Estimation of Endotracheal Tube Size By The Physical Indices Based Formulae versus Ultrasonography In Paediatric Patients Posted For Surgery under General Anaesthesia: A Randomised Comparitive Study.

Abstract

Background: Choosing appropriate size EndoTrachealTube (ETT) is a salient aspect in paediatric anaesthesia for successful intubation. Inappropriate size of ETT leads to many complications. In paediatric age group the narrowest diameter of the upper airway is the subglottic region and it determines the size of ETT to be inserted. This randomised comparative study was conducted to compare the estimation of ETT size by Ultrasonography with the physical indices formula based method in paediatric patients undergoing surgeries under general anaesthesia. Aim: This study was conducted to appreciate the role of ultrasound in determining the appropriate size of uncuffed ETT in paediatric patients posted for surgery under general anaesthesia. Objectives: To calculate ETT size by Cole s age based formula (ETT ID in mm=age/4+4), to calculate ETT size by height based formula(ETT ID in mm=height in cm /30+2), to calculate ETT size by ultrasonographic estimation of subglottic diameter(ETT OD in mm=subglottic diameter in mm), to assess the positivity of leak test at different inflation pressure, to assess the incidence of inadequate ventilation, aspiration and laryngospasm Methodology: This randomised comparative study was conducted on 93 ASA I and II patients of either gender aged between 5-12 years posted for elective surgeries under GA. The patients were randomly selected and divided by computer generated random number tables in to three groups with 31 patients in each group. In Group A ETT size was calculated using age based formula (ETT ID=age/4+4), in Group B ETT size was calculated using height based formula (ETT ID in mm=height in cm /30+2) and in Group C ETT size was calculated by ultrasonographic estimation of subglottic diameter(ETT OD in mm= subglottic diameter in mm). Data was analysed using chi-square test and ‘t’ test. Results: Significant difference was observed in positivity of leak test among the three groups:At Inflation pressure<10 cm H2O : In Group A and Group C leak test was never positive, where as in Group B it was positive in 3patients (9.7%), at 20-30 cm H2O :In Group A leak test was positive in 5 patient (16%), in Group B leak test was positive in 7 patients(22.6%) and in Group C it was never positive, at 10 – 20 cm H2O : In Group A leak test was positive in 26 patients (84%) , in Group B leak test was positive in 21 patients (67.7%) and in Group C leak test was positive in 31 patients (100%).The percentage of successful intubations in Group A was 84% Group B was 67.7% and in Group C was 100% Conclusion: Ultrasonography is a better tool to estimate the size of uncuffed ETT than compared to age based and height based formula in paediatric patients.