Heijdra et al. (A-27) state that many patients with severe chronic obstructive pulmonary disease

(COPD) have low arterial oxygen saturation during the night. These investigators conducted a study to determine whether there is a causal relationship between respiratory muscle dysfunction and nocturnal saturation. Subjects were 20 (five females, 15 males) patients with COPD randomly assigned to receive either target-flow inspiratory muscle training (TF-IMT) at 60 percent of their maximal inspiratory mouth pressure (PImax) or sham TF-IMT at 10 percent of PImax. Among the data collected were the following endurance times (Time, s) for each subject at the beginning of training and 10 weeks later:

Time (s) TF-IMT 60% PImax Time (s) TF-IMT 10% PImax Week 0 Week 10 Week 0 Week 10 330 544 430 476 400 590 400 320 720 624 900 650 249 330 420 330 144 369 679 486 440 789 522 369 440 459 116 110 289 529 450 474 819 1099 570 700 540 930 199 259 Source: Data provided courtesy of Dr. Yvonne F. Heijdra.