目的　使用自制盒内气囊 (bag in box)装置 ,探讨在不中断常频机械通气 (CMV)下测定健康和急性肺损伤家兔肺功能残气量 (FRC)的可行性、敏感性、重复性与安全性。方法　Bag in box装置是依据密闭式重复呼吸氦稀释法原理 ,在不中断CMV情况下测定FRC的一种装置。健康家兔 10只 ,随机分为健康组和损伤组 ,每组各 5只。麻醉后气管插管 ,接呼吸机进行CMV。损伤组静脉注射油酸造成急性肺损伤模型。每次在气囊中预充氦气 (体积分数分别为 0 1氦气、0 3氧气、0 6氮气 )6 0ml。分别测定 :(1)重复呼吸 15、2 0、2 5、30、35次时气囊中氦气浓度 ;(2 )改变呼气末正压 (PEEP) ,健康组先增加 2、4cmH2 O、然后减少 2、4cmH2 O ;损伤组先增加 2cmH2 O、然后减少 2cmH2 O。每次改变PEEP后测定FRC 3次取平均值 ,并计算变异系数。实验中监测血压、心率、气囊中氧气浓度、动脉血气。结果 (1)健康组经 2 5～ 30次 (时间 37～ 45s)、损伤组经 2 0～ 2 5次 (时间 30～ 37s)重复呼吸均可使氦气在气囊和兔肺脏间达到平衡 ;(2 )改变PEEP后 ,FRC测定值与PEEP呈正相关 (r =0 78,P <0 0 5 ) ,FRC连续 3次测定值的变异系数 <0 0 7;(3)健康组除PaCO2 升高 15mmHg (P <0 0 5 )外 ,血压、心率、PaO2 无明显变化 (P >0 0 5 ) ;损? Objective To investigate the feasibility, sensitivity and reproducibility of the lung functional residual capacity (FRC) in healthy and acute lung injury rabbits without interruption of frequent mechanical ventilation (CMV) using a homemade bag in box device safety. Method The Bag in box device is a device for measuring FRC without interruption of CMV based on the principle of closed repeated respiration helium dilution. Healthy rabbits 10 were randomly divided into healthy group and injury group, each group of five. After anesthesia tracheal intubation, ventilator CMV. Intravenous injection of oleic acid caused acute lung injury in the injury group. Each time in the balloon helium pre-filled (volume fraction were 0 1 helium, 0 3 oxygen, 0 6 nitrogen) 60ml. Were measured: (1) repeated breathing 15,2 0,2 ​​5,30,35 times when the helium concentration in the balloon; (2) change in positive end expiratory pressure (PEEP), healthy group first increased 2,4cmH2O, then Reduce 2,4cmH2O; injury group first increase 2cmH2O, and then reduce 2cmH2O. The FRC was averaged 3 times after each change of PEEP, and the coefficient of variation was calculated. Blood pressure, heart rate, oxygen concentration in the balloon and arterial blood gas were monitored during the experiment. Results (1) Helium was balanced between balloon and rabbit lungs in healthy group after 25 ~ 30 times (37 ~ 45s) and repeated 20 ~ 25 times (30 ~ 37s) (2) The change of FREP was positively correlated with PEEP (r = 0 78, P <0 05) and the coefficient of variation (FRC) of FRC was less than 0 0 7 15mmHg (P <0 05), blood pressure, heart rate, PaO2 no significant change (P> 0.05); loss?