低流速法测定急性呼吸窘迫综合征静态肺压力-容积曲线的比较性实验研究

Low flow technique to perform static pressure-volume curve during mechanical ventilation

目的 探讨低流速法代替气道闭合法测定急性呼吸窘迫综合征 (ARDS)静态肺压力 容积曲线的可行性。方法 采用内毒素 (LPS)诱导的绵羊ARDS模型 ,利用低流速法和气道闭合法测定肺压力 容积曲线 ,并用双向直线回归法确定相应曲线低位转折点压力 (Pinf) ,低流速法和气道闭合法测定的Pinf分别表示为Pinfd和Pinfb。结果 Pinfd与Pinfb分别为 (8 91± 0 82 )cmH2 O与 (8 5 9±0 78)cmH2 O ,两者比较差异无显著性 ,具有显著相关性 (r=0 93,P <0 0 5 )。相同潮气量情况下 ,两种方法测定的相应气道压力呈正相关 (r =0 99,P <0 0 0 5 )。低流速法和气道闭合法测定的肺顺应性分别为 (19± 7)L/cmH2 O和 (2 0± 7)L/cmH2 O ,差异无显著性 (P >0 0 5 )。低流速法测定肺压力 容积曲线的时间需 3～ 4min ,气道闭合法需 30～ 35min。结论 低流速法测定肺压力 容积曲线准确安全 ,简便省时 。

Objective To describe a fast, simple method to acquire static pressure-volume (P-V) curve of the respiratory system and to compare it with airway occlusion technique. Methods ARDS sheep model was induced by intravenously infusing 3～6 μg/kg LPS, static P-V curves were determined by low flow technique and airway occlusion technique. Static compliance (Cst), lower inflection point (Pinfd and Pinfb) and airway pressure were compared between the two methods. Results Pinf were (8.91±0.82) cm H 2O and (8.59±0.78) cm H 2O determined by low flow technique and airway occlusion technique respectively, the correlation between which was good (r=0.93, P<0.05). Cst determined by low flow technique was similar to that determined by airway occlusion technique [(19±7) L/cm H 2O vs (20±7) L/cm H 2O, P>0.05]. The time needed to acquire a static P-V curve by low flow technique was 3～4 minutes versus 30～35 minutes by airway occlusion technique. Conclusion Accuracy and reliability of low flow technique are sufficient for clinical use, it is much less time consuming than the airway occlusion technique.