Wu Chien Liang, Lin Fung J, Lee Shih Yi, Lee Chao Hsien, Peng Ming Jen, Chen Pei Jan, Kuo Hsu Tah
Division of Pulmonary and Critical Care Medicine, Mackay Memorial Hospital, 10449 Taipei, Taiwan.
J Crit Care. 2007 Jun;22(2):129-36. doi: 10.1016/j.jcrc.2006.06.009. Epub 2007 Jan 31.
Acute respiratory failure requiring mechanical ventilation in severe community-acquired pneumonia has been shown to be a significant negative prognostic factor. We analyzed the early evolution of the Pao(2)/Fio(2) ratio and evaluated its clinical value as an outcome predictor.
This is a prospective study conducted in a tertiary referral hospital. In 62 adult patients requiring early mechanical ventilation due to severe community-acquired pneumonia, we measured serial changes in Pao(2)/Fio(2) ratio and other clinical variables within the first 48 hours of mechanical ventilation and compared the difference between survivors and nonsurvivors.
The initial Pao(2)/Fio(2) ratio was lower in nonsurvivors (n = 27) than in survivors (n = 35) (158.0 +/- 55.8 vs 117.9 +/- 50.6, P = .025). Over the next 48 hours, the ratio increased significantly in survivors but not in nonsurvivors (analysis of variance, P < .001). An increase in Pao(2)/Fio(2) ratio greater than 56 mm Hg had a sensitivity of 75% and a specificity of 81% of survival. A definite causative pathogen was identified in 36 patients (58%) and the 3 most commonly isolated pathogens were Streptococcus pneumoniae, Staphylococcus aureus, and Klebsiella pneumoniae. Ten patients received inadequate initial empirical antimicrobial therapy, in which the Pao(2)/Fio(2) ratio change was significantly less than those who were adequately treated (analysis of variance, P < .001). Mortality was much higher (86% [6/7]) in patients who received inadequate antibiotics and where Pao(2)/Fio(2) ratio change was less than 56 mm Hg. On multivariate analysis, trend changes in Pao(2)/Fio(2) ratio over 48 hours, shock, and Acute Physiology and Chronic Health Evaluation II score were documented to be independent predictors of mortality.
A progressive improvement of Pao(2)/Fio(2) ratio during the first 48 hours of mechanical ventilation indicates favorable outcome. Serial measurement of this ratio should be considered in decision making for therapeutic strategy.
在严重社区获得性肺炎中，需要机械通气的急性呼吸衰竭已被证明是一个重要的不良预后因素。我们分析了动脉血氧分压（Pao₂）/吸入氧分数值（Fio₂）比值的早期变化，并评估了其作为预后预测指标的临床价值。
这是一项在三级转诊医院进行的前瞻性研究。在62例因严重社区获得性肺炎需要早期机械通气的成年患者中，我们在机械通气的头48小时内测量了Pao₂/Fio₂比值及其他临床变量的系列变化，并比较了存活者与非存活者之间的差异。
非存活者（n = 27）的初始Pao₂/Fio₂比值低于存活者（n = 35）（158.0±55.8 vs 117.9±50.6，P = 0.025）。在接下来的48小时内，存活者的该比值显著升高，而非存活者则无变化（方差分析，P < 0.001）。Pao₂/Fio₂比值升高大于56 mmHg时，对存活的敏感性为75%，特异性为81%。在36例患者（58%）中确定了明确的致病病原体，最常分离出的3种病原体为肺炎链球菌、金黄色葡萄球菌和肺炎克雷伯菌。10例患者初始经验性抗菌治疗不充分，其Pao₂/Fio₂比值变化显著小于治疗充分的患者（方差分析，P < 0.001）。接受不充分抗生素治疗且Pao₂/Fio₂比值变化小于56 mmHg的患者死亡率高得多（86% [6/7]）。多因素分析显示，48小时内Pao₂/Fio₂比值的趋势变化、休克及急性生理与慢性健康状况评分II是死亡率的独立预测因素。
机械通气头48小时内Pao₂/Fio₂比值的逐步改善表明预后良好。在制定治疗策略的决策时应考虑对该比值进行系列测量。
