Association of Inspiratory Effort With Dyspnea During Assisted Mechanical Ventilation in Critically Ill Patients

During assisted mechanical ventilation, breathing results from the interaction between the patient and the ventilator. Optimal titration of pressure support is essential to maintain a balance between over-assistance and under-assistance. Excessive respiratory may lead to dyspnea and cause respiratory muscle fatigue, whereas excessive assistance promotes muscle atrophy and delays weaning. Although normal inspiratory effort values in healthy subjects are well defined, acceptable limits in critically ill patients remain unclear. Inspiratory effort is traditionally quantified by the pressure-time product (PTP), but its measurement is technically demanding. Simpler indices such as swings of esophageal pressure (δPes) and airway occlusion pressure at 100 ms (P0.1) are used more often, both with important limitations. Dyspnea, a frequent and distressing symptom among mechanically ventilated critically ill patients, may serve as a physiological marker of unacceptably high effort. This single-center prospective observational study conducted in the intensive care unit (ICU) of the University Hospital of Heraklion aims to (1) determine whether the ratio mean to maximal inspiratory pressure (Pmean/Pmax) correlates more strongly with dyspnea intensity than PTP, δPmus, P0.1 and (2) identify a Pmean/Pmax threshold predictive of clinically significant dyspnea. These findings are expected to define objective upper limits of acceptable inspiratory effort and guide ventilator titration to improve patient comfort and safety.