Continuous Distending Pressure in the Respiratory Distress Syndrome of the Newborn: Who,When,and Why?

Abstract

Continuous distending pressure (CDP), as continuous positive airway pressure (CPAP), was reported in 1971 as a treatment of the respiratory distress syndrome (RDS) in premature infants. The thought was that CDP provided a "therapeutic grunt" and prevented alveolar collapse at end-expiration in infants suffering surfactant deficiency, thus raising PaO₂. Some workers have also considered CDP useful in recurrent apnea of prematurity, in low-birth-weight infants without serious lung disease, and as a way to reduce the rate of surfactant consumption, to help reduce pulmonary vascular resistance, to stabilize the rib cage, and to reduce shunting across a patent ductus arteriosus. Several methods have been used to apply CDP, such as face chamber, continuous negative pressure, endotracheal tube, nasal prongs, and face mask, all generating a pressure gradient across the lung; however, except for use of the face mask, no real evidence indicates that one method is better than another. The amount of pressure used varies among workers, but all techniques produce high-pressure side effects, with the rate of pneumothorax ranging from 12 to 24%. Because of this, many institutions delay using CDP until RDS is quite severe, by which time atelectasis may be so advanced that CDP is not effective, because its value lies in keeping air sacs open, not in recruiting them once they have closed. Thus, although CDP has been accepted worldwide as a therapeutic mode that prevents air sac collapse, it has rarely actually achieved this. It is true that RDS mortality has fallen remarkably in the past decade, but there is little evidence that CDP has played an important role in this development. Nonetheless, earlier use of CDP with techniques for establishing the critical opening pressure of air sacs, or the combined use of high-frequency oscillation ventilatory techniques in association with low-level CDP, should be investigated. These approaches may prove effective in RDS without introducing the high mean airway pressures that have been the bane of continuous distending pressure therapy.