Hemodynamic Responses to Oscillatory Thigh Cuff Inflations




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Experimental generation of 0.1 Hz oscillations (~10-s cycle) in arterial pressure and cerebral blood flow (CBF) increases tolerance to simulated hemorrhage, and protects cerebral tissue oxygenation. In this study we evaluated a clinically applicable method of inducing 0.1 Hz oscillations in arterial pressure and CBF via repeated thigh cuff inflations. We also characterized the effect of common carotid artery (CCA) stiffness on the magnitude of cerebral blood flow oscillations, and evaluated the effects of intermittent thigh cuff inflation on several markers of cardiac function. We hypothesized that: 1) the amplitude of arterial pressure and CBF oscillations at 0.1 Hz would increase in response to repeated thigh cuff inflations at 0.1 Hz, 2) the magnitude of 0.1 Hz CBF oscillations would be positively correlated to the stiffness of the CCA, and 3) measurements of cardiac function would increase in response to thigh cuff induced oscillations of arterial pressure at 0.1 Hz. Thirteen healthy human participants were tested (6 male, 7 female; 27.1 ± 4.3 y). In response to 10-min of intermittent thigh cuff inflations at 0.1 Hz, the amplitude of 0.1 Hz oscillations increased for mean arterial pressure (MAP; 24.4 ± 20.1 mmHg2 vs. 932.0 ± 758.1 mmHg2; P<0.01) and middle cerebral artery velocity (MCAv; 17.5 ± 13.8 (cm/s)2 vs. 325.5 ± 279.9 (cm/s)2; P<0.01). There was also a large increase in MAP-MCAv coherence at 0.1 Hz (0.60 ± 0.24 a.u. vs. 0.90 ± 0.11 a.u.; P<0.01) during the oscillatory period compared to baseline. There was a moderate positive relationship between CCA stiffness and amplitude of MCAv power at 0.1 Hz during intermittent thigh cuff inflations (r=0.68, P=0.01), but not at rest (r=-0.08, P=0.80). When compared to baseline, no changes were observed during the oscillatory period for heart rate (P=0.47), stroke volume (P=0.87), cardiac output (P=0.55), MAP (P=0.20), or dP/dTmax (P=0.61). Future studies directly examining sympathetic nerve activity are needed to better elucidate the effects of induced 0.1 Hz hemodynamic oscillations on neural regulation of the cardiovascular system. In conclusion, we have shown that intermittent thigh cuff inflations can be used to increase hemodynamic variability at a target frequency, and therefore could be a therapy for treating tissue hypoperfusion following severe blood loss injuries.