4-WEEK NEGATIVE-PRESSURE VENTILATION IMPROVES RESPIRATORY-FUNCTION INSEVERE HYPERCAPNIC COPD PATIENTS

Studies on respiratory muscle resting by negative pressure ventilation (NPV) in patients with stable COPD have given conflicting results. Pr obable explanations lie in criteria of patients' selection, method of NPV application, and lack of supervision of respiratory muscle rest. T hirteen hypercapnic patients with COPD were, therefore, randomly assig ned to either a NPV group or a control group. The NPV was applied by a n airtight jacket (pneumosuit), 5 h a day, 5 consecutive days a week f or 4 weeks. Both NPV group and control group performed in-hospital pul monary rehabilitation program for a 4-week period. Arterial blood gase s, spirometry, maximal inspiratory pressure (MIP) and maximal expirato ry pressure (MEP), breathing pattern, and electromyogram (EMG) of the diaphragm and parasternal intercostal muscles were measured on the pre intervention day, and at the end of the second and fourth weeks of tre atment (days 13 and 27, respectively). The short-term effect of NPV on EMG suppression was also checked throughout the ventilatory sessions in three different days (1, 12, and 26, respectively). A 6-min walking test (WT) and level of dyspnea by a modified Borg scale were evaluate d on the preintervention and the last days. Negative pressure ventilat ion resulted in a significant reduction in EMG activity of both diaphr agm and parasterial muscles, associated with significant increase in M IP, tidal volume, and ventilation, and increase in PaO2 and decrease i n PaCO2. A significant relationship between change in MIP and change i n PaCO2 was observed (r=0.72, p < 0.01). Improvement in 6-min WT and d yspnea sensation was also observed, both being the sole changes in the control group. These data seem to indicate a beneficial role of respi ratory muscle rest in improving respiratory function. Adequate supervi sion by personnel familiar with the equipment is likely to contribute to successful treatment.