An acute reduction in the fraction of inspired oxygen increases airway constriction in infants with chronic lung disease.

Infants with chronic lung disease have acute episodes of hypoxemia that are often accompanied by wheezing. To test whether a sudden reduction in FIO2 might increase airway obstruction in such infants, we measured the flow-volume relationship, O2 saturation, and skin-surface CO2 tension in 19 sedated infants, 11 with chronic lung disease, and 8 control infants, before and during 10 min of continuous hypoxemia. In the infants with chronic lung disease, a 20 to 25% reduction in FIO2 caused acute hypoxemia (O2 saturation, 77 +/- 8%) and an associated decrease in mid-expiratory flow from 103 +/- 55 to 69 +/- 37 ml/s (mean +/- SD; p less than 0.05) in the absence of a significant change in tidal volume or skin-surface CO2 tension. In the infants without lung disease, breathing 17% O2 led to a significant increase in minute ventilation (26 +/- 25%; p = 0.05), but there was no consistent change in mid-expiratory flow. To further study the effects of an acute reduction in FIO2 on pulmonary function in infants with chronic lung disease, we measured lung mechanics in 6 infants and end-expiratory lung volume in 5. Baseline lung resistance was high (49 +/- 35 cm/l/s) and increased by 55 +/- 30% (p less than 0.05) in response to hypoxemia. Baseline dynamic lung compliance was low (2.5 +/- 1.5 ml/cm) and decreased by 24 +/- 10% (p less than 0.05). Functional residual capacity increased from 26 +/- 13 to 33 +/- 14 ml/kg (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)