Effect of chest physiotherapy on blood gases of neonates treated by intermittent positive pressure respiration.

The effect of standardized chest physiotherapy and hyperinflation on the blood gases of neonates being treated for tetanus by intermittent positive pressure respiration was investigated. It was found that physiotherapy and suction to remove secretions did not improve oxygen pressures but produced a small drop in both Paco., and Pao2. This was associated with a widening of the alveolar to arterial gradient for oxygen. During the hour that followed, blood oxygen pressure slowly returned to pre-physiotherapy levels. This could be hastened by hyperinflation (increasing the pressure delivered to the baby) after physiotherapy. Although hyperinflation restored blood oxygen pressures, it did so by a mechanism which left alveolar to arterial oxygen gradients unchanged. Moderate hyperinflation without physiotherapy produced small increases in blood oxygen tension, but also failed to restore completely arterial oxygen pressures of neonates on I.P.P.R. The results are discussed.