Trial reportAmerican journal of physiology. Regulatory, integrative and comparative physiology2013
Hypercapnia-induced increases in cerebral blood flow do not improve lower body negative pressure tolerance during hyperthermia.
Trial report in American journal of physiology. Regulatory, integrative and comparative physiology, 2013. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 14 papers, 1 of them a synthesis that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
14 citing papers in PubMed, 1 synthesis or guideline pooled it, 26 citations in OpenAlex.
- Meta-analysis of heat-induced changes in cardiac function from over 400 laboratory-based heat exposure studies.Nature communications · 2025Pooled it
- Cerebral and peripheral haemodynamics at rest and in response to orthostasis during 3 days of simulated heatwave.Experimental physiology · 2026Article
- Cerebrovascular regulation during heat stress.Experimental physiology · 2026Review
- The effect of oscillatory hemodynamics on the cardiovascular responses to simulated hemorrhage during isocapnia.Journal of applied physiology (Bethesda, Md. : 1985) · 2023Article
- The effect of hypercapnia on regional cerebral blood flow regulation during progressive lower-body negative pressure.European journal of applied physiology · 2021Article
- An assessment of hypercapnia-induced elevations in regional cerebral perfusion during combined orthostatic and heat stresses.The journal of physiological sciences : JPS · 2020Article
- Impact of environmental stressors on tolerance to hemorrhage in humans.American journal of physiology. Regulatory, integrative and comparative physiology · 2019Article
- Tolerance to a haemorrhagic challenge during heat stress is improved with inspiratory resistance breathing.Experimental physiology · 2018Article
- Effect of acute hypoxemia on cerebral blood flow velocity control during lower body negative pressure.Physiological reports · 2018Article
- Mechanisms of orthostatic intolerance during heat stress.Autonomic neuroscience : basic & clinical · 2016Review
- Cerebral blood velocity regulation during progressive blood loss compared with lower body negative pressure in humans.Journal of applied physiology (Bethesda, Md. : 1985) · 2015Article
- Human cardiovascular responses to passive heat stress.Comprehensive Physiology · 2015Review
- Cerebral oxygenation and hyperthermia.Frontiers in physiology · 2014Review
- Cerebral Hemodynamics and Vagally Mediated HRV Associated with High- and Low-frequency Yoga Breathing: An Exploratory, Randomized, Crossover Study.International journal of yogaArticle
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
4 authors at 3 institutions in 3 countries.
Funding
Abstract
Heat-related decreases in cerebral perfusion are partly the result of ventilatory-related reductions in arterial CO2 tension. Cerebral perfusion likely contributes to an individual's tolerance to a challenge like lower body negative pressure (LBNP). Thus increasing cerebral perfusion may prolong LBNP tolerance. This study tested the hypothesis that a hypercapnia-induced increase in cerebral perfusion improves LBNP tolerance in hyperthermic individuals. Eleven individuals (31 ± 7 yr; 75 ± 12 kg) underwent passive heat stress (increased intestinal temperature ∼1.3°C) followed by a progressive LBNP challenge to tolerance on two separate days (randomized). From 30 mmHg LBNP, subjects inhaled either (blinded) a hypercapnic gas mixture (5% CO2, 21% oxygen, balanced nitrogen) or room air (SHAM). LBNP tolerance was quantified via the cumulative stress index (CSI). Mean middle cerebral artery blood velocity (MCAvmean,) and end-tidal CO2 (PetCO2) were also measured. CO2 inhalation of 5% increased PetCO2 at ∼40 mmHg LBNP (by 16 ± 4 mmHg) and at LBNP tolerance (by 18 ± 5 mmHg) compared with SHAM (P < 0.01). Subsequently, MCAvmean was higher in the 5% CO2 trial during ∼40 mmHg LBNP (by 21 ± 12 cm/s, ∼31%) and at LBNP tolerance (by 18 ± 10 cm/s, ∼25%) relative to the SHAM (P < 0.01). However, hypercapnia-induced increases in MCAvmean did not alter LBNP tolerance (5% CO2 CSI: 339 ± 155 mmHg × min; SHAM CSI: 273 ± 158 mmHg × min; P = 0.26). These data indicate that inhaling a hypercapnic gas mixture increases cerebral perfusion during LBNP but does not improve LBNP tolerance when hyperthermic.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.