Physical countermeasures to increase orthostatic tolerance

Standing upright challenges the cardiovascular system as the pull of gravity displaces about 70% of the circulating blood volume to below heart level, much of it to the compliant veins of the dependent limbs and the pelvic organs. In patients with autonomic failure due to neurodegenerative diseases, the normal cardiovascular adjustments to this challenge are impaired and symptomatic orthostatic hypotension becomes a common risk on standing or even sitting quietly. These patients learn to sway and shift, so that the pumping action of the muscles can be utilised to counter gravitational displacement of blood by squeezing venous blood from the legs upward. Augmentation of venous return in the upright posture can also be achieved by deliberate tensing of lower limb and abdominal muscles [1, 2], as depicted in Fig.1. This article is protected by copyright. All rights reserved