Lung mechanics - airway resistance in the dynamic elastance model

The selection of optimal positive end-expiratory pressure (PEEP) levels during mechanical ventilation therapy of patients with acute respiratory distress syndrome (ARDS) remains a problem for clinicians. A particular mooted strategy states that minimizing the energy transferred to the lung during mechanical ventilation could potentially be used to determine the optimal, patient-specific PEEP levels. Furthermore, the dynamic elastance model of pulmonary mechanics could possibly be applied to minimize the energy by localization of the patients’ minimum dynamic elastance range. The sensitivity of the dynamic elastance model to variance in the airway resistance was analyzed. Additionally, the airway resistance was determined by using three other established identification methods and was compared to the constant resistance obtained by the dynamic elastance model. For increasing PEEP, the alternative identification methods showed similar decreasing trends of the resistance during inspiration. This declining trend is apparently an exponential decrease. Results showed that the constant airway resistance, presumed by the dynamic elastance model, has to be rechecked and investigated.