Biomimetic lung simulator for regional intrapulmonary pressure measurement during mechanical ventilation

Background Mechanical ventilation generates complex mechanical stresses within the lung that may vary substantially between different lung regions. Although global airway pressure parameters are routinely used to guide ventilation strategies, regional pressure transmission and mechanical behavior within the lung remain incompletely understood. This study aimed to investigate regional intrapulmonary pressure dynamics during mechanical ventilation under controlled experimental conditions. Methods A biomimetic thorax-lung simulator incorporating an explanted porcine lung was used to measure regional intrapulmonary pressures during pressure-controlled ventilation. The lung was placed within a negative-pressure thoracic chamber with an actuated diaphragm analogue and an anatomically realistic upper airway model. Pressure signals were recorded simultaneously at seven anatomical locations including the trachea, main bronchi, and upper and lower lobes of both lungs. Ventilation was performed across positive end-expiratory pressure (PEEP) levels ranging from 0 to 20 mbar combined with a driving pressure set at 15 mbar. Regional pressure transmission, hysteresis behavior, and short-term variability of pressure signals were analyzed using anatomical pressure mapping, hysteresis loops, and nonlinear Poincaré analysis. Results Absolute inspiratory and expiratory pressures increased proportionally with increasing PEEP across all lung regions, and regional pressure gradients relative to tracheal pressure remained small, indicating efficient pressure transmission throughout the bronchial tree. However, dynamic mechanical behavior differed between central airway and peripheral lung regions. Peripheral regions, particularly the lower lobes, exhibited increased hysteresis and higher pressure variability at low PEEP levels. Increasing PEEP reduced hysteresis areas and variability indices, indicating improved mechanical stability and more homogeneous pressure transmission. Following ventilation at high PEEP, hysteresis areas remained reduced even after PEEP was lowered, suggesting persistent recruitment of peripheral lung regions. Conclusions Although static pressure transmission during mechanical ventilation appears largely homogeneous, regional dynamic mechanical behavior varies substantially across lung regions. Peripheral lung compartments demonstrate increased mechanical instability at low PEEP levels, which can be stabilized by higher PEEP. These findings highlight the importance of regional lung mechanics and may help improve understanding of PEEP-related stabilization of peripheral lung regions during mechanical ventilation.