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Volume-targeted versus pressure-limited ventilation in the neonate

  • Review
  • Intervention

Authors


Abstract

Background

Inflammation caused by lung overdistension (volutrauma) is thought to be important in the pathogenesis of bronchopulmonary dysplasia (BPD). Preterm infants with variable lung compliance are particularly at risk. Volume-targeted neonatal ventilators have been developed as alternatives to traditional pressure-limited ventilators. They deliver consistent, appropriate tidal volumes with the aim of reducing lung damage. It is suggested that these would provide an effective, safer means of ventilating the newborn infant.

Objectives

To determine whether volume-targeted ventilation compared with pressure-limited ventilation leads to reduced rates of death and BPD in newborn infants. Secondary objectives were to determine whether use of volume modes affected clinical outcomes such as incidence of airleak, growth, duration of ventilation or cranial ultrasound findings.

Search strategy

The search strategy comprised searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2004), MEDLINE PubMed 1966 to November 2004, and hand searches of reference lists of relevant articles and conference proceedings.

Selection criteria

All randomised and quasi-randomised trials comparing the use of volume-targeted versus pressure-limited ventilation in neonates in the first 28 days of life.

Data collection and analysis

Two authors assessed the methodological quality of eligible trials and extracted data independently. When appropriate, meta-analysis was conducted to provide a pooled estimate of effect. For categorical data the relative risk (RR) and risk difference (RD) were calculated with 95% confidence intervals. Number needed to treat was calculated when RD was statistically significant. Continuous data were analysed using weighted mean difference (WMD).

Main results

Four randomised trials were identified that addressed the outcomes of this review, recruiting a total of 178 preterm infants. All were recruited during the first 72 hours of life. Caregivers and those evaluating the outcomes of trials were not masked. All trials report high rates of follow-up, although one trial with uneven patient distribution may have had some post-randomisation attrition. No significant difference was found for death by hospital discharge, and no trials reported the combined outcome of death or BPD. When secondary outcomes were examined, pooled analysis of the trials showed that volume-targeted ventilation resulted in significant reductions in duration of ventilation [WMD -2.93 days (-4.28, -1.57)] and rates of pneumothorax [typical RR 0.23 (0.07, 0.76), RD -0.11 (-0.20, -0.03), NNT 9]. There was also a significant difference in rates of severe (Grade 3 or 4) intraventricular haemorrhage favouring the volume-targeted group [typical RR 0.32 (0.11, 0.90), RD -0.16 (-0.29, -0.03), NNT 6]. There was a reduction in the incidence of BPD (supplemental oxygen at 36 weeks) amongst surviving infants, of borderline statistical significance [typical RR 0.34 (0.11, 1.05), RD -0.14 (-0.27, 0.00), NNT=7]. No significant differences were found for failure of mode of ventilation, use of neuromuscular paralysis, patent ductus arteriosus, airleak of any sort or pulmonary interstitial emphysema alone, cranial ultrasound abnormalities or periventricular leucomalacia. None of the trials addressed growth, death after discharge from hospital or neurodevelopmental outcome.

Authors' conclusions

Although rates of death and BPD were not significantly different between the two ventilator strategies, statistically significant effects favouring volume targeting were shown for some clinically important outcomes. However, the numbers of trials and infants randomised are small and further studies are required to confirm the role of volume targeting in neonatal ventilation.

Plain language summary

Volume-targeted versus pressure-limited ventilation in the neonate

Approximately two thirds of all infants admitted to neonatal intensive care nurseries require positive pressure ventilation. The majority of neonates are ventilated because of lung immaturity and hyaline membrane disease, respiratory difficulties that resolve for most of these infants. Use of ventilators can cause lung inflammation and ventilator-induced lung injury, particularly in the preterm neonate with a compliant chest wall, highlighting the importance of protective ventilation strategies. Volume-targeted modes of ventilation allow the clinician to set the tidal volume directly. The review authors identified four randomised trials recruiting a total of 178 preterm infants. All were recruited during the first 72 hours of life. This review found some clinically important benefits of volume targeting. These included significant reductions in duration of positive pressure ventilation (WMD -2.93 days) and rates of pneumothorax (NNT 9) and severe intraventricular haemorrhage (NNT 6). Rates of death by hospital discharge and bronchopulmonary dysplasia (requiring supplemental oxygen at 36 weeks) were not significantly different between the two ventilator strategies. Antenatal steroids and surfactant were available in all participating units and there were no significant differences in their use within individual trials. None of the trials addressed growth, death after discharge from hospital or neurodevelopmental outcome.

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