Schultz Martins Ricardo, Wallace Phillip J, Steele Scott W, Scott Jake S, Taber Michael J, Hartley Geoffrey L, Cheung Stephen S
Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada.
N2M Consulting Inc., St. Catharines, ON, Canada.
Front Psychol. 2021 Dec 22;12:788027. doi: 10.3389/fpsyg.2021.788027. eCollection 2021.
Increases in body temperature from heat stress (i.e., hyperthermia) generally impairs cognitive function across a range of domains and complexities, but the relative contribution from skin versus core temperature changes remains unclear. Hyperthermia also elicits a hyperventilatory response that decreases the partial pressure of end-tidal carbon dioxide (PCO) and subsequently cerebral blood flow that may influence cognitive function. We studied the role of skin and core temperature along with PCO on cognitive function across a range of domains. Eleven males completed a randomized, single-blinded protocol consisting of poikilocapnia (POIKI, no PCO control) or isocapnia (ISO, PCO maintained at baseline levels) during passive heating using a water-perfused suit (water temperature ~ 49°C) while middle cerebral artery velocity (MCA) was measured continuously as an index of cerebral blood flow. Cognitive testing was completed at baseline, neutral core-hot skin (37.0 ± 0.2°C-37.4 ± 0.3°C), hot core-hot skin (38.6 ± 0.3°C-38.7 ± 0.2°C), and hot core-cooled skin (38.5 ± 0.3°C-34.7 ± 0.6°C). The cognitive test battery consisted of a detection task (psychomotor processing), 2-back task (working memory), set-shifting and Groton Maze Learning Task (executive function). At hot core-hot skin, poikilocapnia led to significant (both < 0.05) decreases in PCO (∆-21%) and MCA (∆-26%) from baseline, while isocapnia clamped PCO (∆ + 4% from baseline) leading to a significantly ( = 0.023) higher MCA (∆-18% from baseline) compared to poikilocapnia. There were no significant differences in errors made on any task (all > 0.05) irrespective of skin temperature or PCO manipulation. We conclude that neither skin temperature nor PCO maintenance significantly alter cognitive function during passive hyperthermia.
热应激导致的体温升高（即体温过高）通常会损害一系列领域和复杂程度的认知功能，但皮肤温度变化与核心体温变化的相对贡献仍不清楚。体温过高还会引发过度通气反应，降低呼气末二氧化碳分压（PCO），进而减少可能影响认知功能的脑血流量。我们研究了皮肤温度、核心体温以及PCO在一系列领域的认知功能中所起的作用。11名男性完成了一项随机、单盲方案，在使用水灌注服进行被动加热（水温约49°C）期间，分为低碳酸血症组（POIKI，无PCO控制）或等碳酸血症组（ISO，PCO维持在基线水平），同时连续测量大脑中动脉速度（MCA）作为脑血流量的指标。在基线、中性核心-热皮肤（37.0±0.2°C - 37.4±0.3°C）、热核心-热皮肤（38.6±0.3°C - 38.7±0.2°C）和热核心-冷却皮肤（38.5±0.3°C - 34.7±0.6°C）状态下完成认知测试。认知测试组合包括检测任务（心理运动处理）、2-back任务（工作记忆）、定势转移和格罗顿迷宫学习任务（执行功能）。在热核心-热皮肤状态下，低碳酸血症导致PCO（∆-21%）和MCA（∆-26%）相对于基线显著降低（均P<0.05），而等碳酸血症使PCO保持稳定（相对于基线∆+4%），导致MCA相对于低碳酸血症显著升高（P = 0.023，相对于基线∆-18%）。无论皮肤温度或PCO如何操作，任何任务中的错误均无显著差异（均P>0.05）。我们得出结论，在被动体温过高期间，皮肤温度和PCO维持均不会显著改变认知功能。
