Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
J Appl Physiol (1985). 2013 Nov;115(10):1506-18. doi: 10.1152/japplphysiol.00808.2013. Epub 2013 Aug 22.
The ventilation pattern of many ectothermic vertebrates, as well as hibernating and diving endotherms, is episodic where breaths are clustered in bouts interspersed among apneas of varying duration. Using mechanically ventilated, anesthetized freshwater turtles (Trachemys scripta), a species that normally exhibits this episodic ventilation pattern, we investigated whether episodic ventilation affects pulmonary gas exchange compared with evenly spaced breaths. In two separate series of experiments (a noninvasive and an invasive), ventilation pattern was switched from a steady state, with evenly spaced breaths, to episodic ventilation while maintaining overall minute ventilation (30 ml·min(-1)·kg(-1)). On switching to an episodic ventilation pattern of 10 clustered breaths, mean CO2 excretion rate was reduced by 6 ± 5% (noninvasive protocol) or 20 ± 8% (invasive protocol) in the first ventilation pattern cycle, along with a reduction in the respiratory exchange ratio. O2 uptake was either not affected or increased in the first ventilation pattern cycle, while neither heart rate nor overall pulmonary blood flow was significantly affected by the ventilation patterns. The results confirm that, for a given minute ventilation, episodic ventilation is intrinsically less efficient for CO2 excretion, thereby indicating an increase in the total bodily CO2 store in the protocol. Despite the apparent CO2 retention, mean arterial Pco2 only increased 1 Torr during the episodic ventilation pattern, which was concomitant with a possible reduction of respiratory quotient. This would indicate a shift in metabolism such that less CO2 is produced when the efficiency of excretion is reduced.
许多变温脊椎动物，以及冬眠和潜水恒温动物的通气模式是间歇性的，呼吸在呼吸暂停期间成簇出现，呼吸暂停的持续时间不等。使用机械通气、麻醉的淡水龟（Trachemys scripta），一种通常表现出这种间歇性通气模式的物种，我们研究了间歇性通气是否会影响与均匀间隔呼吸相比的肺气体交换。在两个独立的实验系列（非侵入性和侵入性）中，通气模式从均匀间隔呼吸的稳定状态切换到 10 次簇状呼吸的间歇性通气，同时保持整体分钟通气量（30 ml·min(-1)·kg(-1)）。在切换到 10 次簇状呼吸的间歇性通气模式时，第一次通气模式周期中 CO2 排泄率降低了 6±5%（非侵入性方案）或 20±8%（侵入性方案），同时呼吸交换率降低。在第一次通气模式周期中，O2 摄取要么不受影响，要么增加，而心率和整体肺血流量均不受通气模式的显著影响。结果证实，对于给定的分钟通气量，间歇性通气本质上对 CO2 排泄效率较低，从而表明在方案中总身体 CO2 储存增加。尽管存在明显的 CO2 潴留，但平均动脉 Pco2 在间歇性通气模式期间仅增加 1 托，这与呼吸商可能降低同时发生。这表明代谢发生了转变，当排泄效率降低时，产生的 CO2 减少。
