Is Fibreoptic Scoring a Valuable Means to Assess Proper Positioning of the Classic Laryngeal Mask Airway in Paediatric Patients? (Correspondence) (Letter to the Editor‪)‬

The recent article of von Ungern-Sternberg et al (1) describing the fibreoptic assessment of paediatric sized classic laryngeal mask airways (cLMA) was of great interest to us. Their findings indicated that a complete view of the glottic aperture by fibreoscopy was present in 55% of smaller size cLMAs and 75% of larger size cLMAs, but the quality of ventilation by the cLMA was judged as good or adequate and no signs of airway obstruction were noted in any patient. Therefore, we believe it would be more appropriate to conclude that fibreoptic scoring of the cuff position is not an accurate test to assess ventilation function of the cLMA in paediatric patients. When fibreoptically evaluated, moreover, position of the cLMA should not be arbitrarily considered correct when only the glottis or the glottis and posterior surface of the epiglottis are seen. When the epiglottis is seen in the cLMA aperture, a correct positioning of cLMA is also possible. In fact, the value of fibreoscopy as a means of assessing proper positioning and ventilation function of the cLMA has been questioned due to the following reasons. First, the cLMA is designed to enclose the larynx. It has been confirmed that the internal length of the long axis of the cLMA aperture always is greater than the distance between the upper border of the thyroid cartilage and the lower border of the cricoid cartilage (2). Because of individual variation in the size of the larynx, the cLMA sometimes encloses the epiglottis, even when the tip of the cLMA cuff correctly occupies the hypopharynx. For this reason, it is difficult to determine if the cLMA is positioned correctly based on the view of the epiglottis through the fibreoscopy (3). Second, during the fibreoptic examination, a well-placed cLMA should reveal a direct view of the cords (1). Because the epiglottis has been lifted anteriorly, only the base of the epiglottis should be visible at best. By this scoring standard, fibreoscopy often reveals a relatively high incidence of malpositioning of a cLMA in paediatric patients. Also, the incidence of downfolding of the epiglottis is reported to be 5% in infants and 4 to 50% in children (3-5). However, no study has shown that both the ability to obtain adequate ventilation and the ability to generate an adequate airway seal pressure differ significantly between the anatomically well-placed positioning and the misplacement of the cLMA by the fibreoscopy. Third, there is no evidence to support the existence of significant association between malpositioning of the cLMAs by fibreoscopy and complications related to use of the cLMAs, such as airway obstruction, airway trauma or gastric distension with the potential for regurgitation. Fourth, previous studies have demonstrated that complete or partial obstruction of the glottic aperture by the epiglottis can not result in an increased air flow resistance and work of breathing during airway maintenance with the cLMA in children (6). Also, no child develops upper airway obstruction during the airway maintenance, even in patients whose cLMA aperture view is completely covered with the anterior epiglottis (5,6). In our opinion, therefore, there is no need to evaluate the fibreoptic score of the cuff position in every child in whom the cLMA is used, but it is important to know that when the cLMA is well positioned, patent airway and proper clinical performance of the device can be ensured.