Elective high frequency jet ventilation versus conventional ventilation for respiratory distress syndrome in preterm infants.

BACKGROUND: This section is under preparation and will be included in the next issue.

OBJECTIVES: The objective of this review was to determine whether the elective (commencing soon after initiation of mechanical ventilation) use of high frequency jet ventilation (HFJV), as compared to conventional ventilation (CV) in preterm infants with respiratory distress syndrome (RDS), would decrease the incidence of chronic lung disease (CLD) without adverse effects.

SEARCH STRATEGY: Randomized trials from MEDLINE were identified by means of MeSH and text words 'high frequency ventilation', 'high frequency jet ventilation', 'jet ventilation' from the years 1980 to 1997. The EMBASE database, the Oxford Database of Perinatal Trials, the Neonatal Trials Register of the Neonatal Review Group of the Cochrane Collaboration and the Cochrane library were also accessed. Proceedings of recent SPR/APS meetings were hand searched. Information was obtained from experts in the field, and cross references were checked.

SELECTION CRITERIA: All randomized controlled trials of elective high frequency jet ventilation versus conventional ventilation in preterm infants born at less than 35 weeks GA or with a birth weight less than 2000 gms with respiratory distress were included in the systematic review. Trials which used HFJV to 'rescue' preterm infants due to severe respiratory distress usually beyond 24 hours, and trials that used HFJV for a mandatory time period and then switched back to CV, were not included in this review.

DATA COLLECTION AND ANALYSIS: The standard methods of the Neonatal Cochrane Review Group were used, including independent trial assessment and data extraction. Data were analysed using relative risk (RR) and risk difference (RD). From 1/RD the number needed to treat (NNT) for benefits and number needed to harm (NNH) for adverse outcomes were calculated.

MAIN RESULTS: Overall analysis of the three trials showed that HFJV is associated with a reduction in CLD at 36 weeks postmenstrual age in survivors [RR 0.58 (0.34, 0. 98), RD -0.138 (-0.268, -0.007), NNT 7 (4, 90)]. The use of home oxygen therapy was evaluated in only one study (Keszler 1997) and a lower rate was found in the HFJV group [RR 0.24 (0.07, 0.79), RD -0. 176 (-0.306, -0.047), NNT 5 (3, 21)]. Overall there was a trend towards an increase in the risk of PVL in the HFJV group, which was not significant. Subgroup analyses shows a significant increase in risk of PVL in the trial by Wiswell 1996 [RR 5.0 (1.19, 21.04), RD 0.250 (0.069, 0.431), NNH 4.0 (2.3,14.5)] where a 'low volume strategy' was the standard protocol for HFJV. In the other trial by Keszler 1997, where the intention was to use a 'high volume strategy', there was no significant difference in the incidence of PVL, RR 0.42 (0.14, 1.30). In the overall analysis, there were no significant differences in the incidence of neonatal mortality, IVH all grades or in grades 3 or 4 IVH. In the subgroup where 'low volume strategy' was used there was a non-significant trend toward an increase in risk of IVH all grades and grades 3 or 4 IVH.

REVIEWER'S CONCLUSIONS: The overall analysis shows a benefit in pulmonary outcomes in the group electively ventilated with HFJV. Of concern is the significant increase in acute brain injury in one trial which used lower mean airway pressures when ventilating with HFJV. There are as yet no long term pulmonary or neurodevelopmental outcomes from any of the trials. Until further studies ascertain the most appropriate strategy to routinely ventilate premature infants with HFJV safely, ventilation with HFJV cannot be recommended for preterm infants with RDS.