Jet ventilation in severe airway stenosis: how pressure and frequency shape airway pressure and ventilation.

BACKGROUND

Jet ventilation is widely used during rigid bronchoscopy, particularly in patients with airway narrowing, yet evidence guiding the selection of driving pressure and frequency in severely narrowed airways remains limited.

OBJECTIVES

To investigate how jet driving pressure and frequency interact with airway geometry to determine airway pressure, ventilation, and gas exchange during normal-frequency jet ventilation (NFJV) and high-frequency jet ventilation (HFJV) in normal and severely narrowed airways.

METHODS

Jet ventilation was applied to a 3D printed adult airway model under two conditions: a normal airway and a severely narrowed airway simulating 90% fixed circumferential stenosis. Airway pressure, tidal volume, intrinsic positive end-expiratory pressure (PEEP), inspiratory and expiratory flow rates, and oxygen concentration were measured.

RESULTS

Driving pressure was the primary determinant of airway pressure, tidal volume, and inspiratory flow under both ventilation modes. Under NFJV, airway pressure increased more steeply with pressure in the normal airway, whereas under HFJV, increasing pressure led to progressive pressure accumulation in the narrowed airway, resulting in higher airway pressures at elevated settings. Intrinsic PEEP was consistently higher in the narrowed airway and was amplified by increasing pressure and frequency. Across both modes, tidal volume decreased with increasing frequency and exhibited attenuated pressure responsiveness. Although measured oxygen concentration was higher in the narrowed airway, expiratory flow was markedly reduced, indicating impaired expiratory clearance.

CONCLUSIONS

Severe airway narrowing fundamentally alters the pressure-frequency-ventilation relationship during jet ventilation. In narrowed airways, escalation of driving pressure or frequency may increase pressure load and intrinsic PEEP without proportionally improving effective ventilation. Optimization should therefore prioritize adequate tidal volume, expiratory emptying, and CO2 monitoring rather than airway pressure or oxygen concentration alone.