Efficacy of Positive vs Negative Pressure Ventilation in Unloading the Respiratory Muscles: Discussion (2)

Efficacy of Positive vs Negative Pressure Ventilation in Unloading the Respiratory Muscles: Discussion (2)We attempted to match Ve during assisted ventilation to the level during QB. However, an additional goal was to maximize subject comfort during the AV The small differences in Ve and etC02 during PPV as compared with NPV were not significant. Although reduction in diaphragm EMG can be achieved with hyperventilation by mechanical means, we do not believe that this is the main reason for reduced iEMG in our patients.* In the study of Henke and coworkers, reduction of iEMG was related mainly to reduction of the etC02 below the apneic threshold of normal subjects during non-REM sleep. In awake subjects, considerably greater reductions in etC02 are required to silence spontaneous respiratory activity. Our subjects showed no correlation between the reduction in PaC02 and iEMG. buy prednisone

These data agree with those of Rochester et al and Rodenstein et al* who also failed to find relationships between changes in C02 tensions and decreases in iEMG. Conversely, our data strongly suggest that the reduction in diaphragmatic activity resulted from mechanical unloading of the diaphragm. This is shown by the excellent correlation between the changes in the PTI of the diaphragm and iEMG. Even in the study of sleeping subjects, a partial role for mechanical factors was demonstrated by the fact that a reduction of iEMG persisted even after C02 tensions were restored to isocapnic levels. Previous studies have shown that nonchemoreceptor influences, including a reduction in mechanical loading, can produce an inhibition of the respiratory system.


Category: Lung function

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