COMPARISON OF HELIOX AND OXYGEN AS WASHING GASES FOR THE NITROGEN WASHOUT TECHNIQUE IN PRETERM INFANTS

The nitrogen washout technique usually involves exposure of the patien t to 100% oxygen for several minutes. This may be dangerous in preterm infants who are at risk of retinopathy of prematurity (ROP). We wante d to know whether heliox (79% He, 21% O-2) can be used instead of oxyg en when determining functional residual capacity (FRC). FRC measuremen ts were made in 14 preterm infants [median (range) gestational age at birth 34 wk (27-37 wk), and at time of study 36 wk (33-40 wk)] who wer e breathing room air. FRC was measured using a computerized infant pul monary function system, beginning in random order with either 100% O-2 followed by heliox or vice versa, There was no systematic difference between the two methods with regard to lung volume measurements: mean (SD) FRC values, corrected for body weight, were 22.9 (7.1) mL/kg for O-2 and 23.4 (7.0) mL/kg for heliox. We did not observe a systematic i nfluence of the type of washing gas used (heliox or oxygen) on FRC in these infants, Our results suggest that the use of heliox instead of p ure oxygen may be a suitable and safer alternative for FRC measurement s with the nitrogen washout technique in preterm infants who are breat hing low concentrations of inspired oxygen and are still at risk of RO P.