Wavelet decomposition is proposed as a novel approach for determining
pulmonary arterial input impedance throughout the breathing cycle. The
canine pulmonary arterial input impedance was evaluated throughout th
e ventilatory cycle at 5, 10, and 15 cmH(2)O of positive end-expirator
y pressure. The impedance spectrum was obtained by Fourier transformat
ion of wavelets generated by decomposing the pulmonary arterial pressu
re and flow waveforms. With wavelet decomposition, each heart beat is
viewed individually as a transient pulse rather than as an interval wi
thin a continuous function of pressure and flow. The advantage of usin
g this approach is the ability to obtain stable estimates of input imp
edance spectra with high-frequency resolution over the entire frequenc
y range with only a limited data set of pressure and flow decomposed t
o wavelets as short as singular extrapolated cardiac cycles. This meth
od was used to define the changes of input impedance that occur during
the ventilatory cycle. Results show that the impedance spectrum under
goes notable changes during the breathing cycle and demonstrate the ut
ility of the proposed method.