ABSTRACT. Background. The diaphragm is the major inspiratory muscle in the neonate; however, human neonatal diaphragm development has not been extensively studied. We hypothesized that diaphragm thickness (t di ) would be positively related to postmenstrual age (PMA), body weight, body length, head circumference, and nutritional intake.Objectives. To evaluate the evolution of diaphragm growth and motion in the healthy, preterm infant.Methods. We used ultrasound to measure t di at the zone of apposition to the rib cage and diaphragm excursion (e di ) during inspiration. Thirty-four stable, preterm infants (16 males and 18 females) between 26 and 37 weeks' PMA were studied during quiet sleep at weekly intervals until the time of discharge or transfer from the neonatal intensive care unit. All infants were clinically stable and not receiving ventilatory support.Results. We found that 1) t di increased from 1.2 ؎ 0.1 to 1.7 ؎ 0.05 mm between 26 to 28 and 35 to 37 weeks' PMA; 2) t di was positively correlated with PMA (r ‫؍‬ 0.40), body weight (r ‫؍‬ 0.52), body length (r ‫؍‬ 0.53), and head circumference (0.49), but not with postnatal nutritional intake (r ‫؍‬ 0.09); and 3) e di decreased with increasing PMA.Conclusions. Our findings suggest that diaphragm development in premature infants scales with body dimensions. We speculate that the increase in t di with age is likely attributable to increased diaphragm muscle mass, and the reduced e di with age may be resulting from a reduction in chest wall compliance. Pediatrics 2001; 108(5). URL: http://www.pediatrics.org/cgi/content/full/ 108/5/e91; diaphragm, development, ultrasound.ABBREVIATIONS. t di , diaphragm thickness; FRC, functional residual capacity; ⌬t di , change in diaphragm thickness; PMA, postmenstrual age; BL, body length, HC, head circumference; NI, nutritional intake; GA, gestational age; e di , diaphragm dome excursion; BW, body weight.

Vancomycin crosses the placenta in a predictable manner in concentrations that exceed the usual group B streptococci breakpoint. Adverse events were common, suggesting that longer infusion times and weight adjusted doses should be used.

We conclude that the improvement in arterial oxygen saturation with CPAP occurred despite the presence of a shorter and a less mobile diaphragm, and that other physiological and mechanical alterations accompanying the application of CPAP offset its negative effects on diaphragm function. We speculate that with excessive CPAP, however, diaphragm dysfunction along with the previously described adverse hemodynamic effects may outweigh its benefits on oxygenation.