required for controlling and regulating the pressure of the air or gas from the external source for supply to the cuff. Such systems suffer from the disadvantage that they are slow to react, and in general are unable to accurately. track transitions between the inspiratory and expiratory phases of breathing cycles.
U.S. Pat. No. 4,825,862 of Sato discloses apparatus for regulating cuff pressure in an endotracheal tube. The apparatus comprises a pressure regulator for regulating the pressure of a separate gas supply to the cuff in response to pressure variation in breathing cycles. However, the regulator disclosed in this U.S. specification is a mechanically operated regulator, and in general, would be relatively slow to react, and in general, would be unable to react with the speed required to vary the pressure during individual breathing cycles. However, irrespective of whether the regulator of the apparatus of Sato would be capable of tracking the pressure variation of the ventilating medium during each breathing cycle, the apparatus of Sato requires a separate gas supply, in other words, the apparatus of Sato would have to be connected to an external gas supply, for example, a hospital compressed air system or other such external source.
U.S. Pat. No. 5,235,973 of Levin son also discloses a cuff pressure controller for controlling cuff pressure of an endotracheal tube in which the cuff pressure is held at a high pressure during the inspiratory phase of a breathing cycle, and is held at low pressure during the expiratory phase. However, the cuff pressure controller of Levinson requires the supply of gas from a separate external gas source for inflating the cuff of the endotracheal tube. Additionally, pressure control valves for controlling the pressure of the gas supply to the cuff are also required.
Accordingly, there is therefore a need for apparatus for controlling cuff pressure of an endotracheal tube for minimising leak past of ventilating medium into the mouth of the subject during the inspiratory phase of a breathing cycle, and which avoids the need for having a separate external pressurised gas source for inflating the cuff.
The present invention is directed towards providing such apparatus.
According to the invention there is provided apparatus for controlling cuff pressure in a cuff of an endotracheal tube, the apparatus comprising a control means for controlling the pressure of an inflating medium for inflating the cuff at respective first and second pressure levels during the inspiratory and expiratory phases, respectively of each breathing cycle of a subject, wherein the apparatus comprises an inflating medium supply means for supplying inflating medium to the cuff, and the control means controls the inflating medium supply means for supplying the inflating medium at the second pressure level to the cuff during the expiratory phase of each breathing cycle.
In one embodiment of the invention the inflating medium supply means is a variable pressure inflating medium supply means.
In another embodiment of the invention the control means controls the inflating medium supply means for supplying the inflating medium at the first pressure level to the cuff during the inspiratory phase of each breathing cycle.
In another embodiment of the invention a monitoring means is provided for determining the transitions between the respective inspiratory and expiratory phases during a series of sequential breathing cycles, and the control means is responsive to the monitoring means for controlling the inflating medium supply means for supplying the inflating medium to the cuff at the respective first and second pressure levels during the inspiratory and expiratory phases, respectively, of each breathing cycle.
Preferably,the monitoring means monitors the pressure of the ventilating medium to the subject, and the control means is responsive to the monitoring means for controlling the inflating medium supply means for supplying the inflating medium a
Caradyne (R&D) Limited
Dawson Glenn K.
Swanson & Bratschun LLC
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