Preoxygenation for Tracheal Aspirations in Intensive Care

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 These longstanding recommendations were reiterated in 2022, based on outdated studies involving systematic suctioning that required disconnecting the patient from the ventilator.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.