ABSTRACT
BACKGROUND: Flow-controlled ventilation (FCV), a novel mode of mechanical ventilation characterised by constant flow during active expiration, may result in more efficient alveolar gas exchange, better lung recruitment and might be useful in limiting ventilator-induced lung injury. However, data regarding FCV in mechanically ventilated patients with acute lung injury or acute respiratory distress syndrome (ARDS) are scarce. OBJECTIVES: We hypothesised that the use of FCV is feasible and would improve oxygenation in moderate COVID-19 ARDS compared to conventional ventilation. DESIGN: Open-label repeated-measures controlled trial. SETTING: From February to April 2021, patients with moderate COVID-19 ARDS were recruited in a tertiary referral intensive care unit. PATIENTS: Patients with moderate ARDS (PaO2/FIO2 ratio 100-200 mmHg, SpO2 88-94% and PaO2 60-80 mmHg) were considered eligible. Exclusion criteria were: extremes of age (< 18 years, > 80 years), obesity (body mass index > 40 kg/m2), prone positioning at the time of intervention, mechanical ventilation for more than 10 days and extracorporeal membrane oxygenation. Eleven patients were recruited. INTERVENTION: Participants were ventilated in FCV mode for 30 min, and subsequently in volume-control mode (VCV) for 30 min. MAIN OUTCOME MEASURES: Feasibility of FCV to maintain oxygenation was assessed by the PaO2/FiO2 ratio (mmHg) as a primary outcome parameter. Secondary outcomes included ventilator parameters, PaCO2 and haemodynamic data. All adverse events were recorded. RESULTS: FCV was feasible in all patients and no adverse events were observed. There was no difference in the PaO2/FIO2 ratio after 30 min of ventilation in FCV mode (169 mmHg) compared to 30 min of ventilation in VCV mode subsequently (168 mmHg, 95% CI of pseudo-medians (- 10.5, 3.6), p = 0.56). The tidal volumes (p < 0.01) and minute ventilation were lower during FCV (p = 0.01) while PaCO2 was similar at the end of the 30-min ventilation periods (p = 0.31). Mean arterial pressure during FCV was comparable to baseline. CONCLUSIONS: Thirty minutes of FCV in patients with moderate COVID-19 ARDS receiving neuromuscular blocking agents resulted in similar oxygenation, compared to VCV. FCV was feasible and did not result in adverse events. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT04894214.