Clearing the airways is a complex phenomenon involving the production of secretions, the nature of mucus (viscosity, elasticity, stringiness, and adhesiveness), ciliary movement, and coughing. In intubated and ventilated patients, endotracheal suctioning occur when the patient is "unable to clear the airways of obstructions hindering the free passage of air." These suctioning can lead to transient desaturation exacerbated by a decrease in cardiac output due to increased mean arterial pressure, promoting cardiac arrhythmias. To minimize these effects, it is recommended to perform additional preoxygenation, by increasing the fraction of O2 in the air delivered to the patient by the ventilator 2-3 minutes before the procedure. These longstanding recommendations were reiterated in 2022, based on outdated studies involving systematic suctioning that required disconnecting the patient from the ventilator.

Currently, suctioning are performed on-demand, based on the patient's congestion status, either through the endotracheal tube cap or a "closed system." Desaturations have become infrequent without establishing that additional preoxygenation can prevent them. Moreover, additional preoxygenation is not without risks. By inducing de-nitrogenation atelectasis with a loss of lung volume, it can exacerbate pre-existing lung injuries in the most severe patients. In less severe cases, preoxygenation leads to transient hyperoxia, with various deleterious effects impacting patient prognosis. Thus, a short-term risk, such as deep desaturations, must be balanced against a medium-term risk of hyperoxia and de-nitrogenation.

Clearing the airways is a complex phenomenon involving the production of secretions, the nature of mucus (viscosity, elasticity, stringiness, and adhesiveness), ciliary movement, and coughing. Endotracheal suctioning are performed when the patient is "unable to clear the airways of obstructions hindering the free passage of air." Classically, endotracheal suctioning cause transient desaturation exacerbated by a decrease in cardiac output due to an increase in mean arterial pressure, promoting cardiac arrhythmias. To minimize these effects, it is recommended to perform additional preoxygenation, i.e., increasing the fraction of O2 in the air delivered to the patient by the ventilator 2-3 minutes before the procedure. These longstanding recommendations were reiterated in 2022, based on outdated studies involving systematic suctioning and/or disconnecting the patient from the ventilator.

Today, suctioning are performed on-demand, based on the patient's congestion status, either through the endotracheal tube cap or a "closed system." Desaturations have become rare without establishing that additional preoxygenation can prevent them. Moreover, additional preoxygenation is not without risks. In the short term, it induces de-nitrogenation atelectasis resulting in a loss of lung volume that can worsen pre-existing lung injuries in the most severe patients. In less severe cases, preoxygenation is responsible for transient hyperoxia, with various deleterious effects impacting patient prognosis. Thus, a short-term risk, such as deep desaturations, is juxtaposed with a medium-term risk of hyperoxia and de-nitrogenation.

The investigators hypothesize that the absence of additional preoxygenation is not inferior, in terms of deep desaturations, to the strategy with additional preoxygenation, and it would avoid exposing patients to the risks of de-nitrogenation-induced atelectasis and hyperoxia.

The investigators retained a margin of non-inferiority for the relative risk of 1.1, i.e. an increase of 10% of deep desaturations.

The main analysis will be performed on the per-protocol population (more conservative in non-inferiority trials).The per-protocol population will include patients who had at least one suctioning and for whom the additional preoxygenation strategy allocated by randomisation was followed in at least 70% of all suctioning reported in the patient's care record. Patients who stopped their participation in the study before endpoint timeframe and those who had never had an suctioning will not be included in the per protocol population.

The unit of analysis will be the patient, and a rate of suctioning leading to deep desaturation will be calculated for each patient, as described in the primary endpoint. The mean rate of suctioning leading to deep desaturation will then be calculated by treatment group (with additional preoxygenation / without additional preoxygenation).

Inclusion Criteria:

• 18 years of age or older
• Hospitalized in ICU, under invasive mechanical ventilation for less than 24 hours
• Information and signature of consent by patient or relative/trusted person, or emergency inclusion procedure

Exclusion Criteria:

• Patient on ECMO
• Not affiliated to a social security system
• Pregnant
• Under legal protection (curatorship, guardianship or safeguard of justice)
• Patient under AME
• Patient included in another interventional study that may have an impact on the evaluation criteria of the present study

The procedures carried out with the French data privacy authority (CNIL, Commission nationale de l'informatique et des libertés) do not provide for the transmission of the database, nor do the information and consent documents signed by the patients.

Consultation by the editorial board or interested researchers of individual participant data that underlie the results reported in the article after deidentification may nevertheless be considered, subject to prior determination of the terms and conditions of such consultation and in respect for compliance with the applicable regulations.

Beginning 3 months and ending 3 years following article publication. Requests out of these time frame can also be submitted to the sponsor

Researchers who provide a methodologically sound proposal.