Occlusion pressure and breathing pattern in children with chronic obstructive pulmonary disease

The control of breathing at rest was studied in 30 children (3 to 17 years old) with chronic obstructive pulmonary disease (COPD). Five of them were tested several times during the follow-up of the COPD. Breathing pattern was evaluated and mouth occlusion pressure (PO.1) was measured. Results in COPD children were compared to previously reported values in healthy controls. PO.1 was significantly increased. In 11 children breathing O2, PO.1 decreased but remained at higher levels than predicted. However, the decrease in PO.1 in COPD was not significantly greater than in healthy children. These results may be explained by the relative mild hypoxemia in those children. The increase in PO.1 was significantly correlated with the increase in lung resistance (p less than 0.02) and with the decrease in dynamic lung compliance (p less than 0.01). Most of the COPD children were normocapnic. However, modifications in the breathing pattern were observed. The inspiratory time (TI) was significantly shortened, the expiratory time was prolonged and the TI over the total duration of the respiratory cycle was lowered. The respiratory frequency was unchanged. The tidal volume, normalized for body weight (VTBW), was increased. The mean inspiratory flow (VTBW/TI) was significantly augmented, but not as much as PO.1: in consequence, the effective inspiratory impedance was higher than predicted. Thus, as adults, COPD children had a greater inspiratory neural drive. In contrast to normocapnic COPD adults, they had a modified respiratory timing.