Synchronized mechanical ventilation for respiratory support in newborn infants.
BACKGROUND
During synchronized mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. Thus, if synchronous ventilation is provoked, it is likely that adequate gas exchange should be achieved at lower peak airway pressures, reducing barotrauma and hence airleak and chronic lung disease. Synchronous ventilation can be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient assisted ventilation.


OBJECTIVE
To compare (i) the efficacy of synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation or triggered ventilation (patient triggered ventilation (PTV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation (ii) different types of triggered ventilation


METHODS
Searches were made from 1985-2000 of the Oxford Database of Perinatal Trials, Medline (MeSH terms: mechanical ventilation; triggered ventilation; newborn infant); previous reviews, abstracts, symposia proceedings, hand searching of journals in the English language and contacting expert informants.


METHODS
Randomized or quasi randomized clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (PTV/SIMV) to conventional mechanical ventilation (CMV) in neonates. Randomized trials comparing different triggered ventilation modes (PTV and SIMV) in neonates.


METHODS
Data regarding clinical outcomes including mortality, airleaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intracerebral haemorrhage (grades 3 and 4), chronic lung disease (oxygen dependency beyond 28 days) and duration of weaning/ventilation. Data subdivided into three groups: (i) HFPPV vs CMV; (ii) PTV/SIMV vs CMV; (iii) PTV vs SIMV. Data analysis was conducted according to the standards of the Neonatal Cochrane Review Group.


RESULTS
The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of airleak (typical relative risk for pneumothorax was 0.69 (95% CI 0.51, 0.93). PTV/SIMV compared to CMV was associated with a shorter duration of ventilation (weighted mean difference -31.8 hours, 95% CI -54.1, -9.6). PTV 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). No disadvantage to HFPPV or triggered ventilation was noted regarding other outcomes but neither ventilatory mode was associated with a significant reduction in the incidence of chronic lung disease.


CONCLUSIONS
Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in airleak 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 optimization of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials.
Greenough
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A
Dept of Child Health, King's College School of Medicine and Dentistry, Bessemer Road, London, UK, SE5 9PJ. a.greenough@kcl.ac.uk
Milner
A D
AD
Dimitriou
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G
D006801:Humans; D007231:Infant, Newborn; D015201:Meta-Analysis as Topic; D011175:Positive-Pressure Respiration / Q000379:methods; D016032:Randomized Controlled Trials as Topic; D012121:Respiration, Artificial / Q000379:methods*