Rationale: Despite the lack of clear clinical protocols, High Flow Nasal Oxygen (HFNO) is used as post-extubation respiratory support. Although HFNO seems to reduce the need for re-intubation, scepticism on its use persists as the mechanism of action in post-extubation patients remains undefined. Monitoring weaning from invasive mechanical ventilation while monitoring respiratory effort might help to determine the added value of HFNO surrounding extubation. We hypothesize that HFNO, compared to conventional oxygen therapy (COT), prevents de-recruitment of the lung and reduces respiratory effort, and so provides a physiologic clarification for the reduction in the need for reintubation.

Objective: Determine the physiological effect of HFNO compared to COT in the extubation phase regarding respiratory effort and lung aeration.

Study design: A physiologic, randomized clinical study comparing two standard of clinical care therapies.

Study population: Adult patients on invasive mechanical ventilation (IMV) for >72 hours, who are scheduled for extubation.

Intervention (if applicable): Before extubation, patients are randomized to receive COT (reference group) or HFNO as oxygenation regimen after extubation.

Main study parameters/endpoints: The main outcome is the difference in change in lung respiratory muscle effort (mean ΔPES) at 24 hours post-extubation between the study groups. Secondary parameters are differences in changes in respiratory effort at 2 and 4 hours post-extubation, difference in change in lung aeration (mean ΔEELI), differences in tidal volume, dyspnea score, and respiratory and sputum parameters between patients undergoing different post-extubation oxygenation regimens.

Inclusion Criteria:

• Aged ≥ 18 years
• Receiving IMV > 48 hours for any cause
• Successfully completing spontaneous breathing trial (SBT) as per local clinical guideline
• Provided written informed consent, through legal representatives on indication

Exclusion Criteria:

• Any clinical situation preventing appropriate execution of study procedures
• The presence of a tracheostomy
• Any feature that precludes HFNO-initiation
• Indication for NIV such as hypercapnia at end of SBT, or Obstructive/central Sleep Apnoea Syndrome or Obesity Hypoventilation Syndrome with CPAP use in medical history
• Contra-indication for nasogastric tube or inability to perform adequate PES measurements.
• Known diaphragm paralysis defined as elevated hemi-diaphragm on X-ray and evidence of paralysis during ultrasound (i.e. paradoxal diaphragm movement during sniffing)
• Known pregnancy or current breast-feeding