Regional lung function in infants

Measurement of regional ventilation and blood flow in infants with the use of an intravenous bolus of Xenon reliably estimates the ventilation-perfusion abnormalities responsible for hypoxemia and eventually hypercapnea.A composite ventilation-perfusion index ( ci/ ) of >0.85 was found in well infants with Pao2 >90 torr, and < 0.55 in sick infants with Pao2 < 50 torr. Indices of < 0.6 were associated with CO2 retention; indices of < 0.55 were found in patients requiring mechanical ventilation.Redistribution of blood flow away from a poorly ventilated region during air breathing but not during oxygen breathing suggests that alveolar hypoxia is an effective stimulus to increase regional vascular resistance. It is predictable that the lack of redistribution during oxygen breathing contributes to CO2 retention.The findings of this study substantiate the use of Xenon bolus technique for a better understanding of the regional contribution to the pathophysiology in the infantʼs lung.