Influence of the mode of heating on cerebral blood flow, non-invasive intracranial pressure and thermal tolerance in humans
Gibbons TD, Ainslie PN, Thomas KN, Wilson LC, Akerman AP, Donnelly J, Campbell HA, Cotter JD
The Journal of physiology · 34 citations
Review labels
Neutral facts our review recorded about how this study was done. They describe method, never whether we like the result.
How it was studied
- Design
- Controlled clinical trial (classified by our AI screen)
- Studied in
- People
- Main outcome
- Health markers and function
Who paid for it
- Funding
- Funding not disclosed
Publication
- Published
- 2021-02-15 · J Physiol · vol. 599 · issue 7 · pp. 1977–1996
- Publisher
- Wiley
- Cited
- 39 citations · more than 90% of similar papers · 2.5× the field average
- References
- 87 works
- Access
- Paywalled
- Research areas
- Thermoregulation and physiological responses · Climate Change and Health Impacts · Thermal Regulation in Medicine
- Keywords
- Cerebral blood flow, Orthostatic vital signs, Heat stress, Medicine, Blood pressure, Cardiology, Stroke (engine), Human brain, Internal medicine, Anesthesia, Thermodynamics, Biology, Animal science
- MeSH
- humans, heat stress disorders, exercise, heating, blood pressure, cerebrovascular circulation, intracranial pressure, female
8 authors
From NZ, CA
- Travis Dylan Gibbons · correspondingUniversity of Otago
- Philip Neil AinslieUniversity of British Columbia; University of British Columbia, Okanagan Campus
- Kate Nicole ThomasUniversity of Otago
- Luke C. WilsonUniversity of Otago
- Ashley Paul AkermanUniversity of Ottawa
- Joseph E. DonnellyUniversity of Auckland; Auckland University of Technology
Abstract
Key points
The human brain is particularly vulnerable to heat stress; this manifests as impaired cognition, orthostatic tolerance, work capacity and eventually, brain death. The brain's limitation in the heat is often ascribed to inadequate cerebral blood flow (CBF), but elevated intracranial pressure is commonly observed in mammalian models of heat stroke and can on its own cause functional impairment. The CBF response to incremental heat strain was dependent on the mode of heating, decreasing by 30% when exposed passively to hot, humid air (sauna), while remaining unchanged or increasing with passive hot-water immersion (spa) and exercising in a hot environment. Non-invasive intracranial pressure estimates (nICP) were increased universally by 18% at volitional thermal tolerance across all modes of heat stress, and therefore may play a contributing role in eliciting thermal tolerance. The sauna, more so than the spa or exercise, poses a greater challenge to the brain under mild to severe heating due to lower blood flow but similarly increased nICP.
Abstract
The human brain is particularly vulnerable to heat stress; this manifests as impaired cognitive function, orthostatic tolerance, work capacity, and eventually, brain death. This vulnerability is often ascribed to inadequate cerebral blood flow (CBF); however, elevated intracranial pressure (ICP) is also observed in mammalian models of heat stroke. We investigated the changes in CBF with incremental heat strain under three fundamentally different modes of heating, and assessed whether heating per se increased ICP. Fourteen fit participants (seven female) were heated to thermal tolerance or 40°C core temperature (Tc ; oesophageal) via passive hot-water immersion (spa), passive hot, humid air exposure (sauna), cycling exercise, and cycling exercise with CO2 inhalation to prevent heat-induced hypocapnia. CBF was measured with duplex ultrasound at each 0.5°C increment in Tc and ICP was estimated non-invasively (nICP) from optic nerve sheath diameter at thermal tolerance. At thermal tolerance, CBF was decreased by 30% in the sauna (P c was achieved with passive heating, and preventing hypocapnia during exercise did not improve exercise or thermal tolerance (P ≥ 0.146). Therefore, the regulation of CBF is dramatically different depending on the mode and dose of heating, whereas nICP responses are not. The sauna, more so than the spa or exercise, poses a greater challenge to the brain under equivalent heat strain.
Abstract via Europe PMC. Copyright remains with the authors or publisher.
Community trust
Loading…
How much do you trust this study's findings?
Comments
Sign in to rate, comment on or flag this study.Sign inSomething wrong here?
Flag this study if its information, labels or funding look wrong. An editor reviews every flag.
Sign in to rate, comment on or flag this study.Sign inEducational information about published research. Not medical advice, and not a recommendation to start or stop anything.