Flow-controlled ventilation improves gas exchange in lung-healthy patients - a randomised interventional cross-over study.

Weber, Jonas; Schmidt, Johannes; Straka, Leonie; Wirth, Steffen; Schumann, Stefan

BACKGROUND Flow-controlled ventilation (FCV) is a new ventilation mode that provides constant inspiratory and expiratory flow. FCV was shown to improve gas exchange and lung recruitment in porcine models of healthy and injured ventilated lungs. The primary aim of our study was to verify the influences of FCV on gas exchange, respiratory mechanics and haemodynamic variables in mechanically ventilated lung-healthy patients. METHODS After obtaining ethical approval and informed consent, we measured arterial blood gases, respiratory and haemodynamic variables during volume-controlled (VCV) and flow-controlled ventilation (FCV) in 20 consecutive patients before they underwent abdominal surgery. After baseline (BL) ventilation, patients were randomly assigned to either BL-VCV-FCV or BL-FCV-VCV. Thereby, BL ventilation settings were kept, except for the ventilation mode related differences (FCV is supposed to be used with an I:E ratio of 1:1). RESULTS Compared to BL and VCV, PaO2 was higher [PaO2 : FCV: 38.2 (7.1), BL ventilation: 35.0 (5.8), VCV: 35.2 (7.0) kPa, p <0.001] and PaCO2 lower [PaCO2 : FCV: 4.8 (0.5), BL ventilation: 5.1 (0.5), VCV: 5.1 (0.5) kPa, p <0.001)] during FCV. With comparable plateau pressure [BL: 14.9 (1.9), VCV: 15.3 (1.6), FCV: 15.2 (1.5) cm H2 O), p = 0.185], tracheal mean pressure was higher during FCV [(BL: 10.2 (1.1), VCV: 10.4 (0.7), FCV: 11.5 (1.0) cm H2 O, p <0.001)]. Haemodynamic variables did not differ between ventilation phases. CONCLUSION FCV improves oxygenation and carbon dioxide elimination within a short time, compared to VCV with identical tidal volume, inspiratory plateau pressure and end-expiratory pressure.