{"title":"The combined effects of temperature and posture on regional blood flow and haemodynamics","authors":"Jason T. Fisher , Urša Ciuha , Igor B. Mekjavić","doi":"10.1016/j.jtherbio.2024.103937","DOIUrl":null,"url":null,"abstract":"<div><p>Under simultaneous ambient temperature and postural stressors, integrated regional blood flow responses are required to maintain blood pressure and thermoregulatory homeostasis. The aim of the present study was to assess the effect of ambient temperature and body posture on regional regulation of microvascular blood flow, specifically in the arms and legs.</p><p>Participants (N = 11) attended two sessions in which they experienced transient ambient conditions, in a climatic chamber. During each 60-min trial, ambient temperature increased from 15.7 (0.6) °C to 38.9 (0.6) °C followed by a linear decrease, and the participants were either standing or in a supine position throughout the trial; relative humidity in the chamber was maintained at 25.9 (6.6) %. Laser doppler flowmetry of the forearm (SkBF<sub>arm</sub>) and calf (SkBF<sub>calf</sub>), and haemodynamic responses (heart rate, HR; stroke volume, SV; cardiac output, CO; blood pressure, BP), were measured continuously. Analyses of heart rate variability and wavelet transform were also conducted.</p><p>SkBF<sub>arm</sub> increased significantly at higher ambient temperatures <em>(p</em> = 0.003), but not SkBF<sub>calf</sub>. The standing posture caused lower overall SkBF in both regions throughout the protocol, regardless of temperature (<em>p</em> < 0.001). HR and BP were significantly elevated, and SV significantly lowered, in response to separate and combined effects of higher ambient temperatures and a standing position (all <em>p</em> < 0.05); CO remained unchanged. Mechanistic analyses identified greater sympathetic nerve activation, and higher calf myogenic activation at peak temperatures, in the standing condition.</p><p>Mechanistically and functionally, arm vasculature responds to modulation from both thermoregulation and baroreceptor activity. The legs, meanwhile, are more sensitive to baroreflex regulatory mechanisms.</p></div>","PeriodicalId":17428,"journal":{"name":"Journal of thermal biology","volume":"123 ","pages":"Article 103937"},"PeriodicalIF":2.9000,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0306456524001554/pdfft?md5=540b11534d1a7507e28b0f99826ebde3&pid=1-s2.0-S0306456524001554-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of thermal biology","FirstCategoryId":"99","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0306456524001554","RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Under simultaneous ambient temperature and postural stressors, integrated regional blood flow responses are required to maintain blood pressure and thermoregulatory homeostasis. The aim of the present study was to assess the effect of ambient temperature and body posture on regional regulation of microvascular blood flow, specifically in the arms and legs.
Participants (N = 11) attended two sessions in which they experienced transient ambient conditions, in a climatic chamber. During each 60-min trial, ambient temperature increased from 15.7 (0.6) °C to 38.9 (0.6) °C followed by a linear decrease, and the participants were either standing or in a supine position throughout the trial; relative humidity in the chamber was maintained at 25.9 (6.6) %. Laser doppler flowmetry of the forearm (SkBFarm) and calf (SkBFcalf), and haemodynamic responses (heart rate, HR; stroke volume, SV; cardiac output, CO; blood pressure, BP), were measured continuously. Analyses of heart rate variability and wavelet transform were also conducted.
SkBFarm increased significantly at higher ambient temperatures (p = 0.003), but not SkBFcalf. The standing posture caused lower overall SkBF in both regions throughout the protocol, regardless of temperature (p < 0.001). HR and BP were significantly elevated, and SV significantly lowered, in response to separate and combined effects of higher ambient temperatures and a standing position (all p < 0.05); CO remained unchanged. Mechanistic analyses identified greater sympathetic nerve activation, and higher calf myogenic activation at peak temperatures, in the standing condition.
Mechanistically and functionally, arm vasculature responds to modulation from both thermoregulation and baroreceptor activity. The legs, meanwhile, are more sensitive to baroreflex regulatory mechanisms.
期刊介绍:
The Journal of Thermal Biology publishes articles that advance our knowledge on the ways and mechanisms through which temperature affects man and animals. This includes studies of their responses to these effects and on the ecological consequences. Directly relevant to this theme are:
• The mechanisms of thermal limitation, heat and cold injury, and the resistance of organisms to extremes of temperature
• The mechanisms involved in acclimation, acclimatization and evolutionary adaptation to temperature
• Mechanisms underlying the patterns of hibernation, torpor, dormancy, aestivation and diapause
• Effects of temperature on reproduction and development, growth, ageing and life-span
• Studies on modelling heat transfer between organisms and their environment
• The contributions of temperature to effects of climate change on animal species and man
• Studies of conservation biology and physiology related to temperature
• Behavioural and physiological regulation of body temperature including its pathophysiology and fever
• Medical applications of hypo- and hyperthermia
Article types:
• Original articles
• Review articles