Mortola Jacopo P
Department of Physiology, McIntyre Basic Sciences Building, room 1121, McGill University, 3655 Sir William Osler Promenade, H3G 1Y6, Montreal, Quebec, Canada.
Eur J Appl Physiol. 2004 Mar;91(2-3):119-29. doi: 10.1007/s00421-003-0978-0. Epub 2003 Oct 21.
This article reviews human and animal studies about the circadian patterns of physiological variables involved with the respiratory function. Some measures reflecting the mechanical properties of the lungs, such as functional residual capacity, forced expiratory volumes and airway resistance, change periodically with the time of the day. Also resting pulmonary ventilation (V(E)), tidal volume, and breathing rate follow circadian patterns. In humans, these patterns occur independently of the daily changes in activity, whereas, to some extent, they are linked to changes in the state of arousal. Differently, in some rodents, the circadian oscillations of the breathing pattern occur independently of the daily rhythms of either activity or state of arousal. Recent measurements of the breathing pattern for unlimited periods of time in undisturbed animals have indicated that the circadian changes occur in close temporal phase with those of oxygen consumption, carbon dioxide production, and body temperature. However, none of these variables can fully explain the circadian pattern of breathing, the origin of which remains unclear. Both in humans and in rats the V(E) responses to hypercapnia or hypoxia differ at various times of the day. In rats, the daily differences in V(E) responses are buffered by changes in metabolic rate, such that, unlike humans, the hyperventilation (defined as the increase in ventilation-metabolism ratio) remains constant throughout the 24 h. The presence of a biological clock is a major advantage in the adaptation to the environment, although it forces some variables to deviate periodically from their mean value. In humans, these deviations become apparent in conditions of hypoxia. Hence, a daily time-window exists in which the respiratory system is less capable of responding to challenges, a factor which may contribute to the findings that some cardio-respiratory symptoms and diseases peak at particular times of the day.
本文综述了关于呼吸功能相关生理变量昼夜节律模式的人体和动物研究。一些反映肺机械特性的指标，如功能残气量、用力呼气量和气道阻力，会随一天中的时间周期性变化。静息肺通气量（V(E)）、潮气量和呼吸频率也遵循昼夜节律模式。在人类中，这些模式独立于日常活动变化而出现，而在一定程度上，它们与觉醒状态的变化有关。不同的是，在一些啮齿动物中，呼吸模式的昼夜振荡独立于活动或觉醒状态的昼夜节律。最近在未受干扰的动物中对呼吸模式进行的长时间测量表明，昼夜变化与氧气消耗、二氧化碳产生和体温的变化在时间相位上密切相关。然而，这些变量都不能完全解释呼吸的昼夜模式，其起源仍不清楚。在人类和大鼠中，V(E)对高碳酸血症或低氧血症的反应在一天中的不同时间都有所不同。在大鼠中，V(E)反应的每日差异被代谢率的变化所缓冲，因此，与人类不同，整个24小时内过度通气（定义为通气-代谢比增加）保持恒定。生物钟的存在是适应环境的一个主要优势，尽管它迫使一些变量周期性地偏离其平均值。在人类中，这些偏差在低氧条件下变得明显。因此，存在一个每日时间窗口，在此期间呼吸系统对挑战的反应能力较弱，这一因素可能有助于解释一些心肺症状和疾病在一天中的特定时间达到峰值的现象。
