Influence of bi-level non-invasive ventilation in exercise tolerance and respiratory muscle strength in chronic obstructive pulmonary disease patients

Objective

To evaluate the effects of bi-level ventilation (BiPAP^®) on respiratory muscle strength and exercise tolerance in COPD patients.

Method

Ten patients with clinical and spirometric diagnoses of COPD, with FEV₁ 45 ± 8% and 69 ± 9 years old, clinically stable, were submitted to non-invasive ventilation (BiPAP^®) by nasal mask, while comfortably seated. Patients attended three sessions per week, during 12 weeks, 30 min each session. The positive inspiratory pressure varied between 12 and 14 cmH₂O, and the positive expiratory pressure between 4 and 6 cmH₂O, according to patient's comfort. Patients underwent clinical and physiotherapy evaluation pre and post treatment. The respiratory muscle strength was evaluated by maximal inspiratory pressure (PImax) and by expiratory pressure (PEmax), measured by residual volume and total pulmonary capacity, respectively. Three maximum efforts were performed in equipment graduated in cmH₂O (Ger Ar, SP, Brazil), and the maximum value considered for analysis. Exercise tolerance was evaluated with the incremental test (IT) symptoms limited. The IT was performed in a treadmill (Imbramed model Milenium ATL RS, Brazil), with progressive speed, beginning with 2.0 km/hour, during 2 min, increasing 0.5 km/hour every 2 min. The perception of dyspnea (Borg Scale), systolic blood pressure (SBP), diastolic blood pressure (DBP), oxygen peripherical saturation (SpO₂), heart rate (HR) and walking distance were measured every 2 min. Statistical analysis was by the Wilcoxon test, with P < 0.05.

Results

Statistically significant differences were observed for PImax (from 54 ± 17 to 77 ± 19; with P < 0.007), PEmax (from 75 ± 20 to 109 ± 36; with P < 0.007), SpO₂ (from 88 ± 5 to 91 ± 4; with P < 0.02), SBP (from 168 ± 24 to 146 ± 14; with P < 0.02), dyspnea (from 3 ± 3 to 0.6 ± 1; with P < 0.01) and walking distance (from 466 ± 341 to 723 ± 300; with P < 0.015). However, significant differences in HR and DBP were not seen.

Conclusion

According to these results, it is possible to conclude that BiPAP^®, promoting respiratory muscle rest, permitted better conditions in respiratory muscle strength development. Moreover, BiPAP^® improved oxygenation and reduced the symptoms of dyspnea, and was able to improve exercise tolerance in patients with COPD.