Am. J. Respir. Crit. Care Med., Vol 153, No. 5, May 1996, 1474-1480.
Lung sounds during allergen-induced asthmatic responses in patients with asthma
HJ Schreur, Z Diamant, J Vanderschoot, AH Zwinderman, JH Dijkman and PJ Sterk
Department of Pulmonology, University Hospital, Leiden, The Netherlands.
We postulated that the distinct pathophysiologic mechanisms of airway
narrowing during the early (EAR) and the late (LAR) asthmatic responses to
inhaled allergens are reflected by the generation or transmission of lung
sounds in asthma. Therefore, we measured FEV1 and recorded lung sounds in
eight mildly asthmatic subjects before a standardized allergen challenge
(PRE), during the EAR, during the recovery phase at 2 h (MID), during the
LAR at 7 h, and after inhalation of a bronchodilator (POST). The recordings
were made during flow- and volume- standardized quiet breathing, and during
maximal forced breathing maneuvers. Airflow-dependent power spectra were
analyzed for lung sound intensity (LSI), quartile power points (Q25, Q50,
Q75), and extent of wheezing (W). These sound characteristics were compared
among the various stages of the challenge in the presence (EAR, LAR) and
absence (PRE, MID, POST) of acute airway obstruction using ANOVA. LSI, Q25
- Q75, and W were all elevated during airway obstruction. When matched for
percent fall in FEV1, during the EAR and the LAR (mean +/- SD: 26.7 +/-
4.0, and 28.9 +/- 5.7, respectively; p = 0.385), the increase in Q25, and
Q50 with airflow during quiet expiration, as well as the extent of
wheezing, were higher during the LAR than during the EAR (p < or = 0.042
and p < or = 0.012, respectively). At similar levels of FEV1 (p > or
= 0.156), LSI on expiration was higher at POST than at PRE or MID (p <
or = 0.067), whereas Q25 (p < or = 0.047) and Q50 (p < or = 0.064)
were lower at POST than at PRE. During forced expiration W was higher at
MID and POST than at PRE (p < or = 0.014). We conclude that LSI,
frequency content, and the extent of wheezing vary during the subsequent
stages of allergen-induced bronchoconstriction in asthma despite matched
values of FEV1. This suggests that airflow-standardized phonopneumography
is a sensitive method for detecting differences in the pathophysiology of
airway narrowing in asthma.
