The laryngeal mask airway (LMA) is one of the most important airway devices, which was developed after the endotracheal tube. Introduced into clinical practice in 1983, use of the LMA rapidly became widespread because of its advantages in providing an airway [1,2]. The LMA Classic (LMA North America, Inc., San Diego, California, USA), the first designed LMA model, was developed progressively, and new LMA models such as the LMA ProSeal (LMA North America, Inc.) and LMA Flexible (LMA North America, Inc.) have been produced. Owing to technological advances over time, the areas of usage and safety of the LMA have increased. The LMA Supreme is a new extraglottic airway device, which brings together features of both the LMA ProSeal and LMA Fastrach (LMA North America, Inc.). The LMA ProSeal can be used for controlled ventilation and for longer operations. The LMA Fastrach has a fixed curved handle to facilitate insertion and fixation .
In accordance with the above listed features, in our study, we aimed to compare the LMA Classic with the LMA Supreme for insertion features (the success of inserting the LMA, the time for insertion and the number of attempts), assessing leak pressure, haemodynamic parameters and adverse effects.
After approval by the institutional human studies committee and obtaining patient consent, 70 patients with ASA physical status I or II (aged 18–70 years, weight 50–90 kg) undergoing herniorrhaphy and varicose vein surgery were included in the study. Patients with respiratory tract disease, known airway problems or any condition that increases the risk of gastro-oesophageal regurgitation were excluded. The patients were randomly assigned to a LMA Supreme group or a LMA Classic group for airway management using the sealed envelope method.
The insertion of LMAs was conducted by the same anaesthesia resident with experience of both devices (LMA Classic ≥1000 procedures, LMA Supreme ≥50 procedures).
Demographic parameters (sex, age, height and weight), determination criteria of difficult airway (Mallampati, mouth opening, neck circumference, sternomental distance and thyromental distance) and the duration of operation were recorded. Patients were monitored for heart rate (HR) by three-channel ECG, noninvasive blood pressure, peripheral oxygen saturation (SpO2), end-tidal CO2 (ETCO2) (Datex-Ohmeda S/5 Compact Critical Care Monitor; GE Healthcare, Helsinki, Finland), bispectral index (BIS) (A-2000 BIS monitoring system; Aspect Medical Systems, BIS XP, Framingham, Massachusetts, USA) and neuromuscular transmission (T1) (TOF-Watch SX Organon Instruments, Boxlet, Netherlands). For anaesthesia induction, 1 μg kg−1 fentanyl and 0.6 mg kg−1 rocuronium bromide were administered, and 1% propofol was used until the BIS value was below 60. In order to provide consistent conditions for inserting the laryngeal mask, insertion was made when the BIS was between 50 and 60 and T1 was 0. A size 4 LMA was used for women and a size 5 for men. LMA Classics were inserted in the LMA Classic group, whereas LMA Supremes were inserted in the LMA Supreme group, and the cuffs were inflated until the air leak sound coming from the mouth ceased (≤45 cm3 air). Cuff pressure was measured (cuff pressure gauge; VBM Medizintechnik GmbH, Sulz a.N., Germany) and recorded at the beginning and at 20 min into the operation. Fresh gas flow was adjusted to 3 l min−1 without nitrous oxide during each measurement. In order to insert the laryngeal mask, a maximum of two attempts were made for each group. In case of failure, another LMA model was tried. When insertion of both LMA models failed, orotracheal intubation was performed in these patients. The success rate of inserting the LMA, the duration of insertion, the number of attempts and the insertion complications were recorded for each group.
HR, mean arterial pressure (MAP) and Spo2 were recorded for each patient before and after LMA insertion, during the operation (15, 30 and 45 min) and before and after extubation. Fresh gas flow was adjusted to 6 l min−1 (O2/N2O 50%/50%) during the operation. Sevoflurane was used as an inhalation agent for anaesthesia maintenance. Tidal volume was adjusted to 8 ml kg−1 and frequency to 12 breaths min−1 by volume-controlled mechanical ventilation (Datex-Ohmeda S/5 Avance; GE Healthcare). During the operation, the percentage of the tidal volume leakage, Ppeak, Pmean, ETCO2 and leakage pressure values of all patients were measured three times and mean values were recorded. In order to calculate the leakage percentage, the expiratory tidal volume was deducted from the inspiratory tidal volume, and the result was divided by the inspiratory tidal volume. The leakage pressure was determined, as in the studies of Keller et al.  and Shimbori et al. , by closing the expiratory valve of the circle system at a fixed gas flow of 3 l min−1, noting the airway pressure at which equilibrium was reached. Nitrous oxide was not used during testing. While performing manual positive pressure ventilation, the maximum Ppeak pressure causing air leakage from the mouth (audible) was accepted as the leakage pressure. Patients were paralysed during the measurements, and ventilation was assisted manually between each measurement. For adverse effects such as haemorrhage, hoarseness, aphasia, nausea, vomiting and agitation after extubation, the patients were monitored for at least 1 h in the recovery room. When modified Aldrete scores were 10 and above, patients were transferred to the ward.
Sample size was calculated after a pilot study of 10 patients and was based on a difference of 20% between the groups for insertion time for a type 1 error of 0.05 and a power of 0.8.
Results are expressed as mean ± SD. All statistical analyses were carried out using SPSS for Windows version 15.0 (SPSS Inc., Chicago, Illinois, USA). The t-test was used for comparison of quantitative variants. Qualitative variants were compared using the chi-squared test. A P value of less than 0.05 was considered statistically significant.
In terms of demographic data, there was no difference between the groups (Table 1). The duration of operation was 38.6 ± 6.6 and 39.3 ± 5.2 min for the LMA Supreme group and the LMA Classic group, respectively (P = 0.645).
Difficult airway determination criteria parameters
The Mallampati scores and neck circumferences, sternomental distance, thyromental distance and mouth opening values of the patients were measured before operation and were similar in both groups (Table 2). The patients in the LMA Classic group and the LMA Supreme group were considered as having similar airway characteristics.
The parameters of laryngeal mask insertion
In the LMA Classic group, the LMA was successfully inserted in 27 patients (77%) at the first attempt and in 31 patients (88.5%) at the second attempt. In the LMA Supreme group, the LMA was successfully inserted in 31 patients (88.5%) at the first attempt and in 34 patients (97%) at the second attempt. Three out of four patients in whom the LMA Classic could not be inserted had the LMA Supreme applied. There was one patient in whom neither the LMA Supreme nor the LMA Classic could be inserted. The two patients in whom the laryngeal mask could not be inserted and intubated had Mallampati scores of III. The duration for laryngeal mask insertion for the LMA Supreme group was shorter and the cuff pressures were lower, and a significant difference was determined between the groups (P < 0.001) (Table 3). There was no complication during insertion in either of the groups.
There was not any difference between the two groups in Ppeak, Pmean and ETCO2 values measured by the ventilator. In the LMA Supreme group, the tidal volume leakage percentage was found to be significantly lower, whereas the leakage pressure was significantly higher than in the LMA Classic group (P < 0.001) (Table 4).
There was no difference between the groups in terms of haemodynamic parameters. All the recorded values of MAP and HR were found to be statistically similar (Tables 5 and 6).
Postoperative adverse effects
After their operations, three patients complained of nausea and vomiting, four patients were agitated and one patient had a sore throat in the LMA Supreme group, whereas eight patients complained of nausea and vomiting, eight patients were agitated and two patients had a sore throat in the LMA Classic group (Table 7).
Although ease of insertion and haemodynamic and ventilation parameters were similar in both groups, the duration of laryngeal mask insertion for the LMA Supreme group was shorter and the cuff pressure was lower; the oropharyngeal leakage pressure was higher, and a significant difference was determined between the groups.
In our study, the LMA was successfully inserted in 77% of patients at the first attempt in the LMA Classic group and in 88.5% of patients at the first attempt in the LMA Supreme group. Laryngeal mask insertion could be performed for endotracheal intubation by inexperienced anaesthetists with a high success rate . In a study by McCrirrick et al. , 27 anaesthetists who had no experience of LMA insertion before were successful (94%) in LMA Classic insertion. Timmermann et al.  in their study, in which they performed a collaborative study with anaesthesia residents who had completed their first year of training, obtained a 90% success rate at the first attempt and a 100% success rate at the second attempt for inserting the LMA Supreme. Eschertzhuber et al.  inserted the LMA ProSeal and LMA Supreme with success rates of 92 and 95%, respectively, at the first attempt. Our success rate with the LMA Supreme was 88.5%, which is similar to the results in these studies. Studies have shown that the success rate and duration of LMA Classic insertion are more advantageous than with the LMA ProSeal . The duration of laryngeal mask insertion for the LMA Supreme group was shorter, and a significant difference was determined between the groups in our study.
Brimacombe et al.  had a success rate of 82% for LMA ProSeal insertion and a success rate of 91% for LMA Classic insertion at the first attempt in their multicentre study of 384 cases. They determined a significant difference between the groups. Also in the same study, the LMA Classic was inserted in approximately 31 ± 30 s, whereas the duration of insertion for the LMA ProSeal was found to be 41 ± 49 s. As the operations in which we performed our study were inguinal hernia and varicose vein operations with short duration and not requiring gastric aspiration, use of the LMA ProSeal, which allows insertion of a gastric tube, was considered unnecessary. Moreover, in the literature [10,11], it is stated that the LMA Classic is superior to the LMA ProSeal in success and duration of insertion; therefore, we used the LMA Classic in our study. There is limited evidence in the literature for comparing the LMA Classic with the LMA Supreme from the perspective of insertion parameters. Even experienced anaesthetists have difficulties in providing an airway in patients who have difficult airway criteria. According to our study results, the LMA Supreme has advantages and is easier to use in providing an airway when compared with the LMA Classic with regard to the parameters for insertion. The LMA Supreme has additional advantages compared with the LMA Classic. In the literature, it was recommended that the LMA cuff should be inflated with a minimum volume to prevent oropharyngeal air leakage . Studies and animal experiments have shown that, when the pressure of the laryngeal mask and usage duration are increased, the pressure to the pharynx mucosa and the risk of probable damage are increased [12–16]. Similar to our study, in a study by Timmermann et al. , oropharyngeal air leakage was found to be 29.1 ± 4.8 cmH2O, with a cuff pressure of 60 cmH2O with the LMA Supreme. Various LMA models designed over the years were compared with each other regarding cuff pressures and the pressure of oropharyngeal air leakage. According to our study results, the LMA Supreme is considered to be a safer airway device than the LMA Classic for providing ventilation up to higher peak pressures with lower cuff pressures and without air leakage. Ppeak and ETCO2 values measured with a mechanic ventilator during operation were found to be similar to the values found in patients in studies using either the LMA Classic or an endotracheal tube [17,18]. In our study, the LMA Supreme was found to be as well tolerated as the LMA Classic regarding the ventilation parameters. Although not having much experience using it, this LMA model has ventilation parameters similar to other known LMA models, and it obviously does not cause CO2 accumulation. There have been many studies that have shown that laryngeal masks cause less haemodynamic change during insertion and reduce the requirement for intraoperative anaesthetic agents when compared with an intubation tube [19–22]. Cork et al.  compared the LMA Classic with an endotracheal tube for haemodynamic response during intubation and extubation and found that the LMA Classic was better than the endotracheal tube. As the LMA Supreme appears to have a more rigid structure than other LMA models, an increased haemodynamic response and frequent adverse effects such as oral haemorrhage and sore throat could be expected during insertion. But, our study has shown that there was no difference between the LMA Supreme and the LMA Classic with respect to adverse effects.
The LMA Supreme is superior to the LMA Classic because of its ease of insertion, low cuff pressure and high oropharyngeal leakage pressure.
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