A mathematical model approach quantifying patients' response to changes in mechanical ventilation: Evaluation in pressure support

Purpose: This article evaluates how mathematical models of gas exchange, blood acid-base status, chemical respiratory drive, and muscle function can describe the respiratory response of spontaneously breathing patients to different levels of pressure support. Methods: The models were evaluated with data from 12 patients ventilated in pressure support ventilation. Models were tuned with clinical data (arterial blood gas measurement, ventilation, and respiratory gas fractions of O ₂ and CO ₂) to describe each patient at the clinical level of pressure support. Patients were ventilated up to 5 different pressure support levels, for 15 minutes at each level to achieve steady-state conditions. Model-simulated values of respiratory frequency (fR), arterial pH (pHa), and end-tidal CO ₂ (FeCO ₂) were compared to measured values at each pressure support level. Results: Model simulations compared well to measured data with Bland-Altman bias and limits of agreement of fR of 0.7 ± 2.2 per minute, pHa of -0.0007 ± 0.019, and FeCO ₂ of -0.001 ± 0.003. Conclusion: The models describe patients' fR, pHa, and FeCO ₂ response to changes in pressure support with low bias and narrow limits of agreement.