PEEP for preterm infants receiving conventional mechanical ventilation for respiratory distress syndrome or bronchopulmonary dysplasia

Adequate gas exchange is readily accomplished in full term infants with appropriately developed lungs. In contrast, premature infants with respiratory distress syndrome (RDS) or bronchopulmonary dysplasia (BPD) often require medical support to achieve gas exchange. Conventional mechanical ventilation (CMV) is a common therapy used to accomplish this.

CMV allows for oxygenated air to be driven into an infant's lungs from a ventilator through a tube that is placed inside the infant's trachea. The gas exchange is facilitated by a set of pressures applied during a respiratory cycle supported or maintained by the ventilator. One of these pressures is known as positive end expiratory pressure (PEEP) and can be thought of as a continuous pressure that is applied throughout the respiratory cycle. It plays an important role in keeping the lungs open and preventing collapse so that all areas of the lungs can participate in gas exchange.

While it is generally accepted that some level of PEEP is important and necessary to accomplish adequate gas exchange, it is not clear what level of PEEP results in the greatest benefit. While too little PEEP likely fails to provide adequate gas exchange, too much PEEP may lead to over distension of the lungs resulting in harm.

This review was performed to assess what the best level of PEEP is for preterm infants requiring CMV for either RDS or BPD. It also searched for evidence of any strategies that have been effective in determining the best level of PEEP for infants on an individual case by case basis.

The results of this review highlight that there has been very little good quality research in the form of randomized controlled trials assessing the effects of different PEEP levels. Only a single study, performed in infants receiving CMV for RDS, met our criteria for inclusion. This study was small and the results were not sufficient to lead to any recommendations on the best PEEP level for infants with RDS. No study met the inclusion criteria for the review for either BPD or for strategies attempting to identify an individualized PEEP level. This review draws attention to the need for more randomized controlled trials addressing these unanswered questions.

Authors' conclusions: 

There is insufficient evidence to guide selection of appropriate PEEP levels for RDS or CMV. There is a need for well designed clinical trials evaluating the optimal application of this important and frequently applied intervention.

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Background: 

Conventional mechanical ventilation (CMV) of neonates has been used as a treatment of respiratory failure for over 30 years. While CMV facilitates gas exchange, it may simultaneously damage the lung. Positive end expiratory pressure (PEEP) has received less attention than other ventilation parameters when considering this balance of benefit and possible harm. While an appropriate level of PEEP may exert substantial benefits in ventilation, both inappropriately low or high levels may lead to harm. An appropriate level of PEEP for neonates may also be best achieved by an individualized approach.

Objectives: 

1. To compare the effects of different levels of PEEP in preterm newborn infants requiring CMV for respiratory distress syndrome (RDS).

2. To compare the effects of different levels of PEEP in preterm infants requiring CMV for bronchopulmonary dysplasia (BPD).

3. To compare the effects of different methods for individualizing PEEP to an optimal level in preterm newborn infants requiring CMV for RDS.

Search strategy: 

The search was performed in accordance with the standard search strategy for the Cochrane Neonatal Review Group. The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), Ovid MEDLINE, EMBASE, study references and experts were utilized for study identification.

Selection criteria: 

All randomized and quasi-randomized controlled trials studying preterm infants (less than 37 weeks gestational age) requiring CMV with endotracheal intubation and undergoing randomization to either different PEEP levels (RDS or BPD) or two or more alternative methods for individualizing PEEP levels (RDS only) were included. Cross-over trials were included but we limited the findings to those in the first cross-over period.

Data collection and analysis: 

Data collection and analysis were performed in accordance with the recommendations of the Cochrane Neonatal Review Group.

Main results: 

An initial evaluation identified 10 eligible articles. Ultimately, a single study met our inclusion criteria. The study addressed the effects of different levels of PEEP in preterm newborn infants requiring CMV for RDS. Only short term physiologic measures were reported. All results were limited to a small sample size without statistically significant results. No trials addressing the effect of PEEP in infants with BPD or strategies to individualize the management of PEEP were identified.

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