Ventilation strategies and outcome in randomized trials of high frequency ventilation

¹ University Children's Hospital Ulm, Germany
² University of Alabama at Birmingham, United States

^* To whom correspondence should be addressed. E-mail: uhthome{at}web.de.

Accepted 19 May 2005

	Abstract

Objective:Randomised controlled trials comparing elective use of high frequency ventilation (HFV) with conventional mechanical ventilation (CMV) in preterm infants yielded conflicting results. We hypothesised that the variability of results may be explained by differences in study design, ventilation strategies, delay of initiation of HFV, and use of permissive hypercapnia.

Study design:Randomised controlled trials comparing the elective use of HFV with any form of CMV were identified. Trials were classified according to the ventilation strategies used for HFV and CMV and oscillator device used. For cumulative meta-analyses, trials were arranged by the following covariables: mean duration until randomisation, PaCO2 limits, publication date, and sample size. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using fixed and random effects models.

Results:17 randomised trials enrolling 3776 patients were included. Unlike previous meta-analyses, there was no significant difference in the incidence of bronchopulmonary dysplasia or death (OR 0.87, 0.75-1.00) and severe IVH grade 3-4 (1.14, 0.96-1.37). The incidence of air leaks (1.23, 1.06-1.44) was significantly increased with HFV. Subgroup analyses and cumulative meta-analyses demonstrated that trial results were related to the ventilation strategies used for HFV and CMV. No influence was found for the mean time to randomisation, the degree of permissive hypercapnia, or the sample size.

Conclusions:Heterogeneity among trials of elective HFV in comparison to CMV in preterm infants is mainly due to differences in ventilatory strategies. Optimising the CMV strategy appeared to be equally effective as HFV in order to improve pulmonary outcome in preterm infants.

Keywords: bronchopulmonary dysplasia, mechanical ventilation, meta-analysis, preterm infant, review

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