THORACIC GAS-COMPRESSION PROFILE DURING FORCED EXPIRATION IN HEALTHY AND ASTHMATIC SCHOOLCHILDREN

Gas compression profile may aid in the diagnosis of airway obstruction . However, the behaviour of this parameter in repeated tests and the d eviations in patients with bronchial asthma have not been thoroughly d escribed. Thirty-six health subjects aged 6-16 years were studied in t wo test sessions with a pressure/flow plethysmograph, and 57 asthmatic patients of similar age were studied once. Three volumes of compresse d thoracic gas (V-comp) were obtained: with 25%, 50% and 75% of vital capacity (VC) expired. Relative V-comp was calculated using the actual amount of gas remaining in the lungs. Regarding the best and second b est manoeuvre, coefficient of variation (CoV) in V-comp ranged from 47 % to 79% (controls) and from 48 to 112% (patients). Regarding the best manoeuvre in the first and second test session (controls), CoV in V-c omp ranged from 73 to 159%. Bronchodilator response had an extreme ind ividual variation, and the changes were insignificant in both groups. In the paediatric population, the poor repeatability of V-comp invalid ates its use in clinical assessment of pulmonary function.