CHEST SURFACE MAPPING OF LUNG SOUNDS DURING METHACHOLINE CHALLENGE

Wheeze as an indicator of airway obstruction during bronchoprovocation lacks sensitivity. We therefore studied whether induced airway narrow ing is revealed by changes in normal (vesicular) lung sounds. Fifteen subjects with asthma and nine healthy controls, aged 8-16 years, perfo rmed a standardized methacholine challenge. Respiratory sounds were re corded with eight contact sensors, placed posteriorly over the right a nd left superior and basal lower lobes, and anteriorly over both upper lobes, the right middle lobe, and the trachea. Average spectra of nor mal inspiratory and expiratory sounds, excluding wheeze, were characte rized in 12 asthmatics and 9 controls at flows of 1 +/- 0.2 L/sec. Air way narrowing was accompanied by significant changes in lung sounds, b ut not in tracheal sounds. Lung sounds showed a decrease in power at l ow frequencies during inspiration and an increase in power at high fre quencies during expiration. These changes already occurred at a decrea se in forced expiratory volume in 1 sec of less than 10% from baseline and were fully reversed after inhalation of salbutamol. Thus, lung so unds were sensitive to changes in airway caliber, but were not specifi c indicators of bronchial hyperresponsiveness. (C) 1997 Wiley-Liss, In c.