Journal of Applied Physiology, Vol 53, Issue 3 766-769, Copyright © 1982 by American Physiological Society
Components of effective elastance and their maturational changes in human newborns
T. Gerhardt and E. Bancalari
The newborn's ability to compensate for a sudden increase in respiratory
load remains unclear. The mouth occlusion pressure (Pmo) and the effective
elastance (E'rs) were determined in 58 neonates ranging in gestational age
from 28 to 41 wk. These results were compared with the esophageal pressure
change (delta Pes) and with lung elastance (EL) obtained during regular
breathing. Since E'rs = Pmo/delta Pes X EL, E'rs is proportional to an
active component, Pmo/delta Pes and a passive component, EL. Although EL is
1.10 +/- 0.31 (mean +/- SD) cmH2O/ml at 28 wk gestation, this value
decreases to 0.20 +/- 0.04 cmH2O/ml at full-term. The active component
Pmo/delta Pes changes in the opposite direction. It is 0.92 +/- 0.25 at 28
wk gestation, indicating that there is no load compensation in the very
premature infant. It increases to 2.06 +/- 0.50 in the full-term newborn,
reflecting a linear increase in the ability for load compensation with
advancing gestational age. The E'rs is largely determined by EL and is,
therefore, not a good measure to compare load compensating ability. The
quotient Pmo/delta Pes, being independent of tidal volume, lung maturation,
and growth, reflects load compensating activity better than E'rs.
