The effects of noninvasive ventilators on COPD remain controversial because of their obscure mechanisms. A randomized crossover study, using iron lung and positive pressure nasal ventilation (BiPAP) each for 40 min, was performed in 11 stable patients with severe COPD. Throughout the study, we monitored surface EMGdi, EMGst, ECG, SaO2, ETCO2, and the movements of RC and AB. Afterwards the data were replayed to calculate VT, RR, PR, VT/TI, iEMG, and phase angle. No statistically significant improvement was found in view of the above parameters. However, the percentage of iEMGst change after 40-min BiPAP ventilation, compared with the baseline, was much more significant in patients with FEV1 below 0.55 L than those with FEV1 above 0.55 L (n = 4:7, delta iEMGst -62.93 percent +/- 23.27 percent versus 32.45 percent +/- 42.79 percent, p = 0.0056). delta iEMGst correlated significantly with FEV1 during BiPAP ventilation (p < 0.05, r = 0.59). We conclude that the iEMGst during short-term BiPAP ventilation correlates with the severity of the disease.

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