Standardized low-flow ventilation with PEEP maintenance during bronchoscopy in mechanically ventilated ICU patients: a pilot trial.

BACKGROUND

Fiberoptic bronchoscopy in mechanically ventilated ICU patients can markedly increase airway resistance and peak inspiratory pressure (PIP), limit effective tidal volume delivery, and provoke transient hypoxemia, hypercapnia, dynamic hyperinflation, and hemodynamic instability. However, per-procedural ventilator management remains heterogeneous.

METHODS

This single-center trial with before-and-after design assessed the feasibility and safety of implementing a standardized low-flow ventilation protocol, and characterized its physiological effects (particularly peak inspiratory pressure), during bronchoscopy in adults intubated and ventilated in volume-assist-control mode.

RESULTS

During the observational phase (n = 36), ventilator settings reflected usual practice (increased pressure alarm and reduced PEEP; no routine flow reduction). Following a 1-month training period, the intervention phase (n = 35) implemented an inspiratory flow rate of 20 L/min, unchanged PEEP, and a reduced respiratory rate to achieve an I:E ratio of 1:2. Physiologic and ventilator data were automatically recorded at 1-min intervals. The primary endpoint was peak inspiratory pressure (PIP), a physiological endpoint reflecting the mechanical effect of the intervention. Secondary endpoints included minute ventilation (MV), end-tidal CO2 (EtCO2), oxygenation metrics, ventilator alarms, and hypotension, feasibility and procedural safety. PIP decreased substantially (45 [35, 65] cmH2O vs. 82 [59, 93] cmH2O; p < 0.001), resulting in a reduction in the time spent with pressure alarms (3.4% vs. 24%; p < 0.0001). However, MV (5.2 [4.6, 5.9] L/min vs. 6.4 [4.1, 7.3] L/min; p = 0.2), and EtCO2 (36 [30, 40] mmHg vs. 31 [27, 39] mmHg; p = 0.4) did not differ significantly. PEEP was maintained in the intervention group (8 [6, 10] cmH2O vs. 2 [0, 5] cmH2O; p = 0.001). The protocol was demonstrated short-term procedural safety signals, as average SpO2 (98.9 [93.7, 100.0]% vs. 99.9 [96.8, 100.0], p = 0.082), and hypotension incidence (8.6% vs. 14%; p = 0.7) did not differ significantly.

CONCLUSIONS

This protocol implementation study demonstrates that standardized low-flow ventilation with PEEP maintenance is feasible and safe during bronchoscopy in mechanically ventilated patients, with a significant reduction in peak inspiratory pressure as a robust mechanical signal. Alveolar ventilation and hemodynamic tolerance were preserved. These findings support the conduct of further research to evaluate clinical outcomes.