Measures of reversibility in response to bronchodilators in chronic airflow obstruction: relation to airway calibre.

A study was carried out to examine the independence from starting prebronchodilator FEV1 of four indices commonly used to express airflow (FEV1) reversibility in response to bronchodilators. In 121 patients with chronic airflow obstruction with a mean prebronchodilator FEV1 of 1.81 (43.9% of predicted values) the change in FEV1 expressed as a percentage of the patient's predicted FEV1 was the least dependent on starting FEV1. Reversibility, expressed as a percentage of the prebronchodilator value or as a percentage of the maximal possible increase (predicted minus starting FEV1) was correlated with starting FEV1.