Nagano O, Tokioka H, Ohta Y, Goto K, Katayama H, Hirakawa M
Department of Anesthesiology and Resuscitology, Okayama University Hospital, Okayama City, Japan.
Acta Anaesthesiol Scand. 2001 Nov;45(10):1255-61. doi: 10.1034/j.1399-6576.2001.451014.x.
In lung protective strategy, positive end-expiratory pressure (PEEP) slightly higher than the Pflex (the airway pressure corresponding to the lower inflection point (LIP) on the inspiratory pressure-volume (P-V) curve measured with ZEEP) is generally recommended. However, this method to determine optimal PEEP lacks a theoretical background and there is no clinical report that investigated how the P-V relationship would be with such PEEP. Therefore, we measured inspiratory P-V curves at different PEEP levels to increase our knowledge about the inspiratory P-V curve with PEEP.
In eight consecutive patients with ALI/ARDS, inspiratory P-V curves were repeatedly measured at different PEEP levels by low flow inflation technique and LIP was assessed in all inspiratory P-V curves. Afterwards, the minimum PEEP level at which LIP was not identifiable (PEEP(LIP)(-)) was determined and the relationship between Pflex and PEEP(LIP)(-) was investigated.
Pflex and PEEP(LIP)(-) could be determined in all patients. Pflex was 9.4+/-2.0 cmH2O (range: 7 to 12 cmH2O) and PEEP(LIP)(-) was 7.9+/-1.6 cmH2O (range: 5 to 10 cmH2O) (mean+/-SD, P=0.0877). PEEP(LIP)(-) was lower than the Pflex in five patients, and significantly lower than the Pflex + 2 cmH2O (P=0.0024).
From the analysis of inspiratory P-V curves at different PEEP levels, PEEP 2 cmH2O higher than the Pflex may not be necessary to prevent cyclic collapse and reopening of alveoli, at least in some ALI/ARDS patients. Further studies are needed to confirm this preliminary result.
在肺保护性通气策略中，通常建议呼气末正压（PEEP）略高于Pflex（在零呼气末正压（ZEEP）条件下测量的吸气压力-容积（P-V）曲线上与下拐点（LIP）对应的气道压力）。然而，这种确定最佳PEEP的方法缺乏理论依据，且尚无临床报告研究采用这种PEEP时P-V关系会如何。因此，我们在不同PEEP水平下测量吸气P-V曲线，以增进我们对PEEP条件下吸气P-V曲线的了解。
连续纳入8例急性肺损伤/急性呼吸窘迫综合征（ALI/ARDS）患者，采用低流量充气技术在不同PEEP水平下反复测量吸气P-V曲线，并评估所有吸气P-V曲线的LIP。之后，确定无法识别LIP时的最低PEEP水平（PEEP(LIP)(-)），并研究Pflex与PEEP(LIP)(-)之间的关系。
所有患者均可确定Pflex和PEEP(LIP)(-)。Pflex为9.4±2.0 cmH₂O（范围：7至12 cmH₂O），PEEP(LIP)(-)为7.9±1.6 cmH₂O（范围：5至10 cmH₂O）（均值±标准差，P = 0.0877）。5例患者的PEEP(LIP)(-)低于Pflex，且显著低于Pflex + 2 cmH₂O（P = 0.0024）。
通过分析不同PEEP水平下的吸气P-V曲线，至少在部分ALI/ARDS患者中，高于Pflex 2 cmH₂O的PEEP可能并非预防肺泡周期性萎陷和复张所必需。需要进一步研究来证实这一初步结果。
