Objective:

To assess whether decelerating vs.square flow will delay choke flow during total liquid ventilation with perfluorocarbon.

Methods:

After establishing airway access in 3 adult New Zealand rabbits(3.5±0.5 kg), total liquid ventilation initiated in standard square wave flow by instilling 20 ml/kg of preoxygenated perfluorocarbon as FRC and 17.5 ml/kg as tidal volume with RR of 5 cycles/minute(I:E 1:2). Dwell time was introduced at the end of expiration in increments of 250 msec to increase drainage velocity and thus, identify the expiratory time at which choke(Paw -20 mmHg) flow occurred(ET choke).The ETchoke at 9 decelerating waveforms were compared to square wave.Waveforms were created by altering the time at plateau velocity (Vp:10%, 33%, 66% or 100% of ET at plateau velocity) and decelerating to 10%, 33%, 66% or 100% of Vp at the end of expiration.VT, FRC and RR were kept constant.

Result:

ETchoke was less for all 9 decelerating scenarios compared to square wave.The best decelerating scenarios reduced the ETchoke by >1second compared to square wave.

Conclusion:

Decelerating expiratory flow delays choke compared to square wave.Reducing ET choke may allow enhanced gas exchange via introduction of dwell time or increased respiratory rate.