Flow-Controlled Ventilation as a Rescue Strategy in Advanced COVID-19 ARDS: A Retrospective Observational Study

Background: Acute respiratory distress syndrome (ARDS), particularly in COVID-19-related severe respiratory failure, remains a major challenge in intensive care. Flow-controlled ventilation (FCV) may improve gas exchange by enabling precise airway pressure control; however, clinical data on its prolonged use in ARDS are limited. Methods: This single-center retrospective observational study included adult patients with moderate to severe ARDS who underwent FCV during invasive mechanical ventilation. FCV was delivered using the Evone^® ventilator with the Tritube^®. Demographic data, ventilatory settings, and arterial blood gas values were analyzed before and during 48 h of FCV and for 8 h after transition to conventional ventilation. Results: Seven patients with COVID-19-related ARDS were included. Following initiation of FCV, PaO₂ increased within the first 8 h (median increase: +24 mmHg), accompanied by a median 38% improvement in the PaO₂/FiO₂ ratio, which remained above baseline throughout follow-up. Arterial PCO₂ progressively declined, with the most pronounced reduction observed within the first 24 h (median decrease: -14 mmHg; approximately 22%). After transition back to conventional ventilation, mild deterioration in gas exchange parameters was observed; however, none returned to baseline values. All patients died during their ICU stay, mainly due to secondary infections and pulmonary embolism. Conclusions: In advanced COVID-19-related ARDS unresponsive to conventional ventilation, prolonged FCV application was technically feasible under controlled ICU conditions and associated with descriptively observed improvements in gas exchange parameters. However, late initiation of FCV did not translate into survival benefit. Prospective studies are required to define the optimal timing and patient selection for FCV. The present findings primarily support the technical feasibility and short-term physiological effects of FCV rather than clinical efficacy.