Surgery – Truss – Pad
Patent
1995-09-21
1997-10-14
Cohen, Lee S.
Surgery
Truss
Pad
128716, 128725, 7335501, A61B 500
Patent
active
056761546
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a method to sense the breathing of a man or an animal, a breathing sensor adapted to perform the method and a device to sense the breathing of a human or an animal.
SUMMARY OF THE INVENTION
The expression "to sense the breathing" in this document is referred primarily to achieve a signal which to a substantial extent follows the breathing air flow.
In many different situations there may be a reason to sense the breathing of a man or an animal. Various states of illness, intensive care, examinations of performances and breathing supervision during sleep are examples of such occasions when one wishes to measure the breathing rate and an eventual disruption of the breathing or study a wave shape corresponding to the breathing.
Many different methods have been tried to sense the breathing. Examples of such are those which are based on pressure changes in the breathing air flow that for example may influence a membrane, the curve of which is sensed by a strain gauge transducer or by another method. Another method is to let a thermistor be cooled by the breathing air flow and to sense the voltage level across the same, and an additional method is to sense the movement of a ball in the air flow.
An object of the present invention is to achieve a method and a device to sense the breathing and a breathing sensor of a new, simple and reliable type which can be utilized in a flexible way when there is desire to sense the breathing. An object is also to achieve breathing sensors which easily can be carried by a patient and which do not need to incorporate electric cables at the proximity of the body. An additional object is to achieve breathing sensors which are easy to keep clean and when needed sterile and which are so cheap that if desired they can be utilized as disposable products. Further objects and purposes appear in greater detail in connection with the following specification.
The method and the device to sense the breathing and the breathing sensor according to the present invention is based on the fact that the humidity of the breathing air varies strongly between in- and exhalation. At inhalation the relative humidity in the breathing air flow at the nose or the mouth approximately is the same as that of the ambient air, i.e. frequently far below 100% while at exhalation it is basically saturated with water vapour, i.e. 100% relative humidity.
If one allows the breathing air to pass a surface that is colder than 37.degree. C. water will condense on the surface when expiration air passes. Mist is formed on the surface. If, for example, said surface constitutes the end of an optical fibre, the condensation course can be studied in the following way. Light or other electromagnetic beam is guided into the optical fibre which beam in turn can be guided by means of an optical fibre from a source which can be a laser, laser diode, light emitting diode or some other light bulb. The optical beam that reaches at the far end of the fibre partly will be reflected and partly leak out. If the end of the fibre becomes coated by mist tis relation will be changed so that a smaller part of the ray will be reflected back when the fibre is moist than when it is dry. The reason for this is that the small drops of water constituting the mist form small lenses which let out radiation in more angles than what is the case of the dry fibre. The breathing then can be sensed as intensity variations of the reflected light by any appropriate method which is exemplified below.
It is also possible to detect the intensity variations of the beam that is transmitted in order to sense the breathing from this variation. This can for example be carried out by means of a photo detector or another fibre end which captures a part of the transmitted radiation at the proximity of the first end of the fibre. It is also possible to use the principle according to the present invention in another way. For example a loop of an optical fibre can be utilized, where the sensor surface is constituted by a window of arbitr
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Cohen Lee S.
Huang Stephen
Optovent AB
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