Sustained vs. Intratidal Recruitment in the Injured Lung During Airway Pressure Release Ventilation: A Computational...

Area of Science:

• Pulmonary Medicine
• Computational Biology
• Mechanical Ventilation

Background:

• Cyclic alveolar recruitment and derecruitment (R/D) cause heterogeneous stress in injured lungs.
• Alveolar R/D rates can be altered in acute lung injury, affecting optimal ventilation parameters.

Purpose of the Study:

• To simulate the effects of Airway Pressure Release Ventilation (APRV) on acinar recruitment using a computational model.
• To investigate how varying inspiratory pressure levels and exhalation durations influence lung mechanics during APRV.

Main Methods:

• A computational model simulating a ventilator, breathing circuit, endotracheal tube, and a porcine lung with injured and transitional zones was developed.
• Lung injury was simulated via inflation-dependent surface tension; APRV parameters (inspiratory pressure, exhalation duration) were systematically varied.

Main Results:

• Higher inspiratory pressures (40 cmH2O vs. 28 cmH2O) consistently increased both sustained acinar recruitment and intratidal R/D.
• Longer exhalation durations decreased sustained recruitment but increased intratidal R/D and decreased elastance.

Conclusions:

• Computational modeling highlights the complex interplay of R/D, recruitment, and strain stiffening on lung elastance during APRV.
• Higher inspiratory pressures increase recruitment but also intratidal R/D; shorter exhalation times are recommended with higher pressures to mitigate this.