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Comparison of the EasyTube® and endotracheal tube during general anesthesia in fasted adult patients
Journal of Clinical Anesthesia (2009) 21, 341–347
Original contribution
Comparison of the EasyTube® and endotracheal tube during general anesthesia in fasted adult patients☆ Veit Lorenz MD (Resident)a , James M. Rich CRNA b , Karl Schebesta MD (Resident)a , Sevak Taslakian MD (Resident)a , Michael Müllner MD (Resident)c , Michael Frass MD (Professor) c , Ernst Schuster PhD (Professor)d , Udo M. Illievich MD (Professor) e , Alan D. Kaye MD, PhD (Professor) f , Sonia Vaida MD (Associate Professor)g , Peter Krafft MD (Professor) a,⁎ a
Department of Anesthesiology, General Intensive Care and Pain Management, Medical University of Vienna, 1090 Vienna, Austria b Department of Anesthesiology and Pain Management, Baylor University Medical Center, Dallas, TX 75246, USA c Department of Internal Medicine I, Intensive Care Unit, Medical University of Vienna, 1090 Vienna, Austria d Core Unit for Medical Statistics and Informatics, Medical University of Vienna, 1090 Vienna, Austria e Department of Anesthesiology and General Intensive Care, Wagner-Jauregg Hospital Linz, 4020 Linz, Austria f Department of Anesthesiology, LSU School of Medicine, New Orleans, LA 70112, USA g Department of Anesthesiology, Penn State Milton S. Hershey Medical Center, Hershey, PA 17033, USA Received 11 January 2008; revised 18 September 2008; accepted 19 September 2008
Keywords: Alternative airways; Combitube®; EasyTube®, Endotracheal tube, General anesthesia
Abstract Study Objective: To evaluate the effectiveness, safety, ease of placement, and ventilatory parameters of a new alternate airway device, the EasyTube® (EzT; Teleflex Ruesch, Research Triangle Park, NC), in comparison to the endotracheal tube (ETT). Design: Prospective, randomized controlled trial. Setting: University Hospital. Subjects: 200 adult ASA physical status I and II patients scheduled for surgery. Interventions: Patients were randomized to two groups, one to receive ventilation via the EzT (n = 100) or the ETT (n = 100). After preoxygenation and induction with fentanyl and propofol, patients received muscle relaxation. The respective airway device was then inserted and mechanical ventilation was instituted. Measurements: Ease of insertion, number of insertion maneuvers, time until airtight seal of the airway was achieved, duration of surgery, leak pressure as well as arterial oxygen saturation (SpO2), and endtidal carbon dioxide (ETCO2) data, were recorded. Main Results: Mallampati airway class was higher in the EzT group (P b 0.029), while thyromental distance showed no difference between the two groups. Ease of insertion was noted in the EzT group (P b 0.043). Number of insertions was equal in both groups; insertion time was shorter with the EzT (15.5 ± 3.6 sec vs. 19.3 ± 4.6 sec; P b 0.0001). Leak pressure and SpO2 were not significantly different,
☆ Support was provided solely from institutional and/or departmental sources. There was no additional salary for one of the authors. ⁎ Corresponding author. Tel.: +43 1 40400 4100; fax: +43 1 40400 4028. E-mail address: [email protected] (P. Krafft).
0952-8180/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jclinane.2008.09.008
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V. Lorenz et al. while ETCO2 was lower with the ETT (P b 0.024). Adjustments had to be made for two EzT group patients. No difference in frequency of laryngo-pharyngeal discomfort was observed in either group. Conclusion: Insertion of an EzT appears to reduce time and facilitate placement of an airway device when compared with direct laryngoscopy and tracheal intubation. © 2009 Elsevier Inc. All rights reserved.
1. Introduction
2.1. Inclusion and exclusion criteria
Alternate airway devices have become increasingly popular during the last two decades [1-6]. Their use has revolutionized airway management in the operating room (OR) [7,8] as well as with in-hospital [9] and out-of-hospital resuscitation [10]. The Combitube® (Covidien, Mansfield, MA) has gained widespread acceptance in the prehospital setting [11]. However, the Combitube has a number of shortcomings, such as a double-lumen design down to the distal end with no possibility for passing a fiberoptic laryngoscope (fiberscope) into the trachea if the endotracheal tube (ETT) is in the esophageal position. The design of a new alternate airway device, the EasyTube® (EzT; Teleflex Ruesch, Research Triangle Park, NC) is similar to that of the Combitube; however, it overcomes several disadvantages of the Combitube [12,13]. First, the pharyngeal lumen ends just below the oropharyngeal balloon, so that the distal end consists of a slim single-lumen only versus the Combitube's double-lumen design. We hypothesized that insertion of an EzT is easier and less traumatic than with the Combitube. Second, the open end of the pharyngeal lumen allows passage of a fiberscope and inspection of the trachea. Third, the oropharyngeal balloon of the EzT is latex-free. Finally, the EzT is available in a smaller 28-French (Fr) version that may be used in patients 90 to 130 cm. The EzT is also classified for use during elective surgery. However, no previous studies have prospectively evaluated the performance of the EzT in a larger series of patients. The aim of the present study was, therefore, to investigate whether the EzT performs similarly to an ETT and thus might be used safely in patients in whom tracheal intubation is to be avoided or not easily possible.
Patients were included consecutively during the working period of two respective anesthesiologists. Patients undergoing miscellaneous surgical interventions, including laparoscopic procedures involving peritoneal insufflation or Trendelenburg positioning, were recruited (47 laparoscopic procedures were performed, 22 in the ETT group, and 25 in the EzT group). Exclusion criteria included age b18 years; significant acute or chronic lung disease; patients presenting with a current or recent sore throat; those with known esophageal disease (GERD), thus excluding insertion of an esophageal device; patients with cervical spine disease; and surgical procedures with a scheduled duration of less than 30 minutes or more than 90 minutes. Patients presenting with increased risk of aspiration of gastric contents (eg, GERD) were not excluded from the study. Furthermore, severely obese patients were not excluded (Table 1).
2. Materials and methods The study was approved by the Ethical Committee of the Medical University of Vienna, Vienna, Austria. Written, informed consent was obtained from all patients prior to enrollment into this prospective, randomized controlled trial. We recruited 200 adult ASA physical status I and II patients, who were scheduled for surgery. Patients were randomized to two groups by computer-generated randomization list to receive either an EzT (n = 100) or an ETT (n = 100) for ventilation. Both airways were prepared for each patient since the sealed, numbered, opaque randomization envelopes were opened just before airway insertion.
2.2. Patients' evaluation, monitoring and ventilation Preoperatively, patients' airways were assessed and classified according to the Mallampati test as modified by Samsoon and Young [14,15], and thyromental distance was measured [16]. A thyromental distance less than 6 cm was considered a predictor of difficult intubation. Furthermore, interincisor distance was assessed in all patients and a mouth opening N two cm was rated as unrestricted. Patients were monitored by routine, standard noninvasive measures including electrocardiogram, pulse oximetry, temperature, non-invasive blood pressure measurement (every 5 min), and capnography (Merlin; Hewlett-Packard, Boeblingen, Germany). Patients were premedicated with oral midazolam 0.1 mg/kg and were preoxygenated with 100% oxygen for three minutes. General anesthesia was then induced by an intravenous (IV) bolus injection of propofol one to three mg/kg and fentanyl two to three μg/kg. Muscle relaxation was achieved with vecuronium bromide 0.1 mg/ kg. Muscle relaxation was used so as to minimize postoperative complaints (eg, dysphagia, hoarseness) in patients undergoing elective surgery. Three minutes after administration of the muscle relaxant, the first attempt of airway insertion was performed. After insertion of either the EzT or ETT, anesthesia was maintained with inhaled sevoflurane supplemented by small doses of fentanyl one to two μg/kg as needed. Patients underwent positive pressure ventilation (PPV) in a volume-controlled mode; the targeted tidal volume was 6 mL/kg; inspired oxygen concentration (FIO2)
EasyTube® vs. ETT during anesthesia Table 1
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Patients' characteristics
Age (yrs) Height (cm) Weight (kg) BMI (kg/m2) Gender (M:F) ASA physical status I:II Mallampati class 1/2/3/4 airway Thyromental distance b6 cm Duration of surgery (min) Type of surgery: abdominal gynecological urological
EzT group (n = 100)
ETT group (n = 100)
P
56.2 ± 13.8 (24–86) 74 ± 9 (149–192) 76.4 ± 9.5 (59–102) 25.4 ± 3.9 (17.8–34.2) 46 : 54 63 : 37 59/28/12/1 16 46.5 ± 11.2 (30–75)
57.3 ± 14.0 (24–88) 173 ± 9 (150–192) 74.6 ± 8.6 (56–95) 24.9 ± 3.4 (17.9–34.1) 47 : 53 63 : 37 75/22/3/0 14 46.3 ± 11.1 (30–86)
n.s. n.s. n.s. n.s. n.s. n.s. 0.029 n.s. n.s. n.s.
67 24 9
63 26 11
Values are expressed as means ± SD and ranges. EzT = (EasyTube; Teleflex Ruesch, Research Triangle Park, NC), ETT = endotracheal tube, BMI = body mass index.
ranged from 0.25 to 0.35; respiratory rate was set to achieve an end-tidal CO2 (ETCO2) concentration of 36 to 40 mmHg. Neither CO2 insufflation nor nitrous oxide was used.
2.3. Description and insertion of EasyTube® The EasyTube® (EzT; Teleflex Medical Ruesch, Research Triangle Park, NC; Fig. 1) is a new disposable, esophagealtracheal double-lumen airway [12,13]. Similar to the Combitube®, it allows ventilation in either the esophageal or tracheal position; however, it enters the esophagus in most cases. The EzT may be positioned in the esophagus blindly or with the help of a laryngoscope. The 41-Fr size was used in all patients in the EzT group. The EzTs were inserted by two anesthesiologists who read the instructions for EzT use and performed two insertions in a manikin (VBM Medical Technique, Sulz, Germany). Before the start of the study, they had used the Combitube at least 5 times during general anesthesia. The device was inserted blindly without the use of a laryngoscope. The patient's mouth was opened with one hand and the EzT was inserted flat, almost parallel to the patient's chest, so as to match the curve of the patient's airway and to facilitate the insertion. The EzT was inserted into the patient's mouth until the printed black ring lay between the patient's teeth or alveolar processes. The oropharyngeal balloon was then inflated with 40 to 80 cm3 of air via valve No. 1 (blue pilot balloon), followed by inflation of the distal cuff with 7 to 10 cm3 of air. For inflation of the oropharyngeal balloon, the minimal volume technique was used [4,5]. The oropharyngeal balloon is first filled with 40 cm3 of air. If an airtight seal is not achieved (as indicated by a difference between inspiratory and expiratory minute ventilation), balloon inflation is increased in steps of 10 cm3 until no leak is observed (maximum 80 cm3). Three attempts were allowed before insertion was rated impossible, at which time conventional laryngoscopic endotracheal intubation was performed.
2.4. Conventional endotracheal intubation Conventional endotracheal intubation was performed using standard ETTs (7.0 mm ID in women, 8.0 mm ID in men; Tyco Healthcare Mallinckrodt, Athlone, Ireland) and direct laryngoscopy (MacIntosh blade No. 3). Three attempts were allowed before insertion was rated impossible and intubation was switched to EzT in case of failure of tracheal intubation.
2.5. Confirmation of placement In both groups, confirmation of the tube's position was done by auscultation, pulse oximetry, and ETCO 2 measurement.
2.6. Measurements Ease insertion was rated on a nominal scale as easy, moderate, difficult, or impossible. The number of insertion attempts was recorded. Time until an airtight seal of the airway was achieved was measured using a stopwatch starting from grasping the EzT or the ETT until inflation of cuffs or balloons. In addition, duration of surgery was noted. Measurement of leak pressure was performed by closure of the expiratory valve of the circle system with a flow of three L/ min and observation when the airway pressure reached equilibrium. The limit was set at 40 cm H2O airway pressure. Before placement, as well as after 15 and 30 minutes following insertion, arterial oxygen saturation (SpO2) and ETCO2 were recorded. After removal of the respective devices, the airways were investigated for traces of or gross blood. After recovery as well as 24 hours after the end of anesthesia, patients were asked about laryngopharyngeal discomfort by an anesthesiologist who was blinded as to group assignment. Three types of complaints were evaluated:
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V. Lorenz et al.
Fig. 1 EasyTube (EzT; Teleflex Ruesch, Research Triangle Park, NC) 28-Fr for patients with a height of 90 to 130 cm (left) and EzT 41-Fr for patients greater than 130 cm (right). Note the single ventilatory hole at the distal end of pharyngeal lumen No. 1 just under the latex-free oropharyngeal balloon. The distal end of tracheo-esophageal lumen No. 2 resembles a single-lumen endotracheal tube. The pharyngeal lumen allows passage of a fiberoptic laryngoscope.
sore throat (constant pain, independent of swallowing), dysphagia (discomfort with swallowing provoked by drinking), and hoarseness. Complaints were graded using a nominal scale as absent, mild, moderate, or severe. Potential learning and training effects were evaluated regarding time of insertion as well as insertion difficulty.
2.7. Statistical analysis Data were tested for normal distribution, and analysis was performed by Chi-squared statistics and unpaired t-tests, as appropriate. If the sample size was less than 51, the ShapiroWilk statistic was computed; otherwise, the usual Kolmogorov D statistic was used. Sample size studied (n = 200) was estimated on the basis of a power of 0.9 and a α of 0.05. Evaluation of training effect regarding time of insertion was performed by linear regression analysis, insertion difficulty was evaluated by chi-square test. Results are presented as means ± SD; a P-value b 0.05 was considered statistically significant.
3. Results No significant differences were noted between the two groups regarding age, height, weight, or gender (Table 1). ASA physical status I and II were allocated similarly between the groups. Mallampati class 3 airway was found significantly more often in the EzT group (P b 0.029;
Table 1), while thyromental distance showed no difference between the two groups. Mouth opening was unrestricted in all patients of Group ETT, while interincisor distance was less than two cm in two patients from the EzT group. Insertion of the EzT was possible without any difficulties in those patients. Neither duration of, nor type of, surgery differed between the EzT and ETT groups. The number of insertion attempts needed until successful positioning was achieved was similar in both groups (N one attempt necessary in 5 EzT and in 7 ETT group pts); however, insertion time was shorter with the EzT (15.5 ± 3.6 sec vs. 19.3 ± 4.6 sec; P b 0.0001; Table 2). Ease of insertion was greater in the EzT group (P b 0.043; Table 2). Operators encountered no greater difficulty with patients at the extremes of height or weight. All EzT insertions resulted in esophageal placement of the airway and ventilation was performed through the pharyngeal lumen via the longer blue tube. Leak pressure was not significantly different between the groups (Table 2). Adjustments with respect to insertion depth had to be made in two EzT group patients (P = ns). There was no difference in groups in SpO2 at 0, 15, or 30 minutes. At 0 minute, ETCO2 was similar in both groups, but at 15 and 30 minutes, ETCO2 was significantly lower in Group ETT (P b 0.024). No difference in frequency of laryngo-pharyngeal discomfort (sore throat, dysphagia, hoarseness) was observed. All complaints were graded as mild immediately after recovery from, as well as 24 hours after, the end of anesthesia (Table 2).
EasyTube® vs. ETT during anesthesia Table 2
345
Results EzT group (n = 100)
Ease of insertion 1/2/3/4 78/20/2/0 Number of insertions (1/2/3) 95/5/0 Time of insertion (sec) 15.5 ± 3.6 (10-24) Leak pressure (cm H2O) 35.5 ± 4.4 (24-40) SpO2 (%) 0 min 97.7 ± 1.2 (95–100) SpO2 (%) 15 min 97.8 ± 1.0 (96–100) SpO2 (%) 30 min 98.2 ± 1.2 (95–100) ETCO2 (mm Hg) 0 min 37.2 ± 2.3 (31–42) ETCO2 (mm Hg) 15 min 37.8 ± 2.4 (32–46) ETCO2 (mm Hg) 30 min 37.4 ± 2.3 (32–42) Laryngopharyngeal discomfort after recovery (all complaints were graded as mild): sore throat (0/24hrs) 7/1 dysphagia (0/24hrs) 2/0 hoarseness (0/24hrs) 1/0
ETT group (n = 100)
P
64/28/8/0 93/5/2 19.3 ± 4.6 (11-37) 34.5 ± 4.9 (24-42) 97.7 ± 1.1 (96–100) 97.9 ± 1.2 (96–100) 98.0 ± 1.2 (96–100) 37.2 ± 2.1 (33–44) 37.2 ± 1.8 (34–42) 36.4 ± 1.8 (32–41)
0.043 n.s. 0.0001 n.s. n.s.* n.s. n.s. n.s. 0.024 0.024 n.s.
9/2 1/0 6/4
Values are expressed as means ± SD and ranges. EzT = (EasyTube; Teleflex Ruesch, Research Triangle Park, NC), ETT = endotracheal tube, SpO2 = arterial oxygen saturation as measured by pulse oximetry, ETCO2 = end-tidal carbon dioxide concentration.
No training effects were registered. Linear regression coefficient concerning duration of the insertion process showed slightly longer time needed for device insertion during the course of the study for physician No. 1 (0.07933; P = 0.0343), and no significant change for physician No. 2 (0.05000; P = 0.3165). Similar results were obtained for EzT insertion difficulty (P = 0.2695 for physician No. 1, and P = 0.3358 for physician No.2).
4. Discussion Results of the present study suggest that the EzT is suitable for airway management with controlled PPV during elective surgery of moderate duration. Ease of insertion favored the EzT over direct laryngoscopy and tracheal intubation. However, blind insertion of an EzT, as with any other supraglottic device, requires only sufficient mouth opening to perform a blind insertion into the patient's hypopharynx. In contrast, tracheal intubation requires mouth opening, insertion of a laryngoscope, performance of laryngoscopy, and placement of the ETT. The study showed patient's safety and comfort with the EzT during PPV at least during elective surgery. The EzT provides relatively high leak pressures, comparable to those obtained with an ETT. No direct training effect could be shown. Rapid airway control and sufficient ventilatory support are crucial during anesthesia and especially during management of (prehospital) emergency situations. Tracheal intubation remains the gold standard for airway management in emergencies, but often fails in situations of (un)anticipated difficult airways [9,17]. Several supraglottic airway devices have been designed, including the Laryngeal Mask Airway (LMA), laryngeal tube, perilaryngeal airway, Combitube, EzT, to name several. With the exception of the Combitube, which
has been tested under extreme circumstances [18], most of the other supraglottic airways have several disadvantages in emergencies, eg, diameter too large to allow insertion in patients with a small interincisor distance or trismus, no definite protection against aspiration of gastric contents or air leakage even at relatively low airway pressures (b 20 cmH2O). Furthermore, most devices need tape fixation to prevent accidental dislocation. Bercker et al [19] compared the seal of 7 supraglottic devices with respect to their risk of aspiration of gastric contents. Using an experimental setup of increased esophageal pressure, the LMA classic, LMA ProSeal®, IntubatingLMA Fastrach®, laryngeal tube, laryngeal tube LTS II, Combitube, and EzT were inserted into cadavers whose esophagus was connected to a 130 cm high water column. Slow and quick increases in esophageal pressure were simulated and the water pressure at which a leak occurred was registered. The Combitube, EzT, and intubating-LMA Fastrach® resisted a water pressure of more than 120 cm H2O. With respect to aspiration risk, those authors recommend the use of devices with higher seal and an additional lumen for drainage of gastric contents. Considering that Bercker et al used a volume of 60 cm3 to inflate the oropharyngeal balloons/rims in all devices, one might suggest that an even better seal may be achieved with the EzT, when the recommended inflation volume of 80 cm3 of air is used in emergency situations. The EzT device is slim, allowing insertion in patients with limited mouth opening. In addition, the design of the oropharyngeal balloon provides a tight seal and enables the use of high ventilatory pressures. However, no previous studies have prospectively evaluated the performance of the EzT in a larger series of patients. To minimize risk to patients, we tested this new device in patients undergoing elective surgery and compared EzT with the gold standard,
346 namely, direct laryngoscopy and tracheal intubation. The primary intention of this approach was not to establish an alternative to tracheal intubation in routine patients, but to investigate the safety and performance of the new EzT under controlled conditions. The ETT was chosen as a control group, since EzT will probably represent an alternative airway to the ETT in (prehospital) emergency situations where ETT placement fails or is impossible. Furthermore, those patients with GERD, morbid obesity, and those undergoing laparoscopic surgery in the Trendelenburg positioning, were recruited to the study. With respect to patient safety, we chose to compare EzT with the ETT as opposed to other supraglottic airways that might have had poorer aspiration protection. However, further studies are required to study the EzT in true emergency situations, and to compare the EzT with other supraglottic devices, especially the LMA and the laryngeal tube. Results of the present study show that the EzT performs safely and effectively during general anesthesia and mechanical ventilation. Our data suggest that the EzT is comparable to the ETT with respect to oxygenation and ventilation, and it might even have minor advantages. Insertion time, for example, was shorter despite the operators' lack of experience with the EzT. Even the significantly higher percentage of Mallampati class 3 airways within the EzT group did not impede successful insertion and ventilation. However, Mallampati class may be a parameter only insufficiently reflecting the degree of difficulty encountered during placement of a supraglottic device. The EzT is inserted slightly more quickly and easily than the ETT; however, the quicker insertion time (15 vs 19 sec) seems to be clinically irrelevant. The frequency of sore throat was similar with both devices (EzT 7% and ETT 9%) and it disappeared after 24 hours. This low frequency of only 7% postoperative sore throat in Group EzT is attributable to the slim design of the device. No episodes of major complications were observed in the study. Our study has several limitations since it is the first evaluation of a new supraglottic airway in patients undergoing elective anesthesia and surgery. One limitation is that intraoperative data were obtained by an unblinded observer. Furthermore, only three (Mallampati class and thyromental and interincisor distance) of 11 anatomical parameters identified by the ASA task force as pointing to difficult airways, were evaluated. Mallampati airway class and thyromental distance might reflect difficult laryngoscopy but do not necessarily reflect difficult insertion of a supraglottic airway. Since the EzT is a rather new device, our study was confined to those patients undergoing surgery with an expected duration of 30 to 90 minutes, and we can only speculate on the EzT's performance over a longer period of time. However, in true emergency situations we would not hesitate to use the EzT up to 8 hours [20]. Another study limitation might be that all patients received muscle relaxants for insertion of both the EzT and ETT. One of the major advantages of supraglottic airway devices is their ease of insertion without the need for muscle relaxation. Even
V. Lorenz et al. in elective surgery, the potential of spontaneous breathing is an advantage of alternate devices [21,22]. In conclusion, the EzT performed similarly to direct laryngoscopy and tracheal intubation in efficacy and safety, at least in elective patients undergoing routine surgical procedures. Further studies are warranted to clarify whether the EzT results in even greater patient satisfaction due to its lesser invasiveness, and to investigate the performance of this new supraglottic airway in true emergency situations.
References [1] Ulrich-Pur H, Hrska F, Krafft P, et al. Comparison of mucosal pressures induced by cuffs of different airway devices. Anesthesiology 2006;104:933-8. [2] Benumof JL. Laryngeal mask airway and the ASA difficult airway algorithm. Anesthesiology 1996;84:686-99. [3] Agrò F, Frass M, Benumof JL, Krafft P. Current status of the Combitube: a review of the literature. J Clin Anesth 2002;14:307-14. [4] Rich JM, Mason AM, Bey TA, Krafft P, Frass M. The critical airway, rescue ventilation, and the combitube: Part I. AANA J 2004;72: 17-27. [5] Rich JM, Mason AM, Bey TA, Krafft P, Frass M. The critical airway, rescue ventilation, and the combitube: Part II. AANA J 2004;72: 115-24. [6] Akca O, Wadhwa A, Sengupta P, et al. The new perilaryngeal airway (CobraPLA) is as efficient as the laryngeal mask airway (LMA) but provides better airway sealing pressures. Anesth Analg 2004;99: 272-8. [7] Benumof JL. Management of the difficult airway. With special emphasis on awake tracheal intubation. Anesthesiology 1991;75: 1087-110. [8] Hartmann T, Krenn CG, Zoeggeler A, Hoerauf K, Benumof JL, Krafft P. The oesophageal – tracheal Combitube Small Adult. Anaesthesia 2000;55:670-5. [9] Mort TC. Laryngeal Mask Airway and bougie intubation failures: the Combitube as a secondary rescue device for in-hospital emergency airway management. Anesth Analg 2006;103:1264-6. [10] Lefrancois DP, Dufour DG. Use of the esophageal tracheal combitube by basic emergency medical technicians. Resuscitation 2002;52: 77-83. [11] Krafft P, Schebesta K. Alternative management techniques for the difficult airway: esophageal-tracheal Combitube. Curr Opin Anaesthesiol 2004;17:499-504. [12] Thierbach AR, Piepho T, Maybauer MO. A new device for emergency airway management: the EasyTube™. Resuscitation 2004;60:347. [13] Thierbach AR, Piepho T, Maybauer M. The EasyTube for airway management in emergencies. Prehosp Emerg Care 2005;9:445-8. [14] Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can J Anaesth 1985;32:429-34. [15] Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987;42:487-90. [16] Tse JC, Rimm EB, Hussain A. Predicting difficult endotracheal intubation in surgical patients scheduled for general anesthesia: a prospective blind study. Anesth Analg 1995;81:254-8. [17] Schwartz DE, Matthay MA, Cohen NH. Death and other complications of emergency airway management in critically ill adults. A prospective investigation of 297 tracheal intubations. Anesthesiology 1995;82:367-76. [18] Rabitsch W, Moser D, Inzunza MR, et al. Airway management with endotracheal tube versus Combitube during parabolic flights. Anesthesiology 2006;105:696-702.
EasyTube® vs. ETT during anesthesia [19] Bercker S, Schmidbauer W, Volk T, et al. A comparison of seal in seven supraglottic airway devices using a cadaver model of elevated esophageal pressure. Anesth Analg 2008;106:445-8. [20] Frass M, Frenzer R, Mayer G, Popovic R, Leithner C. Mechanical ventilation with the esophageal tracheal combitube (ETC) in the intensive care unit. Arch Emerg Med 1987;4:219-25.
347 [21] Gaitini L, Vaida S, Somri M, Fradis M, Ben-David B. Fiberopticguided exchange of esophageal-tracheal Combitube in spontaneously breathing versus mechanically ventilated patients. Anesth Analg 1999;88:193-6. [22] Gaitini LA, Vaida SJ, Mostafa S, et al. The Combitube in elective surgery: a report of 200 cases. Anesthesiology 2001;94:79-82.
Original contribution
Comparison of the EasyTube® and endotracheal tube during general anesthesia in fasted adult patients☆ Veit Lorenz MD (Resident)a , James M. Rich CRNA b , Karl Schebesta MD (Resident)a , Sevak Taslakian MD (Resident)a , Michael Müllner MD (Resident)c , Michael Frass MD (Professor) c , Ernst Schuster PhD (Professor)d , Udo M. Illievich MD (Professor) e , Alan D. Kaye MD, PhD (Professor) f , Sonia Vaida MD (Associate Professor)g , Peter Krafft MD (Professor) a,⁎ a
Department of Anesthesiology, General Intensive Care and Pain Management, Medical University of Vienna, 1090 Vienna, Austria b Department of Anesthesiology and Pain Management, Baylor University Medical Center, Dallas, TX 75246, USA c Department of Internal Medicine I, Intensive Care Unit, Medical University of Vienna, 1090 Vienna, Austria d Core Unit for Medical Statistics and Informatics, Medical University of Vienna, 1090 Vienna, Austria e Department of Anesthesiology and General Intensive Care, Wagner-Jauregg Hospital Linz, 4020 Linz, Austria f Department of Anesthesiology, LSU School of Medicine, New Orleans, LA 70112, USA g Department of Anesthesiology, Penn State Milton S. Hershey Medical Center, Hershey, PA 17033, USA Received 11 January 2008; revised 18 September 2008; accepted 19 September 2008
Keywords: Alternative airways; Combitube®; EasyTube®, Endotracheal tube, General anesthesia
Abstract Study Objective: To evaluate the effectiveness, safety, ease of placement, and ventilatory parameters of a new alternate airway device, the EasyTube® (EzT; Teleflex Ruesch, Research Triangle Park, NC), in comparison to the endotracheal tube (ETT). Design: Prospective, randomized controlled trial. Setting: University Hospital. Subjects: 200 adult ASA physical status I and II patients scheduled for surgery. Interventions: Patients were randomized to two groups, one to receive ventilation via the EzT (n = 100) or the ETT (n = 100). After preoxygenation and induction with fentanyl and propofol, patients received muscle relaxation. The respective airway device was then inserted and mechanical ventilation was instituted. Measurements: Ease of insertion, number of insertion maneuvers, time until airtight seal of the airway was achieved, duration of surgery, leak pressure as well as arterial oxygen saturation (SpO2), and endtidal carbon dioxide (ETCO2) data, were recorded. Main Results: Mallampati airway class was higher in the EzT group (P b 0.029), while thyromental distance showed no difference between the two groups. Ease of insertion was noted in the EzT group (P b 0.043). Number of insertions was equal in both groups; insertion time was shorter with the EzT (15.5 ± 3.6 sec vs. 19.3 ± 4.6 sec; P b 0.0001). Leak pressure and SpO2 were not significantly different,
☆ Support was provided solely from institutional and/or departmental sources. There was no additional salary for one of the authors. ⁎ Corresponding author. Tel.: +43 1 40400 4100; fax: +43 1 40400 4028. E-mail address: [email protected] (P. Krafft).
0952-8180/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jclinane.2008.09.008
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V. Lorenz et al. while ETCO2 was lower with the ETT (P b 0.024). Adjustments had to be made for two EzT group patients. No difference in frequency of laryngo-pharyngeal discomfort was observed in either group. Conclusion: Insertion of an EzT appears to reduce time and facilitate placement of an airway device when compared with direct laryngoscopy and tracheal intubation. © 2009 Elsevier Inc. All rights reserved.
1. Introduction
2.1. Inclusion and exclusion criteria
Alternate airway devices have become increasingly popular during the last two decades [1-6]. Their use has revolutionized airway management in the operating room (OR) [7,8] as well as with in-hospital [9] and out-of-hospital resuscitation [10]. The Combitube® (Covidien, Mansfield, MA) has gained widespread acceptance in the prehospital setting [11]. However, the Combitube has a number of shortcomings, such as a double-lumen design down to the distal end with no possibility for passing a fiberoptic laryngoscope (fiberscope) into the trachea if the endotracheal tube (ETT) is in the esophageal position. The design of a new alternate airway device, the EasyTube® (EzT; Teleflex Ruesch, Research Triangle Park, NC) is similar to that of the Combitube; however, it overcomes several disadvantages of the Combitube [12,13]. First, the pharyngeal lumen ends just below the oropharyngeal balloon, so that the distal end consists of a slim single-lumen only versus the Combitube's double-lumen design. We hypothesized that insertion of an EzT is easier and less traumatic than with the Combitube. Second, the open end of the pharyngeal lumen allows passage of a fiberscope and inspection of the trachea. Third, the oropharyngeal balloon of the EzT is latex-free. Finally, the EzT is available in a smaller 28-French (Fr) version that may be used in patients 90 to 130 cm. The EzT is also classified for use during elective surgery. However, no previous studies have prospectively evaluated the performance of the EzT in a larger series of patients. The aim of the present study was, therefore, to investigate whether the EzT performs similarly to an ETT and thus might be used safely in patients in whom tracheal intubation is to be avoided or not easily possible.
Patients were included consecutively during the working period of two respective anesthesiologists. Patients undergoing miscellaneous surgical interventions, including laparoscopic procedures involving peritoneal insufflation or Trendelenburg positioning, were recruited (47 laparoscopic procedures were performed, 22 in the ETT group, and 25 in the EzT group). Exclusion criteria included age b18 years; significant acute or chronic lung disease; patients presenting with a current or recent sore throat; those with known esophageal disease (GERD), thus excluding insertion of an esophageal device; patients with cervical spine disease; and surgical procedures with a scheduled duration of less than 30 minutes or more than 90 minutes. Patients presenting with increased risk of aspiration of gastric contents (eg, GERD) were not excluded from the study. Furthermore, severely obese patients were not excluded (Table 1).
2. Materials and methods The study was approved by the Ethical Committee of the Medical University of Vienna, Vienna, Austria. Written, informed consent was obtained from all patients prior to enrollment into this prospective, randomized controlled trial. We recruited 200 adult ASA physical status I and II patients, who were scheduled for surgery. Patients were randomized to two groups by computer-generated randomization list to receive either an EzT (n = 100) or an ETT (n = 100) for ventilation. Both airways were prepared for each patient since the sealed, numbered, opaque randomization envelopes were opened just before airway insertion.
2.2. Patients' evaluation, monitoring and ventilation Preoperatively, patients' airways were assessed and classified according to the Mallampati test as modified by Samsoon and Young [14,15], and thyromental distance was measured [16]. A thyromental distance less than 6 cm was considered a predictor of difficult intubation. Furthermore, interincisor distance was assessed in all patients and a mouth opening N two cm was rated as unrestricted. Patients were monitored by routine, standard noninvasive measures including electrocardiogram, pulse oximetry, temperature, non-invasive blood pressure measurement (every 5 min), and capnography (Merlin; Hewlett-Packard, Boeblingen, Germany). Patients were premedicated with oral midazolam 0.1 mg/kg and were preoxygenated with 100% oxygen for three minutes. General anesthesia was then induced by an intravenous (IV) bolus injection of propofol one to three mg/kg and fentanyl two to three μg/kg. Muscle relaxation was achieved with vecuronium bromide 0.1 mg/ kg. Muscle relaxation was used so as to minimize postoperative complaints (eg, dysphagia, hoarseness) in patients undergoing elective surgery. Three minutes after administration of the muscle relaxant, the first attempt of airway insertion was performed. After insertion of either the EzT or ETT, anesthesia was maintained with inhaled sevoflurane supplemented by small doses of fentanyl one to two μg/kg as needed. Patients underwent positive pressure ventilation (PPV) in a volume-controlled mode; the targeted tidal volume was 6 mL/kg; inspired oxygen concentration (FIO2)
EasyTube® vs. ETT during anesthesia Table 1
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Patients' characteristics
Age (yrs) Height (cm) Weight (kg) BMI (kg/m2) Gender (M:F) ASA physical status I:II Mallampati class 1/2/3/4 airway Thyromental distance b6 cm Duration of surgery (min) Type of surgery: abdominal gynecological urological
EzT group (n = 100)
ETT group (n = 100)
P
56.2 ± 13.8 (24–86) 74 ± 9 (149–192) 76.4 ± 9.5 (59–102) 25.4 ± 3.9 (17.8–34.2) 46 : 54 63 : 37 59/28/12/1 16 46.5 ± 11.2 (30–75)
57.3 ± 14.0 (24–88) 173 ± 9 (150–192) 74.6 ± 8.6 (56–95) 24.9 ± 3.4 (17.9–34.1) 47 : 53 63 : 37 75/22/3/0 14 46.3 ± 11.1 (30–86)
n.s. n.s. n.s. n.s. n.s. n.s. 0.029 n.s. n.s. n.s.
67 24 9
63 26 11
Values are expressed as means ± SD and ranges. EzT = (EasyTube; Teleflex Ruesch, Research Triangle Park, NC), ETT = endotracheal tube, BMI = body mass index.
ranged from 0.25 to 0.35; respiratory rate was set to achieve an end-tidal CO2 (ETCO2) concentration of 36 to 40 mmHg. Neither CO2 insufflation nor nitrous oxide was used.
2.3. Description and insertion of EasyTube® The EasyTube® (EzT; Teleflex Medical Ruesch, Research Triangle Park, NC; Fig. 1) is a new disposable, esophagealtracheal double-lumen airway [12,13]. Similar to the Combitube®, it allows ventilation in either the esophageal or tracheal position; however, it enters the esophagus in most cases. The EzT may be positioned in the esophagus blindly or with the help of a laryngoscope. The 41-Fr size was used in all patients in the EzT group. The EzTs were inserted by two anesthesiologists who read the instructions for EzT use and performed two insertions in a manikin (VBM Medical Technique, Sulz, Germany). Before the start of the study, they had used the Combitube at least 5 times during general anesthesia. The device was inserted blindly without the use of a laryngoscope. The patient's mouth was opened with one hand and the EzT was inserted flat, almost parallel to the patient's chest, so as to match the curve of the patient's airway and to facilitate the insertion. The EzT was inserted into the patient's mouth until the printed black ring lay between the patient's teeth or alveolar processes. The oropharyngeal balloon was then inflated with 40 to 80 cm3 of air via valve No. 1 (blue pilot balloon), followed by inflation of the distal cuff with 7 to 10 cm3 of air. For inflation of the oropharyngeal balloon, the minimal volume technique was used [4,5]. The oropharyngeal balloon is first filled with 40 cm3 of air. If an airtight seal is not achieved (as indicated by a difference between inspiratory and expiratory minute ventilation), balloon inflation is increased in steps of 10 cm3 until no leak is observed (maximum 80 cm3). Three attempts were allowed before insertion was rated impossible, at which time conventional laryngoscopic endotracheal intubation was performed.
2.4. Conventional endotracheal intubation Conventional endotracheal intubation was performed using standard ETTs (7.0 mm ID in women, 8.0 mm ID in men; Tyco Healthcare Mallinckrodt, Athlone, Ireland) and direct laryngoscopy (MacIntosh blade No. 3). Three attempts were allowed before insertion was rated impossible and intubation was switched to EzT in case of failure of tracheal intubation.
2.5. Confirmation of placement In both groups, confirmation of the tube's position was done by auscultation, pulse oximetry, and ETCO 2 measurement.
2.6. Measurements Ease insertion was rated on a nominal scale as easy, moderate, difficult, or impossible. The number of insertion attempts was recorded. Time until an airtight seal of the airway was achieved was measured using a stopwatch starting from grasping the EzT or the ETT until inflation of cuffs or balloons. In addition, duration of surgery was noted. Measurement of leak pressure was performed by closure of the expiratory valve of the circle system with a flow of three L/ min and observation when the airway pressure reached equilibrium. The limit was set at 40 cm H2O airway pressure. Before placement, as well as after 15 and 30 minutes following insertion, arterial oxygen saturation (SpO2) and ETCO2 were recorded. After removal of the respective devices, the airways were investigated for traces of or gross blood. After recovery as well as 24 hours after the end of anesthesia, patients were asked about laryngopharyngeal discomfort by an anesthesiologist who was blinded as to group assignment. Three types of complaints were evaluated:
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V. Lorenz et al.
Fig. 1 EasyTube (EzT; Teleflex Ruesch, Research Triangle Park, NC) 28-Fr for patients with a height of 90 to 130 cm (left) and EzT 41-Fr for patients greater than 130 cm (right). Note the single ventilatory hole at the distal end of pharyngeal lumen No. 1 just under the latex-free oropharyngeal balloon. The distal end of tracheo-esophageal lumen No. 2 resembles a single-lumen endotracheal tube. The pharyngeal lumen allows passage of a fiberoptic laryngoscope.
sore throat (constant pain, independent of swallowing), dysphagia (discomfort with swallowing provoked by drinking), and hoarseness. Complaints were graded using a nominal scale as absent, mild, moderate, or severe. Potential learning and training effects were evaluated regarding time of insertion as well as insertion difficulty.
2.7. Statistical analysis Data were tested for normal distribution, and analysis was performed by Chi-squared statistics and unpaired t-tests, as appropriate. If the sample size was less than 51, the ShapiroWilk statistic was computed; otherwise, the usual Kolmogorov D statistic was used. Sample size studied (n = 200) was estimated on the basis of a power of 0.9 and a α of 0.05. Evaluation of training effect regarding time of insertion was performed by linear regression analysis, insertion difficulty was evaluated by chi-square test. Results are presented as means ± SD; a P-value b 0.05 was considered statistically significant.
3. Results No significant differences were noted between the two groups regarding age, height, weight, or gender (Table 1). ASA physical status I and II were allocated similarly between the groups. Mallampati class 3 airway was found significantly more often in the EzT group (P b 0.029;
Table 1), while thyromental distance showed no difference between the two groups. Mouth opening was unrestricted in all patients of Group ETT, while interincisor distance was less than two cm in two patients from the EzT group. Insertion of the EzT was possible without any difficulties in those patients. Neither duration of, nor type of, surgery differed between the EzT and ETT groups. The number of insertion attempts needed until successful positioning was achieved was similar in both groups (N one attempt necessary in 5 EzT and in 7 ETT group pts); however, insertion time was shorter with the EzT (15.5 ± 3.6 sec vs. 19.3 ± 4.6 sec; P b 0.0001; Table 2). Ease of insertion was greater in the EzT group (P b 0.043; Table 2). Operators encountered no greater difficulty with patients at the extremes of height or weight. All EzT insertions resulted in esophageal placement of the airway and ventilation was performed through the pharyngeal lumen via the longer blue tube. Leak pressure was not significantly different between the groups (Table 2). Adjustments with respect to insertion depth had to be made in two EzT group patients (P = ns). There was no difference in groups in SpO2 at 0, 15, or 30 minutes. At 0 minute, ETCO2 was similar in both groups, but at 15 and 30 minutes, ETCO2 was significantly lower in Group ETT (P b 0.024). No difference in frequency of laryngo-pharyngeal discomfort (sore throat, dysphagia, hoarseness) was observed. All complaints were graded as mild immediately after recovery from, as well as 24 hours after, the end of anesthesia (Table 2).
EasyTube® vs. ETT during anesthesia Table 2
345
Results EzT group (n = 100)
Ease of insertion 1/2/3/4 78/20/2/0 Number of insertions (1/2/3) 95/5/0 Time of insertion (sec) 15.5 ± 3.6 (10-24) Leak pressure (cm H2O) 35.5 ± 4.4 (24-40) SpO2 (%) 0 min 97.7 ± 1.2 (95–100) SpO2 (%) 15 min 97.8 ± 1.0 (96–100) SpO2 (%) 30 min 98.2 ± 1.2 (95–100) ETCO2 (mm Hg) 0 min 37.2 ± 2.3 (31–42) ETCO2 (mm Hg) 15 min 37.8 ± 2.4 (32–46) ETCO2 (mm Hg) 30 min 37.4 ± 2.3 (32–42) Laryngopharyngeal discomfort after recovery (all complaints were graded as mild): sore throat (0/24hrs) 7/1 dysphagia (0/24hrs) 2/0 hoarseness (0/24hrs) 1/0
ETT group (n = 100)
P
64/28/8/0 93/5/2 19.3 ± 4.6 (11-37) 34.5 ± 4.9 (24-42) 97.7 ± 1.1 (96–100) 97.9 ± 1.2 (96–100) 98.0 ± 1.2 (96–100) 37.2 ± 2.1 (33–44) 37.2 ± 1.8 (34–42) 36.4 ± 1.8 (32–41)
0.043 n.s. 0.0001 n.s. n.s.* n.s. n.s. n.s. 0.024 0.024 n.s.
9/2 1/0 6/4
Values are expressed as means ± SD and ranges. EzT = (EasyTube; Teleflex Ruesch, Research Triangle Park, NC), ETT = endotracheal tube, SpO2 = arterial oxygen saturation as measured by pulse oximetry, ETCO2 = end-tidal carbon dioxide concentration.
No training effects were registered. Linear regression coefficient concerning duration of the insertion process showed slightly longer time needed for device insertion during the course of the study for physician No. 1 (0.07933; P = 0.0343), and no significant change for physician No. 2 (0.05000; P = 0.3165). Similar results were obtained for EzT insertion difficulty (P = 0.2695 for physician No. 1, and P = 0.3358 for physician No.2).
4. Discussion Results of the present study suggest that the EzT is suitable for airway management with controlled PPV during elective surgery of moderate duration. Ease of insertion favored the EzT over direct laryngoscopy and tracheal intubation. However, blind insertion of an EzT, as with any other supraglottic device, requires only sufficient mouth opening to perform a blind insertion into the patient's hypopharynx. In contrast, tracheal intubation requires mouth opening, insertion of a laryngoscope, performance of laryngoscopy, and placement of the ETT. The study showed patient's safety and comfort with the EzT during PPV at least during elective surgery. The EzT provides relatively high leak pressures, comparable to those obtained with an ETT. No direct training effect could be shown. Rapid airway control and sufficient ventilatory support are crucial during anesthesia and especially during management of (prehospital) emergency situations. Tracheal intubation remains the gold standard for airway management in emergencies, but often fails in situations of (un)anticipated difficult airways [9,17]. Several supraglottic airway devices have been designed, including the Laryngeal Mask Airway (LMA), laryngeal tube, perilaryngeal airway, Combitube, EzT, to name several. With the exception of the Combitube, which
has been tested under extreme circumstances [18], most of the other supraglottic airways have several disadvantages in emergencies, eg, diameter too large to allow insertion in patients with a small interincisor distance or trismus, no definite protection against aspiration of gastric contents or air leakage even at relatively low airway pressures (b 20 cmH2O). Furthermore, most devices need tape fixation to prevent accidental dislocation. Bercker et al [19] compared the seal of 7 supraglottic devices with respect to their risk of aspiration of gastric contents. Using an experimental setup of increased esophageal pressure, the LMA classic, LMA ProSeal®, IntubatingLMA Fastrach®, laryngeal tube, laryngeal tube LTS II, Combitube, and EzT were inserted into cadavers whose esophagus was connected to a 130 cm high water column. Slow and quick increases in esophageal pressure were simulated and the water pressure at which a leak occurred was registered. The Combitube, EzT, and intubating-LMA Fastrach® resisted a water pressure of more than 120 cm H2O. With respect to aspiration risk, those authors recommend the use of devices with higher seal and an additional lumen for drainage of gastric contents. Considering that Bercker et al used a volume of 60 cm3 to inflate the oropharyngeal balloons/rims in all devices, one might suggest that an even better seal may be achieved with the EzT, when the recommended inflation volume of 80 cm3 of air is used in emergency situations. The EzT device is slim, allowing insertion in patients with limited mouth opening. In addition, the design of the oropharyngeal balloon provides a tight seal and enables the use of high ventilatory pressures. However, no previous studies have prospectively evaluated the performance of the EzT in a larger series of patients. To minimize risk to patients, we tested this new device in patients undergoing elective surgery and compared EzT with the gold standard,
346 namely, direct laryngoscopy and tracheal intubation. The primary intention of this approach was not to establish an alternative to tracheal intubation in routine patients, but to investigate the safety and performance of the new EzT under controlled conditions. The ETT was chosen as a control group, since EzT will probably represent an alternative airway to the ETT in (prehospital) emergency situations where ETT placement fails or is impossible. Furthermore, those patients with GERD, morbid obesity, and those undergoing laparoscopic surgery in the Trendelenburg positioning, were recruited to the study. With respect to patient safety, we chose to compare EzT with the ETT as opposed to other supraglottic airways that might have had poorer aspiration protection. However, further studies are required to study the EzT in true emergency situations, and to compare the EzT with other supraglottic devices, especially the LMA and the laryngeal tube. Results of the present study show that the EzT performs safely and effectively during general anesthesia and mechanical ventilation. Our data suggest that the EzT is comparable to the ETT with respect to oxygenation and ventilation, and it might even have minor advantages. Insertion time, for example, was shorter despite the operators' lack of experience with the EzT. Even the significantly higher percentage of Mallampati class 3 airways within the EzT group did not impede successful insertion and ventilation. However, Mallampati class may be a parameter only insufficiently reflecting the degree of difficulty encountered during placement of a supraglottic device. The EzT is inserted slightly more quickly and easily than the ETT; however, the quicker insertion time (15 vs 19 sec) seems to be clinically irrelevant. The frequency of sore throat was similar with both devices (EzT 7% and ETT 9%) and it disappeared after 24 hours. This low frequency of only 7% postoperative sore throat in Group EzT is attributable to the slim design of the device. No episodes of major complications were observed in the study. Our study has several limitations since it is the first evaluation of a new supraglottic airway in patients undergoing elective anesthesia and surgery. One limitation is that intraoperative data were obtained by an unblinded observer. Furthermore, only three (Mallampati class and thyromental and interincisor distance) of 11 anatomical parameters identified by the ASA task force as pointing to difficult airways, were evaluated. Mallampati airway class and thyromental distance might reflect difficult laryngoscopy but do not necessarily reflect difficult insertion of a supraglottic airway. Since the EzT is a rather new device, our study was confined to those patients undergoing surgery with an expected duration of 30 to 90 minutes, and we can only speculate on the EzT's performance over a longer period of time. However, in true emergency situations we would not hesitate to use the EzT up to 8 hours [20]. Another study limitation might be that all patients received muscle relaxants for insertion of both the EzT and ETT. One of the major advantages of supraglottic airway devices is their ease of insertion without the need for muscle relaxation. Even
V. Lorenz et al. in elective surgery, the potential of spontaneous breathing is an advantage of alternate devices [21,22]. In conclusion, the EzT performed similarly to direct laryngoscopy and tracheal intubation in efficacy and safety, at least in elective patients undergoing routine surgical procedures. Further studies are warranted to clarify whether the EzT results in even greater patient satisfaction due to its lesser invasiveness, and to investigate the performance of this new supraglottic airway in true emergency situations.
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