White Matthew D
Laboratory for Exercise and Environmental Physiology, 8888 University Dr., School of Kinesiology, Simon Fraser Univ., Burnaby, British Columbia, Canada V5A 1S6.
J Appl Physiol (1985). 2006 Aug;101(2):655-63. doi: 10.1152/japplphysiol.00210.2006. Epub 2006 Mar 24.
The pattern of breathing during a hyperthermia-induced hyperventilation varies across different species. Thermal tachypnea is a first phase panting response adopted during hyperthermia when tidal volume is minimized and the frequency of breathing is maximized. Blood-gas tensions and pH are maintained during this hyperventilation, and the associated heat loss helps the animal regulate its body temperature. A second pattern of breathing adopted in hyperthermia is thermal hyperpnea; this response is the focus of this review. This form of hyperventilation is evident after an increase in core temperature and it is apparent in humans. Increases of tidal volume as well as frequency of breathing are evident during this response that results in a respiratory alkalosis. The cause of thermal hyperpnea is not resolved; evidence of the potential mechanisms underlying this response support that modulators of the response act in either a multiplicative or additive manner with body temperatures. The details of the designs and methodologies of the studies supporting or refuting these two views are discussed. A physiological rationale for thermal hyperpnea is presented in which it is suggested this response serves a heat-loss role and contributes to selective brain cooling in hyperthermic humans. Ongoing research in this area is focused on resolving the mechanisms underlying thermal hyperpnea and its contribution to cranial thermoregulation. The direct application of this research is for the care of febrile and hyperthermic patients.
热应激诱导的过度通气期间的呼吸模式在不同物种间存在差异。热喘是热应激期间出现的第一阶段喘息反应，此时潮气量最小化，呼吸频率最大化。在这种过度通气过程中，血气张力和pH值得以维持，且相关的热量散失有助于动物调节体温。热应激时采用的第二种呼吸模式是热深快呼吸；这种反应是本综述的重点。这种形式的过度通气在核心体温升高后很明显，在人类中也很显著。在此反应过程中，潮气量和呼吸频率均增加，导致呼吸性碱中毒。热深快呼吸的原因尚未明确；支持该反应潜在机制的证据表明，该反应的调节因子与体温呈相乘或相加的作用方式。本文讨论了支持或反驳这两种观点的研究设计和方法的细节。文中提出了热深快呼吸的生理原理，即该反应起到散热作用，并有助于热应激状态下人类的选择性脑冷却。该领域正在进行的研究聚焦于解析热深快呼吸的潜在机制及其对颅脑体温调节的作用。这项研究的直接应用在于发热和热应激患者护理。
