Cardiovascular control and stabilization via inclination and mobilization during bed rest

Cardiovascular deconditioning has long been recognized as a characteristic of the physiological adaptation to long-term bed rest in patients. The process is thought to contribute to orthostatic intolerance and enhance secondary complications in a significant way. Mobilization is a cost-effective and simple method to maintain the cardiovascular parameters (i.e., blood pressure, heart rate) stable, counter orthostatic intolerance and reduce the risk of secondary problems in patients during long-term immobilization. The aim of this project is to control the cardiovascular parameters such as heart rate and blood pressure of bed rest patients via automated leg mobilization and body tilting. In a first step, a nonlinear model predictive control strategy was designed and evaluated on five healthy subjects and 11 bed rest patients. In a next step, a clinically feasible study was conducted on two patients. The mean values differed on average less than 1 bpm from the predetermined heart rate and less than 2.5 mmHg from the desired blood pressure values. These results of the feasibility study are promising, although heterogeneous disease etiologies and individual medication strongly influence the mechanically induced reactions. The long-term goal is an automation of the control of physiological signals and the mobilization of bed rest patients in an early phase of the rehabilitation process. Therefore, this new approach could help to strengthen the cardiovascular system and prevent secondary health problems arising from long-term bed rest

Temporal and thermal variations in site-specific thermoregulatory sudomotor thresholds: precursor versus discharged sweat production

Temporal and thermal differences between the initiation of precursor, eccrine sweat and its surface discharge were investigated during passive heating. Sudomotor activity was evaluated using electrodermal (precursor) and ventilated sweat capsule measurements (dorsal fingers, dorsal hand, forehead, forearm). Passive heating significantly elevated auditory canal (0.5oC) and mean body temperatures (0.9oC). At each site, the precursor sudomotor thresholds occurred at a lower mean body temperature (P \u3c .05), with an average elevation of 0.35oC (SD 0.04). However, discharged thresholds were delayed until this temperature had risen 0.53oC (SD 0.04), producing significant phase delays across sites (mean: 4.1 min [SD 0.5]; P \u3c .05). It is concluded that precise sudomotor threshold determinations require methods that respond to sweat accumulating within the secretory coil, and not discharged secretions, reinforcing the importance of electrodermal techniques