Systemic and cerebral circulatory adjustment within the first 60 s after active standing: An integrative physiological view

Abstract

Transient cardiovascular and cerebrovascular responses within the first minute of active standing provide the means to assess autonomic, cardiovascular and cerebrovascular regulation using a real-world everyday stimulus. Traditionally, these responses have been used to detect autonomic dysfunction, and to identify the hemodynamic correlates of patient symptoms and attributable causes of (pre)syncope and falls.This review addresses the physiology of systemic and cerebrovascular adjustment within the first 60 s after active standing. Mechanical factors induced by standing up cause a temporal mismatch between cardiac output and vascular conductance which leads to an initial blood pressure drops with a nadir around 10 s. The arterial baroreflex counteracts these initial blood pressure drops, but needs 2-3 s to be initiated with a maximal effect occurring at 10 s after standing while, in parallel, cerebral autoregulation buffers these changes within 10 s to maintain adequate cerebral perfusion. Interestingly, both the magnitude of the initial drop and these compensatory mechanisms are thought to be quite well-preserved in healthy aging.It is hoped that the present review serves as a reference for future pathophysiological investigations and epidemiological studies. Further experimental research is needed to unravel the causal mechanisms underlying the emergence of symptoms and relationship with aging and adverse outcomes in variants of orthostatic hypotension.

The validity and reliability of an open source biosensing board to quantify heart rate variability

“…Prior to the standing protocol, participants completed other tasks in a seated position. Therefore, a minimum washout period of one minute was given to ensure cardiovascular metrics had normalized due to the postural shift (i.e., seated to standing) [35]. Further, in conjunction with previous research, this position was chosen as it has shown to elicit greater [36,37] or equivalent [38,39] reproducibility compared to the supine/seated position.…”

“…However, the one exception within the current investigation was pNN50 metrics, which displayed a larger between-day coefficient of variation (23.3%) (Table 2). This likely is attributable to the notion sympathetic activity increases when HRV is quantified within the orthostatic posture compared to seated or supine positions [35,36]. This will elevate heart rate and lower HRV metrics, especially relevant for the pNN50 metric, as there is a reduced duration of time between subsequent heart beats.…”

The sympathies of the body: functional organization and neuronal differentiation in the peripheral sympathetic nervous system

“…The continuous requirement for integrated balancing action on the cardiovascular system by the autonomic nervous system during everyday life is nicely illustrated by the adjustments required within the first minute of standing up (Harms et al 2021 ). The concerted action of the sympathetic and parasympathetic nervous system on heart performance and vasculature control that may be requested at intervals of less than minutes demand a balancing system of high reliability.…”

Central Hypovolemia Detection During Environmental Stress—A Role for Artificial Intelligence?

“…Standing up creates a heart-brain hydrostatic gradient resulting in a reduction of CBF and a fall in CO by posture or cardiac disease contributes to it (Scheinberg and Stead, 1949 ; Hellstrøm et al, 1994 ; Ide et al, 1998 ; Pott et al, 2000 ; Van Lieshout et al, 2003 ; Bronzwaer et al, 2017b ; Junejo et al, 2019 , 2020 ; Vlastra et al, 2020 ; Claassen et al, 2021 ). Together with the acute vasodilatation in the active leg muscles, this sequence of events initiates autonomic cardiovascular reflex activity with an increase in HR and peripheral vascular resistance until an early steady state has been reached after ~2 min in the upright position with slightly reduced CO, elevated HR, and increased diastolic BP and with an impact on CBF and brain cortical oxygenation (Piorry, 1826 ; Hill, 1895 ; Sjöstrand, 1952 ; Gauer and Thron, 1965 ; Blomqvist and Stone, 1984 ; Bode, 1991 ; Levine et al, 1994 ; Wieling et al, 1996 ; Pott et al, 2000 ; Shoemaker et al, 2001 ; Van Lieshout et al, 2001 ; Harms et al, 2003 , 2010 , 2020 ; Immink et al, 2006 ). The effects of exercising in the upright vs. seated position on cardiac preload are exemplified by a lower HR during ergometer rowing than during treadmill running (Yoshiga and Higuchi, 2002 ).…”