Airflow effects on amplitude and spectral content of normal breath
sounds.
Gavriely, Noam, and David. W. Cugell.
Anesthesia Department, and Pulmonary Division, Department of
Medicine, Northwestern University Medical School, Chicago Illinois,
60611; and the Department of Physiology and Biophysics, Bruce
Rappaport Faculty of Medicine and the Rappaport Institute., Technion,
Haifa, Israel 31096
APStracts 2:0395A, 1995.
While it is well known that breath sounds (BS) amplitude increases
with air flow, the exact quantitative relationships and their
distribution within the relevant frequency range have not yet been
determined. To evaluate these relationships, the spectral content of
tracheal and chest wall BS were measured during breath hold,
inspiration and expiration in six normal men. Average spectra were
measured at six flow rates from 0.5 to 3.0 l/sec. The areas under the
spectral curves of BS, minus the corresponding areas under the breath
hold spectra, (BSA) were found to have a power relationships with
flow (FL), best modelled as BSA = k x (FL)[alpha]. The overall
mean+/-SD value of the power ([alpha]) was 1.66+/-0.35, significantly
less than the previously reported second power. Isoflow inspiratory
chest wall sound amplitudes were 1.99+/-0.70 to 2.43+/-0.65 fold
larger than the amplitudes of the corresponding expiratory sounds,
whereas tracheal sounds amplitudes were not dependent on respiratory
phase. Isoflow BS from the left posterior base were 32% louder than
those from the right lung base (p<0.01). BS amplitude-flow
relationships were not frequency dependent during expiration, but
were significantly stronger in higher than in lower frequencies
during inspiration over both posterior bases. These data are
compatible with sound generation by turbulent flow in a bifurcating
network with: (1) flow separation, (2) downstream movement of eddies,
and (3) collision of fast moving cores of the in-flowing air with
carinae - all occurring during inspiration but not during expiration.
Received 28 February 1995; accepted in final form 29 August 1995.
APS Manuscript Number A232-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.