Figure 2
Meta-analysis of the effect of prone positioning on 28- to 30-day mortality in acute respiratory distress syndrome patients related to the ratio of partial pressure of arterial oxygen/fraction of inspired oxygen. The evidence gathered in our meta-analysis shows obvious heterogeneity, which was measured using the Mantel–Haenszel (M-H) χ2 test (P = 0.004) and the I2 heterogeneity test (I2 = 56%). A random-effects model was used. The z-test result for overall effects was not statistically significant (P = 0.007). In the ≤300 mmHg ratio of partial pressure of arterial oxygen/fraction of inspired oxygen (P/F) subgroup, the z-test for overall effects was not statistically significant (P = 0.18). In the subgroup of patients with P/F ratios between 100 and 200 mmHg, the z-test result for overall effects was not statistically significant (P = 0.30). In the subgroup of patients with P/F ≤ 100 mmHg, the z-test result for overall effects was statistically significant (P = 0.003). “Weight” is the contribution of each study to the overall risk ratio. CI, Confidence interval; I2, Percentage of total variation across studies from between-study heterogeneity rather than by chance; PP, Prone positioning; SP, Supine positioning.