Anesth Pain Med 2013; 8: 271-278 ￭Clinical Research￭

Analysis of predictive factors for difficult ProSeal insertion and suboptimal positioning

*Department of and Pain Medicine, Samsung Medical Center, Ewha Womans University School of Medicine, Seoul, Korea

Joo Hyun Jun*, Jong Hak Kim, Hee Jung Baik, Youn Jin Kim, and Doo Gyun Yun

Background: There has been controversy about predicting INTRODUCTION difficult LMA insertion and suboptimal position. Our aim was to evaluate bedside predictors for difficult LMA ProSealTM (PLMA) The laryngeal mask airway (LMA) is used as a supraglottic insertion and suboptimal position. Methods: As the potential predictive factors for difficult PLMA device providing a secure airway for patients undergoing insertion and suboptimal position, we considered male gender, elective surgical procedures requiring general . In increased body mass index (BMI), seven individual items suggesting addition to conventional use as device maintaining airway, difficult airway [modified Mallampati classification ≥ III, inter-incisor LMA is widely used as an intubation conduit in case of failed distance ≤ 5 cm, thyromental distance ≤ 6.5 cm, head/neck movement ≤ 90o, history of difficult intubation, buck of teeth ≥ intubation or guide for diagnostic and therapeutic fiberoptic moderate, upper lip bite test (ULBT) ≥ II] and ≥ 3 of total airway bronchoscopy because the distal end of an optimally placed score which is the sum of scores assessed by a score of 0, 1, 2 LMA faced the laryngeal inlet [1-3]. Therefore, LMA should in seven individual items. The PLMA position was assessed by be inserted in anatomically optimal position to minimize fiberoptic bronchoscopy to determine whether these predictors predict suboptimal position of PLMA (fiberoptic score ＜ 3, as graded unwanted events and maximize their intended function in on a standard fiberopitc scale). We also investigated the effect of various anesthetic practices. predictive factors on the failure of the first insertion of PLMA and However, the success rate of LMA insertion varies from 77– time required for successful Proseal LMA insertion on the first – attempt. 90%, and suboptimal positioning of the LMA occurs in 30 66% Results: 154 patients were enrolled in the study. The total airway of cases [4-7]. Moreover, an emergency pathway is needed for score did have a significant relationship with the fiberoptic findings. the algorithm if the LMA fails to secure The male gender and ULBT I of investigated predictors did the airway in the ‘cannot ventilate, cannot intubate’ situation significantly correlate with failure on the first insertion of PLMA. We did not find any significant relationship between the predictive [8]. Incomplete mask sealing due to LMA malposition increases factors and PLMA insertion time on the first attempt. the risk of orpharyngeal air leakage or gastric insufflations Conclusions: The male gender and ULBT I indicate difficult PLMA [9,10]. Epiglottic downfolding makes difficult to visualize insertion, and the total airway score ≥ 3 indicates suboptimal laryngeal opening for effective conduit for or position of PLMA. (Anesth Pain Med 2013; 8: 271-278) bronchoscopy. Therefore, it is necessary to recognize when Key Words: Difficult airway, Fiberoptic score, Laryngeal mask LMA insertion will be difficult and prepare for an emergency airway. alternative pathway. There has been controversy about predicting difficulty with Received: April 2, 2013. LMA insertion and suboptimal position of LMA. Some authors Revised: 1st, April 18, 2013; 2nd, July 26, 2013. reported that the Mallampati classification predicts difficulty in Accepted: August 8, 2013. achieving an adequate airway with the LMA [11], whereas Corresponding author: Jong Hak Kim, M.D., Department of Anesthesiology and Pain Medicine, Ewha Womans University School of Medicine, 911-1, others reported that insertion and placement of LMA are Mok-dong, Yangcheon-gu, Seoul 158-710, Korea. Tel: 82-2-2650-5285, independent of the Mallampati classification [12,13]. This study Fax: 82-2-2655-2924, E-mail: [email protected] It was presented The 88th Annual Scientific Meeting of the Korean was undertaken to assess whether bedside predictive factors TM Society of Anesthesiologists, November 2011, Grand Hilton, Seoul, predict suboptimal position of ProSeal LMA (PLMA). We Korea. also investigated the effect of predictive factors on the

271 272 Anesth Pain Med Vol. 8, No. 4, 2013 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏 difficulty in PLMA insertion. insertion as having no gas leak at an airway pressure of 20

cmH2O, bilaterally equal breath sounds on chest auscultation, the MATERIALS AND METHODS absence of air influx in the gastrointestinal tract, and a normal rectangular shaped capnogram. A failed PLMA insertion was Patients, ranging from 18 to 65 years old, of American characterized as not having advanced into the pharynx, a severe Society of Anesthesiologists physical status 1 or 2, and who gas leak through the airway or the drain tube, an absence of were undergoing elective surgery under general anesthesia were normal lung ventilation, or an abnormal end-tidal carbon dioxide included in our study. Our ethics committee approved this pressure (PETCO2). If insertion was failed, positive pressure study and we obtained written informed consent from all ventilation was administered via a face mask for 1 minute, and patients. Patients with cervical spine injury, severe cardio- then PLMA insertion was reattempted. Unsuccessful insertion vascular disease, gastroesophageal reflux, poor dentition, or air- after three attempts was regarded as failure. way anatomic abnormalities that required awake fiberoptic in- We recorded the success/failure, number of attempts, and the tubation were excluded from the study. Their demographic data time required for PLMA insertion for each patient. The PLMA are shown in Table 1. insertion time was measured from when the operator first Prior to anesthesia induction in the operating room, all pa- opened the patient’s mouth to when he removed his hand from tients underwent airway assessment according to seven pre- the patient after inserting the PLMA. We analyzed the data for dictive factors including the modified Mallampati classification, insertion time of the 132 patients in which PLMA insertion interincisor distance, thyromental distance, head/neck movement was successfully accomplished on the first attempt. [14,15], history of difficult intubation, the presence of buck The position of the PLMA was fiberoptically (LF-GP, teeth, and the upper lip bite test (ULBT) [16,17]. A score of 0, Olympus, Japan) observed from the mask aperture bar and a 1, or 2 was assigned for each criteria and the sum of all the fiberoptic score was assigned. The fiberoptic scoring system scores constituted the total airway score (Table 2). was as follows: 4: only vocal cords were visualized; 3: the Patients were then preoxygenated with 100% oxygen for two vocal cords and the posterior epiglottis were visualized; 2: the minutes. Anesthesia was induced with intravenous fentanyl 1 vocal cords and the anterior epiglottis were visualized; 1: μg/kg, 0.04 mg/kg, and followed by propofol 2 unable to visualize vocal cords but PLMA adequately mg/kg. Maintenance of anesthesia was achieved with a functioning; 0: unable to visualize vocal cords and PLMA continuous infusion of 1% propofol at 6 mg/kg/hr, and failing to function [18]. A fiberoptic score of 3 or more was neuromuscular relaxation was achieved with rocuronium 0.3 regarded as appropriate PLMA positioning, whereas a score mg/kg. After 3 minutes of controlled ventilation via a facemask less than 3 meant suboptimal PLMA positioning. We analyzed with 100% oxygen 6 L/min, a researcher experienced with the data for fiberoptic scores (FS ≥ 3 or FS ＜ 3) of the PLMA (ProSealTM LMA, LMA North America Inc., USA) and 148 patients who had successful insertion of PLMA within who had not participated in the airway assessment, placed the PLMA. The PLMA size was chosen according to the patient’s weight: ＜ 50 kg: size 3; 50–70 kg: size 4; and ＞ 70 kg: size Table 2. Preoperative Assessment of the Airway Score for Predicting 5. After inserting the PLMA, the cuff was inflated according to Difficult Airway the “just seal” method, with the minimum volume of air 0 1 2 required to prevent gas leak. We defined a successful PLMA Modified Mallampati class Class I/II Class III Class IV Inter-incisor distance ＞5 cm 5–4 cm ＜4 cm Thyro-mental distance ＞6.5 cm 6.5–6.0 cm ＜6 cm o o o Table 1. Demographic Data (n = 154) Head/Neck movement ＞90 90 ＜90 History of D/I No Questionable Definite Age (yr) 41.2 ± 14.5 Buck teeth No Mild Moderate Gender (M/F) 84/70 ULBT I II III Height (cm) 165.3 ± 9.8 Weight (kg) 65.0 ± 11.1 D/I: difficult intubation, ULBT: upper lip bite test, ULBT I: Lower BMI (kg/m2) 23.8 ± 3.3 incisors can hide mucosa of the upper lip, ULBT II: Lower incisors partially hide mucosa of the upper lip, ULBT III: Lower incisors Values are mean ± SD or number of patients. BMI: body mass index. unable to touch mucosa of the upper lip. Joo Hyun Jun, et al：Predictors for difficult PLMA insertion 273 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏 three attempts. analysis for fiberoptic scores. In our study, we expected that PLMA placement would be difficult in the following situations: male gender, increased RESULTS body mass index, a modified Mallampati classification of III or more, interincisor distance of 5 cm or less, a thyromental One hundred fifty four patients were enrolled in our study. distance of 6.5 cm or less, head/neck movement of 90o or There was no one who had history of difficult intubation. less, history of difficult intubation, the presence of buck teeth, Thus, as predictor, history of difficult intubation was excluded an ULBT score of III or more, or a total airway score of 3 from analysis. Of the 154 patients, 84 were male gender, 2 or more. We analyzed the relationship between these predictive were found to have a modified Mallampati classification of at factors and the success/failure of PLMA insertion, the time least III, 117 had an interincisor distance of 5 cm or less, and required for proper insertion on the first attempt, and the 9 had a thyromental distance of 6.5 cm or less. One hundred fiberoptic score. twelve patients exhibited head/neck movement of 90o or less, 12 had buck teeth, 56 had an ULBT of II or more, and 78 Statistical analyses were found to have a total airway score of 3 or more. The SPSS software Version 17.0 was used for all statistical Failure of PLMA insertion after three attempts occurred in 6 analyses. The age, height, weight, and BMI of the patients, as out of 154 patients, meaning that overall success rate of well as the time required for successful insertion on the first attempt were expressed as means ± standard deviations. The success/failure of PLMA insertion on the first attempt and the Table 3. The Characteristics of Pateints with Failure of Proseal LMA fiberoptic scores were expressed as frequencies. P values ＜ Insertion (n = 6) 0.05 were considered statistically significant. Predictors (n = 6) For the 148 patients who had successful insertion of PLMA Gender M 4 within three attempts, the fiberoptic scores (FS ≥ 3 or FS ＜ F 2 3) were also analyzed in relation to each predictive criteria Modified Mallampati class I/II 6 using the chi-square test or Fisher’s exact test. The unpaired III/IV 0 t-test was used for analyzing the difference in BMI according to Interincisor distance ＞ 5 cm 1 ≤ 5 cm 5 the fiberoptic scores (FS ≥ 3 or FS ＜ 3). Multivariate logistic Thyromental distance ＞ 6.5 cm 6 analysis for fiberoptic scores ＜ 3 was performed with two ≤ 6.5 cm 0 models including gender, BMI, and total airway score (model 1) Head/Neck movement ＞ 90o 0 o or individual items suggesting difficult airway (model 2). ≤ 90 6 Buck teeth No 5 The success/failure of PLMA insertion on the first attempt Mild or Moderate 1 was evaluated in relation to each predictive factor using the ULBT I 5 chi-square test or Fisher’s exact test. The unpaired t-test was II/III 1 used for analyzing the difference in BMI according to the Total airway score ≤ 2 3 ≥ 3 3 success/failure of PLMA insertion on the first attempt. Multivariate logistic analysis for failure of PLMA insertion was Values are number of patients. Failure of Proseal LMA Insertion: performed with the same models as those in the analysis for unsuccessful insertion after three attempts, not having advanced into the pharynx, a severe gas leak through the airway or the drain fiberoptic scores. tube, an absence of normal lung ventilation, or abnormal end-tidal For the 132 patients who had successful PLMA insertion on carbon dioxide pressure, ULBT: upper lip bite test, ULBT I: Lower the first attempt, the unpaired t-test was used for analyzing the incisors can hide mucosa of the upper lip, ULBT II: Lower incisors difference in PLMA insertion time according to each predictive partially hide mucosa of the upper lip, ULBT III: Lower incisors unable to touch mucosa of the upper lip, Total airway score: A factor except BMI. Nonparametric Spearman correlation was score of 0, 1, or 2 was assigned for each criteria (the modified used to examine the relationship between PLMA insertion time Mallampati classification, interincisor distance, thyromental distance, on the first attempt and increased BMI. Multivariate linear head/neck movement, history of difficult intubation, the presence of buck teeth, and the upper lip bite test) and the sum of all the regression analysis for PLMA insertion time on the first scores constituted the total airway score. Total airway score ≥ 3: attempt was performed with the same models as those in the difficult airway predicted. 274 Anesth Pain Med Vol. 8, No. 4, 2013 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏

Table 4. The Fiberoptic Score (FS) and Predictors (n = 148) Table 5. Independent Risk Factors for the Fiberoptic Score (FS) ＜ 3 (n = 148): Result of Multivariate Analysis FS ≥ 3 FS ＜ 3 Predictors P value (n = 71) (n = 77) Adjusted Predictors for FS ＜ 3 95% CI P value OR Gender (M) 35 (49.3%) 45 (58.4%) 0.322 BMI (kg/m2) 23.6 ± 3.6 23.9 ± 3.0 0.686 Model 1 Modified Mallampati class (III/IV) 0 (0%) 2 (2.6%) 0.497 Gender (M) 1.527 [0.782–2.984] 0.215 Interincisor distance (≤5 cm) 52 (73.2%) 60 (77.9%) 0.567 BMI (kg/m2) 1.010 [0.913–1.116] 0.851 Thyromental distance (≤6.5 cm) 4 (5.6%) 5 (6.5%) 1.000 Total airway score (≥3) 2.465 [1.264–4.806] 0.008* Head/Neck movement (≤90o) 47 (66.2%) 59 (76.6%) 0.202 Model 2 Buck teeth (mild or moderate) 7 (9.9%) 4 (5.2%) 0.222 Gender (M) 1.508 [0.725–3.135] 0.272 ULBT (II/III) 26 (36.6%) 29 (37.7%) 1.000 BMI (kg/m2) 1.007 [0.911–1.114] 0.884 Total airway score (≥3) 28 (39.4%) 47 (61.0%) 0.013* Interincisor distance (≤5 cm) 1.264 [0.534–2.993] 0.594 Thyromental distance (≤6.5 cm) 1.377 [0.321–5.910] 0.666 Values are mean ± SD or number of patients. The P value was Head/Neck movement (≤90o) 1.428 [0.631–3.230] 0.393 obtained with Fisher’s exact test or unpaired t-test. There is Buck teeth (mild or moderate) 0.579 [0.158–2.117] 0.409 significant correlation between total airway score of ≥ 3 and FS ＜ ULBT (II/III) 0.922 [0.454–1.870] 0.821 3. FS: fiber optic score, FS ≥ 3: only vocal cord seen or cord and posterior epiglottis seen, FS ＜ 3: cord plus anterior epiglottis seen The P value was obtained with logistic regression analysis. Each or cord not seen, but function adequate. BMI: body mass index, model includes all variables listed in the table and finally total airway ULBT: upper lip bite test, ULBT I: Lower incisors can hide mucosa of score (≥ 3) remained as a significant predictor for suboptimal the upper lip, ULBT II: Lower incisors partially hide mucosa of the position of PLMA. OR: odds ratio, CI: confidence interval, BMI: body upper lip, ULBT III: Lower incisors unable to touch mucosa of the mass index, ULBT: upper lip bite test, ULBT I: Lower incisors can upper lip. Total airway score: A score of 0, 1, or 2 was assigned for hide mucosa of the upper lip, ULBT II: Lower incisors partially hide each criteria (the modified Mallampati classification, interincisor mucosa of the upper lip, ULBT III: Lower incisors unable to touch distance, thyromental distance, head/neck movement, history of difficult mucosa of the upper lip. Total airway score: A score of 0, 1, or 2 intubation, the presence of buck teeth, and the upper lip bite test) was assigned for each criteria (the modified Mallampati classification, and the sum of all the scores constituted the total airway score. interincisor distance, thyromental distance, head/neck movement, Total airway score ≥ 3: difficult airway predicted. *P ＜ 0.05. history of difficult intubation, the presence of buck teeth, and the upper lip bite test) and the sum of all the scores constituted the total airway score. Total airway score ≥ 3: difficult airway predicted. PLMA insertion was 96%. Among these 6 patients, 4 were male gender, 3 had a total airway score of 3 or more. All 6 patients had at least one predictive factor of difficult airway airway score ≥ 3 (P = 0.008, adjusted odds ratio = 2.465, (Table 3). 95% confidence interval = 1.264–4.806) was found to be a significant predictive factor for fiberoptic score ＜ 3 (Table 5). The suboptimal position of PLMA and predictors The failure on the first insertion of PLMA and Of the 148 patients who had successful PLMA insertion, 77 Predictors patients (52%) were found to have suboptimal position (fiberioptic score ＜ 3). When compared those with a Failure of PLMA insertion on the first attempt occurred in fiberoptic score of at least 3, to those with a fiberoptic score 23 patients resulting in a first attempt failure rate of 14%. We of less than 3, we found no significant difference between the compared those with success of PLMA insertion on the first two groups in relation to the predictive factors (P ＞ 0.05), attempt to those with failure of PLMA insertion. The predictive except for the total airway score (P = 0.013) by univariate factors did not influence on the failure of PLMA insertion on analysis (Table 4). Male gender, increased BMI, inter-incisor the first attempt by univariate analysis (P ＞ 0.05) (Table 6). distance ≤ 5 cm, thyromental distance ≤ 6.5 cm, head/neck Male gender, increased BMI, inter-incisor distance ≤ 5 cm, movement ≤ 90o, buck of teeth ≥ moderate, upper lip bite thyromental distance ≤ 6.5 cm, head/neck movement ≤ 90o, test ≥ II and total airway score ≥ 3 were analyzed for buck of teeth ≥ moderate, upper lip bite test ≥ II and total multivariate analysis. As predictor, a modified Mallampati airway score ≥ 3 were analyzed for multivariate analysis. As classification was excluded from multivariate analysis because predictor, a modified Mallampati classification was excluded none of patients with a fiberoptic score of 3 or more had a from multivariate analysis because none of patients who failed modified Mallampati classification ≥ III (Table 4). Total on the first insertion of PLMA had a modified Mallampati Joo Hyun Jun, et al：Predictors for difficult PLMA insertion 275 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏

Table 6. The Success/Failure on the First Insertion of Proseal LMA Table 7. Independent Risk Factors for Failure on the First Insertion and Predictors (n = 154) of Proseal LMA: Result of Multivariate Analysis

Success Failure Predictors for failure on the first Adjusted Predictors P value 95% CI P value (n = 132) (n = 22) insertion OR

Gender (male) 68 (51.5%) 16 (72.7%) 0.07 Model 1 BMI (kg/m2) 23.8 ± 3.4 23.5 ± 2.4 0.734 Gender (male) 2.556 [0.937–6.975] 0.067 Modified Mallampati class (III/IV) 2 (1.5%) 0 (0%) 1.00 BMI (kg/m2) 0.965 [0.832–1.119] 0.636 Interincisor distance (≤5 cm) 101 (76.5%) 16 (72.7%) 0.79 Total airway score (≥3) 1.020 [0.408–2.551] 0.966 Thyromental distance (≤6.5 cm) 8 (6.1%) 1 (4.5%) 1.00 Model 2 Head/Neck movement (≤90o) 97 (73.5%) 15 (68.2%) 0.61 Gender (Male) 3.551 [1.119–11.267] 0.031* Buck teeth (mild or moderate) 9 (6.8%) 3 (13.6%) 0.38 BMI (kg/m2) 0.973 [0.832–1.138] 0.733 ULBT (II/III) 52 (39.4%) 4 (18.2%) 0.06 Interincisor distance (≤5 cm) 1.364 [0.416–4.474] 0.608 Total airway score (≥3) 67 (50.8%) 11 (50%) 1.00 Thyromental distance (≤6.5 cm) 2.001 [0.178–22.543] 0.575 Head/Neck movement (≤90o) 0.772 [0.244–2.439] 0.660 Values are mean ± SD or number of patients. The P value was Buck teeth (mild or moderate) 2.574 [0.562–11.783] 0.223 obtained with Fisher’s exact test or unpaired t-test. There were no ULBT (II/III) 0.296 [0.091–0.963] 0.041* significant correlations between the success/failure on the first insertion of Proseal LMA and the predictors. BMI: body mass index, The P value was obtained with logistic regression analysis. Each ULBT: upper lip bite test, ULBT I: Lower incisors can hide mucosa model includes all variables listed in the table and finally male of the upper lip, ULBT II: Lower incisors partially hide mucosa of gender and ULBT (I) remained as a significant predictor for failure the upper lip, ULBT III: Lower incisors unable to touch mucosa of on the first insertion of PLMA. OR: odds ratio, CI: confidence the upper lip. Total airway score: A score of 0, 1, or 2 was interval, BMI: body mass index, ULBT: upper lip bite test, ULBT I: assigned for each criteria (the modified Mallampati classification, Lower incisors can hide mucosa of the upper lip, ULBT II: Lower interincisor distance, thyromental distance, head/neck movement, incisors partially hide mucosa of the upper lip, ULBT III: Lower history of difficult intubation, the presence of buck teeth, and the incisors unable to touch mucosa of the upper lip. Total airway upper lip bite test) and the sum of all the scores constituted the score: A score of 0, 1, or 2 was assigned for each criteria (the total airway score. Total airway score ≥ 3: difficult airway predicted. modified Mallampati classification, interincisor distance, thyromental distance, head/neck movement, history of difficult intubation, the presence of buck teeth, and the upper lip bite test) and the sum of classification ≥ III (Table 6). Male gender (P = 0.031, all the scores constituted the total airway score. Total airway score ≥ 3: difficult airway predicted. adjusted odds ratio = 3.551, 95% confidence interval = 1.119– 11.267) was found to be a significant predictive factor for failure of PLMA insertion (Table 7). However, ULBT II/III (P significant relationship between the predictive factors and = 0.041, adjusted odds ratio = 0.296, 95% confidence interval PLMA insertion time on the first attempt (Data not shown). = 0.091–0.963) was inversely correlated with failure of PLMA insertion on the first attempt (Table 7). In other words, patients DISCUSSION with ULBT I had more failure of PLMA insertion on the first attempt than ULBT II/III. The purpose of this study was to evaluate the effects of bedside predictive factors on the fiberoptic scores of PLMA Time required for successful PLMA insertion on the placement and the difficulty in inserting PLMA. first attempt according to predictors Suboptimal anatomic positioning is a frequent case, even if In 132 patients who had successful PLMA insertion on the LMA have clinically optimal function [19-21]. We regarded a first attempt, the PLMA insertion time on the first attempt fiberoptic score of 3 or more without epiglottic folding as according to the predictive factors were not significantly appropriate PLMA positioning. In our study, the frequency of different (P ＞ 0.05) (Table 8). Male gender, increased BMI, a fiberoptic score less than 3 was 52.0%, which was similar modified Mallampati classification ≥ III, inter-incisor distance to the results of Brimacombe et al. (50.3%) [7], but different ≤ 5 cm, thyromental distance ≤ 6.5 cm, head/neck movement from the result of Brimacombe and Keller (22%) [5]. This ≤ 90o, buck of teeth ≥ moderate, upper lip bite test ≥ II and discrepancy may have been caused by the difference in muscle total airway score ≥ 3 were analyzed for multivariate analysis. relaxant dosage, or by the operator’s skill when inserting the In the multiple linear regression model, we did not find any PLMA. Clinically unrecognized malposition of LMA, as 276 Anesth Pain Med Vol. 8, No. 4, 2013 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏

Table 8. Time required for Successful Proseal LMA Insertion on the because direct visualization is needed. Therefore, it is First Attempt according to Predictors (n = 132) important to predict LMA suboptimal position, reposition and

Insertion Time on the fiberoptically reassess to demonstrate ideal anatomic placement. Predictors P value First Attempt (sec) Campbell et al. [19] reported that placement of LMA is independent of the Mallampati classification and Wilson score. Gender M (n = 68) 9.0 ± 5.0 0.533 We also did not find any significant relationship between the F (n = 64) 8.5 ± 4.9 each predictive factor and the fiberoptic findings. However, our Modified mallampati class results show that a total airway score of 3 or more I/II (n = 130) 8.8 ± 5.0 0.95 significantly affects our fiberopitc scores of LMA placement. III/IV (n = 2) 8.7 ± 2.1 Interincisor distance This finding is different from the result of Campbell et al. ＞ 5 cm (n = 31) 8.9 ± 5.1 0.857 This difference may be attributed to the different methods ≤ 5 cm (n = 101) 8.7 ± 4.9 assessing airway, that is, total airway score in our study, Thyromental distance Wilson score in Campbell et al’s study. ＞ 6.5 cm (n = 8) 8.9 ± 5.0 0.124 ≤ 6.5 cm (n = 124) 6.2 ± 2.5 It has been controversial which predictors can predict the Head/neck movement ease of LMA insertion. Brimacombe [13] reported that the o ＞ 90 (n = 35) 8.9 ± 5.3 0.87 modified Mallampati classification did not help to predict the ≤ 90o (n = 97) 8.7 ± 4.9 ease of LMA insertion. In contrast, McCrory and Moriarty Buck teeth No (n = 123) 8.8 ± 5.0 0.97 [11] reported that LMA insertion became more difficult when Mild/moderate (n = 9) 8.8 ± 5.0 a difficult intubation was predicted by a modified Mallampati ULBT classification of III or higher. With regard to the head/neck I (n = 80) 8.5 ± 4.6 0.37 movement, Brimacombe and Berry [23] reported that the II/III (n = 52) 9.3 ± 5.4 Total airway score success rate of LMA insertion was not influenced by ≤ 2 (n = 65) 8.7 ± 4.9 0.83 limitations in head/neck movement. However, Ishimura et al. ≥ 3 (n = 67) 8.9 ± 5.1 [24] reported a case in which LMA insertion was impossible Values are mean ± SD or number of patients. The P value was due to head/neck movement limitation, and concluded that an obtained with unpaired t-test. There were no significant differences in angle between the oral and the pharyngeal axes of less than the PLMA insertion time on the first attempt according to the 90o at the tongue made LMA insertion difficult. Our study predictive factors. ULBT: upper lip bite test, ULBT I: Lower incisors can hide mucosa of the upper lip, ULBT II: Lower incisors partially showed that the predictive factors had no effect on the time hide mucosa of the upper lip, ULBT III: Lower incisors unable to required for successful insertion on the first attempt. Only touch mucosa of the upper lip. Total airway score: A score of 0, 1, male gender of investigated predictors did significantly or 2 was assigned for each criteria (the modified Mallampati correlate with failure on the first insertion of PLMA, which classification, interincisor distance, thyromental distance, head/neck movement, history of difficult intubation, the presence of buck teeth, was consistent with the result of Ramachandran et al. [25]. and the upper lip bite test) and the sum of all the scores constituted However, increased BMI did not correlate with failure on the the total airway score. Total airway score ≥ 3: difficult airway first insertion of PLMA, which was different from the result predicted. of Ramachandran et al. [25]. This difference may have been caused because none of our patients had a BMI over 30 verified by fiberoptic bronchoscopy, was associated with gastric kg/m2. Besides, in the present study, the incidence of failed air insufflation [9,10,22]. Moreover, Brimacombe et al. [22] PLMA insertion after three attempts occurred only in 6 out of reported a case that gastric insufflation is possible with the 154 patients. Failure of PLMA insertion on the first attempt PLMA, despite a good seal and a negative malposition test. also occurred in 22 patients, so there were not enough failures Thus, fiberoptic confirmation of LMA position is important to of PLMA insertion to prove correlation between failure rate of reduce the risk of gastric insufflation. Fortunately, we did not insertion and predictive factors. Therefore, more research have a case with gastric insufflation. When LMA is used as recruiting large number of patients is needed to correlate failed an intubation conduit in case of failed intubation or guide for PLMA insertion and predictive factors. Also, ULBT II/III was diagnostic and therapeutic fiberoptic bronchoscopy, ideal inversely correlated with failure of PLMA insertion on the first intra-oral positioning of an LMA may be highly desirable attempt. This is because there may be a difference in the Joo Hyun Jun, et al：Predictors for difficult PLMA insertion 277 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏 anatomic factors that make each airway instrumentation shorter than the 12 s reported by Cook and Gibbison [27]. difficult. According to Brain [26], the intubation difficulties This difference may have been caused by a discrepancy in the were associated with an apparently anteriorly placed larynx. In method of insertion, estimation of time, or variation in the contrast, difficulty with insertion of the LMA was associated operator’s skill. with an apparently posteriorly placed larynx, which tends to None of our patients had a BMI over 30 kg/m2, a modified block the downward progress of the tip of the mask. Besides, Mallampati classification of IV, or a thyromental distance of conventional tracheal intubation provides a direct view of the less than 6 cm. There were 7 patients with an interincisor airway whereas PLMAs are inserted blindly. If so, that would distance less than 4 cm and one patient with severe buck limit the efficacy of using the predictors of difficult intubation teeth. Our study was limited by the fact that higher rates of to predict the difficulty with PLMA insertion. Therefore, patients (50.6%) were expected to have a difficult airway (total further study for development of predictors of difficult LMA airway score ≥ 3) than those in Lee et al’s study (23.6%) insertion is also needed. using airway score. This may be attributed to the use of same The modified Mallampati classification can only predict a point (3 or more) in different airway scoring system which is difficult airway according to the tongue and pharynx structure. modified as adding ULBT item. In spite of this limitation in Thus, we wanted to include various criteria that are useful in our study, on both univariate and multivariate analyses, 3 or predicting difficult intubations and see if they could predict more of total airway score was found to be a significant difficult PLMA insertion and fiberoptic scores. The airway predictor for suboptimal position of PLMA though not for score, which was used in the study of Lee et al. [17], is a test failure on the first insertion of PLMA. This finding suggests method to predict difficult tracheal intubation with more that the factors predicting difficult airway cannot predict accuracy, sensitivity and specificity than the modified difficult PLMA insertion, but can do suboptimal position of Mallampati classification. Khan et al. [16] and Lee et al. [17] PLMA. However, the sensitivity of total airway score of 3 or reported that ULBT showed significantly higher specificity and more for predicting suboptimal PLMA placement is 61%, accuracy, but lower sensitivity for predicting difficult intubation which is still not very sensitive. Therefore, additional work than the modified Mallampati classification. Moreover Lee et al. needs to be done in order to be better able to predict [17] suggested that incorporating ULBT as a factor of airway suboptimal position of PLMA. score seems to be better for more reliable prediction. Thus, we In conclusion, we found that of investigated predictors, male performed airway assessment for seven items including ULBT gender and ULBT I did significantly predict failure on the first to comprehensively predict the anatomic structure that causes a insertion of PLMA. However, all of investigated predictors had difficult airway. And we estimated the seven items as a score no effect on the time required for successful insertion on the of 0, 1 or 2, respectively, with their sum being the total airway first attempt. We also found that the total airway score, which score, and regarded the patients with a score ≥ 3 would have is a comprehensive summation of all the difficult intubation cri- difficult airway. We also investigated separately predictive teria did correlate with the fiberoptic bronchoscope findings. factors of difficult intubation because a possible correlation When ideal placement is either highly desirable or necessary, it between LMA use and each factor could not be revealed, if it is important to reduce the suboptimal positioning of the PLMA, was summated in a multifactorial risk score. And since male particularly in patients who are predisposed to difficult in- gender and increased BMI were independent risk factor for tubation and who have a total airway score of 3 or more. failed LMA in the study of Ramachandran et al. [25], we also included these factors as predictive factor for difficult PLMA REFERENCES insertion and fiberoptic scores. The success rate of PLMA insertion on the first attempt in 1. Berkow LC, Schwartz JM, Kan K, Corridore M, Heitmiller ES. this study was 86%, which was similar to the 85% success Use of the Laryngeal Mask Airway-Aintree Intubating Catheter-fi- rate reported in the study by Cook and Gibbison (84.5%) [27] beroptic bronchoscope technique for difficult intubation. J Clin and Kim et al. (89.5%) [28]. The success rate over three Anesth 2011; 23: 534-9. 2.Somri M, Barna Teszler C, Tome R, Kugelman A, Vaida S, attempts was 96%, which was also similar to the result of Gaitini L. Flexible fiberoptic bronchoscopy through the laryngeal Figueredo et al. (98%) [6]. The time required for successful mask airway in a small, premature neonate. Am J Otolaryngol insertion on the first attempt was 8.7 ± 4.9 s, which was 2005; 26: 268-71. 278 Anesth Pain Med Vol. 8, No. 4, 2013 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏

3. Dosemeci L, Yilmaz M, Gurpinar F, Ramazanoglu A. The use of lip bite test (a simple new technique) with modified Mallampati the laryngeal mask airway as an alternative to the endotracheal classification in predicting difficulty in endotracheal intubation: a tube during percutaneous dilatational tracheostomy. Intensive Care prospective blinded study. Anesth Analg 2003; 96: 595-9. Med 2002; 28: 63-7. 17. Lee SM, Kim DS, Ryu SJ, Chang TH, Kim SH, Kim KH. The 4. Fullekrug B, Pothmann W, Werner C, Schulte am Esch J. The evaluation of predictability of difficult intubation using upper lip laryngeal mask airway: anesthetic gas leakage and fiberoptic bite test. Korean J Anesthesiol 2005; 49: 287-92. control of positioning. J Clin Anesth 1993; 5: 357-63. 18. Brimacombe J, Berry A. A proposed fiber-optic scoring system to 5. Brimacombe J, Keller C. The ProSeal laryngeal mask airway: A standardize the assessment of laryngeal mask airway position. randomized, crossover study with the standard laryngeal mask Anesth Analg 1993; 76: 457. airway in paralyzed, anesthetized patients. Anesthesiology 2000; 19. Campbell RL, Biddle C, Assudmi N, Campbell JR, Hotchkiss M. 93: 104-9. Fiberoptic assessment of laryngeal mask airway placement: blind 6. Figueredo E, Martinez M, Pintanel T. A comparison of the insertion versus direct visual epiglottoscopy. J Oral Maxillofac ProSeal laryngeal mask and the in spontaneously Surg 2004; 62: 1108-13. breathing anesthetized patients. Anesth Analg 2003; 96: 600-5. 20. Keller C, Brimacombe J. Pharyngeal mucosal pressures, airway 7. Brimacombe J, Keller C, Fullekrug B, Agro F, Rosenblatt W, sealing pressures, and fiberoptic position with the intubating versus Dierdorf SF, et al. A multicenter study comparing the ProSeal and the standard laryngeal mask airway. Anesthesiology 1999; 90: Classic laryngeal mask airway in anesthetized, nonparalyzed 1001-6. patients. Anesthesiology 2002; 96: 289-95. 21. Nandi PR, Nunn JF, Charlesworth CH, Taylor SJ. Radiological study 8. Practice guidelines for management of the difficult airway: an of the laryngeal mask. Eur J Anaesthesiol Suppl 1991; 4: 33-9. updated report by the American Society of Anesthesiologists Task 22. Brimacombe J, Keller C, Berry A. Gastric insufflation with the Force on Management of the Difficult Airway. Anesthesiology ProSeal laryngeal mask. Anesth Analg 2001; 92: 1614-5. 2003; 98: 1269-77. 23. Brimacombe J, Berry A. Laryngeal mask airway insertion. A 9. Latorre F, Eberle B, Weiler N, Mienert R, Stanek A, Goedecke comparison of the standard versus neutral position in normal R, et al. Laryngeal mask airway position and the risk of gastric patients with a view to its use in cervical spine instability. insufflation. Anesth Analg 1998; 86: 867-71. Anaesthesia 1993; 48: 670-1. 10. Weiler N, Latorre F, Eberle B, Goedecke R, Heinrichs W. 24. Ishimura H, Minami K, Sata T, Shigematsu A, Kadoya T. Respiratory mechanics, gastric insufflation pressure, and air leakage Impossible insertion of the laryngeal mask airway and of the laryngeal mask airway. Anesth Analg 1997; 84: 1025-8. oropharyngeal axes. Anesthesiology 1995; 83: 867-9. 11. McCrory CR, Moriarty DC. Laryngeal mask airway positioning is 25. Ramachandran SK, Mathis MR, Tremper KK, Shanks AM, related to Mallampati grading in adults. Anesth Analg 1995; 81: Kheterpal S. Predictors and clinical outcomes from failed laryngeal 1001-4. mask airway unique: a study of 15,795 patients. Anesthesiology 12. Brimacombe J, Berry A. Mallampati classification and laryngeal 2012. mask airway insertion. Anaesthesia 1993; 48: 347. 26. Brain AI. Three cases of difficult intubation overcome by the 13. Brimacombe J. Analysis of 1500 laryngeal mask uses by one laryngeal mask airway. Anaesthesia 1985; 40: 353-5. anaesthetist in adults undergoing routine anaesthesia. Anaesthesia 27. Cook TM, Gibbison B. Analysis of 1000 consecutive uses of the 1996; 51: 76-80. ProSeal laryngeal mask airway by one anaesthetist at a district 14. el-Ganzouri AR, McCarthy RJ, Tuman KJ, Tanck EN, Ivankovich general hospital. Br J Anaesth 2007; 99: 436-9. AD. Preoperative airway assessment: predictive value of a 28. Kim YK, Jeon HY, Yang HS. Comparison of the clinical multivariate risk index. Anesth Analg 1996; 82: 1197-204. effectiveness of the CobraTM perilaryngeal airway and the 15. Wilson ME, Spiegelhalter D, Robertson JA, Lesser P. Predicting ProSealTM laryngeal mask airway during anesthesia with controlled difficult intubation. Br J Anaesth 1988; 61: 211-6. ventilation. Anesth Pain Med 2007; 2: 160-5. 16. Khan ZH, Kashfi A, Ebrahimkhani E. A comparison of the upper