# Ex-PALM: a negative pressure ventilation system for air leak evaluation in ex vivo lungs

## TL;DR

Ex-PALM is a new system for testing air leaks in lungs outside the body, offering precise control and measurement for better understanding and treatment of post-surgery complications.

## Contribution

Ex-PALM introduces a novel ex vivo system for evaluating air leaks with dynamic ventilation control and biomechanical parameter extraction.

## Key findings

- Ex-PALM enables accurate ventilation control with standard deviations of ±0.08 cm H2O and ±2.1 mL for moderate air leaks.
- Leak quantification in Ex-PALM is comparable to the Thopaz+ system, with no significant differences in lower leak ranges.
- The system replicates coughing with peak pressure targets and matches theoretical pressure predictions with high accuracy (R2 > 0.95).

## Abstract

Prolonged air leaks (PAL) are considered to be one of the leading causes of postoperative complications following lung surgery. There are currently no clinically relevant methods for efficiently and systematically evaluating the underlying causes of PAL. Here, we introduce a new intuitive, physiologically-representative system for ex vivo negative pressure ventilation of lungs, equipped with PAL-oriented features.

Reproducibility and system capabilities were assessed using a lung simulation model capable of controlling the effective area of the defect, then validated with ex vivo specimens.

Our system enables dynamic control of ventilation using either pressure (PCV) or volume (VCV) targets, with respective standard deviations of ±0.08 cm H2O and ±2.1 mL with moderate air leaks (<1,000 mL/min) and respective standard deviations of ±0.18 cm H2O and ±11 mL with severe air leaks (>1,000 mL/min). Additionally, leak quantification features proved comparable to that of the Thopaz+ (Medela Healthcare, Baar, Switzerland), a standard commercial digital thoracic drainage system, offering sufficient resolution to differentiate among clinically relevant air leaks. In the lower leak ranges (<400 mL/min) across all methods of evaluations, there were no significant differences between measured leak rates. For higher leak ranges, although there remained no significant differences between the Ex-PALM methods evaluated, the Thopaz + proved to systematically report lower leak rates values (Thopaz+ 420.0 ± 10.0 mL/min vs. PCV-derived 449.0 ± 19.9 mL/min, p < 0.05) and (Thopaz+ 1,200.0 + 0.0 mL/min vs. PCV-derived 1,239.7 ± 21.1 mL/min, p < 0.001). Unlike current systems, coughing was predictably replicated using peak pressure targets ranging from 100 to 300 cm H2O with a standard deviation of ±1.30 cm H2O from target. Our system allows extraction of biomechanical parameters at every breath, with theoretically expected pressures matching experimental measurements with a goodness fit value (R2) above 0.95 for the vast majority of breaths.

The Ex vivo Pulmonary Air Leak Model (Ex-PALM) provides a preclinical PAL testing platform with high translational potential and applications in studying biomechanical mechanisms of PAL and developing intraoperative mitigation strategies.