Objective: To evaluate the reproducibility of Negative Expiratory Pressure (NEP) technique in detecting expiratory flow limitation (EFL) on chronic obstructive pulmonary disease (COPD) patients.
Methods: 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.
Results: 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.
Conclusion: 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.