NOCTURNAL SATURATION IMPROVES BY TARGET-FLOW INSPIRATORY MUSCLE TRAINING IN PATIENTS WITH COPD

Nocturnal desaturations during rapid eye movement (REM) sleep, caused by nonobstructive hypoventilation, occur frequently in patients with c hronic obstructive pulmonary disease (COPD). This is partly caused by decreased activity of the intercostal and accessory muscles due to a l ower motor command. The diaphragm has to compensate for the diminished activity of these muscles during REM sleep. However, in patients with COPD strength and endurance of the diaphragm may be affected by its u nfavorable position on the length-tension curve because of hyperinflat ion. The aim of this study was to establish the causal relationship be tween respiratory muscle function and nocturnal saturation in patients with COPD. We hypothesized that target-flow inspiratory muscle traini ng (TF-IMT) would improve nocturnal saturation. In 20 patients with st able COPD (FEV(1) 35.5 +/- 14.1% of predicted) and a mean nocturnal sa turation below 92% we measured maximal inspiratory pressure (PImax), t ransdiaphragmatic pressure (Pdi), maximal sustainable inspiratory pres sure (SIPmax), endurance time, and nocturnal saturation in Weeks 0, 4, and 10. During these 10 wk 10 patients underwent TF-IMT at 60% of PIm ax and 10 control patients received sham TF-IMT at 10% of PImax. PImax , Pdi, SIPmax, and the endurance time as well as the nocturnal saturat ion improved significantly in the 60% training group (by 3.0 +/- 1.5 k Pa, 3.4 +/- 1.9 kPa, 1.5 +/- 1.4 kPa, 189 +/- 149 s, and 1.9 +/- 2.2%, respectively), whereas no changes occurred in the sham training group . Also, significant correlations were observed between the changes in Pdi, SIPmax, and endurance time on the one hand and the change in noct urnal saturation on the other. We conclude that TF-IMT improves the no cturnal saturation in patients with severe COPD by increasing respirat ory muscle strength and endurance.