Prediction of Optimal Pediatric Endotracheal Tube Size "Aged Based Formula Versus Ultrasonography"

Introduction:

Pediatric tracheal intubation requires considerable expertise and can represent a challenge to many anesthesiologists(Marciniak et al.,2009). Anatomically; the larynx of a pediatric patient assumes a funnel shape with its narrowest part at the level of the cricoid ring, which cannot be seen during conventional laryngoscopy (Karsli et al.,2002).

Choosing the correct endotracheal tube (ETT) size needed for intubation of pediatric patients is important because an inappropriately too large tracheal tube can cause upper airway damage (e.g., local ischemia, ulceration, scar formation) and the potential for subsequent subglottic stenosis. In contrast, an ETT that is too small may result in insufficient ventilation, poor reliability of end-tidal gas monitoring, leakage of anesthetic gases into the operating room environment, and an enhanced risk of aspiration(Karsli et al.,2002).

Different algorithms and formula have been proposed to choose the best-fitting size of the endotracheal tube. Age-based formulas, such as those of Cole and Motoyama, have been used to estimate optimal ETT size for more than half a century (Motoyama,1990) and this formula is [inner diameter (ID) in mm = (age in yr/4) +4]. Predictive formulas for appropriate ETT size have also been based on patient weight and height as[ID in mm = 2 + height in cm/30] and [ID in mm = 2.44 + age in yr ×0.1 + height in cm ×0.02 + weight in kg ×0.016] and other formula as the width of the 5th fingernail is used for ID prediction of the ETT [ID in mm = maximum width of the 5th fingernail] (Shibasaki et al.,2010). However, these methods are not always suitable because the size of the airway varies considerably between patients.

Ultrasound guided is helpful for evaluate the subglottic transverse diameter which is safe , sample, painless and non invasive modality for prediction of proper endotracheal tube size (Jagadish G Sutagatti et al., 2017).