Clinical assessment of the efficacy of supraglottic airway devices compared with endotracheal tubes in cats during volume-controlled ventilation.

The efficacies of a supraglottic airway device (SGAD) and an endotracheal tube (ETT) in cats under general anesthesia with volume-controlled ventilation (VCV) were compared. Thirty healthy cats were randomly allocated for airway control using either an SGAD or an ETT. Five tidal volumes (6, 8, 10, 12, and 14 mL/kg) were randomly tested, and respiratory rates were adjusted to achieve a minute ventilation of 100 mL/kg/min. The dose of propofol necessary to insert the SGAD or ETT, the static respiratory pressure, leakage during VCV, and end tidal CO₂ (ETCO₂) were recorded. Dosages of propofol and static respiratory measurements for the SGAD and ETT groups were compared using a t-test. The distribution of leakages and hypercapnia (ETCO₂ > 45 mmHg) were compared using Fisher's exact test. A significance level of < 0.05 was established. No significant difference in dose of propofol was observed between the SGAD and ETT groups (7.1 ± 1.0, 7.3 ± 1.7 mg/kg; = 0.55). Static resistance pressure of the SGAD (22.0 ± 8.1 cmH₂O/L/sec) was significantly lower than that of the ETT (36.6 ± 12.9 cmH₂O/L/sec; < 0.01). Of the 75 trials, leakage was more frequent when using an SGAD (8 events) than when using an ETT (1 event; = 0.03). Hypercapnia occurred more frequently with SGAD (18 events) than with ETT (3 events; < 0.01). Although intubation with an ETT is the gold standard in small animal anesthesia, the use of an SGAD can reduce airway resistance and the work of breathing. Nonetheless, SGAD had more dead space and the tidal volume for VCV needs adjustment.