Page 48 - BH-2-1

Brain & Heart

ORIGINAL RESEARCH ARTICLE
Sleep-induced limb vasodilation in individuals

confined to bed for 24 h

1
Edoardo Casiglia * and Valérie Tikhonoff 2
1 Department of Medicine, Studium Patavinum, University of Padua, Padua, Italy
2 Department of Medicine, Unit of Nutrition, University of Padua, Padua, Italy

Abstract

The sleep/wake rhythm in limbs has been scarcely studied, especially due to the
difficulty associated with continuous monitoring of arterial flow to the forearm and
leg for a 24-h period. Addressing this constraint, we employed indium-gallium-
in-silicone strain-gauge venous-occlusion plethysmography, an automated
method facilitating the measurement of 24-h limb arterial flow in bed-confined
subjects without disturbing their natural sleep. This article presents the state of
the art in this field. Our examination of 60 healthy normotensive individuals
revealed a distinctive sleep/wake rhythm in limb arterial flow, characterized by
elevated values during sleep (32.7% in the forearm, P < 0.0001; 39.1% in the leg,
P < 0.0001). Correspondingly, limb resistance mirrored the trend of flow (-32.7%,
P < 0.0001; -33.5%, P < 0.0001), with these variations attributed to sleep-induced
limb vasodilation. Sleep-associated vasodilation was also evident in 21 hypertensive
individuals (leg resistance: -33.1%, P < 0.0001) and 13 heart transplant recipients
lacking vagal and sympathetic cardiac innervation (resistance: -33.6%, P < 0.0001).
On the contrary, among 11 subjects with an interrupted spinal cord, we observed
*Corresponding author: forearm vasodilation (resistance: -36.6%, P < 0.0001) but observed no leg
Edoardo Casiglia vasodilation if the spinal lesion was under T2 (innervating the leg). Furthermore,
(edoardo.casiglia@unipd.it)
a loss of sleep-induced vasodilation occurred in both the forearm and leg if the
Citation: Casiglia E, Tikhonoff V. injury was above C7 (innervating both forearm and leg). Our conclusion posits the
Sleep-induced limb vasodilation in existence of sleep-induced limb vasodilation, a phenomenon attributed to signals
individuals confined to bed for 24 h.
Brain & Heart. 2024;2(1):1886. traveling along the spinal cord, with the heart playing no discernible role in this
https://doi.org/10.36922/bh.1886 rhythmic process, and arterial hypertension deemed irrelevant. Comprehensive
Received: September 21, 2023 further studies are imperative to elucidate the precise triggers of limb vasodilation
during sleep.
Accepted: December 11, 2023
Published Online: February 15, 2024
Keywords: Arterial flow; Peripheral resistance; Sleep-induced vasodilation; Strain-gauge
Copyright: © 2024 Author(s). plethysmography; 24-h continuous monitoring; Circadian; Spinal cord injury; Heart
This is an Open-Access article
distributed under the terms of the transplant
Creative Commons Attribution
License, permitting distribution,
and reproduction in any medium,
provided the original work is
properly cited. 1. Introduction
Publisher’s Note: AccScience The literature extensively documents circadian rhythms across various human organs and
Publishing remains neutral with functions. 1-11 Notably, arterial blood pressure (BP) rhythms within limbs have undergone
regard to jurisdictional claims in 12-15 16-20
published maps and institutional thorough investigation using both unrestricted intra-arterial and indirect
affiliations. monitoring methodologies. These studies consistently reveal a tendency for BP to be

Volume 2 Issue 1 (2024) 1 https://doi.org/10.36922/bh.1886