Evidence on microcirculatory dynamics that preserves the equivalent perfusion steady state in both inferior limbs
Authors: Rodrigues Luis Monteiro , Rocha Clemente , Silva Henrique , Ferreira Hugo , Gadeau Alain‐Pierre 
Published: June 2021

The microcirculatory physiology critically depends on a highly structured network of vessels arranged to deliver oxygen to the tissues in a optimized way. In turn, oxygen is also a critical regulatory element of these functions, not only acting locally, influencing resistance, but also controlled by other local and systemic (homeostatic) regulators. Using oxygen as a challenger we detected an interesting regional perfusion dynamics taking place in the mouse, after an hindlimb ischemia procedure, where the contralateral non operated limb contributed to recover the equivalent circulatory steady state in both limbs. A similar cooperation perfusion event, involving both limbs, has only been referred as a long‐term vascular adaptation to ischemia in patients with peripheral arterial occlusive disease, but never, to our knowledge, experimentally pursued.More recently the impact of postural vasoconstriction in the human foot perfusion, the veno‐arterial reflex (VAR), measured with photoplethysmography (PPG) revealed a pronounced reduction of perfusion in the dependent foot followed by a reduction in the contralateral foot. This effective impact of VAR in the contralateral limb was here demonstrated for the first time, suggesting a different perspective about a wider regional control in the lower limb perfusionHomeostasis, e.g. that the initial reflex in the depending limb, explained by a myogenic‐endothelial cooperation, seems now to be only a part of a wider mechanism. In the present study, we show evidence of this cooperation between limbs, using non‐invasive techniques such as PPG, Laser Doppler Flowmetry (LDF) and a new non‐contact polarization spectroscopy system. The study includes 49 volunteers, both sexes, divided into two groups ‐ a young (n=34, 19.86 ± 1.58 years old) and older, also healthy group (n=15, 55.22 ± 6.04 years old), submitted to two massage protocols (applied on the ascending and descending direction) in one randomly selected limb, using the contralateral as the control. Each protocol consisted in three phases ‐ resting (I), massage (II) and recovery (III). Signals were registered in both feet (toes) and decomposed by the wavelet transform (WT) (p<0.05). PPG, LDF and spectroscopy all similarly revealed the same features – a significant increase of blood perfusion in both limbs (massaged and non‐massaged) during the maneuver, more pronounced in the younger group suggesting the existence of a similar homeostatic cooperation, evoked to reestablish the local circulation setpoint.The wavelet transform analysis of PPG and LDF curves have shown that in younger volunteers, the myogenic and sympathetic components seem to vary most with massage, when compared with the older group. This also confirms that age influences the efficiency of these regulatory mechanisms, and that this strategy helps to look deeper into the physiological processes here involved.Support or Funding InformationSupported by national funds from FCT ‐ IP within the project UID/DTP/04567/2016.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.