Recent studies show that the I-gel provides a good seal during anesthesia for spontaneously breathing and for controlled ventilation [1,4,9]. However, there are no studies performed which have compared its performance with PLA for laparoscopic surgery.

Enrolled patients were randomly allocated into PLMA or I-gel groups using computer-generated numbers. In the operating room before surgery, the usual monitoring occurred, which included a Bispectral Index (BIS; Aspect Medical Systems, Newton, MA, USA) sensor. The following baseline data were recorded: heart rate, noninvasive blood pressure, oxyhemoglobin saturation, and BIS.

Prior to induction, all patients assumed a neutral position, and IV access was secured. After preoxygenation of the lungs with 6 L/min, using Orchestra® Base Primea (Fresenius Kabi, Brezins, France) as the infusion equipment, total intravenous anesthesia was performed.

Once patients' full muscle relaxation was achieved using rocuronium 0.6 mg/kg intravenously, the selected airway device (PLMA or I-gel) was inserted by a single user (S.C) per the manufacturer's instructions based on patient size. Size selection of the I-gel depended on patient weight (weight < 50 kg: I-gel size 3; 50-90 kg: size 4; and > 70 kg: size 5). Size selection of the PLMA is identical to classic LMA (weight 30-50 kg: size 3; 50-70 kg: size 4; 70-100 kg: size 5). Insertion of PLMA was performed without an introducer; the index finger of operator was placed in the retaining strap.

The PLMA was pressed against the hard palate and advanced into the hypopharynx until resistance was felt. After PLMA placement, the cuff was inflated. A defined volume of air was used; the cuff pressure was set to 60 cmH₂O. (Maximum cuff inflation volume; size 3: 20 ml; size 4: 30 ml; size 5: 40 ml) After insertion of the breathing apparatus and subsequent connection to the ventilation system, correct positioning of it was confirmed by visualizing verification of insertion with visualization of three expiratory carbon dioxide square waveforms and movements of chest wall during mechanical ventilation and a leak pressure greater than 20 cmH₂O. During surgery rocuronium was used to achieve neuromuscular block, which was verified with a peripheral nerve stimulator. At the end of the surgery, pyridostigmine 0.2 mg/kg and glycopyrrolate 0.008 mg/kg was used to reverse the effects of rocuronium. In all experimental cases, the time required for insertion and the number of attempts was obtained. The insertion time of the device was defined as the time between grabbing the device until visualization of 3 expiratory CO₂ waveforms. If the first attempt at insertion was deemed a failure according to the anesthesiologist's judgment, the next try was made via either a jaw thrust maneuver or a change in head position. When and if a third attempt was necessary, a different device size was utilized. Upon failure of third line approaches, additional devices were utilized based on the attending anesthesiologist's preference.

Oropharyngeal leak pressure was determined by closing the expiratory valve of the circle system at a fixed gas flow of 3 L/min and noting the airway pressure (maximum allowed was 40 cm H₂O) at which equilibrium was reached [10].

In both groups, 10 min after insertion (T1) and 15 min after carbon dioxide pneumoperitoneum (T2), measurement of vital signs and changes to airway pressure were observed and recorded. In both groups, a carbon dioxide pneumoperitoneum was induced with a maximal intraabdominal pressure of 15 mmHg. The P_peak, leak pressure, mean airway pressure, compliance and airway resistance were measured by spirometry via an Avance station (Datex-Ohmeda, WI, USA) during measurement time.

We labeled the gap between the inspired versus the expired tidal volume as 'leak volume' and measured it at T1 and T2. The leak fraction was calculated as the leak volume divided by inspired tidal volume at T1 and T2.

We performed a pilot study with 10 patients from the PLMA group to assess the size of our study. The mean value of leak pressure was 26.7 cmH₂O, standard deviations were 4.9 cmH₂0. For our power calculation, we assumed equal standard deviation for both groups. To sense a difference of 5.4 cmH₂0 between the 2 groups with a two-tailed α = 0.05 and a power of 80%, a minimum of 13 per group were needed. A Z-test was performed to prove the lack of difference between the 2 groups. Therefore, we decided to recruit 30 patients to allow for a drop rate of 10%.

Successful insertion and mechanical ventilation of both devices was achieved on the first attempt in all 30 patients, and the time to insertion was similar (26.4 ± 1.4 and 26.4 ± 0.8 for PLMA and I-gel, respectively).

The cuff of the I-gel was made to produce a sealing device that does not need inflation to fit the perilaryngeal anatomy [1]. In a study comparing an LMA and the I-gel, airway leak pressures were similar between the devices [2]. Another study comparing the I-gel with the LMA-Unique showed that leak pressure was significantly higher in the I-gel group and this higher airway leak pressure indicated better seal and I-gel was alternative to the LMA-Unique for mechanical ventilation [4]. Using a cadaver model, Schmidbauer et al. [11] demonstrated that both the PLMA and cLMA made a tighter seal than the I-gel. The PLMA is designed to improve controlled ventilation, airway protection and diagnosis of displacement. Cook et al. [12] concluded that PLMA offered significant benefits over classic LMA and tracheal tube in some circumstances including laparoscopic gynecologic surgery. In the present study, we showed that leak airway pressures 10 min after insertion were similar between PLMA and the I-gel (25.9 ± 5.2 and 24.3 ± 3.4 cmH₂O, respectively). Further, leak pressure did not vary significantly between or within groups 15 min after CO₂ insufflation (28.3 ± 5.9 vs 28.5 ± 5.4, respectively). In addition, leak volumes and leak fractions of these devices before and after CO₂ insufflation were not statistically significantly different. The similarities in airway leak pressures, leak volumes and leak fractions demonstrated that both devices sealed equivalently and protected airway effectively.

Successful insertion and ventilation of both devices were achieved on the first attempt in all patients. Median time to insertion using the PLMA and I-gel was 26.0 sec and 27.0 sec, respectively, this data is similar to other data [2,11]. In addition, the insertion times for the 2 devices were not statistically significantly different. Initially, we thought that that insertion of I-gel would be easier than PLMA due to the absence of a cuff and no requirement of air insufflation. However, insertion time in both devices did not differ.

Several manuscripts have reported safe and successful use of LMA-Classic devices in patients undergoing laparoscopic surgery [7,8]. Likewise, other devices, such as the PLMA, have been investigated and provided effective mechanical ventilation and have been used safely during laparoscopic surgery [13,14]. In the present study, we did not find gastric insufflation, regurgitation, or gastric aspiration during surgery in either group.

The first limitation of our study was instrument selection bias by the anesthesiologist, which was not possible to eliminate, because the anesthesiologist was aware of the device he was using due to the difference in shape between the devices. Second, all insertions were performed by an experienced anesthesiologist; therefore, our results may not be applicable to novice users. Finally, patients enrolled in our study had normal airways; thus, no conclusions can be made regarding patients for whom difficult intubation is expected.