Non-invasive Ventilation Following Extubation (Prophylactic) to Prevent Extubation Failure in Critically Obese Patients: a Prospective, Randomized, Multicenter Study

Mechanical ventilation is the first artificial support used in intensive care unit (ICU). After a period of invasive mechanical ventilation, patients should be separated from the ventilator (weaning period of mechanical ventilation). If weaning and extubation (removal of the tracheal intubation tube) is successful in approximately 80 to 90% of resuscitation patients, 10 to 20% will develop acute respiratory failure (ARF) in the days following extubation . This incidence is higher in the patients most fragile in the respiratory field (obese patients, chronic obstructive pulmonary disease (COPD), elderly, heart failure, postoperative cardio-thoracic and / or abdominal surgery ...) . The management of post-extubation ARF consists of etiological treatment associated with ventilatory support which usually requires the use of new endotracheal intubation to deliver "invasive" artificial ventilation. This invasive ventilation is responsible for excess morbidity and excess mortality . Therefore, it is fundamental for the physician to prevent by all means the occurrence of ARF post-extubation. One of the most important causes of extubation failure is the imbalance between the burden imposed on the respiratory system and its ability to overcome it, leading to gas exchange abnormalities, namely hypoxia and hypercapnia. Ensuring adequate oxygenation is therefore essential after extubation. In ICU, oxygen therapy is commonly used to improve and provide adequate oxygenation .

Obesity, a major public health problem in the industrialized countries, concerns 10 to 20% of resuscitation admissions in France. It is associated with excess morbidity and longer mechanical ventilation time compared to the general population. Effect on mortality is controversial , some studies suggesting a protective or neutral effect of obesity , named "obesity paradox" . At the ventilatory level, several pathophysiological changes are combined and contribute to an increase in the incidence of respiratory complications . Pulmonary volumes are amputated, the Body Mass Index (BMI) being negatively correlated with the functional residual capacity and vital capacity. The compliance of the respiratory system is reduced by the weight of the chest wall. Decreased compliance and increased airway resistance lead to increased respiratory muscle work. All of these pathophysiological changes in the obese patient explain the over-risk of desaturation and ARF in the post-extubation period. In addition to the intrinsic risk factors associated with obesity, the post-extubation period is marked by numerous risk factors for the development of ARF and extubation failure.

However, the exploration of different modern modalities of adequate post-extubation oxygen therapy in obese resuscitation patients to prevent the occurrence of extubation failure or post-extubation ARF has never been studied.

For over 20 years, Non-Invasive Ventilation (NIV) has been an essential modality in the prevention ("preventive NIV") and management ("curative NIV") of respiratory failure in ICU. The advantages of this ventilation modality are: respect for airway defense mechanisms (speech and cough maintenance), elimination of laryngeal and tracheal trauma induced by an intubation tube, improved comfort, reduction of the risk of bronchopulmonary nosocomial infection .

An alternative to NIV is the simple administration of oxygen. Two devices delivering low oxygen flows are commonly used for oxygen therapy after extubation: the Venturi mask and the nasal cannulas. The nasal cannulas are preferred by patients and less likely to be removed, but they can cause discomfort due to dryness of nasal mucosa when oxygen flows greater than 4 L/min are used. The Venturi mask delivers predetermined oxygen concentrations ranging from 24 to 60%, but the mask is generally less comfortable than the nasal cannula and more likely to be displaced or removed . In clinical practice, the Venturi mask is more frequently used after extubation because critically ill patients breathe preferentially through an open mouth rather than the nose.