PEDIATRICS Vol. 108 No. 5 November 2001, p. e91

ELECTRONIC ARTICLE:
Diaphragm Dimensions of the Healthy Preterm Infant

Received Feb 22, 2001; accepted Jun 25, 2001.

Virender K. Rehan^*, JoAnn Laiprasert^*, Michael Wallach, Lewis P. Rubin^§, and F. Dennis McCool

From the Departments of ^* Pediatrics and  Medicine, Memorial Hospital of Rhode Island, Pawtucket, Rhode Island; and the Departments of ^§ Pediatrics and  Radiology, Women and Infants' Hospital, Brown University School of Medicine, Providence, Rhode Island.

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.  Key words:  diaphragm, development, ultrasound.

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