Recently, the FLOW-i anaesthesia ventilator
was developed based on the SERVO-i intensive care ventilator.
The aim of this study was to test the FLOW-i’s tidal
volume delivery in the presence of a leak in the breathing
circuit. We ventilated a test lung model in volume-, pressure-,
and pressure-regulated volume-controlled modes
(VC, PC, and PRVC, respectively) with a FLOW-i. First,
the circuit remained airtight and the ventilator was tested
with fresh gas flows of 6, 1, and 0.3 L/min in VC, PC, and
PRVC modes and facing 4 combinations of different
resistive and elastic loads. Second, a fixed leak in the
breathing circuit was introduced and the measurements
repeated. In the airtight system, FLOW-i maintained tidal
volume (VT) and circuit pressure at approximately the set
values, independently of respiratory mode, load, or fresh
gas flow. In the leaking circuit, set VT = 500 mL, FLOWi
delivered higher VTs in PC (about 460 mL) than in VC
and PRVC, where VTs were substantially less than
500 mL. Interestingly, VT did not differ appreciably from
6 to 0.3 L/min of fresh air flow among the 3 ventilatory
modes. In the absence of leakage, peak inspiratory pressures
were similar, while they were 35–45 % smaller in
PRVC and VC than in PC mode in the presence of leaks. In
conclusion, FLOW-i maintained VT (down to fresh gas
flows of 0.3 L/min) to 90 % of its preset value in PC mode,
which was 4–5 times greater than in VC or PRVC modes.
