Yee W F, Scarpelli E M
Pflugers Arch. 1986 Jun;406(6):615-9. doi: 10.1007/BF00584029.
We have modified the rebreathing method to study CO2 responsivity in very small mammals. Tidal volume (VT) and frequency (f) of pentobarbital-anesthetized mice were measured during rebreathing from a closed circuit, primed with 95% O2, 5% CO2, through which the gas was constantly circulated at 0.5 l X min-1. The circuit consisted of T-tube from a plethysmograph, Tygon tubing with compliant element, CO2 analyzer and pump, in series. Circuit PCO2 (PctCO2), which was recorded continuously during spontaneous breathing, rapidly equilibrated with end-tidal PCO2. CO2 response curves were constructed from extrapolated minute ventilation (V), VT, f and parameters of breath-to-breath timing, respectively, on PctCO2. Analyses of slopes of the response curves, change from onset of rebreathing to peak response, and PctCO2 at which the response peaked revealed that CO2 stimulates V by increasing f and VT and that this is effected by facilitation of central inspiratory-expiratory phase switching and inspiratory drive mechanisms. However, the stimulatory effect of CO2 on phase switching was not sustained, with maximal effect occurring before peak V. The advantages and facility of the modified rebreathing method make it suitable for studies of other small mammals, including neonates.
我们对重复呼吸法进行了改进，以研究极小哺乳动物的二氧化碳反应性。在由95%氧气、5%二氧化碳预充的闭合回路中进行重复呼吸期间，测量戊巴比妥麻醉小鼠的潮气量（VT）和频率（f），气体以0.5升/分钟的流速在回路中持续循环。该回路由来自体积描记器的T形管、带有顺应性元件的泰根管、二氧化碳分析仪和泵串联组成。在自主呼吸期间连续记录的回路二氧化碳分压（PctCO2）与呼气末二氧化碳分压迅速达到平衡。分别根据PctCO2上外推的分钟通气量（V）、VT、f和呼吸间定时参数构建二氧化碳反应曲线。对反应曲线斜率、从重复呼吸开始到峰值反应的变化以及反应达到峰值时的PctCO2进行分析，结果表明二氧化碳通过增加f和VT来刺激V，这是通过促进中枢吸气 - 呼气相转换和吸气驱动机制实现的。然而，二氧化碳对相转换的刺激作用并不持久，最大效应出现在V峰值之前。改进的重复呼吸法的优点和便利性使其适用于包括新生儿在内的其他小型哺乳动物的研究。
