Ventilatory disturbance in children with obstructive lung disease.

Disease in the small airways leads to alteration in the slope of 
phase III of the single breath nitrogen washout following a breath 
of 100% oxygen. Normal children and those with asthma and cystic 
fibrosis were studied by this technique. Measurement of the slope of 
phase III of the single breath washout appeared to be a 
sensitive indicator of abnormal pulmonary function in children with these diseases. 
Results obtained in many children with cystic fibrosis suggested that the 
upper lung regions were predominantly affected. 