Efficacy of Positive vs Negative Pressure Ventilation in Unloading the Respiratory Muscles: Discussion (3)

The reduction in iEMG during NPV in our study is comparable to that achieved by other investigators. Some investigators have found larger increases, but we agree with the conclusions of Ro-denstein and coworkers who stated that the reduced EMG during NPV is most likely the result of practice with the negative pressure ventilators. In the preliminary data of Levy and coworkers, it is emphasized that considerable practice with the negative pressure ventilator was necessary before reductions in the EMG activity could be found. Rodenstein and coworkers’ were unsuccessful in achieving adequate reductions in iEMG during NPV in naive subjects. Criner and Celli compared the rate of decrease of the intrathoracic pressure (dp/dT) during spontaneous and assisted NPV in patients with COPD and neuromuscular disease. buy antibiotics online

They showed that in contrast to patients with neuromuscular disease, spontaneous dp/ dT was in excess of the ventilator dp/dT in patients with COPD and speculated that NPV would generally be unsuccessful in capturing the diaphragm. The patients of Rochester and coworkers, in whom significant reductions in iEMG were seen, had had considerable previous experience with NPV Furthermore, in this study, the iEMG response was greater during NPV with an iron lung as compared with a cuirass. Naive subjects do not show this response, although when actively encouraged to relax, there is a decrement in the EMG.* The importance of practice and relaxation is underscored by the fact that in some patients, persistence of the EMG is seen even in the presence of hypocapnia.


Category: Lung function

Tags: neuromuscular, neuromuscular disease, patients copd, ventilatory muscle