Pulmonary gas exchange response to weaning with pressure-support ventilation in exacerbated chronic obstructive pulmonary disease patients

To assess if pressure-support ventilation (PSV) can improve ventilation-perfusion (V(A)/Q) imbalance observed during the transition from positive-pressure ventilation to spontaneous breathing in intubated chronic obstructive pulmonary disease (COPD) patients during weaning. Prospective study. Respiratory intensive care unit of a tertiary university hospital. Seven mechanically ventilated COPD male patients (age 68+/-6 (SD) years; FEV(1) 26+/-6% predicted) during weaning. Patients were studied during three ventilatory modalities: (1) assist-control ventilation (ACV), tidal volume (V(T)), 8-10 ml. kg(-1); (2) PSV aimed to match V(T)in ACV, 15+/-1 cmH(2)O and (3) spontaneous breathing. Arterial and mixed venous respiratory blood gases, V(A)/Q distributions, hemodynamics and breathing pattern were measured. Compared with both ACV and PSV, during spontaneous breathing patients exhibited decreases in V(T) (of 43%, p