A55-17 Effects of Bronchoscopy and Airway Secretions on Airway Pressures and Mechanical Power Across Different Respiratory Patterns

Abstract Rationale Bronchoscopy during mechanical ventilation can increase airway pressures, particularly when secretions are viscous. Understanding how secretion viscosity modifies respiratory mechanics during bronchoscope insertion may improve procedural safety and ventilator management strategies. Methods An 8.0 mm endotracheal tube ventilated a SimMan® 3G Plus mannequin connected to an ASL 5000™ active lung simulator, forming a closed-pressure hybrid circuit (Figure 1). Ventilation was delivered via an ELISA 500 ventilator in volume-controlled mode under apneic simulation for a 70 kg patient. Four respiratory models were programmed: physiologic, restrictive (ARDS), obstructive, and mixed, with inspiratory times (Ti) of 0.8, 1.2, 0.6, and 1.0 s, respectively. Compliance and resistance were digitally adjusted per model. Three artificial secretions were created: liquid (saline-glycerin 1:1), semiviscous (methylcellulose gel), and thick (gelatin-based). Each was introduced into the airway before measurement. Ventilatory parameters were recorded before and after bronchoscope insertion using an Ambu® aScope 4. Peak inspiratory pressure (Ppeak), plateau pressure (Pplat), auto-PEEP, and mechanical power (MP) were measured three times per condition, and mean values were analyzed. Δ (After - Before) was calculated to isolate the effect of bronchoscopy. Results Insertion of the bronchoscope produced a consistent rise in airway pressures across all models, proportional to secretion viscosity. In the physiologic model, ΔPpeak increased from +4 cmH2O (liquid) to + 15 (thick), while ΔPplat rose +2 to + 4 cmH2O and auto-PEEP +0.2 to + 0.5 cmH2O. In ARDS, changes were smaller (ΔPpeak +4-7; ΔPplat +2-3). The obstructive model showed the greatest increases (ΔPplat +9; Δauto-PEEP +0.4), consistent with dynamic hyperinflation, while the mixed model displayed intermediate responses. Mechanical power rose modestly (+1-2 J/min). Two-way analysis of ΔPplat and Δauto-PEEP revealed significant effects of secretion viscosity (p 0.001) and respiratory pattern (p ≤ 0.01), with an interaction (p 0.02). The magnitude of these changes was greatest in obstructive and mixed models. Conclusions Higher secretion viscosity amplifies airway pressure and auto-PEEP elevations during bronchoscopy, particularly in obstructive and mixed patterns. This hybrid simulation establishes a reproducible platform to explore mechanical behavior under variable secretion loads and represents an initial step toward developing safer bronchoscopic and ventilatory strategies in critical care. This abstract is funded by: NO FUNDING