%0 Journal Article
%T An¨¢lisis computacional de los ruidos respiratorios en la evaluaci¨®n de la obstrucci¨®n bronquial en ni os peque os que no colaboran con las pruebas espirom¨¦tricas Acoustic analysis of respiratory sounds during methacholine challenge in preschool children
%A Ignacio S¨¢nchez D
%A Cecilia Alvarez G
%A Cristi¨¢n Claver¨ªa R
%A Carmen Lisboa B
%J Revista m¨¦dica de Chile
%D 2001
%I Sociedad M¨¦dica de Santiago
%X Background: There are changes in inspiratory breath sound intensity in patients with airway obstruction. Airway narrowing may change sound spectral characteristics. Aim: To define the characteristics of lung sounds at standardized air flow during methacholine challenge and to compare acoustic changes with transcutaneous oxygen tension (PtcO2) during induced airway narrowing. Patients and methods: Forty asthmatic children (20 male) aged 5.2¡À1 years and 40 normal children (18 male), aged 5.6 ¡À 1 years were studied. All patients were free of respiratory tract infections one month before the study. A methacholine challenge from 0.06 to 8 mg/ml was performed; the test was ended when a fall in PtcO2 of >20% from baseline was observed or if the final concentration was reached. Subjects breathed through a pneumotachograph aiming at flows of 0.4 to 0.6 l/s. Respiratory sounds were recorded using contact sensors at the suprasternal notch and at the posterior right lower lobe. From average spectra, power at low (100-200 Hz=P1) and high frequencies (400-2000 =P2) was calculated. Frequencies below which 50% (F50) and 99% (SEF90) of the spectral power between 100 and 2000 Hz was contained, were also calculated. Results: In asthmatics, the metacholine concentration at which a 20% fall in PtcO2 was observed, was lower than in normal children (p< 0.05). There was an increase in P1 (p<0.01) and a reduction in P2 (p<0.01) during inspiration, in subjects that experienced a 20% reduction in PtcO2. Also, there was an increase in F50 and SEF99 during inspiration in lung sounds, but not over the trachea. Conclusions: Lung sounds analysis can be useful for the assessment of airway reactivity in asthmatic children (Rev M¨¦d Chile 2001; 129: 1271-8)
%K Asthma
%K Anti-asthmatic agents
%K Lung diseases
%K obstructive
%K Methacholine chloride
%U http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0034-98872001001100006