'Optiflow + Duet' Interface' vs 'Standard' High Flow Nasal Cannula (OPTIMARF)

Physiological Effects of High Flow Oxygen Therapy Using 'Optiflow + Duet' Interface vs 'Standard' High Flow Nasal Cannula for Acute Respiratory Failure After Extubation. The OPTIMARF Study.

High-flow nasal cannula (HFNC) therapy is increasingly used in the management of acute respiratory failure. Its clinical application has been largely investigated in chronic obstructive pulmonary disease (COPD) patients but only marginally in patients experiencing acute respiratory failure after extubation. Promising data have been published in vitro about new asymmetrical high flow nasal cannula, named 'Optiflow + DUET'. Positive airway pressure, that dynamically changes with breathing, and clearance of anatomical dead space are the key mechanisms of noninvasive respiratory support with nasal high flow. Pressure mainly depends on flow rate and nare occlusion. The hypothesis is that an increase in asymmetrical occlusion of the nares leads to an improvement in dead-space clearance resulting in a reduction in re-breathing and breathing work.

After a 'baseline' trial using Venturi Mask, within the first 120 minutes after extubation, and assessing a arterial oxygen pressure (PaO2) and inspiratory oxygen fraction (FiO2) ratio < 300, patients will be randomly assigned to a first 1h-phase of 'conventional HFNO' or 'DUET HFNO'. At the end of each session several clinical parameters (i.e. DUS, EIT, ABGs, comfort, VAS) will be collected. Specifically, Gas-flow rate will be set at a maximum of 60 L/min, temperature at a maximum of 37°C, while FiO2 will be adjusted to maintain a peripheral saturation (SpO2) between 92 and 98%.

After a 'baseline' trial using Venturi Mask, within the first 120 minutes after extubation, and assessing a PaO2/FiO2 ratio < 300 (as described above), patients will be randomly assigned to a second 1h-phase of 'DUET HFNO' vs 'conventional HFNO'. At the end of each session several clinical parameters (i.e. DUS, EIT, ABGs, comfort, VAS) will be collected. Specifically, Gas-flow rate will be set at a maximum of 60L/min, temperature at a maximum of 37°C, while FiO2 will be adjusted to maintain SpO2 between 92 and 98%.

After a 'baseline' trial using Venturi Mask, within the first 120 minutes after extubation, and assessing a PaO2/FiO2 ratio < 300, patients will be randomly assigned to a first 1h-phase of 'conventional HFNO' or 'DUET HFNO'. At the end of each session several clinical parameters (i.e. DUS, EIT, ABGs, comfort, VAS) will be collected. Specifically, Gas-flow rate will be set at a maximum of 60 L/min, temperature at a maximum of 37°C, while FiO2 will be adjusted to maintain SpO2 between 92 and 98%.

After a 'baseline' trial using Venturi Mask, within the first 120 minutes after extubation, and assessing a PaO2/FiO2 ratio < 300, patients will be randomly assigned to a first 1h-phase of 'DUET HFNO' vs 'conventional HFNO'. At the end of each session several clinical parameters (i.e. DUS, EIT, ABGs, comfort, VAS) will be collected. Specifically, Gas-flow rate will be set at a maximum of 60 L/min, temperature at a maximum of 37°C, while FiO2 will be adjusted to maintain SpO2 between 92 and 98%.

To evaluate changes, between arms, in breathing effort (as assessed by diaphragm thickening fraction (TFdi) through DUS).

To evaluate changes, between arms, in lung aeration (as assessed by the end-expiratory lung impedance (delta EELI) through EIT.

To evaluate changes, between arms, in gas exchange (as assessed by PaO2 mmHg, pCO2 mmHg, pH through ABGs)

To evaluate changes, between arms, in ventilation distribution (as assessed by pendelluft (yes/not), respiratory rates/min, tidal volume (ml), global inhomogeneity index through EIT)

Inclusion Criteria: age >18 years old; invasive mechanical ventilation > 24h; acute respiratory failure within 120 minutes after extubation (defined during a spontaneous trial using Venturi mask and assessing a PaO2/FiO2 ratio < 300; absence of Sars-Cov-2 positivity; absence of cardiological or long-term respiratory disease Exclusion Criteria: pregnancy tracheostomy non-invasive ventilation after extubation second tracheal intubation contraindications for EIT belt facial abnormalities