الفهرس 
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Abstract
In pediatrics, having proper size of endotracheal tube is mandatory. The use of age-based formulas to calculate the ETT size is easy, practical and common today. However, the incidence of appropriate tube size is still not satisfactory, hence increasing incidence of changing tube such as trauma and aspiration. Recent studies found that measuring the minimal transverse subglottic diameter may be helpful in selecting the proper tube size. This study was aimed at proofing that selecting ETT size using ultrasound measurement of subglottic diameter is a accurate method and lead to less frequency of changing tube size than age-based formula especially in older children.
This study was conducted in Ain Shams University Hospitals on 60 children aged between 2 to12 years, of both genders, American society of anesthesiologists (ASA) I or II physical status scheduled for day case surgery under general endotracheal anesthesia. Children were divided randomly according to age into three groups: group I included children aged between 2 to < 5 years, group
Summary
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II included children aged between 5 to < 9 years, and group III included children aged between 9 to12 years.
In all chidern, the size of the ETT was determined according to both ultrasonography and modified cole’s formula. The size of the ETT initially inserted was based on ultrasonographic calculation. Ultrasonography is done using high‑resolution B‑mode linear array ultrasound probe. The probe was positioned at the anterior aspect of neck in the midline with the head extended and neck flexed (sniffing position). The minimal transverse diameter of the subglottic airway (MTDSA) was estimated at the level of cricoid cartilage at zero cmH2O airway pressure. After measurement of the subglottic diameter, the ETT with the nearest outer diameter corresponding to the measured subglottic diameter was selected for intubation.
If there was resistance to ETT insertion into the trachea, or there was no audible leak by cuff leak test at pressure more than 20 cm H2O, the tube was exchanged with one that is 0.5 mm smaller. In contrast, the ETT was exchanged for one that is 0.5 mm larger if leak occured at pressure less than 10 cm
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H2O. Optimal tube size was clinically determined by leakage occurance at airway pressure of 10 to 20 cmH2O.
The results showed that although Ultrasonography and Cole’s formula were sensitive predictors of optimal ETT size selection in pediatrics, the US showed higher predictability than formula (indicated by higher correlation coefficient R) in all groups especially older age group