Flow-controlled ventilation in moderate acute respiratory distress syndrome due to COVID-19: an open-label repeated-measures controlled trial

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 (P_aO₂/F_IO₂ ratio 100-200 mmHg, SpO₂ 88-94% and P_aO₂ 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 P_aO₂/F_iO₂ ratio (mmHg) as a primary outcome parameter. Secondary outcomes included ventilator parameters, P_aCO₂ 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.

Keywords: ARDS; COVID-19; Flow-controlled ventilation; Mechanical ventilation.

Fig. 1

CONSORT flowchart

Fig. 2

Boxplots of P_aO₂/F_IO₂ ratio (A) and mean airway pressure (B) during FCV and VCV. Identical subjects are connected with grey lines. Groups were compared with the paired Wilcoxon signed-rank test. FIO2 fraction of inspired oxygen, FCV flow-controlled ventilation, PaO2 arterial partial pressure of oxygen, VCV volume-controlled ventilation

Fig. 3

Boxplots of PaCO2 (A) and minute volume (B) during FCV and VCV. Identical subjects are connected with grey lines. Groups were compared with the paired Wilcoxon signed-rank test. FCV flow-controlled ventilation, PaCO2 arterial partial pressure of carbon dioxide, VCV volume-controlled ventilation

Fig. 4

Boxplots of mean arterial pressure (A) and heart rate (B) during baseline PCV and FCV. Identical subjects are connected with grey lines. Groups were compared with the paired Wilcoxon signed-rank test. FCV flow-controlled ventilation, PCV pressure-controlled ventilation