Drivers who sit for long periods of time (such as long-distance truck drivers) frequently experience discomfort in the lower extremities, drowsiness, dizziness, and mental fatigue. This is due to disruption of normal blood circulation, i.e., a hemodynamic shift from the central venous pool to the peripheral pool and compromised blood perfusion, which, in turn, is caused by tissue compression and muscular inactivity. A special seat cushion has been developed which utilizes a series of sequentially-inflating internal air passages to produce undulations that progress from the front to the back of the cushion. These undulations are intended to stimulate the circulation of blood through the extremities and thereby alleviate the problems described above. Impedance plethysmography was used to measure the localized hemodynamic responses produced by the pulsating cushion. This technique was used to quantify hemodynamic changes in the calf, knee, thigh and buttock segments of the body during operation of the inflatable seat cushion. The grouped mean indices of arterial perfusion increased significantly (P less than 0.05) in all portions of the lower extremities studied following a five minute operation period of the cushion. The device assisted venous clearance in all segments during each inflation cycle. These hemodynamic responses were more pronounced in the proximal segments of the lower extremities that were closer to the direct pulsating action of the cushion. The arterial perfusion indices increased approximately 8% in the lower leg and knee segments following operation of the seat cushion. Similarly, the blood flow index increased 10.4% in the thigh and 27.9% in the buttock segments. The average indices of venous clearance in the lower leg, knee and thigh segments were 2.9, 5.9 and 15.6 ml respectively for each inflation cycle.
Abstract