Abstract

Introduction: Unanticipated difficult intubation is challenging to anaesthesiologists. The global epidemic of overweight and obesity is rapidly becoming a major health problem and anaesthetists frequently encounter such patients whose airway management is their major responsibility. Intubation Difficulty Scale (IDS) had been used as a validated difficulty score to define difficult intubation. In this study, we intend to find out the incidence of difficult intubation in obese and non-obese patients using Intubation Difficulty Scale.

Objectives: The primary objective of the study is to assess the incidence of Intubation Difficulty Scale (IDS) score ≥ 5 in obese and non-obese patients. The secondary objective is to assess the performance of Modified Mallampati Classification, Mouth opening, Thyromental distance and Sternomental distance in predicting Intubation Difficulty Scale (IDS) score ≥5 in obese and non-obese patients.

Methods: This study is a prospective cohort study. The study population was from the Department of Anaesthesiology, Government Medical College, Thiruvananthapuram with ASA- physical status I & II patients in the age groups 18 to 60 years, scheduled to undergo surgery requiring General Anaesthesia with controlled ventilation using an Endotracheal tube. After obtaining informed written consent and Institutional Research Committee and Ethical Committee clearance, 140 patients requiring General Anaesthesia were categorized into 70 each based on the Body Mass Index (BMI) into obese (BMI≥ 25kg/m²) and non- obese (BMI<25kg/m²)groups. Preoperative airway assessment included Modified Mallampati Classification, mouth opening, Thyromental distance and Sternomental distance. IDS score ≥ 5 was termed Difficult Intubation.

Data was entered in Microsoft Excel and data analyzed using SPSS software version 16. All the quantitative data were analyzed by computing percentages and descriptive statistics, ie: mean, standard deviation and standard error of mean and qualitative data by means of proportions. Suitable statistical tests were applied and results were considered statistically significant whenever p- value of ≤0.05 was obtained.

Results: Overall in 140 patients, the incidence of difficult intubation was found to be 16.4%. 27.1% of obese patients and 5.7% of non-obese patients had difficult intubation. Obese patients were more difficult to intubate than non- obese patients. Obstructive Sleep Apnea (OSA), Modified Mallampati Classification III/IV, Thyromental distance (TMD) < 6.5cms and Sternomental distance (SMD)< 12.5cms were found to be associated with IDS score ≥ 5. SMD <12.5cms was found to be the single best predictor of difficult intubation. IDS score is helpful in evaluating the predictive factors of difficult intubation.

Conclusions: Obese patients are more difficult to intubate than non-obese patients. It is preferable to have a second skilled Anaesthesiologist, during intubation of obese patients with OSA, MMC III/IV, TMD <6.5cms and SMD <12.5cms.

Keywords: Difficult intubation, intubation difficulty scale, obese, non-obese.