The airflow resistance dynam ics at the onset stage during maximal forced expiration in different alternations of breath mechanics

Abstract

The dynamics of airway resistance at the first stage of forced expiration was studied by modified method of bodyplethysmography in 16 males, aged 5 5 ± 1 .4 yrs, with chronic obstructive bronchitis (COB), 19 patients (5 males and 14 females, aged 38±3.1 yrs) with idiopathic fibrosing alveolitis (IFA), and 12 healthy subjects (7 males and 5 females, aged 3 8 ±3 .1 yrs). Instant R_aw values and fitted values of P_a were estimated, then the “ R_aw -P_a ” curve was plotted. The experimental points were approximated linearly, and the equation of R_aw dynamics at the first stage of forced expiration was calculated: R_aw = R_aw (P_a = 0)+b^.P_a , where b is an extent of the approximation line decline. R_aw at P_a= 0 was closer to its quite breath values in healthy persons. It was decreased in patients with COB and was increased in patients with IFA. The “ b ” parameter was increased in COB patients in comparison with healthy persons and was stable in IFA patients.
Therefore, these features of the parameters allow to consider them to be a useful index of airway deformation for differential diagnostics in “flow —volume ” testing.