Determinants of milk flow through nipple units. Role of hole size and nipple thickness
O. P. Mathew
Department of Pediatrics, University of Texas Medical Branch, Galveston 77550.
The aim of the present study was to elucidate the role of hole size and
thickness in determining milk flow through nipple units during bottle
feeding. Commonly used standard nipple units (SMA single-hole, Enfamil
single-hole, and Twist-on) for term and preterm infants, as well as
Nuk-type nipple units (SMA Nuk, Enfamil Natural, and Nuk) were tested. The
size of the nipple hole and wall thickness were determined for each nipple
unit. Airflow was measured by forcing pressurized air through the feed
hole. Simulated sucks were used to measure the milk flow. A marked
variability in airflow and milk flow was observed within and among the
various types of nipple units studied. Within each type of nipple unit,
both milk flow and airflow measurements correlated well with hole size. The
thickness of the nipple units contributed minimally to the observed
variability. We conclude that differences in hole size primarily account
for the observed variability in milk flow. This finding may be clinically
important in that rapid milk flow can lead to apnea and bradycardia in some
preterm infants. The above observations imply that design changes are
necessary to reduce the variability of milk flow within each nipple type.
Moreover, milk-flow measurements made using a simple mechanical system and
airflow measurements used by the industry are equally sensitive to evaluate
nipple flow.
