Warning device for the prevention of ischaemic ulcers in patients who have injured the spinal cord

Ischemic or decubitus ulcers are one of the major medical problems in the handling of patients who have injured their spinal cord. These ulcers mostly develop on the ischial tuberosities and sacrum of patients seated for too long without changing their position. Special seat cushions developed to minimize the pressure have not proved effective for prolonged sitting by the paralyzed patient. These patients do not feel pressure generated pain; therefore they are not given a warning to shift their position, as are normal individuals. Paraplegics, and a number of quadriplegics have sufficient arm strength to shift their position, but fail to shift because they get involved in tasks and forget the lapse of time. Other patients with the ability to shift their position fail to follow the directions. The device described emits an audible or visible warning when the patient has remained seated for 10 min, and is automatically reset when the seat pressure is removed for 4 sec. One alarm emits a very harsh sound which motivates an uncooperative patient to shift his weight. The current drain during the 10 min time period is 120 μA. During the 4 sec time period the current drain is determined principally by the type of warning device used. The highest current drain is 8 mA with the light emitting diode, and the lowest is 2 mA with the unijunction oscillator and earphone. The battery life using a mercury battery such as the Mallory type TR146X is 2,000 to 3,000 hr.