Non-invasive ventilation improves peripheral oxygen saturation and reduces fatigability of quadriceps in patients with COPD

Background and objective:   Non-invasive ventilation (NIV) might improve peripheral muscle function and exercise capacity in severely disabled patients. This study evaluated the physiological impact of NIV on isokinetic concentric strength and endurance of lower limb muscles in patients with severe COPD.
Methods:   This clinical trial tested COPD patients ( n  = 24) and healthy subjects ( n  = 18). Subjects underwent isokinetic dynamometry tests while given either bi-level positive airway pressure ventilation (BV) or sham ventilation (SV), in a randomized order with 30 min of rest prior to each intervention. The inspiratory level of BV was set up to 14 cm H₂O and expiratory pressure up to 6 cm H₂O. Peripheral oxygen saturation (SpO₂), heart rate (HR), systolic (SBP) and diastolic blood pressure (DBP) at the peak of exercise were measured for each intervention.
Results:   Compared with controls, COPD patients had lower values of SpO₂ and HR ( P  < 0.01) during both BV and SV and lower values of DBP ( P  < 0.01) during BV. BV improved SpO₂ ( P  < 0.01), and reduced SBP in both COPD ( P  < 0.01) and control groups ( P  < 0.05) and reduced DBP in COPD patients ( P  < 0.01). BV also reduced the fatigue index in COPD patients when compared with SV ( P  = 0.003). Variation (BV-SV) of total work at the peak of the test was higher in the control group than in the COPD group ( P  < 0.05).
Conclusions:   BV improved SpO₂ and reduced the fatigability of the quadriceps muscle in patients with severe COPD. These results support the need for further evaluation of BV as adjunct during high-intensity strength exercise training in these patients.