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

OBJECTIVE: 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). STUDY DESIGN: Prospective randomized crossover experiment. ANIMALS: Ten New Zealand White rabbits. METHODS: 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. RESULTS: 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. CONCLUSIONS AND CLINICAL RELEVANCE: 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.

Clinical evaluation of the v-gel supraglottic airway device in comparison with a classical laryngeal mask and endotracheal intubation in cats during spontaneous and controlled mechanical ventilation.

OBJECTIVE: To compare airway management during induction of anaesthesia, in spontaneous ventilation and controlled mechanical ventilation (CMV), using a cat-specific supraglottic airway device (the v-gel), a classical laryngeal mask (LM) or an endotracheal tube (ETT). STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: Forty-five healthy cats. METHODS: After premedication, cats were randomly allocated to one of three groups to secure the airway: 1) v-gel; 2) LM; or 3) ETT (cuff pressure: 20 cm H2O). Cats were anaesthetized for elective procedures. The dose of propofol necessary to insert the v-gel, LM or ETT, the number of attempts required to achieve insertion and leakage during spontaneous ventilation and CMV at different peak inspiratory pressures (8, 10, 12, 14 and 16 cm H2O) were recorded. Leakage of >20% of tidal volume was considered as a criterion for exclusion. Significance was set at a p-value of <0.05. RESULTS: Cats in the v-gel group required a median (range) of 3 mg kg(-1) (2-5 mg kg(-1)) of propofol for successful placement, which was significantly less than the 5 mg kg(-1) (3-7 mg kg(-1)) required for endotracheal intubation (p = 0.005). No significant difference in the total dose of propofol was observed between the v-gel and LM [3 mg kg(-1) (2-7 mg kg(-1))] groups or the ETT and LM groups. Significantly more cats in the ETT group were excluded for leakage of >20% during CMV at all pressure settings. CONCLUSIONS AND CLINICAL RELEVANCE: The v-gel is a practical alternative to the LM and ETT for securing the airway after induction of anaesthesia and for CMV up to 16 cm H2O in healthy cats. The v-gel can be inserted at a more superficial level of anaesthesia than the ETT and showed significantly less leakage during CMV than the ETT.