CT Debunks the Myth: Normal Capnograms Don't Guarantee Proper V-Gel Placement in Cats

Computed Tomography Assessment of V-Gel Advanced Supraglottic Airway Device Placement in Cats

José M. Gómez-Silvestre, Ana García-Fernández, José Ignacio Redondo, María de Los Reyes Martí-Scharhausen, Ariel Cañón, Eva Z. Hernández, Agustín Martínez, David McCallum Neilson, Jaime Viscasillas

Background:
Supraglottic airway devices (SGADs), such as the V-Gel Advanced, offer a less invasive alternative to endotracheal intubation in cats. These devices are designed to minimize trauma during airway management. Standard practice often relies on capnography to verify correct placement, but its accuracy has not been critically evaluated. This study aimed to use computed tomography (CT) to assess the actual placement of the V-Gel Advanced in cats with normal capnogram waveforms and to determine whether other factors (e.g., weight, mask size) predict improper positioning.

Methods:
This retrospective study reviewed 69 CT scans of cats with V-Gel Advanced SGADs in place and normal capnograms. CT assessments included closure at three key anatomical sites (oropharynx, larynx, and esophagus), rotation, rostrocaudal position, and contact with the epiglottis. Mask size, fit, distance from incisors, and presence of gas in the stomach were also recorded. Logistic regression was used to evaluate predictors of improper placement. All devices were placed by veterinary students under supervision.

Results:
Only 18.8% of cats had perfect SGAD placement (closure of larynx and esophagus with proper alignment). Incomplete closure was found at the oropharynx in 62%, the larynx in 14.5%, and the esophagus in 73% of cases. Rotational misalignment occurred in 31.7% of cats. The SGAD made contact with the epiglottis in 2.9% of cases. There was no significant correlation between mask fit, body weight, SGAD size, or rostrocaudal positioning and improper placement. Despite normal capnograms, these CT findings indicated a high rate of suboptimal positioning. No clinical complications were documented in anesthesia records.

Limitations:
This was a retrospective study, limiting control over variables such as fresh gas flow and body condition scoring. All animals were in sternal recumbency, precluding analysis of positional effects. Small sample size may have limited statistical power to detect associations between fit and malposition. The study did not quantify gas leakage or assess postoperative outcomes like regurgitation or aspiration.

Conclusions:
Normal capnography waveforms do not ensure proper placement of V-Gel Advanced SGADs in cats. CT findings revealed frequent misalignment and inadequate sealing, suggesting that capnography alone is insufficient to confirm correct positioning. Although no immediate complications were observed, the potential for regurgitation, aspiration, and ineffective ventilation remains. Further research is warranted to refine placement protocols and develop better intraoperative assessment tools.

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