ASSESSMENT OF TIDAL VOLUME OVER TIME IN PRETERM INFANTS USING RESPIRATORY INDUCTANCE PLETHYSMOGRAPHY

Non-invasive techniques for monitoring ventilation in infants are wide ly used in short-term laboratory studies but have not been evaluated i n routine clinical settings. To determine whether respiratory inductan ce plethysmography (RIP) can provide reproducible measurements of tida l volume (V-T) in premature infants over an extended period of time, w e monitored respiration in eight healthy preterm infants over 4.9 +/- 1.0 hours (mean +/- SD). The algebraic sum (Sum) of rib cage (RC) and abdominal (AB) motion signals (obtained by RIP) was calculated and pre sented over the entire recording period as percent of an initial 5 min ute calibration period. V-T was simultaneously measured with a nasal m ask pneumotachometer with infants in prone and supine positions during active and quiet sleep. Infants were studied in the morning (AM) and again in the afternoon (PM). Between these studies they were returned to the nursery wearing the RIP in a continuous record mode. For all pa tients there was a significant linear relationship between V-T (in mL measured by pneumotachometer) and Sum (in % of calibration value, RIP) . Neither the slope of the relationship (0.074 +/- 0.03 in AM vs. 0.07 1 +/- 0.02 in PM), nor its variability as measured by standard error o f the estimate (SEE) (2.3 +/- 0.5 in AM vs. 2.5 +/- 0.8 in PM) changed significantly from AM to PM. The relationship between V-T and Sum, as well as the variability of that relationship, was not altered by posi tion, asynchrony of RC and AB, respiratory rate, or percent RC contrib ution to Sum. We conclude that RIP produces consistent measurements of respiratory effort over 5 hours in healthy preterm infants without ne ed for recalibration and is not affected by routine care. (C) 1997 Wil ey-Liss. Inc.