Reproducibility of the negative expiratory pressure technique in detecting expiratory flow limitation on chronic obstructive pulmonary disease patients

Abstract

To evaluate the reproducibility of Negative Expiratory Pressure (NEP) technique in detecting expiratory flow limitation (EFL) on chronic obstructive pulmonary disease (COPD) patients. EFL was evaluated with NEP technique in 72 subjects having stable COPD on two occasions. Agreement between testing occasions was assessed with the κ statistic for the 3-point and 5-point EFL scores, and with paired t-test for FL index. On the first testing occasion, 18 subjects had no EFL, 18 subjects had EFL in the supine position, and 36 subjects in the sitting and the supine position. Using the 3-point score, agreement was present in 58 of the 72 subjects at time 2 (κ = 0.69, P<0.001), indicating a substantial agreement was found. Using the 5-point score, agreement was seen in 52 of the 72 subjects (κ = 0.65, P<0.001), also indicating a substantial agreement. The difference of FL index between the first and the second occasion was significant in both the sitting (P<0.05) and supine (P<0.05) positions. Both 3-point and 5-point scores provided a reproducible assessment of EFL on COPD patients but the FL index seemed less reproducible. More research were needed before NEP technique was promoted to be used clinically.