静态压力-容积曲线在急性呼吸窘迫综合征肺复张和肺塌陷中的应用

目的在新西兰兔肺泡灌洗的急性呼吸窘迫综合征(ARDS)机械通气过程中,使用静态压力-容积(P-V)曲线描述肺复张及肺塌陷的特征,寻找复张肺泡并减少呼吸机相关性肺损伤的方法。方法在10例新西兰兔肺泡灌洗ARDS模型中,动态CT扫描肺泡逐步复张及逐步塌陷时肺内气体压力、容积及分布,同时测量静态P-V曲线,评估肺复张和肺塌陷的特征。结果吸气时各充气区域容积比例随气道压力的变化而变化(t=2．477-9．794,P均<0．05)。肺复张不仅包括闭合区域开放过程即肺开放,还包括充气不良区域肺泡张大的过程;肺塌陷也不只是闭合区域的产生即肺闭合,还包括充气不良区域的产生。肺开放与肺吸气频数分布不一致(r=0．219,P=0．220);肺闭合与肺呼气频数分布也不一致(r=0．094,P=0．593);静态P-V曲线顺应性仅与充气不良区域容积相关(吸气相r=0．827,P=0．006;呼气相r=0．792,P=0．011);吸气相曲线最大顺应性点压力[(16．2±3．5)cm H2O,1 cm H2O=0．098 kPa]与肺开放压[(16．4±3．4)em H2O]接近(r=0．900,P=0．002),而呼气相曲线最大顺应性点压力[(11．9±2．4)cm H2O]与肺闭合压[(11．3±2．5)cm H2O]接近(r= 0．887,P=0．003)。结论吸气时肺复张和肺泡过度膨胀同时发生。静态P-V曲线顺应性可反映肺增大潜能,并可预测肺开放压和闭合压。

Evaluation of the characteristic of alveolar recruitment and derecruitment with the static pressure-volume curve in rabbits with acute respiratory distress syndrome

OBJECTIVE: To evaluate the value of static pressure-volume (P-V) curve during alveolar recruitment and derecruitment in mechanical ventilated rabbits with acute respiratory distress syndrome (ARDS), and to explore the lung protective ventilation strategies. METHODS: The ARDS rabbit model was duplicated by warm-saline alveolar lavage. Dynamic CT scan was implemented to monitor the intrapulmonary gas volume and distribution during alveolar recruitment and derecruitment gradually. Static P-V curve was measured to reflect the features of alveolar recruitment and derecruitment. RESULTS: Four aeration regions including nonaeration, insufficient aeration, normal aeration and overinflation regions, varied following airway pressure variation (t = 2.477 - 9.794, all P < 0.05). Recruitment of insufficient aeration region was found. Alveolar recruitment was divided two parts, alveolar open at nonaeration region and recruitment at insufficient aeration region. And alveolar derecruitment was divided two parts, alveolar close at nonaeration region and derecruitment at insufficient aeration region. Distribution frequency of alveolar open was different from inspiratory (r = 0.219, P = 0.220). And distribution frequency of alveolar close was different from expiratory (r = 0.094, P = 0.593). The compliance of P-V curve was only positively correlated with the volume of insufficient aeration region (inspiration r = 0.827, P = 0.006; expiration r = 0.792, P = 0.011). The airway pressure with the maximal compliance at inspiratory P-V curve [(16.2 +/- 3.5) cm H2O, 1 cm H2O = 0.098 kPa] was positively correlated with the alveolar opening pressure [(16.4 +/- 3.4) cm H2O, r = 0.900, P = 0.002], and the airway pressure with the maximal compliance at expiratory P-V curve [(11.9 +/- 2.4) cm H2O] was positively correlated with the alveolar closing pressure [(11.3 +/- 2.5) cm H2O, r = 0.887, P = 0.003]. CONCLUSIONS: During inspiration, alveolar recruitment takes place with alveolar overinflation. The compliance of P-V curve is correlated with insufficient region volume, and reflects the potential of lung recruitment, and can predict the alveolar opening pressure and closing pressure.