Detection of small bolus volumes using multiple intraluminal impedance in preterm infants

Background: Multiple intraluminal impedance (MII) is a new technique that allows detection of reflux and swallows via changes in impedance caused by a liquid bolus inside the esophagus. The method is independent of pH. The authors studied the ability of this technique to detect the small bolus volumes potentially occurring in young infants. Methods: Ten preterm infants (median gestational age at birth, 33 weeks; range, 25-36 weeks; age at study, 9 days; range, 2-39 days) underwent 10 instillations each of 0.1 mL to 0.5 mL saline while MII was recorded via a 2.4-mm nasogastric catheter. MII signals were analyzed for swallows, defined as a decrease in impedance starting within 1 minute. From the liquid instillation in the most proximal channel and extending downward, impedance changes during these induced swallows were compared with those occurring during spontaneous swallows. Results: All 100 liquid instillations resulted in a typical impedance pattern, occurring after a median interval of 4.4 seconds (range, 1.8-8.9 seconds). The decrease in impedance was more pronounced than after spontaneous swallows (30% vs. 24%, P < 0.03) and extended downward more rapidly (12.3 cm/s vs. 5.8 cm/s, P < 0.01). Conclusion: Bolus transport of small liquid volumes can be detected via MII (C) 2003 Lippincott Williams Wilkins, Inc.