Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Patent
1991-07-23
1993-03-16
Burr, Edgar S.
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
128912, 12820418, A61M 1600
Patent
active
051935325
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to devices used to improve gas exchange during spontaneous breathing when the patient's ability to breathe is impaired. The device is of the type which comprises a breathing-channel which at its one end opens into the atmosphere and at its other end has an attachment means for connection to a patient's airway via the nose and/or mouth. Further, the device has an inlet or fresh-gas channel which is connected with the breathing-channel at a point between its ends and allows the flow of the flesh gas to be adjusted to obtain an adjustable positive pressure within the breathing-channel.
The principle involved in such a device is that the patient breathes against a pressure above atmospheric pressure, which facilitates spontaneous breathing in certain conditions of impaired pulmonary function. With hitherto well-known devices of this type of simple and thereby inexpensive design, the breathing-channel consists of relatively long tubing, which in turn results in relatively long columns of air. When the patient breathes in, the pressure then tends to fall in the breathing-channel. In order to attain the best possible breathing conditions, however, the pressure in the patient's airway should be as constant as possible during the breathing cycle. Up until now this has been difficult to achieve, even with the well-known devices which are relatively complicated in that they work with movable valves and electronic components. This is particularly true of systems connected via the nose.
The purpose of the present invention is therefore to provide a device of the type under consideration which, while retaining its simplicity, makes it possible to sustain a positive airway pressure with minimal pressure variations and which can thereby replace also the more complicated and relatively expensive well-known devices as well. This is achieved with a device which according to the invention is characterized by the fact that the breathing-channel consists of a first branch-channel which fits into the attachment means and by a second branch-channel, which opens into the atmosphere, the two branch-channels forming an angle with one another.
The fresh-gas channel is situated substantially in the extension of the first branch-channel and is connected to the second branch-channel in a way that causes the stream of fresh-gas to be directed mainly co-axial into the first branch-channel. Each branch-channel's cross-sectional area is several times greater than the smallest cross-sectional area of the inlet channel and the length of each branch-channel is relatively short in that the length is preferably a maximum of five times its inner diameter. In addition, the breathing-channel is built together with the inlet channel into a compact unit which can be secured to the patient's nose and/or mouth by means of a strap, band or ribbon.
Thanks to the particular way in which the inlet channel is attached to the angled breathing-channel, an ejector action is attained in an extremely simple manner which, depending on the size of the fresh-gas flow, generates the desired pressure (CPAP) in the first branch-channel which is connected directly to the patient's airway.
The ejector action counteracts the tendency to decreasing pressure during the inspiration phase, in that breathing-gas and/or atmospheric air is sucked in from the other branch-channel. During the expiration phase the tendency to increasing in pressure is counteracted by the breathing-channel's cross-sectional area, which is several times greater than that of the inlet channel, which allows the expiratory air to be added to the fresh-gas flow without the pressure gradient in the system being appreciably affected. The pressure thereby tends to be constant at constant gas flows, despite variations in the breathing-channel during the breathing cycle.
The device according to the invention thus forms a compact unit in which the air columns in the branch-channels are relatively short in order to avoid backlogs in the gas supply when the pressure tends to fall i
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Moa Conny P. G.
Nilsson Kjell O.
Burr Edgar S.
Lewis Aaron J.
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