Comparision of airway assessment by Mallampati classification and cormack and lehane grading in Indian population

Introduction: This prospective cross-sectional observational study was undertaken to compare preanaesthetic predictive value of Modified Mallampati classification in relation to Cormac Lehane grades in Indian population. Materials and Methods: One hundred patients of either sex, who have underwent general anaesthesia were includes in the study. Inclusion criteria were aged between 18 to 60 years, ASA grades I and II, weighing between 4580 kg. The parameters observed were, Mallampati class (MMT) during pre anaesthetic assessment and their percentages, Cormack and Lehane grades (CL) at intubation and their percentages and correlation of Cormack and Lehane grading and Mallampati classification. Results: Out of 100 patients, men women ratio was 1: 2.1(32: 68), mean age of the patients were 43.15± 12.96yrs, mean BMI of the patients were 23.34 ± 1.34 kg/m2. The corrected chi square test showed a value of 76.8 with a P value of < 0.001.The Spearman correlation co-efficient between Mallampati and Cormac Lehane classification is 0.8 and one tailed value is significant at 5% level. The sensitivity, specificity, positive predictive value and negative predictive value of the Mallampati classification were 42.86%, 82.56%, 28.57% and 89.87% respectively. Conclusion: To increase predictive value of preassessment of difficult airway, Mallampati test should be supplemented by other airway assessment tools.


Introduction
Pre-assessment of airway before anaesthesia is very vital. Assessment tools with repeatability and reliability are therefore important. Mallapati Classification is one such assessment tool which is extensively used by Anaesthesiologists. Developed by Mallampati, 1,2 it was successively modified by Samsoon 3 in 1987. Cormack Lehane (CL) grading 4 is another such assessment of airway at laryngoscopy. It is a gold standard for evaluation of difficulty of intubation as airway is assessed under direct vision. Over the years different airway assessments tools are evaluated against CL classification. The purpose of the present study was to assess the Mallampati classification with the help of CL classification in Indian population without obvious factors predicting difficult intubation, like decreased mouth opening, decreased range of motion of the neck, mass within oropharynx etc.
Aims and Objectives 1. To evaluate the predictive value of Mallampati classification with Cormack and Lehane grading for tracheal intubation. 2. To assess their correlation between the two at direct laryngoscopy.

Materials and Methods
After obtaining clearance from institutional ethics committee, the trial was registered with Clinical Trial Registry of India (No. CTRI/2017/12/010921). The study was on patients undergoing surgery under general anaesthesia, in a city medical college hospital, from November 2017 to April 2018, for a period of six months. The study was prospective, cross sectional and observational in nature.
After obtaining informed consent, 110 patients of either sex were chosen for the study. The sample size was calculated with an estimated sensitivity of 45% from a previous study, and an effect size of 10 per cent, which was equal to a sample size of 99.
All patients between the age of 18 to 60 years and ASA physical status I and II were included in the study. The airway of the patients were assessed by Modified Mallampati (MMT) classes in the following way. Patients were made to sit up straight with their head in neutral position. They were told to open their mouth wide as maximum, with the tongue protruded out. Modified Mallampati classes were assigned as following. In operation room monitors were attached to the patients to regularly monitor ECG, blood pressure, heart rate, oxygen saturation and EtCO2. Anaesthesia was induced with glycopyrolate 0.01 mg/kg, midazolam 0.05 mg/ kg, fentanyl 2mcg/kg and propofol 1 to 2 mg/kg slowly until the loss of verbal communication achieved. To ensure maximal relaxation, 1.5 mg/kg of succinylcholine were administered and laryngoscopy was done after 60-90 seconds using appropriate Mcintosh blade.
Laryngoscopy was done by an anaesthesiologist who has done at least 50 laryngoscopies successfully. Assessment of laryngeal inlet was done according to the Cormack Lehane classification (CL) as follows: Class I: All or almost all of larynx visible. Class II: Posterior part of vocal cord and/or arytenoids cartilage visible. Class III: Only epiglottis visible. Class IV: Neither glottis nor epiglottis visible. Class I and II correspond to easy intubation and Class III and IV denote difficult intubation. Assessment of the airway was agreed upon by a second consultant at the time of assessment. Inclusion Criteria: Healthy patients of either sex, weighing 45-80 kgs, aged between 18-60 years were included in this study. Exclusion Criteria: Emergency surgical procedures, pregnant patients, patients with unstable cervical spine, patients with tumour of larynx, patients with head and neck anomaly, edentulous or loss of a part of denture and unwilling patients were excluded from the study. Parameters: The parameters that were observed: 1. Mallampati class (MMT) during pre anaesthetic assessment and their pecentages. 2. Cormack and Lehane grades (CL) at intubation and their percentages.

Correlation of Cormack and Lehane Grading and
Mallampati Classification. 4. Statistical Analysis: Data obtained was tabulated and analysed by using SPSS17 version software.

Results
There were 110 patients eligible for the study, three of them had their operation cancelled, five patients were administered regional anaesthesia and two opted out of the study. Therefore, hundred patients entered the study.
The number of women patients were 68 and the number of men were 32, men women ratio was 1: 2. The corrected chi square test performed from the above table 2 with 9 degrees of freedom showed a value of 76.8 with a P value of < 0.001.
The Spearman correlation co-efficient between Mallampati and Cormac Lehane classification is 0.8 and one tailed value is significant at 5% level.

Discussion
Securing the airway is one of the most important task of the anaesthesiologist. Prior assessment of the airway helps in planning for difficult airway. There are many bedside tests for assessment of airway apart from assessment by imaging. One of the common bedside test is modified Mallampati classification first proposed by Mallampati. Cormack lehane classification assesses the laryngeal inlet and intubation difficulty at laryngoscopy. It is the gold test against which other bedside tests are assessed.
Our aim was to find out whether Mallampatti is a satisfactory test to predict difficult airway when all other obvious factors for difficult intubation have been eliminated.
One hundred patients were included in the study. All of them were ASA I or II grade patient.
The sex ratio shows predominance of females. Other studies have shown dominance of either sex. One of the causes of female dominance may be due to the fact that majority of the surgical cases were laporoscopic cholecystectomy, as cholecystitis is more common in women.
The mean age of the patients were 43 ± 12.96 yrs. This shows that none of the patients had extremes of age, which might increase presence of other factors of difficult intubation.
The BMI of the patients were within the acceptable limit. Thus the important factor of obesity is satisfactorily ruled out. This was similar to studies by Aswar SG et al. 5 The association between Mallampati classification and Cormack Lehane grade were significant as shown by Chi square test (p<0.001) and Spearman correlation of 1 (p<0.05). Similar results were shown by Aswar et al. 5 and Nasir KK et al 6 Significant correlation was also shown by Cattano D et al. 7 Sensitivity of Mallampati is its ability to detect difficult intubation. The sensitivity in our study is low (42.86%) with a wide confidence interval (95% CI 17.66% to 71.14%). Sensitivity vary widely from 25.52% (Nasir KK et. al.) 6 to 76% (Erzi et. al.) 8 In fact Lee et al 9 has shown that sensitivity can vary between 34% and 66%. Lundstrom 10 has recorded the variation of sensitivity between 0% and 100%. Our study records a sensitivity to that of Deepak et al. (44.44%). 11 The specificity of our study is 82.56%. This is similar to specificity recorded by Nasir KK et al. (83.6%). 6 Even higher specificity were recorded by Aswar 5 However, the incidence of difficult intubation in itself is low as shown by the study, to be only 14%. The results are similar to studies by Huh et al.(12.2%), 13 Aswar et al (6%) 5

Conclusion
To increase predictive value of preassessment of difficult airway, Mallampati test should be supplemented by other airway assessment tools.