Fiberoptic bronchoscopy (FOB) can cause a significant increase in respiratory resistances and airway pressure during mechanical ventilation (MV), which can jeopardize the delivery of the ventilatory assistance. This randomized controlled study tests the hypothesis that new ventilator settings aimed at reducing airway pressure may facilitate FOB during MV. Results of this trial should lead to propose a new ventilatory strategy for critically ill patients needing a FOB procedure under MV.

Introduction : Fiberoptic bronchoscopy (FOB) during mechanical ventilation (MV) is a challenging procedure as it considerably reduces the endotracheal tube internal diameter, increasing respiratory resistances, which may compromise the delivering of the ventilatory assistance. According to respiratory physiology principles applied to MV, the reduction of inspiratory flow and tidal volume are likely to reduce airway pressure during the inspiratory phase when respiratory resistances increase. Based on this assumption, we propose new ventilator settings aimed at reducing airway pressure during FOB. This study represents the first investigation to test special ventilator settings in order to facilitate FOB during MV.

Methods and analysis : This is a single-center randomized controlled trial, in which intubated patients undergoing a FOB will be assigned (1/1) either to receive the new ventilatory strategy or to stay on the ventilator settings previously selected by the attending physician. The intervention group will be applied the specific ventilator settings (inspiratory flow <25 L/min, tidal volume = 5 mL/Kg, inspiratory time = 1 sec, respiratory frequency <20c/min, positive end expiratory pressure(PEEP) = 5 cmH2O). The primary endpoint will be the reduction of the occurrence of a serious adverse event - inability to deliver the ventilatory support, significant arterial desaturation, or hemodynamics instability - during FOB prompting the interruption of the procedure. The sample size was estimated at a minimum of 46 patients to demonstrate a 50% reduction in the occurrence of such a serious adverse event with a power of 90% and an alpha risk of 0.05 (paired Student t-test).

An adjudication committee evaluates images (scope and monitor) to validate primary endpoint. This is done blinding randomization group.

Results of this trial should lead to propose a new ventilatory strategy for critically ill patients needing a FOB procedure under MV.

Inclusion Criteria:

• Age ≥18 years;
• Acute respiratory failure requiring invasive mechanical ventilation in the intensive care unit;
• Indication of either a fiberoptic bronchoscopy (FOB) procedure or a percutaneous tracheostomy under FOB control;
• Patient under sedation with Richmond Agitation and Sedation Scale(RASS) ≤-2,
• Written informed consent obtained by the patient or the patient legal representative

Exclusion Criteria:

• Presence of an absolute contraindication to FOB (respiratory arrest, severe acute respiratory distress syndrome (ARDS), refractory shock, uncontrolled heart rhythm disorder);
• Patients in respiratory distress or with severe patient-ventilator desynchronies ;
• Patients refusing FOB;
• Pregnancy ;
• Moribund patients (according to American Society of Anesthesiologists (ASA) Physical status score classification, class 5: high probability of death within 24 hours) or at high risk of death during the FOB procedure;
• Patients deprived of liberty;
• Patients under curators or guardianship.