[Dynamic observation of pulmonary function by plethysmography in preterm infants with bronchopulmonary dysplasia].

Objective: To study the effect of bronchopulmonary dysplasia (BPD) on lung function in preterm infants.

Methods: According to the presence/absence or the severity of BPD, 72 preterm infants were divided into non-BPD group (n=44), mild BPD group (n=15) and moderate BPD group (n=13). Lung function was assessed by plethysmography on days 7, 14 and 28 after birth.

Results: The preterm infants in the three groups had gradual increases in tidal volume per kilogram (TV/kg), functional residual capacity (FRC), ratio of time to peak tidal expiratory flow to total expiratory time (%T-PF) and ratio of volume to peak tidal expiratory flow to total expiratory volume (%V-PF) on days 7, 14 and 28 after birth, while there were gradual reductions in effective airway resistance per kilogram (Reff/kg) and respiratory rate (RR) (P<0.05). Compared with the non-BPD group on days 7, 14 and 28 after birth, the mild and moderate BPD groups had significantly lower TV/kg, FRC, %T-PF, and %V-PF and significantly higher Reff/kg and RR (P<0.05). On day 7 after birth, the moderate BPD group had significantly higher airway resistance, Reff/kg and FRC/kg than the mild BPD group (P<0.05).

Conclusions: There is a certain degree of pulmonary function impairment in preterm infants with BPD. Dynamic monitoring of lung function by plethysmography is useful for assessing lung development in the neonatal period in these infants.