Intermittent positive pressure breathing may be a useful adjunct therapy for patients with chronic obstructive pulmonary disease. It is, however, quite expensive; moreover, in 1976 its treatment efficacy had not been determined. Although the effectiveness of IPPB had been previously studied, the influence of long-term treatment was not known for the following reasons: The individuals studied had been too few and were not randomly assigned to treatment groups, the patient groups were not homogeneous and their clinical and functional status were not well-documented, and precise descriptions of the manner in which IPPB was administered were not recorded.