Metabolism, Temperature, and Ventilation
Published Online: 1 OCT 2011
Copyright © 2011 American Physiological Society. All rights reserved.
How to Cite
Mortola, J. P. and Maskrey, M. 2011. Metabolism, Temperature, and Ventilation. Comprehensive Physiology. 1:1679–1709.
- Published Online: 1 OCT 2011
In mammals and birds, all oxygen used (o2) must pass through the lungs; hence, some degree of coupling between o2 and pulmonary ventilation (e) is highly predictable. Nevertheless, e is also involved with CO2 elimination, a task that is often in conflict with the convection of O2. In hot or cold conditions, the relationship between e and o2 includes the participation of the respiratory apparatus to the control of body temperature and water balance. Some compromise among these tasks is achieved through changes in breathing pattern, uncoupling changes in alveolar ventilation from e. This article examines primarily the relationship between e and o2 under thermal stimuli. In the process, it considers how the relationship is influenced by hypoxia, hypercapnia or changes in metabolic level. The shuffling of tasks in emergency situations illustrates that the constraints on e-o2 for the protection of blood gases have ample room for flexibility. However, when other priorities do not interfere with the primary goal of gas exchange, e follows metabolic rate quite closely. The fact that arterial CO2 remains stable when metabolism is changed by the most diverse circumstances (moderate exercise, cold, cold and exercise combined, variations in body size, caloric intake, age, time of the day, hormones, drugs, etc.) makes it unlikely that e and metabolism are controlled in parallel by the condition responsible for the metabolic change. Rather, some observations support the view that the gaseous component of metabolic rate, probably CO2, may provide the link between the metabolic level and e. © 2011 American Physiological Society. Compr Physiol 1:1679-1709, 2011.