Abstract
Monitoring within-breath changes in respiratory mechanics during the first days of life can reveal new aspects of perinatal adaptation. Our preliminary measurements exhibit a significant dependence of the mechanical impedance (Zrs) on tidal flow (V'), with different patterns of interdependence between resistance (R) and reactance (X).
Healthy term neonates (n=40) were studied with the forced oscillation technique during natural sleep in the first 3 days of life. Zrs was measured at 16 Hz and steady-state periods of min. 5 breaths were analyzed. The marked increase in R with expiratory V' was accompanied with no change in X (group 0), negative flow-dependence (group N), or positive flow-dependence (group P).
There was no difference in antropometric data between the groups. End-expiratory R (median [25th-75th percentile] was significantly (p<0.001) higher in group P (59.2 hPa.s/l [55.4-99.4]) than group 0 and N (29.9 [25.5-34.0] and 29.2 [25.1-39.2], respectively) in the first day. Maximal expiratory V' was significantly (p<0.01) lower in group P (90 ml/s [70-111]) than group 0 and N (126 [96-145] and 111 [92-137], respectively). The incidence of the different patterns of flow-dependence changed during the 3 days.
We conclude that the pattern of group P reflects a functional central airway obstruction, and maturational changes are reflected by the increasing number of pattern N with time.
(Supported by OTKA Grant #105403).
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