Trial of Inspiratory Muscle Rest and Exercise in Chronic Obstructive Lung Disease

BACKGROUND:

The potential importance of respiratory, chiefly inspiratory-muscle, fatigue had only recently been appreciated. If inspiratory muscles fail, so does ventilation and tissue respiration. There are theoretical reasons to postulate inspiratory muscle failure in chronic obstructive pulmonary disease, and suggestions that it may occur in an acute form with exacerbations and in a chronic form during 'stability'. There are two therapeutic strategies available for prevention and treatment of inspiratory muscle fatigue: training inspiratory muscles to increase their efficiency and resting fatigued muscles. The former should work if chronic fatigue is not present, and the latter should allow recovery from chronic fatigue, so the two approaches are not necessarily mutually exclusive. This proposal was originally designed to test the efficacy of each of these therapies alone and also in combination; however, given the experience of a pretrial period, these goals were scaled back. Since there was reason to believe that VMR may be more effective than IMT, the trial focused on VMR and sham VMR only.

Ventilatory muscle rest was applied using a negative pressure ventilation suit sealed at the patient's hips, arms, and neck. A widebore tube connected to a fitting in the suit above the grid on the chest and upper abdomen transmitted negative pressure to the chest wall from the pump, thereby inflating the lungs.

The evidence for chronic inspiratory muscle fatigue in patients with COLD resided largely in several relatively poorly controlled studies indicating that nocturnal artificial ventilation, which presumably rested the inspiratory muscles, produced improvement in daytime function and blood gases. The trial produced some badly needed data on both the occurrence of inspiratory muscle fatigue in COLD patients and its treatment with VMR.

DESIGN NARRATIVE: