Cerebral blood flow during normocapnic hyperoxia in the unanesthetized pony.
Abstract: The effect of hyperoxia on cerebral blood flow (CBF) was examined in 12 unanesthetized ponies. CBF was determined using radioactive microspheres, 15 micrometer in diam, durijng inspriation of the following gases: 1) room air (control); 2) 40% I2 in N2; and 3) approximately 100% O2 with 2.2-4.5% CO2 added to maintain isocapnia. CBF did not change from control values during either level of hyperoxia. However, cerebrospinal fluid (CSF) carbon dioxide tension (PCO2) increased during 40% O2 (delta 1.0 Torr) and approximately 100% O2 (delta 2.9 Torr). This rise in CSF PCO2, not due to a change in CBF, may have resulted from a decrease in the CO2 carrying capacity of cerebral venous blood during hyperoxia (Haldane effect). Although respiration did not change during 40% O2, expired minute volume increased 25% during approximately 100% O2 due to an increase in tidal volume. This rise in respiration was not associated with changes in any of the conventional stimuli to breathing (arterial pH, O2 tension, or PCO2 or CSF pH). One possible explanation was that cerebral extracellular fluid pH, in the vicinity of the central chemoreceptors, or cerebral intracellular fluid pH changed in a direction unlike CSF pH. An alternate explanation was that the CO2 in the inspired gas activated CO2-sensitive receptors in the lungs.
Publication Date: 1980-01-01 PubMed ID: 7353961DOI: 10.1152/jappl.1980.48.1.10Google Scholar: Lookup
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- Journal Article
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This research article examines the impact of hyperoxia on cerebral blood flow in unanesthetized ponies without a change in CO2 levels. The study found that even with increased oxygen levels, cerebral blood flow did not differ from normal conditions, though carbon dioxide tension in the cerebrospinal fluid did increase.
Research Methodology
- The researchers used 12 unanesthetized ponies for this experiment to observe how hyperoxia affects cerebral blood flow (CBF).
- The method of measuring CBF involved the use of radioactive microspheres, providing accurate blood flow data.
- The ponies were subjected to different gas mixes, including room air, 40% O2 in N2, and approximately 100% O2 with added CO2 to maintain isocapnia (constant carbon dioxide levels).
Research Findings
- The study found no change in CBF values under the hyperoxic conditions compared to the control (room air).
- However, the carbon dioxide tension in the cerebrospinal fluid (CSF PCO2) did increase during hyperoxia.
- The researchers proposed that this increase might come from a decrease in the CO2 carrying capacity of brain venous blood – a phenomenon known as the Haldane effect.
- While there were no observed changes in respiration during 40% O2, the volume of air expired per minute in the approximately 100% O2 condition increased by 25%, due to an increase in tidal volume.
- Interestingly, this increase in respiration didn’t correlate with the conventional triggers for breathing such as arterial pH changes, changes in O2 tension, or fluctuations in CO2 or CSF pH.
Conclusion and Hypotheses
- The researchers theorize that this unexpected increase in respiration may be due to changes in the pH of the cerebral extracellular fluid around central chemoreceptors, or changes in the pH of cerebral intracellular fluid.
- Another proposed hypothesis is that the higher amounts of CO2 in the inhaled gas during the experiment may have triggered CO2-sensitive receptors in the lungs of the ponies, causing the increase in respiration.
Cite This Article
APA
Busija DW, Orr JA, Rankin JH, Liang HK, Wagerle LC.
(1980).
Cerebral blood flow during normocapnic hyperoxia in the unanesthetized pony.
J Appl Physiol Respir Environ Exerc Physiol, 48(1), 10-15.
https://doi.org/10.1152/jappl.1980.48.1.10 Publication
Researcher Affiliations
MeSH Terms
- Acid-Base Equilibrium
- Animals
- Carbon Dioxide / blood
- Cerebrospinal Fluid
- Cerebrovascular Circulation
- Hemodynamics
- Horses
- Hydrogen-Ion Concentration
- Oxygen / blood
- Respiration
Citations
This article has been cited 4 times.- Hauer BE, Negash B, Chan K, Vuong W, Colbourne F, Pagliardini S, Dickson CT. Hyperoxia enhances slow-wave forebrain states in urethane-anesthetized and naturally sleeping rats. J Neurophysiol 2018 Oct 1;120(4):1505-1515.
- Udomphorn Y, Armstead WM, Vavilala MS. Cerebral blood flow and autoregulation after pediatric traumatic brain injury. Pediatr Neurol 2008 Apr;38(4):225-34.
- Shin HK, Dunn AK, Jones PB, Boas DA, Lo EH, Moskowitz MA, Ayata C. Normobaric hyperoxia improves cerebral blood flow and oxygenation, and inhibits peri-infarct depolarizations in experimental focal ischaemia. Brain 2007 Jun;130(Pt 6):1631-42.
- Matta BF, Lam AM, Mayberg TS. The influence of arterial oxygenation on cerebral venous oxygen saturation during hyperventilation. Can J Anaesth 1994 Nov;41(11):1041-6.
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