1 Neonatal Respiratory Unit, Groote Schuur Hospital, Department of Child Health, University of Cape Town, South Africa
Chu, et al.1 recently indicated the presence of a significant aA gradient for PCO2 in infants with hyaline membrane disease. In their study, alveolar CO2 tension was determined by means of a CO2 analyzer. The method makes use of the fact that end tidal gas forms a plateau on the expiratory CO2 curve and that this plateau can be assumed to be representative of alveolar CO2.
In hyaline membrane disease, however, it is not possible to obtain such plateaus and Strang2 has demonstrated that a series of spiked peaks only are produced during expiration.