Cardio-postural deconditioning: A model for post-flight orthostatic intolerance.
Post-flight astronauts experience temporary but sometimes severe postural control dysfunction and decreased orthostatic tolerance. Research points to a possible link between cardiovascular and postural controls and orthostatic tolerance [Claydon,V.E., Hainsworth, R., 2006. Postural sway in patients with syncope and poor orthostatic tolerance. Heart 92, 1688-1689], for which a neurophysiological model has been presented [Souvestre, P.A., Blaber A.P., Landrock C.K., 2008. Space motion sickness: the sensory-motor controls and cardiovascular correlation. Acta Astronautica 63, 745-757]. To validate this model, young and elderly subjects (n=12) were compared with respect to postural mediolateral sway (ML sway) and blood pressure (BP) during quiet standing. Both groups had a peak in the low frequency region (0.03-0.07Hz) of cross-spectral power between ML sway and BP; however, only the young subjects had signal coherence greater than 0.5. Short-range Hurst coefficient from Stabilogram Dynamic Analysis was significantly lower for ML sway in young (0.694+/-0.068) compared to elderly subjects (0.812+/-0.10) (p=0.028). Young subjects were better able to command a closed-loop strategy of motor-control providing a more efficient postural control. Further application of this model with astronauts could lead to further understanding of post-flight orthostatic intolerance.
Blaber
Andrew P
AP
Simon Fraser University, Burnaby, BC, Canada. ablaber@sfu.ca
Landrock
Clinton K
CK
Souvestre
Philippe A
PA
D000328:Adult; D000367:Age Factors; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D002319:Cardiovascular System / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D054971:Orthostatic Intolerance / Q000503:physiopathology*; D004856:Postural Balance; D011187:Posture / Q000502:physiology*; D018489:Space Motion Sickness / Q000209:etiology; D018561:Space Simulation / Q000379:methods; D013057:Spectrum Analysis; D013269:Stochastic Processes; D055815:Young Adult