[Consequences of mechanical ventilation on diaphragmatic function]

Mechanical ventilation is associated with ventilator-induced diaphragmatic dysfunction (VIDD) in animal models and also in humans.

The main pathophysiological pathways implicated in VIDD seems to be related to muscle inactivity but may also be the consequence of high tidal volumes. Systemic insults from side effects of medication, infection, malnutrition and hypoperfusion also play a part. The diaphragm is caught in the cross-fire of ventilation-induced and systemic-induced dysfunctions. Intracellular consequences of VIDD include oxidative stress, proteolysis, impaired protein synthesis, autophagy activation and excitation-contraction decoupling. VIDD can be diagnosed at the bedside using non-invasive magnetic stimulation of the phrenic nerves which is the gold standard. Other techniques involve patient's participation such as respiratory function tests or ultrasound examination.

At this date, only spontaneous ventilatory cycles and perhaps phrenic nerve stimulation appear to diminish the severity of VIDD in humans but several pathways are currently being examined using animal models. Specific pharmacological options are currently under investigation in animal models.