Table 1.
Glossary.
Fig 1.
Lumped-parameter respiratory mechanics model, in both volume-pressure (panel A) and electrical (panel B) system analogs.
Each non-rigid compartment has a volume V (black), pressure P, (black) and associated compliance C (green, for emphasis) that is a function of the transmural pressures (purple) across the compartment boundaries. Air flows (red) across resistances R and inertance I (blue) are positive in the direction of the arrows. Circular yellow arrows indication direction of loop summations in Eq (3). Subscripts: airway opening ao, upper u, collapsible c, small peripheral s, alveolar A, viscoelastic ve, lung elastic el, transmural tm, pleural pl, chest wall cw, muscle mus.
Fig 2.
Lung, chest wall, and total respiratory system compliance curves for high Cw (left) and low Cw (right).
Curves are described by Eqs (9) and (10) and parameterized using the procedures described in Parameterization. Tidal breathing loops with normal Ru (grey) and increased Ru (black) are superimposed for each condition over the lung compliance curve and larger in each inset to display hysteresis.
Table 2.
Tuned steady-state and dynamic simulation parameters that remained unchanged during simulations.
Table 3.
Parameters varying with chest wall compliance and simulation conditions.
Table 4.
Aggregate parameters and output states targeted during simulations.
Table 5.
Initial conditions.
Fig 3.
Simulated periodic steady-state tracings of five breaths.
Depicted are alveolar volume, airflow, alveolar pressure, dynamic elastic lung recoil, and pleural pressure, under high and low Cw conditions, with normal vs. high Ru.
Table 6.
Simulations and time to failure (TTF, in hours), defined as 90% volume loss.
Fig 4.
End-expiratory lung volume (left y-axis) and tidal volume (right y-axis) under high and low Cw conditions, no interventions.
Fig 5.
Breath-to-breath dynamic lung compliance and tidal volume.
Depicted are high and low Cw conditions, with simulated CPAP triggered in the high Cw condition when recruited fraction dropped 10%, 5%, and 3%.