Squatting test: a dynamic postural manoeuvre to study baroreflex sensitivity

Abstract

Squatting is an active posture test that can be used to assess baroreflex sensitivity. Indeed, the shift from squatting to standing imposes a major orthostatic stress leading to rapid and large changes in arterial blood pressure (BP) and heart rate (HR) allowing precise baroreflex assessment. BP and HR can be continuously and non-invasively monitored with a Finapres device. The standing to squatting transition is accompanied by rises in BP, pulse pressure and cardiac output, mainly due to increased venous return, and by a secondary reduction in HR. Conversely, the squatting to standing transition is associated with an immediate drop in BP and both reflex tachycardia and vasoconstriction. This mirror changes in BP and HR, mimicking those observed with the classical pharmacological approach using vasopressor/vasodilating agents, allows the calculation of the so-called baroreflex gain. The present review describes the haemodynamic changes occurring in normal subjects during the shifts from standing to squatting and from squatting to standing and discusses the underlying cardiovascular and autonomic mechanisms. This careful analysis in healthy individuals should help in the understanding of disturbances that may be observed in patients with autonomic dysfunction, such as in diabetic patients with cardiovascular autonomic neuropathy.