Respiratory tissue properties derived from flow transfer function
in healthy humans.
Tomalak, W., R. Peslin, C. Duvivier.
Unit[umlaut]a 14 de Physiopathologie Respiratoire, Institut
National de la Sant[umlaut]a et de la Recherche M[umlaut]adicale.
Universit[umlaut]a H. Poincar[umlaut]a Nancy I, 54500 Vandoeuvre
-les-Nancy, France, and National Institute for Tuberculosis and Lung
Diseases, Pediatric Division, Rabka, Poland
APStracts 3:0572A, 1996.
Assuming homogeneity of alveolar pressure, the relationship between
airways flow and flow at the chest (bs) during forced oscillation at
the airway opening (flow transfer function: FTF) is related to lung
and chest wall tissular impedance (Zt): FTF = 1 + Zt/Zg, where Zg is
alveolar gas impedance which is inversely proportional to thoracic
gas volume (TGV). Using a flow-type body plethysmograph to obtain bs,
FTF has been measured at oscillation frequencies (fos) of 10, 20, 30
and 40 Hz in eight healthy subjects both during quiet breathing and
during deep breathing. The data were corrected for the flow shunted
through upper airway walls, and analyzed in terms of tissue
resistance (Rt) and effective elastance (Eteff) using
plethysmographically measured TGV values. In most subject, Rt was
seen to decrease with increasing fos, and Eteff to vary curvilinearly
with fos2, which is suggestive of mechanical inhomogeneity. Rt
presented a weak volume dependence during breathing, variable in sign
according to fos and among subjects. In contrast, Eteff usually
exhibited a U-shaped pattern with a minimum located a little above or
below functional residual capacity, and a steep increase with
decreasing or increasing volume (30-80 hPa.l-2) on either side. These
variations are in excess of those expected from the sigmoid shape of
the static pressure-volume curve, and may reflect the effect of
respiratory muscle activity. We conclude that FTF measurement is an
interesting tool to study Rt and Eteff, and that these parameters
have probably different physiological determinants.
Received 2 July 1996; accepted in final form 2 February 1996.
APS Manuscript Number A619-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996