They are, however, at variance with the increases in MIP observed by Marino and Braun (MIP — 28 ± —17 cm HaO to — 45 ± —23 cm H20) following ventilatory support for several hours each day. Our findings are also at variance with those reported by Ellis et al in patients with kyphoscoliosis. After three months of nocturnal ventilation, one patient had a fourfold improvement in MIP with no change in VC and another had a threefold improvement with a 20 percent increase in VC. proventil inhaler
We measured inspiratory muscle endurance against a pressure threshold load, a method originally described by Nickerson and Keens and subsequently used to measure endurance among healthy elderly subjects and patients with chronic obstructive pulmonary disease (COPD) undergoing inspiratory muscle endurance training. We set the pressure threshold load constant at 45 percent MIPRV (55 percent MIPFRC) and measured endurance time. We have previously reported the magnitude of variability of this test to be ±1.26 minutes. Thus, the improvement that we observed from an initial endurance time of 7 minutes to 13 minutes at three months and 17 minutes at 14 months likely reflects a real improvement of inspiratory muscle function.