Nipple units for newborn infants: a functional comparison

Milk flow characteristics of nipple units commonly used in the neonatal period were compared in the laboratory using a mechanical system. The number of simulated sucks required to empty 120 mL of formula was determined for each nipple unit. In general, the number of simulated sucks required to empty the bottle decreased when the applied negative pressure was increased from -60 to -120 cm of H2O except for SMA nipple units for premature infants. The Nuk type required less sucks (ie, higher flow) than standard nipple units. Among the Nuk-type nipple units, the SMA nipple had the highest mean flow and Enfamil Natural the lowest mean flow; among the standard nipple units, SMA single-hole had the highest flow and Ross Twist-on had the lowest flow. However, wide variability in performance was observed not only between different types of nipple units but also within the same type. Flow characteristics of nipple units for preterm infants overlapped markedly, with that for term neonates with Enfamil nipples exhibiting the highest flow. Clinical relevance of these differences in flow characteristics among the nipple units is discussed.