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A High, Large Epiglottis Disturbs Proper Positioning of the Laryngeal Mask and Cuffed Oropharyngeal Airway

1998; Lippincott Williams & Wilkins; Volume: 87; Issue: 2 Linguagem: Inglês

10.1097/00000539-199808000-00048

1526-7598

Shin Kawana, Azusa Matsuno, Kenichi Nakabayashi, Syuji Yamamoto, Hiroshi Iwasaki, Hiroaki Watanabe, Akiyoshi Namiki, Toru Hirano,

Foreign Body Medical Cases

The laryngeal mask (LMA) and the cuffed oropharyngeal airway (COPA) are less invasive and easier to place than the endotracheal tube [1,2]. Proper positioning of these devices is, however, less secure than that of endotracheal intubation [3-5]. We report a case of difficult positioning of the LMA and COPA because of a high, large epiglottis, which was revealed by using three-dimensional computed tomography (3D-CT). Case Report A 67-yr-old female patient, weighing 42 kg and 140 cm tall, was scheduled for left knee replacement due to chronic rheumatic arthritis. Mobility of the neck was moderately limited due to atlantoaxial arthrodesis 11 yr earlier. Analgesia was obtained by femoral nerve and sciatic nerve block. After the induction of anesthesia with fentanyl (50 [micro sign]g) and propofol (1.5 mg/kg) IV, the patient was ventilated via a face mask and bag without difficulty. A LMA (size 3; Intavent, Henly-on-Thames, UK) was then inserted using the standard technique, i.e., the tip of the cuff was firmly and continuously applied against the hard palate using the index finger to guide the tube over the back of the tongue. However, it could not be inserted deeply enough, and it moved up when the cuff was inflated. Fiberscopic investigation revealed the epiglottis protruding into the LMA tube between the aperture bars (Figure 1).Figure 1: Fiberscopic view through the laryngeal mask airway. The large epiglottis protruded into the laryngeal mask airway through the aperture bars. The airway became very narrow between the epiglottis and the swollen arytenoid.Pushing the LMA deeper depressed the thick epiglottis downward over the swollen arytenoid and almost closed the airway. However, we found a position in which the patient could breathe through the LMA, although we had to prevent it from moving. Anesthesia was thereafter completed uneventfully. Postoperatively, 3D-CT examination was performed. During scanning, the patient was asked to open her mouth fully without swallowing. Major findings were a large, thick epiglottis; a high epiglottis and hyoid; a short base of the tongue; and a narrow and forward-shifted vestibulum (Figure 2).Figure 2: A sagittal, three-dimensional computed tomography (3D-CT) view of the larynx and the pharynx. A, Normal 3D-CT images of a healthy volunteer. The hyoid is located at the level of C3 and is lower than the mandibular angle. The distance between the oral cavity and the epiglottis is relatively long. B, 3D-CT images of the pharynx and the larynx of our patient. The hyoid is located higher than the mandibular angle. The vestibulum is narrow and shifted forward, probably due to vertebral deformity. The base of the tongue is relatively short compared with that of the healthy volunteer. Vertebral structure is unclear because of arthrodesis. a = epiglottis, b = hyoid, c = vestibulum.Three weeks later, the patient underwent another operation for left elbow replacement. We chose the COPA (Mallinckrodt Medical Inc., Sapporo, Japan), an alternative airway, expecting it to maintain the airway better than with the LMA. Analgesia was obtained by interscalene brachial plexus block. After the administration of propofol 1.5 mg/kg IV, the COPA (size 8) was inserted. Despite a smooth insertion, ventilation was difficult. The fiberscopic view revealed that proximal end of the COPA pushed the epiglottis downward, and the orifice was almost obstructed. Although pulling the COPA upward created some space, the epiglottis then protruded into the COPA. Supporting the chin and adjusting the head position enabled the patient to breathe through the COPA, although the respiratory pattern was moderately retractive. Surgery was, however, completed before endotracheal intubation was required. Discussion The epiglottis is folded downward after the insertion of a LMA in 13%-60% of cases [5]. Aperture bars are designed to prevent the epiglottis from migrating into the tube. In this case, the epiglottis pushed the aperture bars aside and almost got into the LMA tube. Although a downward-folded epiglottis does not generally cause difficult ventilation [6], the large epiglottis and swollen arytenoid in this patient exaggerated obstruction of the airway. Ishimura et al. [4] reported that insertion of the LMA was impossible in a patient with rheumatoid arthritis who had a 90[degree sign] angle between the oral cavity and the pharyngeal axes. Such an acute angle kinks the LMA and prevents further advancement into the hypopharynx. The angle estimated by using 3D-CT was approximately 80[degree sign] in our case, which may have been responsible for the difficult positioning. In our case, however, our concern was unstable positioning of the LMA rather than impossible insertion. Despite the difficulty in deep insertion, the distal tip of the LMA must have advanced to the hypopharynx; otherwise, the epiglottis and vestibulum could not have been recognized by using a fiberscope (Figure 1). The concept of the COPA is based on a Guedel airway with a cuff that lifts the base of the tongue and seals the airway. Choosing an appropriate size is important for airway maintenance, as mentioned in the product packaging. Although the instruction manual advises using a COPA one size larger than expected, the proximal end pushes the epiglottis downward and obstructs the airway if too large a COPA is used. Even the size 8 COPA, the smallest, may be too large for a small female patient, as in this case. The anatomical features of the patient seem to be a more likely explanation. The hyoid is usually located lower than the mandibular angle at rest (Figure 2A). The hyoid and the epiglottis of our patient were clearly located higher than the mandibular angle compared with a normal volunteer (Figure 2). The short base of the tongue would not allow the LMA to be settled over the larynx, nor could the COPA maintain the airway without depressing the epiglottis. This combination of conditions, i.e., the high, large epiglottis; limited neck mobility; and small body, may be responsible for the difficult positioning of both airway devices. The 3D-CT scan provides clearer images of anatomical features [7] than those obtained by using conventional radiological methods [8-10]. The advantages of 3D-CT are short scanning time, high resolution, and repeated evaluation after obtaining data. Although the information can only be obtained postoperatively in most cases, it is advantageous to inform patients with a difficult airway about their anatomical features in case they must undergo another general anesthesia. We report difficult positioning of the LMA and COPA. Our patient's high, large epiglottis disturbed proper positioning. Using 3D-CT is of great help in studying the proper positioning of the LMA and COPA in relation to anatomical features in such cases.