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Continuous distending pressure
  1. Colin Morley
  1. Department of Neonatal Medicine Royal Women’s Hospital 132 Grattan Street Carlton Melbourne Victoria 3035 Australia
  1. Professor Colin Morley. Email:morleyc{at}

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Continuous positive airway pressure (CPAP), positive end expiratory pressure (PEEP), or continuous negative expiratory pressure (CNEP) all provide low pressure distension of the lungs during expiration. It is one of the most effective treatments in neonatal medicine. This personal review sets out why premature babies need help to prevent airway collapse. It describes different techniques for the administration of CPAP and what has been learnt from previous studies and trials. The references quoted in this paper have been obtained by Medline searching on the keywords, continuous distending pressure, CPAP and PEEP, and from papers, chapters, and books on fetal and neonatal physiology and neonatal ventilation, and the Cochrane Collaboration review.

Premature infants find it difficult to maintain functional residual capacity (FRC) and upper airway patency for many reasons:

 1  As term infants initiate breathing, large negative and positive pressures are generated to open the lung.1 2Preterm infants may not generate enough pressure to achieve an effective FRC.

 2  The larynx modulates tidal breathing with partial expiratory closure to maintain the end expiratory lung volume.3 4 The newborn infant with a low lung volume grunts to maintain FRC.5 If the baby cannot maintain laryngeal tone or is intubated lung volume can be lost.

 3  The lung fluid clearance is slower after premature birth so that the lung contains more water, especially after caesarean section. Although there is no direct evidence, in very premature babies, fluid may continue to be secreted after birth, adding to the problems of maintaining alveolar patency.6

 4  Lung volume can be preserved by shortening the expiratory time and preventing the lung emptying completely.3 7 If babies with respiratory distress syndrome fail to do this (because of apnoea or fatigue) atelectasis and subsequently respiratory failure develop.

 5  Premature infants lack the fat …

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