The six minute walking test elicits dynamic hyperinflation in severe COPD patients

Background: Exercise tolerance in patients with COPD is highly variable and poorly related to airways obstruction assessed by FEV1. These patients dev elop dynamic hyperinflation (DH) dining art incremental exercise test which can be evaluated through a reduction III inspiratory capacity (IC)Aim: to evaluate: a) if the six minute walking test (6 MWD) induce DH reducing IC, b) if the reduction III IC is related to tidal expiratory flow limitation t it rest (FL). Subjects and methods: Thirty eight stable COPD patients (28 F L and tell non FL during resting breathing, determined by the negative pres sure technique). Inspiratory capacity was measured before and immediately a fter the 6 MWD test. Dyspnea, SpO(2) arid heart rate here measured before a rid after the test. Results: Inspiratory, capacity was lower III FL patient s cis compared to patients without FL (p <0,005). Although no differences w ere found between groups III 6 MWD, dyspnea and HR, a significant reduction in IC after the walking test was observed only III PL patients (p <0,0001) . In addition, SpO(2) fell significantly (p <0,0001) after walking tit the same group. Conclusions: Our results demonstrate that a moderate exercise s uch as the walking test induces DH anti hypoxemia in patients with COPD and FL and stresses the importance of assessing DH by measuring IC in these pa tients.