Hunter Ted, Lerman Jerrold, Bissonnette Bruno
Department of Anesthesia, Montreal Children's Hospital, Montreal, Quebec, Canada.
Paediatr Anaesth. 2005 Sep;15(9):750-4. doi: 10.1111/j.1460-9592.2005.01559.x.
The effects of low-flow anesthesia on the temperature and humidity of the inspired gas in infants during mechanical ventilation is unknown. This study was designed to evaluate the temperature and humidity of the inspired gas in infants using a pediatric circle absorber system with high and low fresh gas flow (HFGF and LFGF) anesthesia.
Twenty infants participated in this observational, sequential, cross-over study. Each infant was mechanically ventilated with a Kion Anesthesia Workstation, using a pediatric anesthesia circle circuit with both HFGF (6 l.min(-1)) and LFGF (0.6 l.min(-1)) technique. Airway temperature was recorded continuously at 16 sites throughout the breathing circuit. The relative humidity of the inspired gas was measured at the elbow connector adjacent to the CO2 sampling line.
The mean airway temperatures of the inspired gas and the changes in mean airway temperatures throughout the breathing circuit during HFGF and LFGF did not differ significantly. The mean relative humidity of the inspired gas at steady state using a LFGF technique, 33.7 +/- 3.6%, was approximately threefold greater than it was with a HFGF technique, 11.9 +/- 5.1% (P < 0.05).
Low-flow anesthesia with a pediatric circle system in infants neither increases the temperature of the inspired gas, nor achieves the minimum humidity of 50% reported to prevent ciliary damage, although the humidity during LFGF did increase threefold compared with HFGF. To maintain the temperature and humidity of the inspired gas during mechanical ventilation in infants, passive or active gas humidification should be used.
低流量麻醉对机械通气期间婴儿吸入气体的温度和湿度的影响尚不清楚。本研究旨在使用具有高、低新鲜气体流量（HFGF和LFGF）麻醉的小儿循环吸收系统评估婴儿吸入气体的温度和湿度。
20名婴儿参与了这项观察性、序贯性、交叉研究。每个婴儿使用Kion麻醉工作站进行机械通气，采用小儿麻醉循环回路，分别使用HFGF（6 l·min⁻¹）和LFGF（0.6 l·min⁻¹）技术。在整个呼吸回路的16个部位连续记录气道温度。在靠近二氧化碳采样线的肘形连接器处测量吸入气体的相对湿度。
HFGF和LFGF期间，吸入气体的平均气道温度以及整个呼吸回路中平均气道温度的变化无显著差异。使用LFGF技术时，稳态下吸入气体的平均相对湿度为33.7±3.6%，约为使用HFGF技术时（11.9±5.1%）的三倍（P<0.05）。
婴儿使用小儿循环系统进行低流量麻醉既不会提高吸入气体的温度，也无法达到据报道可防止纤毛损伤的最低湿度50%，尽管与HFGF相比，LFGF期间的湿度增加了两倍。为维持婴儿机械通气期间吸入气体的温度和湿度，应使用被动或主动气体加湿。
