Original Article. An assessment of oropharyngeal airway position using a fibreoptic bronchoscope. Summary. Introduction. Methods

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1 Original Article doi: /anae An assessment of oropharyngeal airway position using a fibreoptic bronchoscope S. H. Kim, 1 J. E. Kim, 1 Y. H. Kim, 2 B. C. Kang, 1 S. B. Heo, 3 C. K. Kim 4 and W. K. Park 5 1 Clinical Assistant Professor, 3 Clinical Instructor, 4 Resident, 5 Professor, Department of Anaesthesiology and Pain Medicine, Anaesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea 2 Assistant Professor, Department of Anaesthesiology and Pain Medicine, Haeundae Paik Hospital, Inje University, Busan, Korea Summary Selecting the appropriate oropharyngeal airway for safe and effective airway management is important in clinical practice. In this prospective observational study, we examined the position of the distal end of oropharyngeal airways using a fibreoptic bronchoscope. We enrolled 149 adults (72 men and 77 women). The correct airway size was determined by inserting four adult sizes Guedel airway (Hudson RCI; Teleflex Medical, Research Triangle, Park, NC, USA) (sizes 8, 9, 10 and 11) sequentially in anaesthetised patients. The best fit airway was size 10 in 45 (62%) men, and size 9 in 58 (75%) women. However, when these airways were inserted, the distal end of the airway either touched or passed beyond the epiglottis tip in 20 (27%) men and six (8%) women, respectively. When a size-9 airway was inserted in men and a size-8 airway inserted in women, the distal ends were obstructed by the tongue in three (2%) patients. In conclusion, a size-9 airway in men and a size-8 airway in women are the most acceptable sizes for adults of average height.... Correspondence to: W. K. Park wkp7ark@yuhs.ac Accepted: 9 October 2013 Introduction The oropharynx is the primary site of upper airway obstruction in unconscious or anaesthetised patients, because relaxation of the tongue and muscles of the jaw result in posterior movement of the tongue and epiglottis, which may obstruct the airway [1]. An oropharyngeal (Guedel) airway helps to establish a patent airway by preventing the tongue from covering the epiglottis [2]. Oropharyngeal airways are frequently used as important airway adjuncts in emergency care [3] for short-term airway management during the perianaesthetic period [4], and to facilitate manual ventilation using a facemask [5]. The use of an oropharyngeal airway is simple, but it is essential to select the appropriate size because, if the oropharyngeal airway is too small, the distal end will be obstructed by the tongue. Radiographic assessment of the position of oropharyngeal airways also demonstrated that the distal end of the airway may lodge in the vallecula or can be obstructed by the epiglottis [6]. It may also cause laryngospasm and traumatic injury to laryngeal structures if it is too large [6]. The purpose of this study was to evaluate the position of the distal ends of four Guedel airway sizes using a fibreoptic bronchoscope and to determine the correct size for adults. Methods Following approval by the local Institutional Review Board, written informed consent was obtained from all patients. Adults aged between 20 and 75 years of ASA 2013 The Association of Anaesthetists of Great Britain and Ireland 53

2 Kim et al. Oropharyngeal airway position physical status 1 2 scheduled for elective ear, nose and throat surgery under general anaesthesia were considered eligible for inclusion in the study. Patients with known abnormal airway anatomy, cervical spine pathology, a history of difficult intubation, neurological disease, cardiovascular disease or dental problems were excluded. On arrival in the anaesthetic room electrocardiography, pulse oximetry, and non-invasive blood pressure attached and intravenous access obtained. Patients were given 0.2 mg glycopyrronium intravenously and asked to lie supine with their head maintained in a neutral position and 3 4 cm above the plane of the table using a rubber ring to support the head. Anaesthesia was induced with 1.5 mg.kg 1 propofol, 1.0 lg.kg 1 remifentanil, 0.5 mg.kg 1 rocuronium, and the patients lungs were manually ventilated with oxygen at a flow rate of 4 l.min 1 and 4% 5% sevoflurane via a facemask, with the head held in an extended position by gentle traction on the symphysis menti in an anterocephalic direction. When anaesthesia was considered to be deep enough, Guedel airways (Hudson RCI, Teleflex Medical, Research Triangle Park, NC, USA) were inserted. Four different sizes (8 (8 cm, green), 9 (9 cm, yellow), 10 (10 cm, red) and 11 (11 cm, orange)) were sequentially inserted. The sizes marked on the airways, according to the ISO (International Organization for Standardization) standard, indicate the horizontally measured length from the flanged end to the distal end of the airway. The airway was inserted into the mouth with the tip positioned upwards and rotated 180, then advanced until the flange of the airway made contact with the upper incisors. The curvilinear distance from the incisors to the epiglottis tip was measured with a flexible fibreoptic bronchoscope (Olympus LF-GP; Olympus Optical Co., Tokyo, Japan) after passing the fibrescope through the lumen of the airway. Fibreoptic findings at the distal end of the airway were recorded. When the length of an airway was shorter than the distance from the incisors to the tip of the epiglottis, a piece of tape was placed adjacent to the fibrescope at the position of the flange as a reference point after the distal tip of the fibrescope was placed adjacent to the epiglottis. The distance from the distal end of airway to the epiglottis tip was calculated by subtracting the measured length of the airway itself from the length of the reference point on the fibrescope. The length of the airway itself was measured from the flange to the distal end by passing the fibrescope through the lumen of the airway (size 8 = 9 cm, size 9 = 10 cm, size 10 = 11.5 cm and size 11 = 12.5 cm). When the airway was longer than the distance from the incisors to the epiglottis tip, the airway was partly withdrawn until the distal end was positioned at the tip of the epiglottis. The point of the airway adjacent to the incisors was marked with a marking pen, and the length from the flange to the marking site was measured with a ruler after removing the airway. During insertion of each airway and measurement, the facemask was removed and ventilation ceased. After measurements were performed, the airway was removed and mask ventilation recommenced until the next airway was inserted. After all measurements were completed, orotracheal intubation was performed using an appropriately sized tracheal tube, and anaesthesia was maintained with sevoflurane and remifentanil. An appropriately sized airway was defined as when the distal end was located on the base of tongue with no obstructed view by the tongue or the epiglottis, the distal end did not pass beyond the epiglottis and the proximal flange was in contact with the upper and lower central incisors. Sample sizes of 72 men and 77 women were calculated to obtain an a level of 0.05 and 80% power by the interclass correlation method using a power analysis and sample size package (NCSS, LLC., Kaysville, UT, USA). Data normally distributed were assessed using the Kolmogorov Smirnov test. All statistical data were analysed using SAS software (version 9.2; SAS Institute, Inc., Cary, NC, USA). A p value of less than 0.05 was considered statistically significant. Results One hundred and forty-nine patients (72 males and 77 females) were included in the study and their characteristics are shown in Table 1. The average height of our patients was similar to the average height of the Korean adult population in a 2009 national survey (males = cm, females = cm). In men, whereas the mean length of the size 8, 9 and 10 airways was shorter than the distance from the The Association of Anaesthetists of Great Britain and Ireland

3 Kim et al. Oropharyngeal airway position Anaesthesia 2014, 69, incisors to the epiglottis tip, the size-11 airway was longer (Fig. 1). In women, the length of the size-8 and -9 airways was shorter, but the size-10 and -11 airways were longer. For size-9 airways in men and size-8 airways in women, the mean (SD) differences in distance Table 1 Baseline characteristics of the 149 patients included in the study. Values are mean (SD). Men (n = 72) Women (n = 77) Age; years 43.6 (15.4) 43.7 (15.1) Height; cm (6.5) (6.7) Weight; kg 69.1 (8.7) 58.2 (8.0) Distance between the distal end of oropharyngeal airways and the epiglottis tip (cm) No. 8 No. 9 No. 10 No. 11 Oropharyngeal airway sizes Figure 1 Mean distance between the distal end of the oropharyngeal airway and the epiglottis tip for each airway size in men ( ) and women ( ). The sizes marked on the airways indicate the horizontally measured length (cm) from the flanged end to the distal end of the airway. Error bars indicate SD. between the distal end of the airway and the epiglottis tip were 2.1 (0.7) cm and 2.1 (0.6) cm, respectively. Fibreoptic findings at the distal end of the different sized airways are shown in Table 2. In men, the distal end of the airway appeared to be obstructed by the tongue in seven (9%) patients when the size-8 airway was inserted and in one (1%) patient when the size-9 airway was inserted. The distal end of the airway either touched or passed beyond the epiglottis tip in 20 (27%) patients when the size-10 airway was inserted and did so in 65 (90%) patients when the size-11 airway was inserted. In women, the distal end of the airway appeared to be obstructed by the tongue in two (3%) patients when the size-8 airway was inserted. The distal end either touched or passed beyond the epiglottis tip in six (8%) patients when the size-9 airway was inserted, in 64 (83%) patients when the size-10 airway was inserted, and in 76 (98%) patients when the size- 11 airway was inserted. No patient experienced oxygen desaturation, laryngeal trauma or dental injury during the study. Discussion In the present study, considering the risk of airway obstruction or trauma that may occur with inappropriately sized oropharyngeal airways, the size-9 and size-8 airways appeared to be suitable for the majority of men and women, respectively. When the best fit airway for an individual was defined as positioning of the distal end of the airway as close as possible to the epiglottis tip without any obstruction, the most appropriate airways in our study population were size 10 for men and size 9 for women. However, for these sizes, the distal ends of the airway Table 2 Fibreoptic findings as the scope emerged through the distal end of the oropharyngeal airway. Values are number of patients (proportion). Men (n = 72) Airway size Women (n = 77) Airway size Epiglottis visible 65 (90) 71 (99) 52 (72) 7 (10) 75 (97) 71 (92) 13 (17) 1 (1) Airway obstructed by tongue 7 (10) 1 (1) (3) Airway touches epiglottis tip (8) 3 (4) 0 3 (4) 7 (9) 1 (1) Airway passes beyond epiglottis tip (20) 62 (86) 0 3 (4) 57 (74) 75 (97) 2013 The Association of Anaesthetists of Great Britain and Ireland 55

4 Kim et al. Oropharyngeal airway position either touched or passed beyond the epiglottis tip in a significant number of patients. Thus, inserting these sized airways as the first choice would result in larger airways than required in many adults. When size-9 airways in men and size-8 airways in women were inserted, the distal ends of the airway were obstructed by the tongue in only three (2%) patients, and the epiglottis tip was clearly visible through the distal end of the airway during fibreoptic examination in the vast majority of patients. Our results, therefore, indicate that the appropriate first-choice airway sizes are size-9 in men and size-8 in women. Although external measurements to determine the correct size of airway, such as the distance from the tragus of the ear to the angle of the mouth [7], the distance from the corner of the mouth to the angle of the mandible [7, 8] or the distance from the incisors to the angle of mandible [9], have been used traditionally, our results suggest that the appropriate sized airway may be chosen for the majority of patients without the need for external measurements. When inserting a size-9 airway in men and a size- 8 airway in women, the distances from the distal end of the airway to the epiglottis tip were similar. In our study, the positioning of the distal end of airway within 2 cm of the epiglottis tip is acceptable and avoids obstruction by the tongue. The discrepancy between each person s anatomical difference in tongue size, palate height and mandibular position [10, 11] and a fixed length-to-depth ratio for each airway size may affect the distance between the distal end of the airway and the epiglottis tip when selecting airway sizes. To compare our results with other commonly used Guedel-type airways such as Portex (Smiths Medical, Ashford, UK) and Berman airways (Vital Signs; GE healthcare, Totowa, NJ, USA), we measured the dimensions of each size of airway. Despite the different manufacturers, these airways had the same horizontally measured length from the flanged proximal end to the distal end according to marked sizes and similar curvilinear lengths of internal lumen with only a small discrepancy (0 3 mm) when compared with the airways used in our study. In this study, there were 38 (52%) men who were taller than 170 cm, and 35 (45%) women who were taller than 160 cm. The mean (range) height for men and women in our study was ( ) cm and ( ) cm, respectively, and because of the relatively small range of heights in our study, the results may not be applicable to patients who are taller than 180 cm. Clinically, the correct size of oropharyngeal airway is one that provides a patent airway, allows effective mask ventilation and one that does not cause laryngospasm or trauma to the airway. Although we did not measure respiratory parameters such as tidal volume and peak airway pressure after inserting each airway, we assumed that there would be clear, nonobstructed, ventilation (except in those patients where the fibreoptic view was obstructed by the tongue), because we could confirm airway patency, whilst advancing the tip of the fibrescope to the epiglottis through the oral airway. In the neck extended position, Marsh et al. [6] observed partially obstructed ventilation when the oropharyngeal airway was obstructed by the tongue, but noted clear ventilation even when the airway was obstructed by the epiglottis as assessed radiologically. In conclusion, size-9 and size-8 oropharyngeal (Guedel) airways appear to be the appropriate sizes for clinical use in men and women of average height, respectively. We suggest that these should be the firstchoice sizes and, if there are signs of airway obstruction, use of an airway one size larger should be considered. Competing interests No external funding and no competing interests declared. References 1. Boidin MP. Airway patency in the unconscious patient. British Journal of Anaesthesia 1985; 57: Baskett TF. Arthur Guedel and the oropharyngeal airway. Resuscitation 2004; 63: Roberts K, Allison KP, Porter KM. A review of emergency equipment carried and procedures performed by UK front line paramedics. Resuscitation 2003; 58: Dob DP, Shannon CN, Bailey PM. Efficacy and safety of the laryngeal mask airway vs Guedel airway following tracheal extubation. Canadian Journal of Anesthesia 1999; 46: Koga K, Sata T, Kaku M, Takamoto K, Shigematsu A. Comparison of no airway device, the Guedel-type airway and the Cuffed Oropharyngeal Airway with mask ventilation during manual in-line stabilization. Journal of Clinical Anesthesia 2001; 13: Marsh AM, Nunn JF, Taylor SJ, Charlesworth CH. Airway obstruction associated with the use of the Guedel airway. British Journal of Anaesthesia 1991; 67: The Association of Anaesthetists of Great Britain and Ireland

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