In our study, we found a high first attempt success rate (93%) of LMA Protector™ insertion in thirty moderately obese patients which was comparable to previous studies using LMA Protector™ in non-obese patients [6, 7]. Use of second-generation SADs with a gastric channel and design that allow fibreoptic guided tracheal intubation is crucial in obese patients as it provides efficient airway protection from gastric aspiration, as well as a conduit for intubation in case of an unexpected difficult airway [8, 9].
The average BMI in our study was 32. All female patients received the size 3 LMA Protector, and males the size 4. Their ideal mean (SD) body weights of males 66.9 (4.4) kg and females 46.5 (7.3) kg suggested a nice fit according to manufacturer recommendations that we followed e.g., size 3 for less than 50 kg and size 4 for patients weighing in between 50 to 70 kg.2. Previous studies using Proseal LMA™ that had utilised the size 4 for females and size 5 for males, found that despite yielding higher oropharyngeal leak pressures, the larger mask tended to rise up within the mouth more often, predisposing these patients to increased risk of sore throat and lingual nerve damage .
The insertion of the LMA Protector™ was graded easy/fair for 97% of our patients. The LMA Protector™ was inserted expediently in a mean time of 21.0 (4.0) seconds which is comparable to studies using LMA Supreme™ and Ambu® AuraGain™ . The comparable device insertion times shows that there is no increased difficulty in insertion in obese patients compared to non-obese patients despite its bulkier profile with the 2 gastric ports. This is reassuring, as the LMA Protector™ is a new airway device and investigators had only 10 insertions before commencing the study; it is possible that increased usage and experience with the LMA Protector™ could further improve the success rate and insertion timings [4, 6, 12].
We had one failed insertion where despite an easy insertion, we could not obtain a capnograph tracing after 3 attempts. For the first and second insertion attempt, the investigator (CSH) had used the index finger to guide insertion of the LMA Protector™ which was totally deflated and generously lubricated according to manufacturer’s recommendations. The entry of the device was smooth but there was absence of end tidal carbon dioxide trace and chest rise upon commencing ventilation. Prior to the third insertion attempt, the patient’s head and neck was repositioned, laryngospasm was ruled out, and adequate depth of anaesthesia was confirmed, but again failed to yield an end tidal carbon dioxide trace. Insertion failure was declared, and the airway was successfully rescued with an Ambu® AuraGain™. Being made from medical grade silicone that renders the LMA Protector™ softer and more pliable in nature compared to the polyvinyl chloride (PVC) tip of the Ambu AuraGain, we postulated that the tip of the LMA Protector™ had folded over in the posterior pharynx during insertion. In hindsight, a diagonal shift of the mask during insertion may have been helpful to avoid this downfolding .
We found a high OLP of 31.8 (5.4) cmH20 in this study, which is higher than that reported in non-obese patients. Moser et al. reported an OLP of 28.3 (7.0) cmH20 while Sng et al. reported an OLP of 25.5 cmH20 (IQR 23.0 to 29.0 cmH20) [6, 7]. This high OLP is similar to the OLP of LMA Proseal which was reported to be 27 (7.0) cmH20 but higher than that of Ambu AuraGain 24.1 (7.4) cmH20 [11, 13]. The high OLP can be attributed to the fact that the LMA Protector™ is made of medical grade silicone, with an anatomically shaped airway tube and inflatable cuff that purportedly conforms to the contours of an individual’s hypopharynx. In obese patients, the increased adiposity and hypopharyngeal tissue may render it a snugger fit. Obese patients have poor chest compliance due to their thick chest wall, and often require higher peak inspiratory pressures when positive pressure ventilation is instituted . This high OLP of the LMA Protector™ therefore makes it a suitable SGA to be used in obese patients as it is beneficial to mitigate any air leak that may predispose patients to inadequate ventilation, gastric insufflation, and increased risk of aspiration. The insertion of gastric drain tube into the oesophagus was rated easy in 79% and with the tip of the gastric channel aligned with the oesophagus, there was effective venting of gastric content.
On assessment of the anatomical position of the LMA Protector™, we found a clear view of the vocal cords in 93% of the patients. This could be attributed to the anatomically curved tube of the LMA Protector™ enabling insertion to the optimal position. A good anatomical position, in conjunction with high sealing pressures enables obese patients to be ventilated more safely even with higher peak pressures. A good anatomical position also makes it an effective conduit for endotracheal tube insertion in these obese patients, either as a rescue procedure after difficult or failed initial laryngoscopy, or in those individuals who require a conversion from a SAD to tracheal tube for their surgeries or further postoperative ventilation in the ICU.
In two patients, we did not have an entirely clear view of the vocal cords. The vocal cords were partially seen with the posterior epiglottis in one patient, and partial VC with anterior epiglottis sighted in the other patient. No problems with ventilation were encountered and during maintenance of anaesthesia over a mean surgical duration of 71 min, the LMA Protector™ performed well without the need for airway manipulation to optimize ventilation.
Van Zundert et al. similarly found a high OLP with the LMA protector of 31.7 (2.9) cm H2O as we did. Uniquely, their device insertions were performed under vision of a video laryngoscope using an ‘insert-detect-correct-as-you-go’ technique with standardized corrective measures, and they achieved a near-optimal fibreoptic position in the LMA-Protector of 94%, similar to our results . This is reassuring as our study showed that simple manual insertion of the LMA Protector in obese patients, without “vision” adjuncts, worked just as well.
We had assessed immediate and delayed post-operative complications associated with the LMA Protector™ in our study. The only complication encountered during the immediate phase was mucosal injury, seen in 14 patients (48%). The incidence was high compared to figures from non-obese patients . The airway of an obese patient is shown on MRI to have deposition of excess adipose tissue into nearly all pharyngeal structures including the uvula, the tonsils, the tonsillar pillars, the tongue, aryepiglottic folds, and most predominantly, the lateral pharyngeal walls. This leads to airway narrowing, which can be exaggerated by external compression from superficial depositions of fat in the neck . Therefore, at insertion of LMA, the pharyngeal structures could be easily abraded especially if there is concomitant tissue congestion. Another possible reason for the increased incidence of mucosal injury could be the larger tip of the LMA Protector that may collide with the arytenoids upon its insertion. Additionally, the bulky posterior curvature of LMA Protector and its slightly larger cuff may contribute to a more challenging insertion in the Asian population with their smaller builts and mouth opening in this study. Ensuring a well lubricated LMA Protector and a completely deflated cuff before insertion is paramount.
The LMA Protector™ pilot balloon has an Integrated Cuff Pilot™ which is used for intraoperative cuff pressure monitoring. The provision of continuous intra-cuff pressure monitoring is ideal as intracuff pressure could change, at a given volume, because of temperature changes, muscular tone or administration of nitrous oxide . The use of the Integrated Cuff Pilot™ can prevent nerve or pressure injuries of the airway especially with prolonged usage. We followed up our patients via phone call after discharge from hospital and found a 27% incidence of postoperative sore throat, which was comparable to a study using Proseal LMA™ in obese patients . It was self-limiting and only lasted for a few hours postoperatively. We found a lower incidence of dysphagia (10%) and dysphonia (20%) compared to Rieger et al.  This can perhaps be attributed to the continuous cuff pressure monitoring with the integrated cuff pressure indicator, which is targeted between 40 and 60 mmHg. In addition, the cuff is made of medical grade silicone, which increases its flexibility and hence potentially more pliable and less traumatic to insert into the pharynx . We also did not find any hypoglossal nerve injury with the use of LMA Protector™ as reported by Tham et al. 
Most patients did not have a significant increase in heart rate and mean arterial pressure when compared to baseline, except two patients (7%). This is consistent with a previous study reporting stable haemodynamics as LMA insertion is easy and less stimulating to the patients .
Our study had a few limitations. Firstly, we evaluated the LMA Protector™ in obese patients with BMI of 30–35, and the results cannot be extrapolated to patients beyond BMI > 35. Secondly, our study sample size was a relatively small cohort number, albeit powered adequately. Thirdly, surgical duration in our study lasted a mean of 71 min, with the longest duration 180 min. Any incidence of dysphonia beyond that is still unknown. But our results are reassuring in support of the LMA Protector’s use in the obese.