Ten studies (n=19,169), four RCTs and six sequential studies, were included in the review. Nine studies were included in the meta-analyses.
The pooled odds ratio (based on five sequential studies) for ventilator-associated pneumonia with circuit changes every two days compared to every seven days was 1.501 (95% CI 0.952 to 2.365), which indicated no significant effect of circuit change frequency. When the largest study was excluded from the analysis (not pre-specified), a significant effect in favour of seven day circuit change was obtained. Significant heterogeneity was present in the initial analysis; this was eliminated on exclusion of the large study.
Three RCTs compared circuit changes every two or seven days with no routine changes and found no significant effect on ventilator-associated pneumonia. There was no evidence of significant between-study heterogeneity.
There was a trend to reduced risk of ventilator-associated pneumonia as circuit change intervals were extended, based on data from individual studies.