Hypoxemic Acute Respiratory Failure

Several factors can influence oxygenation monitoring and respiratory support through oxygen therapy: the type of oximeter used, skin pigmentation, and the oxygenation target. It is essential to have an accurate measurement of SpO2 in order to optimize the flow of oxygen or FiO2 administered to patients. The question arises as to the impact of these confounding factors on the FiO2 set during high-flow nasal oxygen therapy. The aim of the study is to evaluate the impact of the oxygenation target and the oximeter used on FiO2 in patients receiving high-flow nasal oxygen therapy.

The passage of air through the nasal cavity generates rhythmic oscillations transmitted by the olfactory bulb to the brain, which induces cerebral activation in functional areas and is associated with better cognitive performance compared to oral breathing. Consequently, the abolition of nasal ventilation in patients intubated via the orotracheal route could have deleterious effects on brain activity. Besides the loss of olfaction, the abolition of nasal ventilation could affect brain activity and respiratory control, consequently altering regional pulmonary ventilation. The hypothesis of the study is that nasal ventilation through the passage of humidified nasal airflow in patients intubated via the orotracheal route would be associated with modulation of cerebral electrical activity and tissue oxygenation and a modification of regional pulmonary ventilation.

The aim of this clinical study is to assess whether apneic oxygenation with High-Flow Nasal Oxygen (HFNO) would decrease the incidence of severe hypoxemia compared to no apneic oxygenation during the intubation procedure (from the start of laryngoscopy to 5 minutes after successful intubation) in patients with hypoxemic acute respiratory failure. The sponsor expects that apneic oxygenation (between the laryngoscopy and the success of intubation) with HFNO compared to no apneic oxygenation could decrease the risk of severe hypoxemia after intubation in hypoxemic critical ill patients. Participants will be enrolled according to eligibility criteria and randomized into one of the following groups: Experimental group : Apneic oxygenation will be used with HFNO between the laryngoscopy and the successful intubation (study intervention). non-invasive ventilation (NIV) alone will be used for the preoxygenation and hypoventilation phase until the laryngoscopy. The nasal cannulas of HFNO will be placed on hold beneath the patient's chin (with HFNO on and set with a flow at 60-70L.min-1, FiO2 1.0) pending laryngoscopy began. At the time of laryngoscopy: after removing the facemask of NIV, the nasal cannulas for HFNO will be placed in the patient's nares then the laryngoscopy will be performed. Control group: The control group will receive usual care, i.e., no oxygen during the apneic phase (between the laryngoscopy and the success of the intubation procedure) During the preoxygenation and hypoventilation phase until laryngoscopy, NIV alone will be used as in the experimental group.

The deleterious effects of alveolar hyperoxia and (severe) hyperoxaemia are well described. Achieving safe and efficient oxygenation may be challenging. The hypothesis of the present study is that closed-loop oxygen control in intubated and mechanically ventilated critically ill patients improves oxygen administration compared with standard manual oxygen titrations. A single-blind, randomised crossover clinical trial assessing the efficacy and safety of the use of a closed-loop oxygen control versus manual oxygen titration in patients receiving mechanical ventilation has been designed. Patients will be randomised to receive first either closed-loop oxygen control (CLOC) or manual oxygen titration (MOT). The percentage of time spent in optimal and sub-optimal SpO2 (oxygen saturation by pulse oximetry) ranges will be calculated for each period.