• Zhonghua yi xue za zhi · Oct 2009

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

    • Ying-Zi Huang, Yi Yang, Song-Qiao Liu, Cong-Shan Yang, and Hai-Bo Qiu.
    • 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.

    ObjectiveTo 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.MethodsFourteen 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.ResultsPEEP 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).ConclusionStress index at post-RM can be an excellent method of PEEP titration for ARDS patients.

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