Surgery – Diagnostic testing – Respiratory
Patent
1997-01-07
1998-12-08
Kamm, William E.
Surgery
Diagnostic testing
Respiratory
600527, 600513, A61B 50205, A61B 502
Patent
active
058462066
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a method and an apparatus for monitoring and estimating a person's wakefulness and, thereby, drowsiness.
BACKGROUND OF THE INVENTION
It is known, e.g. from the article "Determination of sleep state in infants using respiratory variability", PEDIATR. RES. 1987, Haddad, GG, JENG, HJ, LAI, TL, MELLINS RB., that in connection with cardiac/respiratory research on infants, changes in the cardiac/respiratory activity at short, instantaneous (REM/Rapid Eye Movement) sleep differ from a corresponding changes at calm, deep sleep.
BRIEF DESCRIPTION OF THE INVENTION
The object of the present invention is to utilize a corresponding relationship between the cardiac/respiratory function and a person's body movements in order to estimate the person's wakefulness and, thereby, the drowsiness of the person in question.
This is attained by means of the method according to the invention in movements relative to at least one stationary pressure sensitive means which contacts at least a portion of said person's body, the duration and magnitude of true body movements, the amplitude of heartbeat-related body movements as a function of rate, and the amplitude of respiration-related body movements as a function of rate, time-interval between same are measured and compared with previously measured corresponding values to determine possible changes, body movement as well as the time-interval between at least two successive heartbeats and respirations, are measured and compared with previously measured corresponding values to determine possible changes, true body movement changes, and of a reduced degree of wakefulness.
The object is also attained by means of the apparatus according to the invention, which comprises contact at least a portion of said person's body, and to generate an electric signal on its output terminal in response to said person's body movements relative to same, least one stationary pressure sensitive means, and adapted to separate, from said electric signal, signals corresponding to the duration and magnitude of true body movements, to the amplitude of heartbeat-related body movements as a function of rate, and to the amplitude of respiration-related body movements as a function of rate, and output these separated signals on corresponding output terminals, its input terminal, said signal corresponding to true body movements, to calculate the duration and magnitude of the true body movements as well as the time interval between same, and to compare these calculated values with previously calculated corresponding values to determine possible changes, to receive, on their input terminals, said signal corresponding to heartbeat-related and respiration-related body movements, respectively, to calculate the amplitude of every heartbeat-related and every respiration-related body movement, respectively, as well as the time interval between at least two successive heartbeats and respirations, respectively, and to compare these calculated values with previously calculated corresponding values to determine possible changes, calculation and comparison circuits, and adapted to correlate heartbeat-related and respiration-related changes with true body movement changes, correlator, and adapted to compare the resulting change with a preset wakefulness threshold, and circuit, and adapted to trigger alarm when the preset threshold is reached as an indication of a reduced degree of wakefulness.
The advantage of the invention is that, by means of the method and the apparatus according to the invention, it is possible, in an efficient manner, to monitor the degree of wakefulness of e.g. drivers of different types of vehicles (cars/buses/trains/boats/aircrafts) without disturbing the monitored person in that also the body movements of the monitored person are taken into account. Other suitable groups to monitor may be persons having a sedentary occupation such as students, guards, operators in process plants, nuclear power plants, etc.
Moreover, the invention can be applied when studying
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Biosys AB
Kamm William E.
Layno Carl H.
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