Variabilidad de pruebas de función pulmonar en niños sanos, asmáticos y con enfermedad pulmonar crónica

Variabilidad de pruebas de función pulmonar en niños sanos, asmáticos y con enfermedad pulmonar crónica

Introduction. Comparison of sequential pulmonary function tests in the same individual can be used to assess progression of a disease, response to therapy, or response to bronchial provocation. These types of comparisons require an understanding of the factors influencing the variability normally seen in repeat measurements of lung function. To avoid misleading conclusions about changes in serial measurements, the degree of variability of each test must be considered in their interpretation.

Objective. The purpose of this study was to examine the degree of intrasubject variability for pulmonary function testing in healthy, asthmatic and children with chronic lung disease (CLD). The tests examined were spirometry, and body plethysmograph determination of lung volumes.

Materials and methods.We studied 21 healthy children, 19 asthmatic patients and 19 children with CLD. Testings were done on nine occasions, three times within a day, on three different days, over a period of two months. Short-term variability was defined as the coefficient of variation (CV) for the six measurements made on days 1 and 2, and the long-term variability as the CV of the nine measurements made on days 1, 2 and 3.

Results. Based on the CV measures, children with CLD had significantly more variability in all spirometric values compared with healthy and asthmatic children, except for PEF (P < 0.05). Children with CLD had a significantly lower CV for ITGV and FRC compared with the other two groups (P < 0.05). Asthmatic children had a significantly higher CV for RV and RV/TLC compared with healthy and children with CLD (P < 0.05). We propose a method to consider changes in pulmonary function tests as significant.

Conclusions. The degree of variability and an estimate of the per cent change for significance of spirometric and plethysmographic tests must be considered in the interpretation of data to avoid misleading conclusions. The variability of spirometric pulmonary function data in healthy subjects was smaller than that for patients with pulmonary disease, so larger changes for significance were required in patients with pulmonary disease than in normal subjects, so larger changes for significance were required in patients with pulmonary disease than in normal subjects.