Cardiovascular Adjustments to Thermal Stress

Abstract

The sections in this article are: Critique of Some Methods Employed in Humans Total and Regional Cutaneous Blood Flow Cardiac Output Central Blood Volume Regional Blood Flow Measurement of Temperature General Features of the Cutaneous Circulation: A Brief Review Cutaneous Blood Flow Cutaneous Blood Volume Innervation of Cutaneous Arterioles Local Control of Skin Blood Flow: Interaction With Reflexes Reflex and Local Control of Cutaneous Veins Circulatory Adjustments to Heat Stress in Resting Humans Changes in Cardiac Output, Blood Pressure, and Blood Volume Distribution of Cardiac Output in Heat‐Stressed Resting Humans Cardiac Output and Its Distribution in Heat‐Stressed Resting Subhuman Species Distribution of Blood Volume in Heat‐Stressed Resting Humans Mechanisms of Blood Flow Redistribution in Rest Acclimatization in Rest Interaction Between Thermoregulatory and Nonthermoregulatory Reflexes in Control of Skin Blood Flow Cutaneous Vascular Responses to Baroreflexes Cardiopulmonary (Low‐Pressure) Baroreflex Postural Influences: Hydrostatic Problem Upright Posture in Heat Stress: Interaction Between Reflex Vasoconstriction and Vasodilation Exercise Possible Modes of Reflex Interaction: Unsolved Problems Overall Circulatory Adjustments to Heat Stress and Exercise Distribution of Blood Volume Redistribution of Blood Flow During Exercise Central Circulation Adaptation to Heat Stress and Exercise: Acclimatization

Effects of Exposure to High Temperature and Feeding Level on Regional Blood Flow and Oxidative Capacity of Tissues in Piglets

“…Some studies reported an increase in cardiac output in man (Rowell, 1974(Rowell, , 1983, dog (Hales & Dampney, 1975), ox (Whittow, 1965), or chicken (Whittow et al 1964) exposed to high ambient temperatures, whereas no change was observed in the baboon (Hales et al 1979) or sheep (Hales, 1973a). It is of importance to note that those experiments were all performed with animals under acute heat stress, which differs from our study performed with warm-acclimated pigs.…”

“…Most mammals increase their peripheral blood flow at high ambient temperatures to transfer heat through sensible (conduction, convection and radiation) or evaporative heat loss, depending on the efficiency of sudoriparous glands. For instance, in man, skin blood flow is increased at the expense of blood flow to the kidneys, viscera and skeletal muscles (Rowell, 1974(Rowell, , 1983(Rowell, , 1986. This redistribution of blood flow to the skin is usually less pronounced in panting animals like sheep, dogs (Hales, 1973a;Hales & Dampney, 1975) or pigs, which could explain the observation that skin FCO was only increased for the back of piglets and not for the left leg (a tendency for increase was observed for the ear skin).…”

Infrared thermography of human face for monitoring thermoregulation performance and estimating personal thermal comfort

“…When there is thermal stress (i.e., heat and cold) caused by external factors (e.g., increased temperature or humidity) or internal factors (e.g., food intake), human body responds and the thermoregulation system adjusts heat dissipation to the external environment by modifying the blood flow via cutaneous arterioles and veins, causing sweating or shivering [30]. Accordingly, resting skin blood flow in the arterioles in normothermic conditions is approximately 250 mL/min (about 5% of the cardiac output [31]), which results in a heat dissipation of about 80 to 90 kcal/h (~ the level of resting metabolic heat production) [32]. In response to the heat stress, thermoregulatory vasodilation can increase skin blood flow up to 6 to 8 L/min [33] and utilize up to 60% of cardiac output [31].…”

“…Accordingly, resting skin blood flow in the arterioles in normothermic conditions is approximately 250 mL/min (about 5% of the cardiac output [31]), which results in a heat dissipation of about 80 to 90 kcal/h (~ the level of resting metabolic heat production) [32]. In response to the heat stress, thermoregulatory vasodilation can increase skin blood flow up to 6 to 8 L/min [33] and utilize up to 60% of cardiac output [31]. In response to the cold stress, thermoregulatory vasoconstriction can limit the skin blood flow to approach zero.…”

Reflectance spectroscopy: to shed new light on the capillary refill test

“…A patient going into shock redistributes the blood volume from the peripheral to the central circulation. The skin is an important organ in regard to circulatory homeostasis variably absorbing 5-70 % of the cardiac output [4]. Application of a firm blanching pressure to the skin with subsequent observation of the return of blood flow to the blanched area is termed the capillary refill (CR) test.…”