Trial reportThe Journal of physiology2014
Impact of hypocapnia and cerebral perfusion on orthostatic tolerance.
Trial report in The Journal of physiology, 2014. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 26 papers.
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
26 citing papers in PubMed, 46 citations in OpenAlex.
- Nitric oxide synthase inhibition in healthy adults reduces regional and total cerebral macrovascular blood flow and microvascular perfusion.The Journal of physiology · 2021Trial
- The effect of αThe Journal of physiology · 2017Trial
- Impact of remote ischaemic preconditioning on cerebral oxygenation during total knee arthroplasty.International journal of medical sciences · 2017Trial
- Linking Neurocardiovascular Responses in the Active Stand Test to Adverse Outcomes: Insights from the Irish Longitudinal Study on Ageing (TILDA).Sensors (Basel, Switzerland) · 2025Article
- Cerebral blood flow during simulated central hypovolaemia in people with hypertension: does vertebral artery hypoplasia matter?The Journal of physiology · 2025Article
- Static autoregulation in humans.Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism · 2024Review
- A 10-min reduction in cerebral blood flow does not alter post-intervention executive function: evidence from lower-body negative pressure.Experimental brain research · 2024Article
- Worsening Symptoms Is Associated with Larger Cerebral Blood Flow Abnormalities during Tilt-Testing in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).Medicina (Kaunas, Lithuania) · 2023Article
- The effect of oscillatory hemodynamics on the cardiovascular responses to simulated hemorrhage during isocapnia.Journal of applied physiology (Bethesda, Md. : 1985) · 2023Article
- Reduced basal macrovascular and microvascular cerebral blood flow in young adults with metabolic syndrome: potential mechanisms.Journal of applied physiology (Bethesda, Md. : 1985) · 2023Article
- Peaks and valleys: oscillatory cerebral blood flow at high altitude protects cerebral tissue oxygenation.Physiological measurement · 2021Article
- The impact of acute central hypovolemia on cerebral hemodynamics: does sex matter?Journal of applied physiology (Bethesda, Md. : 1985) · 2021Article
- A comparison of protocols for simulating hemorrhage in humans: step versus ramp lower body negative pressure.Journal of applied physiology (Bethesda, Md. : 1985) · 2021Article
- 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
- Differential contribution of cyclooxygenase to basal cerebral blood flow and hypoxic cerebral vasodilation.American journal of physiology. Regulatory, integrative and comparative physiology · 2020Article
- Cerebral Blood Flow Response to Simulated Hypovolemia in Essential Hypertension: A Magnetic Resonance Imaging Study.Hypertension (Dallas, Tex. : 1979) · 2019Article
- Impact of environmental stressors on tolerance to hemorrhage in humans.American journal of physiology. Regulatory, integrative and comparative physiology · 2019Article
- Similarity between carotid and coronary artery responses to sympathetic stimulation and the role of αJournal of applied physiology (Bethesda, Md. : 1985) · 2018Article
- Transcranial Doppler in autonomic testing: standards and clinical applications.Clinical autonomic research : official journal of the Clinical Autonomic Research Society · 2018Review
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
12 authors at 4 institutions in 4 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
We examined two novel hypotheses: (1) that orthostatic tolerance (OT) would be prolonged when hyperventilatory-induced hypocapnia (and hence cerebral hypoperfusion) was prevented; and (2) that pharmacological reductions in cerebral blood flow (CBF) at baseline would lower the 'CBF reserve', and ultimately reduce OT. In study 1 (n = 24; aged 25 ± 4 years) participants underwent progressive lower-body negative pressure (LBNP) until pre-syncope; end-tidal carbon dioxide (P ET , CO 2) was clamped at baseline levels (isocapnic trial) or uncontrolled. In study 2 (n = 10; aged 25 ± 4 years), CBF was pharmacologically reduced by administration of indomethacin (INDO; 1.2 mg kg(-1)) or unaltered (placebo) followed by LBNP to pre-syncope. Beat-by-beat measurements of middle cerebral artery blood flow velocity (MCAv; transcranial Doppler), heart rate (ECG), blood pressure (BP; Finometer) and end-tidal gases were obtained continuously. In a subset of subjects' arterial-to-jugular venous differences were obtained to examine the independent impact of hypocapnia or cerebral hypoperfusion (following INDO) on cerebral oxygen delivery and extraction. In study 1, during the isocapnic trial, P ET , CO 2 was successfully clamped at baseline levels at pre-syncope (38.3 ± 2.7 vs. 38.5 ± 2.5 mmHg respectively; P = 0.50). In the uncontrolled trial, P ET , CO 2 at pre-syncope was reduced by 10.9 ± 3.9 mmHg (P ≤ 0.001). Compared to the isocapnic trial, the decline in mean MCAv was 15 ± 4 cm s(-1) (35%; P ≤ 0.001) greater in the uncontrolled trial, yet the time to pre-syncope was comparable between trials (544 ± 130 vs. 572 ± 180 s; P = 0.30). In study 2, compared to placebo, INDO reduced resting MCAv by 19 ± 4 cm s(-1) (31%; P ≤ 0.001), but time to pre-syncope remained similar between trials (placebo: 1123 ± 138 s vs. INDO: 1175 ± 212 s; P = 0.53). The brain extracted more oxygen in face of hypocapnia (34% to 53%) or cerebral hypoperfusion (34% to 57%) to compensate for reductions in delivery. In summary, cerebral hypoperfusion either at rest or induced by hypocapnia at pre-syncope does not impact OT, probably due to a compensatory increase in oxygen extraction.
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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.