Cerebrovascular autoregulation: lessons learned from spaceflight research

Abstract

This review summarizes our current understanding of cerebral blood flow regulation with exposure to microgravity, outlines potential mechanisms associated with post-flight orthostatic intolerance, and proposes future directions for research and linkages with cerebrovascular disorders found in the general population. It encompasses research from cellular mechanisms (e.g. hind limb suspension: tissue, animal studies) to whole body analysis with respect to understanding human responses using space analogue studies (bed rest, parabolic flight) as well as data collected before, during, and after spaceflight. Recent evidence indicates that cerebrovascular autoregulation may be impaired in some astronauts leading to increased susceptibility to syncope upon return to a gravitational environment. The proposed review not only provides insights into the mechanisms of post-flight orthostatic intolerance, but also increases our understanding of the mechanisms associated with pathophysiological conditions (e.g. unexplained syncope) with clinical applications in relation to postural hypotension or intradialytic hypotension.

The effects of varying gravito-inertial stressors on grip strength and hemodynamic responses in men and women

“…Orthostatic intolerance remains a problem upon return to Earth from the microgravity environment of spaceflight (Goswami et al 2013; Blaber et al 2013). Almost every astronaut returning from space exhibits symptoms of cardiovascular deconditioning (Blaber et al 2011).…”

Genomic Analysis of 727 Patients with Ehlers-Danlos Syndrome I: Clinical Perspective Relates 23 Genes to a Maternally Influenced Arthritis-Adrenaline Disorder

“…The AAD process as a secondary complication can be anticipated in a wide range of disorders, often unrecognized in congenital disorders with malformations, hypotonia, and joint laxity (far left) [53] that should have high yields from genomic testing (as shown by the 78% of tested developmental disability patients having variants in Table 2). On the near right are genetic causes [12] of dysautonomia and far right are diverse conditions with autonomic imbalance, most multifactorial like aging, post-infection, re-adjustment to gravity [60] (right square), and other acquired disorders [61] where protein-coding changes will imply disposition rather than disease.…”

The Effects of Varying Gravito-inertial Stressors on Grip Strength and Hemodynamic Responses Across Gender

“…Orthostatic intolerance refers to the inability of a person to maintain upright posture without syncope, a transient loss of consciousness due to inadequate oxygen delivery to the brain (17). Orthostatic intolerance remains a problem upon return to Earth from the microgravity environment of spaceflight (4, 12). Almost every astronaut returning from space exhibits symptoms of cardiovascular deconditioning (3).…”

“…Artificial gravity (AG) administered during spaceflight or in ground-based analogues of spaceflight may prevent deconditioning in different physiological systems as well as prevent the development of orthostatic intolerance upon return to Earth. Current evidence from studies of ambulatory and deconditioned men and women indicate that 90 minutes of an individualized short- arm centrifuge AG profile significantly increased participants’ orthostatic tolerance limits via increased blood pressure and cerebral blood flow (3, 4, 8, 12–14). However, men and women respond very differently to these stressors (16).…”