Abstract:
Understanding pulmonary function is integral to the diagnosis and prognosis of pulmonary disease. Computational modelling provides a unique perspective to analyse pulmonary pathologies, with the potential to guide real-time decision making in a clinical setting. One aspect of pulmonary models largely neglected to date is the lymphatic system that regulates fluid balance in the lung. This research builds upon a suite of existing pulmonary models, by developing an anatomically representative lymphatic model that consists of capillaries, interstitial spaces and lymphatic vessels to simulate fluid movement through the lung. Model compartments were connected by literature-derived equations for fluid movement, pressure and conductivity to simulate clinically-relevant conditions related to fluid balance in the lung. The model returned physiologically reasonable values for postural changes, high blood pressure, inflammation and vasoconstriction.
Conditions were strongly dependent on ventilation parameters derived from values seen in the literature. Hyperventilation and positive end-expiratory pressure returned unexpectedly high interstitial saturation and lymphatic flux, respectively. The model performed well under a range of conditions, but highlighted several areas that require further research to enable computational models to evaluate pulmonary fluid movement. The mechanisms underlying the link between ventilation and lymphatic clearance are unclear and of particular importance given the reliance on positive-pressure mechanical ventilation for respiratory illnesses. Measurements of pressures within the thoracic cavity, particularly of lymphatics, have historically been challenging due to methodological limitations. Recent advancements in lymphatic measurement techniques may help overcome some of these issues and lead to advancements in the modelling of pulmonary lymphatics. Despite these limitations the model provided good insights into the development of cardiogenic pulmonary edema.