Inhaled Sedation in Critically Ill Patients

Inclusion Criteria: \- Adult patients receiving mechanical ventilation, with an anticipated duration \>48 hours after randomization, and requiring deep sedation (target RASS between -3 and -5). Exclusion Criteria: * Contraindication to isoflurane or propofol * Patients with maternal ancestry from Venezuela, due to the potential presence of an mt-ND4 gene mutation associated with neurological injury after exposure to certain volatile anaesthetic agents * Significant air leak, defined as a leak exceeding 30% of the delivered minute ventilation * Allergy to isoflurane or propofol * Cardiopulmonary arrest * History of ventricular tachycardia or long QT syndrome * Tidal volume \< 300 mL or PaCO₂ \> 50 mmHg at the time of randomization. * Invasive mechanical ventilation for more than 48 hours at the time of randomization. * Pregnancy * Breast feeding * Acute neurological condition * Patients expected to require repeated surgical interventions during their ICU stay. * ECMO * ECCO2R * Active humidification strictly required * Neuromuscular disease or high spinal cord injury likely to prevent discontinuation of mechanical ventilation due to baseline condition * Requirement for benzodiazepine use for a specific indication * Burns * Life expectancy less than 48 hours, or patients with such a level of severity that death during the ICU stay is considered highly likely. * Any condition (e.g., blindness, deafness, dementia) or language barrier that prevents the administration of delirium or cognitive assessment scales. * Lack of informed consent