Cardiovascular response to syncope induced by lower body negative pressure

AIM:To analyze the changes of cardiovascular response to syncope induced by lower body negative pressure (LBNP) in humans. METHODS: Ten healthy male subjects were exposed to LBNP until pre-syncope. Blood pressure, heart rate (HR), cardiac pumping function and autonomic regulation were examined during LBNP. RESULTS: Mean duration of lower body negative pressure was (856±95) s. Heart rate (HR) increased significantly by 41% and 45%, whereas stroke volume (SV) decreased by 49% and 49%, respectively at 60 s and 30 s before end-point of LBNP as compared with baseline. HR increased by 63%, whereas SV decreased by 50% at the end-point of LBNP. Systolic blood pressure was significantly lower, whereas the ratio of low frequency power/high frequency power was significantly higher before the end-point of LBNP as compared with baseline. CONCLUSION: Changes of stroke volume and heart rate may be an important index for consciousness monitoring.