俯卧位通气下急性呼吸窘迫综合征患者氧合的变化

Effect of prone-position ventilation on oxygenation in patients with acute respiratory distress syndrome

目的探讨俯卧位通气下急性呼吸窘迫综合征(ARDS)患者氧合的变化及其机制。方法23例早期ARDS患者(病程<72 h),在镇静、肌松下持续俯卧位通气2 h。呼吸机参数设定为潮气量6-8 ml/kg,吸气时间1.0-1.2 s,吸气流速40 L/min,呼吸频率12-20次/min。吸入氧浓度0.4- 1.0,呼气末正压6-18 cm H2O。观察俯卧位前即刻、俯卧位0.5、2 h及恢复仰卧位2 h的氧合指数(PaO2/FiO2)、呼吸系统静态顺应性(Cst)、心率(HR)、平均动脉压(MAP)、中心静脉压(CVP)、平均肺动脉压(MPAP)。肺动脉楔压(PAWP)、心脏指数(CI)、气道峰压(PIP)及气道阻力(Paw)。俯卧位后PaO2/FiO2比俯卧位前上升超过20%作为氧合改善的判断标准。结果与俯卧位前比较,87%患者俯卧位0.5、2 h、恢复仰卧位2 h时PaO2/FiO2和PaO2升高(P<0.01);Cst HR、MAP、CVP、MPAP、PAWP、CI、Raw、PaCO2、PIP差异无统计学意义;87%氧合改善的患者在俯卧位0.5、2 h时Cst差异无统计学意义, 恢复仰卧位2 h时Cst升高(P<0.05)。结论俯卧位通气可改善早期ARDS患者的氧合,且恢复仰卧位后氧合改善持续存在。

Objective To determine the effect of prone position （PP） ventilation on oxygenation in patients with acute respiratory distress syndrome （ARDS）. Methods Twenty-three patients of both sexes （14 males, 9 females） with ARDS （within 72 h after onset of ARDS）were included in this study. The patients ranged in age from 43-78 years. Ten minutes before the patients were placed in prone position, midasolam 2-5 mg was given i.v. followed by continuous infusion at 2-3 mg·h^-1 for sedation and a bolus of vecuronium 4 mg per hour for muscle relaxation. The patients were mechanically ventilated （VT 6-8 ml·kg^-1, inspiration-time 1.0-1.2 s, RR 12-20 bpm, FiO2 0.4-1.0, PEEP 6-18 cm H2O）. The patients were placed in prone position for 2 h. Radial artery was cannulated and S-G catheter placed. MAP, CVP, MPAP, PAWP, cardiac output, PaO2, PaCO2 peak inspiratory pressure （PIP） and airway resistance （Raw） were measured and recorded immediately before （T0） and 0.5, 2 h after the patients were placed in prone position （T1, T2 ） and 2 h after supine position was resumed（T3）. PaO2/FiO2 and static compliance of the respiratory system （Cst） were calculated. Results In 87% of the patients PaO2/FiO2 was significantly increased during prone position （T1, T2） as compared to the baseline （T0） （P〈0.01） and remained high at T3, but there was no significant change in Cst, HR, MAP, CVP, MPAP, Raw, PAWP, and CO at T1 and T2 as compared to the baseline at T0. In the 87% of the patients with inprovement in PaO2/FiO2, Cst did not change significantly at T1 and T2 but significantly increased at T3 （P〈0.05）. Conclusion Prone position ventilation can improve pulmonary gas exchange in patients with early ARDS even after supine position is resumed.