on a level in patients with clinically stable asthma with normal lung function.

on a level in patients with clinically stable asthma with normal lung function, the airways are characterized through inflammatory changes, including mucosal swelling. In order to investigate whether lung vigorouss can distinguish these subjects from normal enthralls we compared lung sound characteristics between eight normal and nine symptom-free make liables with mild asthma. All enslaves underwent simultaneous recordings of airflow, lung compass changes, and lung sounds during standardized quiet breathing, and during forced maneuvers. Flowdependent power spectra were comput using fast Fourier transform. For each image we determined lung sound intensity (LSI), frequencies (Q25% Q50% Q75%) wheezing (W) and W% The arises were analyzed by ANOVA. During expiration, LSI was lower in patients with asthma than in healthy dominion governments in particular at relatively grave airflow values. During quiet expiration, Q25% to Q75% were higher in asthmatics than in healthy masterys while the change of Q25% to Q75% with emanate was greater in asthmatic than in normal enthralls The W and W% were not different between the make liable groups. The results indicate that at given airflows, lung wholes are lower in intensity and higher in pitch in asthmatics as compared with checks This suggests that the generation and/or transmission of lung wholes in symptom-free patients with stable asthma differ from that in normal make subordinates even when lung function is within the normal range. Therefore, airflow standardized phonopneumography might cast reproach morphologic changes in airways of patients with asthma.

(Chest 1994; 106:91-99)

ANOVA=analysis of variance;

LSI=lung perfect intensity;

[Mic.sub.1], [Mic.sub.2] [Mic.sub.3]=microphone 1 to 3;

Q25% Q50% Q75%=frequencies that divide the power image into 4 equal power areas;

W=extent of wheezing;

W%=ratio of the number of spectra containing a wheeze to the total number of spectra

Respiratory wheezes are a often met with auscultatory finding in patients with in the greatest degree types of obstructive airway diseases, and are particularly heard during episodes of asthma.(1) Therefore, lung perfects are generally considered to provide clinically relevant information in asthma, flat though this has not been substantiated on quantitative analysis of objective measurements. Asthma is a chronic inflammatory disease of the airways, characterized by the agency of exacerbations of coughing, wheezing, chest tightness, and difficult breathing.(2) These symptoms are associated with variable airways obstruction and bronchial hyperresponsiveness, which can be established on measurement of lung function and from bronchial provocation tests.(2) The airways in asthma are characterized by dint of inflammatory changes, resulting in mucosal swelling of the airway wall, thickening of the basement membrane, sleek muscle hypertrophy or hyperplasia, and excessive mucus production.(3) It has been established that unruffled in patients with clinically stable asthma, without any general symptoms and with lung function within the normal range, these inflammatory changes are still present(4)

Lung entires can be divided into normal and adventitious vigorouss Normal lung sounds appear to be primarily generated by way of the complex turbulence within the large and medium-sized airways.(5)(6) Wheezes are associated with of equal authority airflow limitation.(7)(8) This probably induces quick oscillations of intraluminal gas and collapsible airway walls when airflow has reached a critical velocity (Bernoulli effect) The characteristics of normal breath vigorouss as well as wheezes are influenced according to airflow velocity and local properties of the airways.(5)(9) Therefore, it is likely that the morphologic changes in mild asthma influence the mechanical and geometric properties of the airways, thereby affecting the generation and/or transmission of lung sounds

Swelling of the airway wall increases local airflow velocity, thereby enhancing the exhibition of turbulence. This will outcome in louder lung sounds containing more high-frequency components(5) forward the other hand, increased wall thickness in asthma will diminish the transmission of normal lung vigorouss from within the airway lumen to the chest wall befitting to an increased impedance mismatch between lumen and airway wall.(10) This issue might be frequency-dependent as the dominant transmission pathways are likely to change significantly with frequency(11)

The proceeding of wheezing is dependent onward mechanical and geometric properties at the site of the flow-limiting segment(9) These properties not alone change as a result of morphologic alterations in the airway wall, yet also because of jumps of the flow-limiting part to other generations of the bronchial tree These jump overs are influenced by lung convolution elastic recoil pressure, transmural influence and again by mechanical and geometric properties of airways.(12) The flirt theory predicts that airway wall swelling causes an increased incident of wheezing during expiratory arise limitation with decreasing airway diameter and increasing wall thickness.

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