Huang Ying-Zi, Yang Yi, Liu Song-Qiao, Yang Cong-Shan, Qiu Hai-Bo
Department of Critical Care Medicine, Nanjing Zhongda Hospital, School of Clinical Medicine, Southeast University, Nanjing 210009, China.
Zhonghua Yi Xue Za Zhi. 2009 Oct 27;89(39):2739-43.
To investigate the relationship of stress index and positive end-expiratory pressure (PEEP) in patients with acute respiratory distress syndrome (ARDS) and to determine the relationship of stress index, lung recruitment, oxygenation and respiration mechanics.
Fourteen ARDS patients were enrolled. During volume control ventilation with constant inspiratory flow, the pressure-time (P-t) curve was fitted to a power equation: P = a x time(b) + 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.
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 difference (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 that [165 +/- 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 b > 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) ml] (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).
Stress index at post-RM can be an excellent method of PEEP titration for ARDS patients.
探讨急性呼吸窘迫综合征（ARDS）患者压力指数与呼气末正压（PEEP）的关系，并确定压力指数、肺复张、氧合及呼吸力学之间的关系。
纳入14例ARDS患者。在定容控制通气且吸气流量恒定的过程中，将压力-时间（P-t）曲线拟合为幂函数方程：P = a×时间(b)+c，其中系数b（压力指数）描述曲线形状：b = 1，曲线为直线；b < 1，斜率逐渐增加；b > 1，斜率逐渐减小。在实施肺复张手法（RM）后，设置PEEP使b值在0.9至1.1之间。改变PEEP使b值在0.6 < b < 0.8和1.1 < b < 1.3之间。实验条件顺序随机。采用静态压力-容量曲线法测量复张容积（RV）。同时观察血流动力学、肺力学及气体交换情况。
b < 1、b = 1及b > 1时的PEEP分别为(8.3±1.5) cmH₂O、(15.0±1.9) cmH₂O和(18.4±1.9) cmH₂O，差异有统计学意义（P < 0.001）。b = 1及b > 1时的动脉血氧分压（PaO₂/FiO₂）[(350±113) mmHg、(338±124) mmHg]高于RM前[165±60) mmHg]（P < 0.05）。RM后b = 1[(29±4) cmH₂O]及b > 1[(33±7) cmH₂O]时的平台压（Pplat）显著高于b < 1[(22±4) cmH₂O]时（P < 0.05）；b > 1时的Pplat高于RM前[(25±16) cmH₂O]（P < 0.05）。与b = 1[(39±11) ml/cmH₂O]时的静态肺顺应性（Cst）相比，b > 1[(26±7) ml/cmH₂O]时Cst显著降低（P < 0.05）。b = 1及b > 1时的RV[(402±204) ml、(588±269) ml]显著高于RM前及b < 1[(136±111) ml、(175±122) ml]（P < 0.05）。RM前、b < 1、b = 1及b > 1时，心率（HR）、平均动脉压（MAP）及乳酸水平差异无统计学意义（P > 0.05）。
RM后的压力指数可作为ARDS患者PEEP滴定的优良方法。
