Abstract
Objective
To assess the v-gel Advanced Dog supraglottic airway device (SGAD) safety and efficacy compared to a high-volume, low-pressure endotracheal tube (ETT).
Methods
In a prospective randomized study, 30 client-owned mesocephalic canine patients (American Society of Anesthesiologists physical status I or II, scheduled for elective surgery) were to be enrolled and assigned to the SGAD or ETT group (15 SGAD; 15 ETT) by blocked randomization. Endotracheal tube cuffs were inflated to 25 cm H2O with a cuff inflator. The primary outcome was anesthetic circuit pressure decrease (leak) of inspiratory air at escalating anesthetic system pressures, tested at 0, 10, 15, and 20 minutes after airway device placement.
Results
Due to safety concerns, the study was terminated after 6 patients in the SGAD group failed leak pressure testing under 20 cm H2O at all time points. Thirteen canines (6 SGAD, 7 ETT) were enrolled from September through October 2023. The risk of leaking for the SGAD group was significantly higher than that of the ETT group at 12 cm H2O (P = .005) and at 16 cm H2O (P = .001). There were no perioperative or postoperative adverse events or significant differences in characteristics between airway device groups except that the risk for not requiring manipulations to obtain and maintain an effective airway for the SGAD group was 67% less (relative risk, 0.33; exact 90% CI, 0.06 to 0.74) than that of the ETT group.
Conclusions
The SGAD, but not ETT, failed leak pressure testing < 20 cm H2O.
Clinical Relevance
The v-gel Advanced Dog SGAD was not safe to deliver inhalant anesthetics due to the device failing leak pressure testing under 20 cm H2O.
Effective airway access is crucial to the safe delivery and maintenance of inhalant anesthesia in human and veterinary patients. The objective of securing the airway during general anesthesia is to maintain a patent airway, deliver anesthetic agents and oxygen, protect the lungs from fluid aspiration, prevent the escape of waste anesthetic gas to the personnel working environment, and, if necessary, achieve positive pressure ventilation. Intubation with an endotracheal tube (ETT) is considered the “gold standard” in veterinary anesthesia.
However, endotracheal intubation carries potential risks, including esophageal or bronchial intubation, tube obstruction, tracheal rupture, laryngeal edema, and tracheal ischemia or necrosis from cuff overinflation. Recently, veterinary-specific supraglottic airway devices (SGADs), such as the Cat v-gel (Docsinnovent) and Rabbit v-gel (Docsinnovent), have been developed. The v-gel was first described in rabbits, cats, and small dogs (under 10 kg) in 2010.1 In rabbits, the v-gel takes less time to place than ETTs.2,3 In cats, the v-gel is a sound and practical alternative to endotracheal intubation4; requires less propofol, less time, and fewer intubation attempts and results in less upper airway discomfort after device removal5; and can be placed at a lighter plane of anesthesia than the ETT.6
The first canine-specific SGAD, v-gel Advanced Dog (Docsinnovent), was designed for canines and features a semirigid tube with an ovoid moldable bowl, creating a circumferential seal around the larynx. It does not enter the larynx or trachea, offering secure positioning in the oral cavity. The tube includes an integrated gastric channel for inserting a gastric tube, esophageal temperature probe, or esophageal stethoscope, providing additional benefits, such as reflux and aspiration prevention. The reported benefits of the v-gel Advanced Dog are a high-quality pressure seal, avoidance of laryngeal trauma, and rapid insertion.
However, comparative studies on the v-gel Advanced Dog SGAD versus the traditional ETT are lacking. This study aimed to establish the efficacy of the v-gel device compared to ETT, compare leak pressures between the 2 devices, and assess the placement time, number of attempts, and postplacement device adjustments. The hypothesis was that the v-gel Advanced Dog SGAD would be comparable in safety and efficacy to the high-volume, low-pressure ETT. An additional hypothesis was that the v-gel Advanced Dog SGAD would have a significantly lower leak pressure than the ETT. The third hypothesis was that the v-gel Advanced Dog SGAD would have significantly less insertion time than the ETT.
Methods
Thirty client-owned, 20-kg-or-less, mesocephalic canine patients classified as American Society of Anesthesiologists American Society of Anesthesiologists physical status I or II and scheduled to undergo elective surgery under general anesthesia were planned to be included in the study. Exclusion criteria were procedures that required access to the pharynx for surgical and/or diagnostic procedures, patients at high risk of regurgitation (eg, brachycephalic breeds, gastrointestinal tract obstruction), neuromuscular blocking agent in the anesthesia protocol, a compromised airway present, access to the esophagus required (eg, passing of gastroscope, esophageal probes/tube), or if the patient was to undergo a dental procedure. Each patient was randomly assigned by type of intubation to group A or B by blocked randomization (groups of 10; 5 v-gel and 5 ETT) and a sealed envelope blinding technique on the morning of the procedure.7 An anesthesia machine leak check was performed prior to each anesthetic procedure and involved closing the adjustable pressure-limiting valve, occluding the end of the breathing circuit, and pressurizing the system with the flush valve to 30 cm H2O. The O2 flow was increased to 100 mL/min, and the pressure was monitored for 10 seconds. If the pressure increased, the machine had a < 100 mL/min leak. If the pressure equalized, the machine had a 100 mL/min leak. If the pressure decreased, the flow rate would be adjusted until equilibrium was met. If this resulted in a leak of > 300 mL/min, the unit was unacceptable for use. If a machine fell into this category, it would not be used for the study if it could not be corrected to increasing or equalizing pressures by obtaining a new tubing/rebreathing bag. Once finished, the adjustable pressure-limiting valve was released while still occluding the end of the breathing circuit. The reservoir bag was emptied to confirm that there was a patent and safe expiratory airflow.
Maropitant citrate (Cerenia; Zoetis; 10 mg/mL) 1 mg/kg was administered 1 hour preceding premedication to prevent perioperative nausea and vomiting. Patients were premedicated with 0.02 mg/kg acepromazine (acepromazine maleate injection; MWI; 10 mg/mL) and 0.1 mg/kg hydromorphone (hydromorphone HCl injection; Baxter; 2 mg/mL), combined in the same syringe and injected into the epaxial muscles. After 15 minutes, a 22-gauge catheter was placed in the left or right cephalic vein. After a minimum of 3 minutes of preoxygenation via a tight-fitting facemask, general anesthesia was induced with 4 mg/kg propofol (propofol injectable emulsion; Zoetis; 10 mg/mL) to effect. The propofol infusion was stopped once the patient could not support their head and the palpebral reflex and jaw tone were absent. At this point, the intubation in sternal recumbency was initiated with an appropriately sized v-gel SGAD or ETT. One veterinarian (ZS) performed all intubation procedures.
Each v-gel was selected according to the patient’s weight and skull conformation per the manufacturer’s recommendations. A new v-gel was used for each patient. The v-gel was lubricated using a water-based lubricant (VetLube; DocsInnovent Ltd). With an assistant’s help, the patient’s head was extended, and the jaw was opened. Holding the patient’s tongue, the v-gel was advanced along the hard palate with the open airway channel facing ventrally toward the tongue. Advancement was stopped/halted when the v-gel was felt dropping into position and resistance was encountered. A patent airway was confirmed by capnography, with a positive waveform and an end-tidal CO2 reading of ≥ 30 mm Hg. The v-gel was then secured into place by tying gauze around the ring features of the device and the patient’s head.
The ETT size was chosen based on tracheal palpation immediately cranial to the thoracic inlet. A new high-volume, low-pressure cuff Murphy-type ETT (VetOne) was used for each patient. The cuff of the ETT was lubricated using a water-based lubricant. With an assistant’s help, the patient’s head was extended, and the jaw was opened. Once the larynx was exposed, the ETT was advanced over the epiglottis through the arytenoid cartilages and vocal folds into the trachea. Confirmation of a patent airway was determined via visual confirmation of the tube in the larynx and by an acceptable capnograph trace. The tube was then secured into place by tying gauze around the tube and securing it to the patient’s upper jaw. The ETT cuff was inflated to 25 cm H2O using an AG Cuffill Cuff Inflator (Hospitech Respiration Ltd). This ETT cuff pressure was chosen based on recommended cuff pressures between 20 and 25 cm H2O to achieve an effective tracheal seal while minimizing complications.8–11
After placement, all dogs were placed in dorsal recumbency and remained there for the duration of the study. The airway devices were connected to a small-animal anesthetic rebreathing system (Isotec 4; Ohmeda Medical), and patients were fitted with standard anesthesia monitoring equipment. Monitoring included ECG, heart rate, respiratory rate, temperature, and noninvasive blood pressure (systolic arterial pressure, mean arterial pressure, diastolic arterial pressure, pulse oximetry, and end-tidal CO2). Parameters were recorded before premedication (baseline), immediately before induction (preinduction), immediately after intubation (0 minutes), and every 5 minutes thereafter. Anesthetic depth was assessed by eye position, palpebral reflex, and jaw tone. General anesthesia was maintained with isoflurane (Fluriso; VetOne) in 100% oxygen. Intravenous crystalloid solutions (NORMOSOL-R; Hospira Inc) were infused at a rate of 5 mL/kg/h from the induction of general anesthesia until 2 hours after recovery.
Intraoperative device leak tests were performed at 0 minutes, 10 minutes, 15 minutes, and 20 minutes by closing the adjustable pressure-limiting valve and pressurizing the anesthesia machine system with O2 to 12, 16, 18, and 20 cm H2O and monitoring for changes in pressure. Monitoring was done while maintaining an O2 flow rate of 100 mL/min. A leak was defined if the system pressure decreased within 10 seconds of starting the test. Conversely, no leak was defined if the system pressure was maintained or increased within the same timeframe.
Postoperatively, the patients were disconnected from the anesthesia circuit and observed continuously until recovery. The ETT or v-gel was removed once the swallowing reflex returned. The ETT or v-gel was inspected for any signs of blood, indicating trauma to the airways or pharynx. Following the removal of the ETT or v-gel, any perioperative adverse events were documented. Perioperative adverse events were defined as 0, none; 1, mild (gastric insufflation); 2, moderate (dysphagia, dysphonia, hoarseness, airway obstruction, blood staining of device); and 3, severe (hypoxia, regurgitation, aspiration, dental trauma, soft tissue trauma, gross blood on device).
Data collected during the anesthetic event included the number of attempts to intubate, the difficulty of the insertion of the airway device, and airway manipulation to provide an effective airway. Difficulty of insertion was defined as 0, easy; 1, moderately difficult; 2, difficult; and 3, impossible. The airway manipulation was defined as 0, none; 1, minor (adjusting head/neck position or changing the insertion depth); and 2, major (reinserting device).
Following the conclusion of the surgical procedure and data collection, carprofen (Rimadyl; Zoetis; 50 mg/mL) was administered SC at a dose of 2.2 mg/kg to provide postoperative analgesia, followed by oral postoperative analgesia.
At approximately 24 hours after discharge from the hospital, the clients were contacted for a follow-up survey with a standard list of questions regarding signs that might be attributed to airway discomfort (Supplementary Table S1) during the first 24 hours after the procedure.
This study was approved by the VCA Clinical Studies Institutional Review Board (VCSIRB-ZS1A). Owner consent was obtained for all dogs that participated in this study. A power analysis was performed, extrapolating from a study5 in felines comparing v-gel to ETT with a calculated OR of 97.2 for the leakage after placement timepoint (the OR was calculated using MedCalc12) and using G*Power, version 3.1.9.7,13 to calculate the sample size needed for this study. This identified that a sample size of 11 canine patients/group (total sample size = 22) would be needed for Fisher exact testing for proportions of leakage between the 2 independent groups (v-gel vs ETT), with an α of 0.05 and power of 0.95. To account for possible variability for different breeds, a sample size of 15 canine patients/group (total sample size = 30) would be included in the study.
Statistical analysis
Author ZS provided blinded data in an Excel (Microsoft Corp) document for each intubation group (airway device A and airway device B) to author KS. Author KS coded the data in Excel (Microsoft 365 MSO, version 2311; Microsoft Corp). Any incidence of “panting” was recoded to “60” for the respiratory rate at preinduction. The Excel data were then imported into SAS (version 9.4; SAS Institute Inc) for statistical analysis. Characteristic differences between groups were tested using the Fisher exact test for dichotomous variables and the Mantel-Haenszel χ2 test for variables with more than 2 categories. Normality was assessed by univariate analysis for each continuous variable via Shapiro-Wilk normality test, visually assessing histograms, and/or quantile-quantile plots. The nonparametric exact Wilcoxon 2-sample test was used to test differences between groups with non-normal distributions, and the parametric independent two-sample t test was used to test differences between groups with normal distributions. The exact test was used due to the small sample size. Means, SDs, medians, and 2-sided P values were calculated for each continuous vital parameter at baseline and preinduction (where applicable) as well as each anesthetic timepoint (Tables 1 and 2). Relative risk (RR) score statistics and exact unconditional confidence limits, α = 0.1, were utilized to calculate the RR and exact confidence limits of leaking between the 2 airway devices (Table 3) as well as attempts to intubate, number of propofol boluses, intubation difficulty (Table 4), and manipulations required for the airway device (Table 5). A Fisher exact test was used to assess differences between the 2 airway devices. No statistical tests were performed for the postoperative survey data due to both groups having the same outcomes. A 2-sided P value of < .05 was selected to identify a significant difference between groups for Fisher exact, Mantel-Haenszel χ2, exact Wilcoxon 2-sample, and independent two-sample t tests.
Summary data for heart rate, respiratory rate, and temperature by airway device at 6 time points.
| v-gel (n = 6) | ETT (n = 7) | ||||||
|---|---|---|---|---|---|---|---|
| Variables | Mean | SD | Median | Mean | SD | Median | P value |
| Heart rate (beats/min) | |||||||
| Baseline | 127 | 15 | 130 | 136 | 20 | 130 | .372a |
| Preinduction | 111 | 12 | 107 | 102 | 13 | 100 | .233a |
| 0 min | 103 | 25 | 102 | 108 | 22 | 112 | .735a |
| 10 min | 92 | 13 | 89 | 101 | 23 | 98 | .396a |
| 15 min | 98 | 14 | 98 | 74 | 34 | 74 | .134a |
| 20 min | 107 | 17 | 111 | 86 | 18 | 84 | .066a |
| Respiratory rate (breaths/min) | |||||||
| Baseline | 26 | 7 | 26 | 27 | 6 | 28 | .788a |
| Preinduction | 44 | 13 | 38 | 35 | 18 | 32 | .175b |
| 0 min | 17 | 7 | 14 | 20 | 13 | 18 | .659b |
| 10 min | 15 | 6 | 16 | 20 | 8 | 17 | .284a |
| 15 min | 16 | 7 | 17 | 22 | 10 | 19 | .234b |
| 20 min | 18 | 5 | 17 | 27 | 18 | 23 | .277b |
| Temperature (°C) | |||||||
| Baseline | 38.5 | 0.4 | 38.6 | 38.3 | 0.6 | 38.2 | .509a |
| Preinduction | 38.1 | 0.4 | 38.0 | 37.9 | 0.4 | 37.8 | .312a |
| 0 min | 37.8 | 0.3 | 37.8 | 37.7 | 0.6 | 37.8 | .652a |
| 10 min | 36.9 | 1.0 | 36.9 | 37.0 | 0.8 | 37.1 | .909a |
| 15 min | 36.9 | 0.9 | 36.9 | 36.7 | 0.9 | 36.4 | .749a |
| 20 min | 36.7 | 0.8 | 36.8 | 36.5 | 1.0 | 36.4 | .709a |
Summary data for blood pressure, pulse oximetry (SpO2), and end-tidal CO2 (EtCO2) by airway device at 4 time points.
| v-gel (n = 6) | ETT (n = 7) | ||||||
|---|---|---|---|---|---|---|---|
| Variables | Mean | SD | Median | Mean | SD | Median | P value |
| Systolic blood pressure (mm Hg) | |||||||
| 0 min | 102 | 17 | 94 | 102 | 22 | 96 | .944a |
| 10 min | 92 | 10 | 96 | 115 | 35 | 112 | .156b |
| 15 min | 101 | 12 | 99 | 127 | 52 | 96 | .265b |
| 20 min | 101 | 27 | 88 | 111 | 33 | 94 | .468a |
| Diastolic blood pressure (mm Hg) | |||||||
| 0 min | 50 | 11 | 52 | 48 | 11 | 44 | .766b |
| 10 min | 52 | 7 | 51 | 59 | 23 | 46 | .860a |
| 15 min | 55 | 11 | 53 | 76 | 40 | 53 | .243b |
| 20 min | 56 | 20 | 46 | 61 | 25 | 49 | .554a |
| SpO2 (%) | |||||||
| 0 min | 96 | 1 | 97 | 95 | 2 | 94 | .143a |
| 10 min | 96 | 1 | 96 | 96 | 2 | 96 | .846a |
| 15 min | 96 | 1 | 96 | 95 | 1 | 96 | .498a |
| 20 min | 96 | 1 | 96 | 96 | 1 | 96 | .783b |
| EtCO2 (mm Hg) | |||||||
| 0 min | 37 | 11 | 39 | 33 | 8 | 32 | .279a |
| 10 min | 39 | 8 | 42 | 37 | 10 | 43 | .764a |
| 15 min | 41 | 7 | 42 | 36 | 10 | 38 | .355b |
| 20 min | 42 | 8 | 45 | 39 | 10 | 43 | .349a |
Results of airway device leakage at 4 time points at escalating pressures.
| v-gel (total n = 6; n leaks) | ETT (total n = 7; n leaks) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Pressure | 0 min | 10 min | 15 min | 20 min | 0 min | 10 min | 15 min | 20 min | Exact 90% lower CL of RR |
| 12 cm H2O | 5 | 5 | 5 | 5 | 0 | 0 | 0 | 0 | 2.60a,b |
| 16 cm H2O | 6 | 6 | 6 | 6 | 0 | 0 | 0 | 0 | 2.87a,c |
| 18 cm H2O | NP | NP | NP | NP | 0 | 0 | 0 | 0 | NP |
| 20 cm H2O | NP | NP | NP | NP | 1 | 0 | 0 | 0 | NP |
Exact lower CL of the RR for v-gel compared to ETT leaking; both the RR and the exact upper CL are not estimable based on the data. The v-gel not leaking compared to ETT not leaking at 12 cm H2O RR score statistic (exact 90% CI) is 0.17 (0.01 to 0.58).
Fisher exact test, 2-sided P = .005.
Fisher exact test, 2-sided P = .001.
Comparison of airway device insertion characteristics.
| Insertion characteristic | v-gel (n = 6; n [%]) | ETT (n = 7; n [%]) | RR (exact 90% CI) |
|---|---|---|---|
| Attempts to insert | |||
| 1 attempt | 3 (50%) | 6 (86%) | 0.58 (0.17–1.18)a,b |
| 2 attempts | 3 (50%) | 1 (14%) | 3.50 (0.62–46.02)a,b |
| Additional propofol doses | |||
| 0 boluses | 4 (67%) | 6 (86%) | 0.78 (0.33–1.43)a,c |
| 1 bolus | 2 (33%) | 1 (14%) | 2.33 (0.36–31.24)a,c |
| Difficulty of insertion | |||
| Easy | 4 (67%) | 6 (86%) | 0.78 (0.33–1.43)a,c,d |
| Moderately difficult | 2 (33%) | 0 (0%) | 2.33 (0.36–31.24)a,c,d |
| Difficult | 0 (0%) | 1 (14%) | |
Comparison of manipulations by airway device.
| Manipulation characteristic | v-gel (n = 6; n [%]) | ETT (n = 7; n [%]) | RR (exact 90% CI) |
|---|---|---|---|
| No manipulation | 2 (33%) | 7 (100%) | 0.33 (0.06–0.74)a |
| Minor (adjusting head/neck position or change depth of insertion) | 2 (33%) | 0 (0%) | |
| Major (reinserting device) | 2b (33%) | 0 (0%) |
Relative risk score statistic for v-gel requiring no manipulations compared to ETT after merging “minor” and “major,” with exact 90% CI. Mantel-Haenszel χ2 test (before merging) and Fisher exact test (after merging) retrieved the same, 2-sided, P = .021.
One patient had size D6 replaced with size D5; 1 patient had size D6 reinserted.
Results
Within the v-gel group, 5 female and 1 male patients with a mean body weight of 13.5 kg (SD, ± 5.0 kg; median, 13.9 kg) and a mean age of 10.6 months (SD, ± 11.4 months; median, 5.0 months) were enrolled via block randomization. All patients but 1, a female, were intact. Breeds in the v-gel group included Beagle (n = 2), hound mix (n = 2), terrier mix (n = 1), and mixed breed (n = 1). The procedures performed were mass removal (n = 1), orchiectomy (n = 1), and ovariohysterectomy (n = 4). The v-gel sizes were selected based on the manufacturer’s recommendation for mesocephalic dog breeds. The following v-gel sizes were used: D3 (n = 1), D5 (n = 3), and D6 (n = 2). Within the ETT group, 4 female and 3 male patients with a mean body weight of 10.5 kg (SD, ± 5.3 kg; median, 11.6 kg) and a mean age of 7.1 months (SD, ± 3.1 months; median, 5.0 months) were enrolled via block randomization. All 7 of the ETT patients were intact. Breeds within the ETT group included Beagle (n = 2), hound mix (n = 2), and mixed breed (n = 3). The procedures performed were orchiectomy (n = 3) and ovariohysterectomy (n = 4). Endotracheal tube sizes (internal diameter, mm) used included 5 (n = 1), 5.5 (n = 2), 8 (n = 1), 8.5 (n = 1), 9.0 (n = 1), and 9.5 (n = 1).
All surgical procedures were completed in both airway device groups, with no adverse events identified perioperatively. Variables between the v-gel and ETT groups were assessed for differences between groups. There were no statistically significant differences between the groups for the categorical variables sex (Fisher exact, P = .559), castration status (Fisher exact, P = .462), breed (Mantel-Haenszel χ2, P = .810), procedure performed (Mantel-Haenszel χ2, P = .846), or anesthesia machine pressure check (ie, pressure increasing or equalizing; Fisher exact, P = .266). There were also no significant differences between groups for the continuous variables age (exact Wilcoxon 2-sample, P = .917) and weight (independent two-sample t test, pooled, P = .318).
The propofol dose for the v-gel group (mean, 3.8 mg/kg; SD, ± 1.4 mg/kg; median, 3.6 mg/kg) was not significantly different from the ETT group (mean, 3.1 mg/kg; SD, ± 1.1 mg/kg; median, 3.5 mg/kg; independent two-sample t test, pooled, P = .334). The time from the induction propofol dose to airway device placement was also not significantly different between groups (v-gel mean, 9.5 seconds; SD, ± 3.6 seconds; median, 9.2 seconds vs ETT mean, 11.2 seconds; SD, ± 4.4 seconds; median, 11.4 seconds; independent two-sample t test, pooled, P = .476). The comparison of vital parameters at each time point showed no significant differences in heart rate, respiratory rate, temperature (all P > .05; Table 1), systolic or diastolic blood pressure, pulse oximetry, or end-tidal CO2 between airway device groups at any time point (all P > .05; Table 2).
Airway device leak pressures at 4 time points were compared, and it was found that the v-gel group leaked at lower pressures than the ETT group (Table 3). The risk of leaking for the v-gel group was significantly higher (2.60 times higher, exact 90% lower confidence limit of the RR) than that of the ETT group at 12 cm H2O and significantly higher (2.87 times higher, exact 90% lower confidence limit of the RR) than that of the ETT group at 16 cm H2O. Higher pressures were not tested in the v-gel group due to waste anesthetic gas safety restrictions in the VCA Clinical Studies Institutional Review Board protocol. There were no significant differences in attempts to insert, number of propofol boluses, or difficulty of airway device insertion between airway device groups (all P > .05; Table 4). A comparison of airway manipulations to obtain and maintain an effective airway indicates that the risk for not requiring manipulations for the v-gel group was 67% less (RR, 0.33; exact 90% CI, 0.06 to 0.74) than that of the ETT group (P = .021; Table 5). The postoperative survey revealed that all patients from both airway device groups had no postoperative complications (ie, no coughing, no hoarse bark, no retching/gagging/vomiting, and no difficulty eating) and no discomfort (ie, all scores of 1 = no discomfort).
Discussion
No previous studies have compared the safety and efficacy, leak pressure, or insertion time of the canine-specific v-gel Advanced Dog and the traditional ETT. In this prospective randomized study, patients’ vital parameters were not significantly different between groups, and neither the v-gel nor ETT group had any perioperative or postoperative adverse events. This provides assurance that both airway device groups were similar in patient safety and in variables that may have otherwise affected outcomes. However, the risk of leaking for the v-gel group was much higher than that of the ETT group at 12 cm H2O (P = .005) and 16 cm H2O (P = .001), with higher pressures not tested in the v-gel group due to waste anesthetic gas safety concerns. The v-gel Advanced Dog SGAD insertion time did not significantly differ from that of the ETT.
Guidelines recommend maintaining a peak inspiratory pressure between 10 and 20 cm H2O to ensure effective ventilation and prevent leaks in the system for small animals undergoing intermittent positive pressure ventilation.10,14,15 Our findings indicate that while performing adequately in spontaneously breathing patients, the v-gel device is likely unsuitable for positive pressure ventilation due to significant anesthetic gas leakage. Although leakage during intermittent positive pressure ventilation was not quantified in our study, the low pressure threshold required to prevent leaks of the device during spontaneous ventilation likely results in anesthetic gas exposure exceeding the 2 ppm safe limits set by environmental and workplace safety standards.16
The insertion time of the v-gel versus ETT in this study was not significantly different between groups. This result differed from other studies2–5 finding that placement of the feline-specific v-gel and the rabbit-specific v-gel is significantly faster than ETT placement. Our study and others found no significant difference in the placement time between the v-gel and ETT.17 The comparable intubation times with v-gel and ETT in dogs may be due to the canine anatomy, which allows for uncomplicated airway management. This contrasts with the more challenging airway management seen in cats and rabbits, where factors like smaller size, sensitive airways, and a higher propensity for laryngospasm complicate intubation. In summary, our study suggests that using the v-gel in dogs results in similar intubation times as using an ETT, a finding that contrasts with most outcomes observed in cats and rabbits.
The v-gel had a much lower risk of not requiring airway manipulations (RR, 0.33; exact 90% CI, 0.06 to 0.74) compared to the ETT group. This finding is consistent with other reports2,3,18 in cats and rabbits. Although the specific cause is unclear, it is likely that repositioning patients from sternal to dorsal recumbency after v-gel placement contributes to its displacement. This shift may be attributed to gravitational forces or the v-gel’s insufficient bulk to fully occupy the oropharynx, resulting in a less secure fit. While the deviations observed were minor, typically involving slight v-gel rotation relative to the oral cavity plane, the altered positioning was significant enough to prompt investigator intervention for adjustment.
This study has several limitations, including a small sample size, the fact that a single anesthetist performed all intubations, that it was conducted at a single center, and that optional components of the v-gel Advanced Dog were not used. Based on a power analysis, we aimed to enroll 30 canines randomly assigned to 1 of 2 groups, v-gel or ETT. However, the 6 patients in the v-gel group failed leak pressure tests below 20 cm H2O and did not meet the VCA Clinical Studies Institutional Review Board’s standard of care due to patient and personnel health hazards and led to the early termination of this study. The involvement of only 1 anesthetist is another significant limitation. Although this anesthetist had extensive experience with ETT intubation, having performed hundreds of procedures, they had only intubated approximately 15 cases using the v-gel previously. This disparity in experience may have contributed to the lower risk of requiring airway manipulations to maintain an effective airway observed with the ETT. The results may differ in a larger, multicenter study involving more patients and anesthetists. Optional components of the v-gel Advanced Dog, the gastric channel and a support device for the anesthetic circuit (eg, D-grip tube holder; DocsInnovent Ltd), were not utilized in this study. Studies could be conducted with these components to see if the leak pressure passes tests up to and equivalent to 20 cm H2O.
In conclusion, while v-gels offer a promising alternative to traditional endotracheal intubation, this study suggests that their use in canines is limited due to significant challenges associated with airway seals under low inspiratory pressures. This study highlights the need for further product development and innovation to overcome these barriers. In the meantime, v-gels may be better suited for rabbits and felines, where they have demonstrated favorable outcomes. Future research should focus on refining SGAD designs and improving seal efficacy. These advancements may facilitate wider adoption of SGADs in veterinary medicine, ultimately improving patient outcomes and protecting both veterinary professionals and the environment.
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org.
Acknowledgments
None reported.
Disclosures
The authors have nothing to disclose. No AI-assisted technologies were used in the composition of this manuscript.
Funding
Funding was provided by VCA Advanced Veterinary Care Center, Fishers, IN.
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