Conservative oxygen therapy for critically ill patients: a meta-analysis of randomized controlled trials

Abstract

Objective Conservative oxygen strategy is recommended in acute illness while its benefit in ICU patients remains controversial. Therefore, we sought to conduct a systematic review and meta-analysis to examine such oxygen strategies’ effect and safety in ICU patients. Methods We searched PubMed, Embase, and the Cochrane database from inception to Feb 15, 2021. Randomized controlled trials (RCTs) that compared a conservative oxygen strategy to a conventional strategy in critically ill patients were included. Results were expressed as mean difference (MD) and risk ratio (RR) with a 95% confidence interval (CI). The primary outcome was the longest follow-up mortality. Heterogeneity, sensitivity analysis, and publication bias were also investigated to test the robustness of the primary outcome. Results We included seven trials with a total of 5265 patients. In general, the conventional group had significantly higher SpO2 or PaO2 than that in the conservative group. No statistically significant differences were found in the longest follow-up mortality (RR, 1.03; 95% CI, 0.97–1.10; I2=18%; P=0.34) between the two oxygen strategies when pooling studies enrolling subjects with various degrees of hypoxemia. Further sensitivity analysis showed that ICU patients with mild-to-moderate hypoxemia (PaO2/FiO2 >100 mmHg) had significantly lower mortality (RR, 1.24; 95% CI, 1.05–1.46; I2=0%; P=0.01) when receiving conservative oxygen therapy. These findings were also confirmed in other study periods. Additional, secondary outcomes of the duration of mechanical ventilation, the length of stay in the ICU and hospital, change in sequential organ failure assessment score, and adverse events were comparable between the two strategies. Conclusions Our findings indicate that conservative oxygen therapy strategy did not improve the prognosis of the overall ICU patients. The subgroup of ICU patients with mild to moderate hypoxemia might obtain prognosis benefit from such a strategy without affecting other critical clinical results.

Letter the editor: serious methodological concerns about a recently published meta-analysis on oxygen therapy

“…We have with interest read the systematic review with meta-analysis concerning the effects of conservative versus conventional oxygen therapy for critically ill patients by Chen et al [ 1 ]. However, we have several concerns relating to the methodology and findings.…”

“…In the paper by Chen et al [ 1 ], the mortality rates are erroneously quoted from several trials in the meta-analysis of mortality at longest follow-up. In the paper by Schjørring et al [ 2 ], a mortality of 514/1447 and 529/1441 in the higher and lower group is incorrectly quoted.…”

“…1 . Chen et al reported the RR as 1.01 (95% CI 0.94–1.09), so there is a slight difference in the 95% CI [ 1 ].

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“…The literature search is insufficient as the authors fail to identify four relevant papers focusing on: ICU-patients with acute exacerbation of chronic obstructive pulmonary disease [ 6 ]; oxygen therapy after cardiac-arrest [ 7 ]; normobaric oxygen in stroke patients [ 8 ]; and hyperoxaemia in stroke patients [ 9 ]. The first paper should have been identified and included in the meta-analysis, whilst the latter three should have been identified and excluded as per their stated exclusion criteria [ 1 ]. In their PRISMA-diagram, the authors state that six trials were excluded after full-text review and present the trials along with reasons for exclusions (Additional file 3: Table S1).…”

“…Lastly, it appears that the two compared groups have been switched when reporting serious adverse events, despite correct findings are provided in the supplement (Additional file 6) [ 1 ]. If inversed, the results are in line with the meta-analysis provided below (Figs.…”