{"title":"Effects of sodium bicarbonate ingestion on ventilatory and cerebrovascular responses in resting heated humans.","authors":"Akira Katagiri, Naoto Fujii, Kohei Dobashi, Yin-Feng Lai, Bun Tsuji, Takeshi Nishiyasu","doi":"10.1152/ajpregu.00161.2024","DOIUrl":null,"url":null,"abstract":"<p><p>Hyperthermia stimulates ventilation in humans. This hyperthermia-induced hyperventilation may be mediated by the activation of peripheral chemoreceptors implicated in the regulation of respiration in reaction to various chemical stimuli, including reductions in arterial pH. Here, we investigated the hypothesis that during passive heating at rest, the increases in arterial pH achieved with sodium bicarbonate ingestion, which could attenuate peripheral chemoreceptor activity, mitigate hyperthermia-induced hyperventilation. We also assessed the effect of sodium bicarbonate ingestion on cerebral blood flow responses, which are associated with hyperthermia-induced hyperventilation. Twelve healthy men ingested sodium bicarbonate (0.3 g/kg body weight) or sodium chloride (0.208 g/kg). One hundred minutes after the ingestion, the participants were passively heated using hot-water immersion (42°C) combined with a water-perfused suit. Increases in esophageal temperature (an index of core temperature) and minute ventilation (V̇<sub>E</sub>) during the heating were similar in the two trials. Moreover, when V̇<sub>E</sub> is expressed as a function of esophageal temperature, there were no between-trial differences in the core temperature threshold for hyperventilation (38.0 ± 0.3 vs. 38.0 ± 0.4°C, <i>P</i> = 0.469) and sensitivity of hyperthermia-induced hyperventilation as assessed by the slope of the core temperature-V̇<sub>E</sub> relation (13.5 ± 14.2 vs. 15.8 ± 15.5 L/min/°C, <i>P</i> = 0.831). Furthermore, middle cerebral artery mean blood velocity (an index of cerebral blood flow) decreased similarly with heating duration in both trials. These results suggest that sodium bicarbonate ingestion does not mitigate hyperthermia-induced hyperventilation and the reductions in cerebral blood flow index in resting heated humans.<b>NEW & NOTEWORTHY</b> Hyperthermia leads to hyperventilation and associated cerebral hypoperfusion, both of which may impair heat tolerance. This hyperthermia-induced hyperventilation may be mediated by peripheral chemoreceptors, which can be activated by reductions in arterial pH. However, our results suggest that sodium bicarbonate ingestion, which can increase arterial pH, is not an effective intervention in alleviating hyperthermia-induced hyperventilation and cerebral hypoperfusion in resting heated humans.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":null,"pages":null},"PeriodicalIF":2.2000,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"American journal of physiology. Regulatory, integrative and comparative physiology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1152/ajpregu.00161.2024","RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2024/8/5 0:00:00","PubModel":"Epub","JCR":"Q3","JCRName":"PHYSIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Hyperthermia stimulates ventilation in humans. This hyperthermia-induced hyperventilation may be mediated by the activation of peripheral chemoreceptors implicated in the regulation of respiration in reaction to various chemical stimuli, including reductions in arterial pH. Here, we investigated the hypothesis that during passive heating at rest, the increases in arterial pH achieved with sodium bicarbonate ingestion, which could attenuate peripheral chemoreceptor activity, mitigate hyperthermia-induced hyperventilation. We also assessed the effect of sodium bicarbonate ingestion on cerebral blood flow responses, which are associated with hyperthermia-induced hyperventilation. Twelve healthy men ingested sodium bicarbonate (0.3 g/kg body weight) or sodium chloride (0.208 g/kg). One hundred minutes after the ingestion, the participants were passively heated using hot-water immersion (42°C) combined with a water-perfused suit. Increases in esophageal temperature (an index of core temperature) and minute ventilation (V̇E) during the heating were similar in the two trials. Moreover, when V̇E is expressed as a function of esophageal temperature, there were no between-trial differences in the core temperature threshold for hyperventilation (38.0 ± 0.3 vs. 38.0 ± 0.4°C, P = 0.469) and sensitivity of hyperthermia-induced hyperventilation as assessed by the slope of the core temperature-V̇E relation (13.5 ± 14.2 vs. 15.8 ± 15.5 L/min/°C, P = 0.831). Furthermore, middle cerebral artery mean blood velocity (an index of cerebral blood flow) decreased similarly with heating duration in both trials. These results suggest that sodium bicarbonate ingestion does not mitigate hyperthermia-induced hyperventilation and the reductions in cerebral blood flow index in resting heated humans.NEW & NOTEWORTHY Hyperthermia leads to hyperventilation and associated cerebral hypoperfusion, both of which may impair heat tolerance. This hyperthermia-induced hyperventilation may be mediated by peripheral chemoreceptors, which can be activated by reductions in arterial pH. However, our results suggest that sodium bicarbonate ingestion, which can increase arterial pH, is not an effective intervention in alleviating hyperthermia-induced hyperventilation and cerebral hypoperfusion in resting heated humans.
期刊介绍:
The American Journal of Physiology-Regulatory, Integrative and Comparative Physiology publishes original investigations that illuminate normal or abnormal regulation and integration of physiological mechanisms at all levels of biological organization, ranging from molecules to humans, including clinical investigations. Major areas of emphasis include regulation in genetically modified animals; model organisms; development and tissue plasticity; neurohumoral control of circulation and hypertension; local control of circulation; cardiac and renal integration; thirst and volume, electrolyte homeostasis; glucose homeostasis and energy balance; appetite and obesity; inflammation and cytokines; integrative physiology of pregnancy-parturition-lactation; and thermoregulation and adaptations to exercise and environmental stress.