Compensatory hemodynamic changes in response to central hypovolemia in humans: lower body negative pressure: updates and perspectives
Abstract: Central hypovolemia is accompanied by hemodynamic compensatory responses. Understanding the complex systemic compensatory responses to altered hemodynamic patterns during conditions of central hypovolemia—as induced by standing up and/or lower body negative pressure (LBNP)—in humans are important. LBNP has been widely used to understand the integrated physiological responses, which occur during sit to stand tests (orthostasis), diferent levels of hemorrhages (diferent levels of LBNP simulate diferent amount of blood loss) as well as a countermeasure against the cephalad fuid shifts which are seen during spacefight. Additionally, LBNP application (used singly or together with head up tilt, HUT) is useful in understanding the physiology of orthostatic intolerance. The role seasonal variations in hormonal, autonomic and circulatory state play in LBNP-induced hemodynamic responses and LBNP tolerance as well as sex-based diferences during central hypovolemia and the adaptations to exercise training have been investigated using LBNP. The data generated from LBNP studies have been useful in developing better models for prediction of orthostatic tolerance and/or for developing countermeasures. This review examines how LBNP application infuences coagulatory parameters and outlines the efects of temperature changes on LBNP responses. Finally, the review outlines how LBNP can be used as innovative teaching tool and for developing research capacities and interests of medical students and students from other disciplines such as mathematics and computational biology.