Controlled Trial of External Negative Pressure Ventilation in Patients with Severe Chronic Airflow Obstruction

The effect of intermittent external negative pressure ventilation (ENPV) with the Emerson Pulmowrap ventilator upon leg cycle endurance time (ET), maximal transdiaphragmatic pressure (Pdimax), breathing pattern as expressed by the tension time index (TTdi), and sense of well being was studied in 16 patients with severe chronic airflow obstruction (CAO). The patients were randomized to 3 wk of in-hospital pulmonary rehabilitation (Group I, seven patients) or the same program plus ENPV (Group II, nine patients). Both groups were similar in terms of age (65 ± 8 versus 61 ± 13 yr), severity of CAO (FEV1 of 0.64 ± 0.14 versus 0.59 ± 0.18 L), and PaCO2 (44 ± 9 versus 45 ± 7 mm Hg). Blood theophylline levels and nutritional status were also similar in both groups. Baseline ET (2.9 ± 0.6 versus 3.8 ±1.6 min) and Pdimax (45 ± 15 versus 56 ± 18 cm H2O) were decreased in both groups. Baseline TTdi was high but similar in both groups; at rest the values were 0.15 ± 0.05 versus 0.16 ± 0.04, and at end-exercise they we...