Journal of Applied Physiology, Vol 43, Issue 2 322-330, Copyright © 1977 by American Physiological Society
Respiratory parameter estimation using forced oscillatory impedance data
M. J. Tsai, R. L. Pimmel, E. J. Stiff, P. A. Bromberg and R. L. Hamlin
The frequency dependency of the magnitude and phase angle of total
respiratory impedance was measured in apneic dogs at functional residual
capacity during forced oscillation by a special electronics unit.
Regression analysis of these data yielded estimates of total respiratory
resistance (RFO), inertance (IFO), and compliance (CFO). After correcting
for the effects of the endotracheal tube, mean control values (+/-SE) of
RFO, IFO, and CFO for the clinically normal dogs were 1.30+/-0.10
cmH2O-1-1-s, 0.0114+/-0.0022 cmH2O-1-1-s2, and 0.0306+/-0.0009 1-cm H2O-1,
respectively. Estimates obtained with added resistance, a less dense gas,
and abdominal weighting were consistent with predicted effects. In four
dogs with mild respiratory symptoms, mean RFO was significantly elevated
with no change in IFO or CFO. Independent measurements of resistance and
compliance during tidal ventilation correlated well with RFO (r=0.87) and
CFO (r=0.80), but RFO and CFO were, on the average, 71% of the tidal
breathing values. Thus, the method provides precise estimates of RFO, IFO,
and CFO, and allows detection of small changes in these parameters.
