Long-term non-invasive mechanical ventilation improves six minutes walk distance in patients with chronic respiratory failure

AIM: To investigate the effect of long-term non-invasive mechanical ventilation (LTMV) on exercise performance measured by the 6-minute walk test (6MWT) in patients with chronic respiratory failure (CRF). MATERIALS AND METHOD: A prospective study was conducted in a tertiary referral hospital between January 2007 and April 2008 on 21 consecutive patients with a diagnosis of CRF and indications for non-invasive mechanical ventilation (NIV) at home. The patients were evaluated using the 6MWT on two occasions; before the LTMV therapy and in the 6th month of therapy. Dyspnoea and fatigue were evaluated by a modified Borg scale at the beginning and at the end of the 6MWT. Other factors evaluated included the type of NIV device, inspiratory and expiratory pressures, arterial blood gasses (ABG), pulmonary function tests (PFT) and the findings on transthoracic echocardiography (TT E). RESULTS: Of the 21 patients, 14 were male, 14 (66.7% had chronic obstructive pulmonary disease (COPD), 2 (9.5%) had kyphoscoliosis, 2 (9.5%) had obstructive sleep apnoea syndrome (OSAS), 2 (9.5%) had tuberculosis sequelae, and one (4.8%) had obesity hypoventilation syndrome (OHS). The mean 6MWT distance was found to have increased from 237.71 m to 295.14 m with the use of LTMV for 6 months. Improvement was detected in the mean PaO2/ FiO(2) ratio, from 259 mmHg to 269.57 mmHg. No change was observed in the resting dyspnoea scores and fatigue scores with the use of LTMV at the beginning of 6MWT, but the dyspnoea scores at the end of 6MWT showed significant improvement with treatment. Blood gas analysis after LTMV use revealed no change in pH values, SaO2 % or PaO2/ FiO(2) ratio. A borderline significant decrease was found in PaCO2 (p= 0.057). Among PFT values, statistically significant increase was observed only in forced expiratory volume in one second (FEV1). CONCLUSION: LTMV use in patients with CRF results in significant improvement in exercise capacity. 6MWT can be a useful tool for the objective evaluation of functional exercise capacity in patients with CRF.