肺牵张指数指导急性呼吸窘迫综合征最佳呼气末正压的选择

目的 研究以不同的肺牵张指数指导急性呼吸窘迫综合征(ARDS)患者呼气末正压(PEEP)的选择.方法 14例ARDS患者实施肺复张后容量控制通气,用回归法求得方程P=a×timeb+c,b为肺牵张指数.调整PEEP使b<1(0.61(1.11时PEEP分别为(8.3±1.5)cm H2O、(15.0±1.9)cm H2O和(18.4±1.9)cm H2O,差异有统计学意义(P<0.001).b=1和b>1时的PaP2/FiO2明显高于复张前.与b=1时相比,b>1时的肺静态顺应性显著降低(P<0.05).h=1和b>1的复张容积较b<1增大.结论 充分复张后b=1时患者氧合、顺应性、肺复张容积明显改善,可指导ARDS患者最佳PEEP的选择.

Effect of lung stress index upon titration of positive end-expiratory pressure at post-recruitment in patients with acute respiratory distress syndrome

Objective To investigate the relationship of stress index and positive end-expimtory pressure(PEEP)in patients with acute respiratory distress syndrome(ARDS)and to determine the relationship of stress index.lung recruitment,oxygenation and respiration mechanics.Methotis Fourteen ARDS patients were enrolled.During volume control ventilation with constant inspiratory flow.the pressuretime(P-t)curve was fitted to a power equation:P=a×timeb +c,where coefficient b(stress index) describes the shape of curve:b=1,straight curve;b＜1,progressive increase in slope;and b＞1,progressive decrease in slope.Positive end-expiratory pressure(PEEP)was set to obtain b value between 0.9 and 1.1 after application of a recruiting maneuver(RM).PEEP was changed to obtain 0.6＜b＜0.8 and 1.1＜b＜1.3.The sequence of experimental conditions was random.Recruited volume(RV)was measured by static pressure-volume curve method.Hemodynamics,pulmonary mechanics and gas exchange were observed simultaneously.Results PEEP at b＜1,b=1 and b＞1 were(8.3±1.5)cm H2O,(15.0±1.9)cm H2O and(18.4±1.9)cm H2O respectively with a significant difierence(P＜0.001).At b=1 and b＞1,the partial arterial oxygen tension(PaO2/FiO2)(350±113)mm Hg,(338±124 mm Hg)]were higher than that165±60)mm Hg]of pre-RM(P＜0.05).the plateau pressure(Pplat)at b=1(29±4)cm H2O]and b＞1(33±7)cm H2O]post-RM were significantly higher than that at b＜1 (22±4)cm H2O](P＜0.05);the Pplat at b＞1 was higher than that(25±16)cm H2O]pre-RM (P＜0.05).Compared with the static pulmonary compliance(Cst)at b=1(39±11)ml/cm H2O],Cst at h＞1(26±7)ml/cm H2O]decreased significantly(P＜0.05).The RV at b;1 and b＞1(402±204)ml,(588±269)ml]were significantly higher than that at pre-RM and b＜1(136±111)ml,(175±122)m1](P＜0.05).At pre-RM,b＜1,b=1 and b＞1,HR,mean arterial pressure(MAP) and lactate showed no significant difference(P＞0.05).Conclusion Stress index at post-RM can be an excellent method of PEEP titration for ARDS patients.