Abstract
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 p < 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; p = 0.55). Static resistance pressure of the SGAD (22.0 ± 8.1 cmH2 O/L/sec) was significantly lower than that of the ETT (36.6 ± 12.9 cmH2 O/L/sec; p < 0.01). Of the 75 trials, leakage was more frequent when using an SGAD (8 events) than when using an ETT (1 event; p = 0.03). Hypercapnia occurred more frequently with SGAD (18 events) than with ETT (3 events; p < 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.
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Fig. 1.
Diagram illustrating the timeline of the protocol used in this study. Cats were randomly allocated to airway control groups using an ETT or a SGAD. Five tidal volumes (6, 8, 10, 12, and 14 mL/kg) were randomly applied during VCV, and respiratory rates were adjusted to achieve a minute ventilation of 100 mL/kg/min. ETT, endotracheal tube; SGAD, supraglottic airway device; VCV, volume-controlled ventilation.
![jvs-21-e27f1.tif](/upload/SynapseXML/0118jvs/thumb/jvs-21-e27f1.gif)
Fig. 2.
Comparison of average minute ventilation (MVe) in cats during VCV when using a SGAD or an ETT. There was no significant difference between the SGAD and ETT groups at the different tidal volume settings. ETT, endotracheal tube; SGAD, supraglottic airway device; VCV, volume-controlled ventilation.
![jvs-21-e27f2.tif](/upload/SynapseXML/0118jvs/thumb/jvs-21-e27f2.gif)
Fig. 3.
Tidal volume (mL/kg) and respiratory rate (times/min) when using a SGAD or an ETT. No significant difference between the SGAD and ETT groups at different tidal volume settings was detected. ETT, endotracheal tube; SGAD, supraglottic airway device.
![jvs-21-e27f3.tif](/upload/SynapseXML/0118jvs/thumb/jvs-21-e27f3.gif)
Table 1.
Age, sex, body weight, and body condition score of the sample and dose of propofol needed to insert the ETT or SGAD
Table 2.
Static respiratory measurements of the ETT and SGAD groups*
Table 3.
Number of airway leakages (> 20% of the baseline tidal volume) in the ETT group vs. the SGAD group
Tidal volume (mL/kg) | ETT | SGAD | p-value | ||
---|---|---|---|---|---|
No leak | Leak > 20% | No leak | Leak > 20% | ||
6 | 15 | 0 | 13 | 2 | 0.48 |
8 | 15 | 0 | 15 | 0 | 1.00 |
10 | 15 | 0 | 14 | 1 | 1.00 |
12 | 15 | 0 | 13 | 2 | 0.48 |
14 | 14 | 1 | 12 | 3 | 0.60 |
Total | 74 | 1 | 67 | 8 | 0.03 |
Table 4.
Comparison of the occurrence of hypercapnia (ETCO2 > 45 mmHg) between the ETT and SGAD groups