Due to an accident, pneumonia or surgery, patients can have severe shortness of breath or lung damage to such an extent that it compromises vital functions. At such times, mechanical ventilation can be lifesaving. The ventilator temporarily takes over the function of the respiratory muscles to ensure adequate uptake of oxygen and removal of carbon dioxide. Mechanical ventilation can usually be stopped quickly after the initial disease has been treated. Unfortunately, in up to 25-40% of ventilated patients it takes several days to weeks before mechanical ventilation can be discontinued, even after treatment of the initial disease. This phenomenon is termed weaning failure. Weakness of the respiratory muscles, such as the diaphragm, is one of the leading causes of weaning failure.

Like other skeletal muscles, the diaphragm can become weakened if it is used too little. This happens often during mechanical ventilation because of excessive assistance provided by the ventilator or use of sedative medication. Excessive activity of the diaphragm can also lead to damage and weakness, just like in other muscles that have to perform excessive amounts for a prolonged period of time. Additionally, excessive work by the diaphragm might have a direct damaging effect on the lungs, which leads to a vicious cycle. As such, it is very important to find a balance between resting the diaphragm (which may lead to weakness) and placing excessive work on the diaphragm (which can damage the diaphragm and possibly the lungs).

In this study, the investigators want to test whether insufficient activity and excessive activity of the diaphragm during mechanical ventilation can be prevented or reduced. The investigators plan to measure the diaphragm activity in 40 participants on mechanical ventilation. Participants will be randomly assigned to the intervention group or the control group. In the intervention group, ventilator support levels will be adjusted according to the observed diaphragm activity, in an attempt to ensure adequate diaphragm activity. The control group receives usual care. The hypothesis is that adjusting the level of support provided by the ventilator is a feasible method to improve the time that the diaphragm operates within acceptable levels of activity over a 24 hour period.

Inclusion Criteria:

• Informed consent
• Receives partially supported mechanical ventilation
• Estimated duration of mechanical ventilation after inclusion of at least 24 hours, as estimated by the attending physician

Exclusion Criteria:

• Known neuromuscular disease
• Contra-indications for nasogastric intubation (upper airway surgery, bleeding disorders)
• Expected difficulties in obtaining reliable pressure measurements, such as known airleak into pleural space or diaphragmatic herniation