Diaphragm weakness and mechanical ventilation--what's the critical issue?

While animal studies indicate that controlled mechanical ventilation (MV) induces diaphragm weakness and myofiber atrophy, there are no data in humans that confirm MV per se produces diaphragm weakness. Whether or not diaphragm weakness results from MV, sepsis, corticosteroids, hyperglycemia, or a combination of these factors, however, is not the most important issue raised by the recent study from Hermans and colleagues. This study makes an important contribution by providing additional evidence that many critically ill patients have profound diaphragm weakness. If diaphragm weakness of this magnitude is present in most mechanically ventilated patients, a strong argument can be made that respiratory muscle weakness is a major contributor to respiratory failure.