Computed Inspiratory Muscle Pressure to Monitor Inspiratory Effort During Pressure Support Ventilation

This is a prospective validation study with repeated measurements. It aims to validate computed inspiratory muscle pressure (cPmus), a noninvasive estimate of inspiratory muscle pressure provided by the study ventilator (Prunus Padus 9, Shenzhen, China). The reference method is esophageal pressure-derived inspiratory muscle pressure (Pmus). The study will enroll adults receiving invasive pressure support ventilation (PSV).

After obtaining informed consent, participants will undergo simultaneous monitoring with the cPmus algorithm and an esophageal balloon catheter. Pressure support will be adjusted in six levels. Positive end-expiratory pressure (PEEP) will remain unchanged. Each pressure support level will be maintained for 10 minutes. Brief end-expiratory and end-inspiratory occlusion maneuvers will also be performed at each level to obtain additional indices of respiratory drive and inspiratory effort. Esophageal balloon will be removed after completing the last pressure support step.

At each pressure support level, paired values of cPmus and reference Pmus were measured. The corresponding inspiratory pressure-time products, cPTPmus and PTPmus, will also be calculated.

All procedures will follow the study protocol and standardized measurement procedures. Study data will be recorded in case report forms and an electronic database, with checks for completeness, accuracy, and waveform quality.