Pulmonary resistance is elevated early in preterm infants who later develop chronic lung disease. This early increase in pulmonary resistance may play a role in the development of severe bronchopulmonary dysplasia (BPD). A beta-2-agonist (isoetharine HCl) was used as an aerosol in 13 preterm infants with elevated pulmonary resistance. Their birthweight ranged from 880 to 1630 g, their gestational age from 27 to 34 weeks, and their post natal age from 3 to 18 days. All infants had required mechanical ventilation for respiratory distress syndrome and therefore were at risk to develop BPD. Pulmonary mechanics were measured before and 30 minutes after aerosol treatment, determining inspiratory and expiratory flow with a pneumotachometer and esophageal pressure through a water-filled feeding tube. The treatment was well tolerated with no significant changes in blood pressure, heart rate, or respiratory rate. Pulmonary resistance decreased significantly from 130 +/- 35 cm H2O/L/sec to 89 +/- 24 cm H2O/L/sec after the treatment. Dynamic lung compliance increased in 11 of the 13 infants. It is concluded that beta-2-agonist nebulization is effective in reducing the early increase in pulmonary resistance that occurs in preterm infants who are at risk of developing BPD. This effect may be due to relaxation of bronchial smooth muscle, to improved mucociliary transport, and to a reduction in peribronchial edema.

Administration, Inhalation↗

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Pulmonary mechanics in normal infants and young children during first 5 years of life.

To characterize lung function in young children we measured lung compliance and pulmonary conductance in 40 normal infants and children ranging in age from the newborn period to 5 years. Inspiratory and expiratory flow was measured by a pneumotachograph, esophageal pressure through a water-filled feeding tube, and functional residual capacity (FRC) by a N2 washout technique. The esophageal pressure change per breath [(mean +/- SD) 7.3 +/- 1.4 cm H2O] and specific compliance (75 +/- 13 ml/cm H2O/L-FRC) did not change with growth. Specific conductance was high (0.60 L/s/cm H2O/L-FRC) in preterm infants, decreasing rapidly with initial growth but minimally beyond 10 kg of body weight, and stabilizing at 0.10 L/s/cm H2O/L-FRC. During the age period studied, compliance increased approximately x 25 whereas conductance only rose five-fold. The changes in compliance and conductance were well correlated to FRC, body weight, and length. These findings suggest that in the last trimester of pregnancy the airways are already well developed and postnatal lung growth occurs mainly by formation of new alveoli, leading to a proportional increase in FRC and lung compliance. Postnatally, conductance increases much more slowly than FRC, resulting in a rapid drop in specific conductance.

Airway Resistance↗