Experimental evaluation of four airway devices in anaesthetized New Zealand White rabbits

To compare airway management during induction of anaesthesia, spontaneous ventilation (SV) and controlled mechanical ventilation (CMV), using an endotracheal tube (ETT), laryngeal mask (LM), rabbit-specific supraglottic airway device (v-gel) or facemask (FM).

Prospective randomized crossover experiment.

Ten New Zealand White rabbits.

After premedication, rabbits were randomly allocated to four groups: 1) ETT; 2) LM; 3) v-gel or 4) FM. The required dose of propofol, duration and number of attempts to place an airway device and leakage during SV and CMV at different peak inspiratory pressures (6, 10, 12, 14 and 16 cmH₂O) were recorded. Computed tomography (CT) of the head, neck and abdomen were performed before and after CMV.

Significantly less propofol and time [2.0±0.5 mg kg^-1, 82±34 seconds, p<0.001] were needed to place the FM compared to the three other groups [v-gel 5.1±2.1 mg kg^-1, 302±124 seconds; LM 4.8±1.2 mg kg^-1, 275±89 seconds; ETT 5.5±1.4 mg kg^-1, 315±147 seconds]. A leak > 25% of the tidal volume occurred at the lowest pressure in FM [median (range), 6 (6-8) cmH₂O], which was significantly lower than with v-gel [16 (6-no leak at 16) cmH₂O], LM [>16 (6-no leak at 16)] or ETT [>16 (no leak at 16) cmH₂O] (p<0.001). On CT images, the height and width of the larynx were significantly smaller with v-gel in comparison to FM and LM (p=0.004). A significant increase in the amount of gas in the stomach (p=0.007), but not gastric volume, was detected in FM and LM.

The v-gel is a practical alternative to LM and ETT for airway management and CMV, but can compress the larynx. The FM is easily placed, but significant leakage occurs during CMV.