Roch Antoine, Forel Jean-Marie, Demory Didier, Arnal Jean-Michel, Donati Stéphane, Gainnier Marc, Papazian Laurent
Service de Réanimation Médicale, Hôpitaux Sud, Marseille, France.
Crit Care. 2006;10(3):R85. doi: 10.1186/cc4936. Epub 2006 Jun 1.
It is possible that taking a static pressure-volume (PV) measurement could durably affect oxygenation and thus interfere with early evaluation of a therapeutic intervention delivered just after that measurement. The aim of the present study was to investigate the effects over time of a single static PV measurement on gas exchange and haemodynamics; the PV measurements were taken using a super syringe and by using the constant flow method in patients with acute respiratory distress syndrome.
We conducted a prospective, randomized and controlled interventional study in an intensive care unit. The study was conducted in 17 patients with early acute respiratory distress syndrome ventilated with a tidal volume of 6.9 +/- 1.0 ml/kg, a plateau pressure of 27 +/- 7 cmH2O and a positive end-expiratory pressure [PEEP] of 10 cmH2O. They were all evaluated for 1 hour after each of the following two measurements was taken and during a control period (in a randomized order): generation of a PV curve using a 2 l super syringe (PVSS; insufflated volume = 1824 +/- 381 ml, plateau pressure = 46 +/- 9 cmH2O); and generation of a PV curve using the constant flow method on the ventilator (PVCF; insufflated volume = 1120 +/- 115 ml in zero end-expiratory pressure after 20 s expiratory pause, plateau pressure = 46 +/- 11 cmH2O). The maximal airway pressure allowed during PV measurement was 60 cmH2O. PEEP was set to 10 cmH2O immediately after PV measurement. Partial arterial oxygen tension (Pao2), partial carbon dioxide tension (Paco2) and mean arterial pressure were recorded each minute.
PV measurement did not significantly affect Pao2, Paco2, mean arterial pressure and lung mechanics. Two patients exhibited a sustained increase in Pao2 by more than 20% after PVCF (>60 minutes). Two patients exhibited a decrease in Pao2 by more than 20% after PVSS, which was sustained in one. These latter patients had an upper inflection point identified on the PV curve. After PVSS, Paco2 increased by more than 10 mmHg in two patients and returned to baseline values after 15 minutes. One patient exhibited a decrease in mean arterial pressure by more than 10 mmHg for less than 5 minutes after PVSS and one patient after PVCF.
Evaluation of the effects of a strategy aimed at improving oxygenation can be reliably recorded early after a single PV measurement that is not followed by a change in PEEP level. PV measurement using the constant flow method improves oxygenation in a limited number of patients.
进行静态压力-容积（PV）测量可能会持久影响氧合，从而干扰在该测量之后立即进行的治疗干预的早期评估。本研究的目的是调查单次静态PV测量随时间对气体交换和血流动力学的影响；在急性呼吸窘迫综合征患者中，使用超级注射器并采用恒流法进行PV测量。
我们在重症监护病房进行了一项前瞻性、随机对照干预研究。该研究纳入了17例早期急性呼吸窘迫综合征患者，他们接受潮气量为6.9±1.0 ml/kg、平台压为27±7 cmH₂O和呼气末正压（PEEP）为10 cmH₂O的通气治疗。在以下两项测量中的每一项测量后以及在对照期（随机顺序），对他们进行1小时的评估：使用2升超级注射器生成PV曲线（PVSS；注入量=1824±381 ml，平台压=46±9 cmH₂O）；在呼吸机上使用恒流法生成PV曲线（PVCF；呼气暂停20秒后在零呼气末压力下注入量=1120±115 ml，平台压=46±11 cmH₂O）。PV测量期间允许的最大气道压力为60 cmH₂O。PV测量后立即将PEEP设置为10 cmH₂O。每分钟记录动脉血氧分压（Pao₂）、动脉血二氧化碳分压（Paco₂）和平均动脉压。
PV测量对Pao₂、Paco₂、平均动脉压和肺力学没有显著影响。两名患者在PVCF后（>60分钟）Pao₂持续升高超过20%。两名患者在PVSS后Pao₂下降超过20%，其中一名患者持续下降。后一组患者在PV曲线上有一个上拐点。PVSS后，两名患者的Paco₂升高超过10 mmHg，并在15分钟后恢复到基线值。一名患者在PVSS后平均动脉压下降超过10 mmHg持续不到5分钟，一名患者在PVCF后出现这种情况。
在单次PV测量且PEEP水平不变后，可以可靠地早期记录旨在改善氧合的策略的效果。使用恒流法进行PV测量可使少数患者的氧合得到改善。
