Synchronized mechanical ventilation for respiratory support in newborn infants

  • Review
  • Intervention

Authors


Abstract

Background

During synchronized mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient triggered ventilation.

Objectives

To compare the efficacy of:
(i) synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation (HFPPV) or patient triggered ventilation - assist control ventilation (ACV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation (CMV)
(ii) different types of triggered ventilation (ACV, SIMV, pressure regulated volume control ventilation (PRVCV) and SIMV plus pressure support (PS)

Search methods

Searches from 1985-2007 of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2007),
Oxford Database of Perinatal Trials, MEDLINE, previous reviews, abstracts and symposia proceedings; hand searches of journals in the English language and contact with expert informants.

Selection criteria

Randomised or quasi-randomised clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (ACV/SIMV) to conventional mechanical ventilation (CMV) in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS and PRVCV) in neonates.

Data collection and analysis

Data regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks postmenstrual age (PMA) and duration of weaning/ventilation.

Four comparisons were made: (i) HFPPV vs. CMV; (ii)ACV/SIMV vs. CMV; (iii) ACV vs. SIMV or PRVCV vs. SIMV (iv) SIMV plus PS vs. SIMV. Data analysis was conducted using relative risk for categorical outcomes, weighted mean difference for outcomes measured on a continuous scale.

Main results

Fourteen studies were eligible for inclusion. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk for pneumothorax was 0.69, 95% CI 0.51, 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (weighted mean difference -34.8 hours, 95% CI -62.1, -7.4). ACV compared to SIMV was associated with a trend to a shorter duration of weaning (weighted mean difference -42.4 hours, 95% CI -94.4, 9.6). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV vs. CMV and a non-significant trend towards a higher mortality rate using triggered ventilation vs. CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes. Since the last review, two new patient triggered modes have been included: pressure regulated volume control ventilation (PRVCV) and SIMV plus pressure support. Each of these methods of ventilation has only been tested in single randomised trials with no significant advantages in important outcomes.

Authors' conclusions

Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronized ventilation. Further trials are needed to determine whether synchronized ventilation is associated with other benefits, but optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential newer forms of triggered ventilation are tested in adequately powered randomised trials with long-term outcomes before they are incorporated into routine clinical practice.

Plain language summary

Synchronized mechanical ventilation for respiratory support in newborn infants

High frequency positive pressure ventilation and triggered ventilation may reduce air leaks and duration of ventilation respectively in newborns needing mechanical assistance to breathe properly. The majority of newborn babies in need of mechanical assistance to support their breathing, also breathe on their own to some degree. If the baby's attempts to breathe are synchronized with the mechanical breaths from the ventilator, less pressure may be needed. This could reduce the chance of air leak or variations in blood flow to the brain. The review of trials found, when compared to conventional mechanical ventilation (CMV), high frequency positive pressure ventilation (HFPPV) reduced the risk of air leak and triggered ventilation was associated with a shorter duration of ventilation. Newer forms of triggered ventilation have only been evaluated in small randomised trials and have not been demonstrated to have advantages in important clinical outcomes.

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