Assessment of Airway Parameters for Predicting Difficult Laryngoscopy and Intubation in a Tertiary Center in Western Nepal

Abstract

Background: The screening tests used for pre-operative evaluation of airway to predict difficult laryngoscopy and intubation have variable diagnostic accuracy. The unanticipated poor laryngeal view is gold standard for defining difficult intubation. We aimed to find out the prevalence of difficult laryngoscopy and intubation, which airway parameter better predicts difficult intubation and whether difficult laryngoscopy is associated with difficult intubation or not.Methods: This analytic cross sectional study was conducted in 665 ASA I/II adult patients, aged 18-65, without obvious airway pathology undergoing elective surgery under general anesthesia. The pre-operative screening tests included mouth opening, modified mallampatti, ratio of height to thyromental distance, sternomentaldistance and upper lip bite test. Cormack-Lehane grade III/ IV was defined as difficult laryngoscopy and potentially difficult intubation. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy and area under curve at 95% confidence interval was calculated for all five screening tests. Results: The prevalence of difficult laryngoscopy and intubation was 6.6% (44 cases). The upper lip bite test because of its highest specificity, positive predictive value, negative predictive value, accuracy and area under curve (99.7%; 93.9%; 99.7%; 95.2%; 85.1% respectively) with moderate level of sensitivity (70.5%) was better predictor of difficult intubation than other tests. The difficult laryngoscopy was associated with difficult intubation (p=0.00).Conclusions: The prevalence of difficult laryngoscopy and intubation was 6.6%.The upper lip bite test was a better predictor of difficult intubation and there was a significant association of difficult laryngoscopy with difficult intubation.Keywords: Difficult laryngoscopy and intubation; screening tests; upper lip bite test.

2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway *

“…Observational studies reported comparative findings for facial and jaw features and anatomical measurement for difficult versus nondifficult airway patients as well as sensitivity, specificity, positive predictive, negative predictive, and accuracy values for difficult laryngoscopy and intubation. Findings for facial and jaw features, 7–11,13,14,18,27,33,38–40,42,43,45–47,49,51–54,57,58,64,68,123–159 anatomical measurements, 7–11,13–15,18,22,23,27–30,33,35,37–40,45–47,49,51–54,57,58,60, 64,65,68,70,123–132,134–154,156,158–203 and ultrasound anatomical measurements 69,139,162,170,194,196,203–213 were shown to have very high predictive and comparative variability, with sensitivity, specificity, and significance values ranging from low to very high across all patient measures (Category B2-E evidence). No single characteristic was identified as consistently being more predictive than another, and multivariate measures intended to predict difficult airways were too few and diverse among the studies to determine a common set of predictors.…”

Difficult airway management in an emergency in Nepal

“…6 While study conducted by Lakhe G ( Jan 2021) among 665 ASA I/II adult patient the prevalence of difficult laryngoscopy and intubation was 6.6%, ULBT was better predictor of difficult intubation and there was significant association with difficult intubation. 7 Another study conducted by Gurung PK (Apr 2019) among 100 ASA I /II patient incidence of difficult intubation was 6% where ULBT had specificity of 98.9% and accuracy of 95 %, however there was no difference in sensitivity and negative predictive value when compared to MMC. 8 In a study conducted by 11 Maximum number of intubation that should be tried is 3 or 4 attempts in children to prevent airway edema, while duration should not exceed more than 30 sec, in such condition flexible fibro-optic bronchoscope is first line while choledochoscope can be second line for airway management.…”

Airway management in hospital. Methodological recommendations of the All-Russian public organization “Federation of Anesthesiologists and Reanimatologists” (third edition)

“…В Кокрановском обзоре 2018 г. и ряде других работ была показана наибольшая прогностическая ценность теста с закусыванием верхней губы в сравнении с другими традиционными признаками трудной интубации [59][60][61][62]. В целом, по общепринятому мнению экспертов, которое основано на большом количестве исследований (в т. ч. Кокрановский обзор 2019 г.…”