The oxygen tension for half saturation (P50) was determined for venous blood in thirteen patients with the adult respiratory distress syndrome undergoing intensive therapy. The mean value for P50 was found to be significantly lower than the value found in ten normal control subjects (22.9 mmHg and 26.7 mmHg respectively; t = 3.03, P< O.OJ). The extent of reduction in P50 was not related to serum phosphate level nor was it a predictor of short-term outcome. It is unlikely that the slight left-shifted oxygen-haemoglobin dissociation curve contributes in a major way to an oxygen delivery deficiency and its cause is unexplained.

Background: Acute respiratory distress syndrome (ARDS) leads to life-threatening acute hypoxemic respiratory failure in clinic and usually requires mechanical ventilation. Low tidal volume ventilation is now universally accepted as management treatment for this condition. However, recruitment maneuvers (RM) and positive end-expiratory pressure (PEEP) remain controversial. Therefore, we performed a network meta-analysis to identify the RM and PEEP levels of patients with ARDS.Methods: We searched PubMed, OVID, Embase, and the Cochrane Central Register of Controlled Trials (Central) databases. The primary outcome was death in the 28th day, and the secondary outcomes included death in hospital, ventilator-free days, and barotrauma. Data for study characteristics, methods, and outcomes were extracted. The relative effect sizes were estimated by risk ratios (RRs) for binary variables and standard mean difference (SMD) for continuous variables. Relative ranking of the interventions was conducted using surface under the cumulative ranking. Multiple intervention comparisons based on the Bayesian and frequentist frameworks were performed to integrate the efficacy of all included strategies.Results: Thirty randomized controlled trials comprising 4410 patients were included in the network meta-analysis. None of the ventilation strategies was significantly superior over others for all outcomes. According to the relative rank probabilities, low PEEP showed the lowest probability of harming death in the 28th day, whereas RM+low PEEP showed the highest probability of benefitting death in hospital and ventilator-free days. Low PEEP showed the highest probability of benefitting barotrauma. The overall quality of the evidence per grade was moderate to low.Conclusions: No ventilation strategy is significantly superior over others. RM+low PEEP has the highest probability of benefitting survival. The evidence has low overall quality and should be further studied.