Methodology:

After obtaining the approval of ethical committee and written informed consent, a total of 50 paediatric patients undergoing surgery under general anesthesia with endotracheal intubation will be included in the study.

After having met inclusion and exclusion criteria, and having obtained informed consent, patients will be randomized based on computer generated randomization table into one of the two groups of 25 each

Group A: (N=25)

Intubated with an Endotracheal tube of the size as determined by the age based formula.

Group B: (N=25)

Intubated with an Endotracheal tube of the size as determined by ultrasonographic assessment of subglottic diameter. By sonosite M TURBO linear probe of frequency 7-15MHz.

A thorough pre-anesthetic evaluation will be done on the day   before surgery with necessary investigations like complete blood count (CBC), chest X-ray, mini renal profile & liver function test will be done if required

Child will be kept NBM for at least 6 hours prior to surgery.

On the day of surgery, in the recovery room after confirming the NBM status and consent will be ascertained. Child will be given Inj.Glycopyrrolate (0.005mg/kg) and Inj. Ketamine(5mg/kg) IM and then shifted to operation theatre.

Inside the operation theatre standard monitoring devices like ECG, pulse oximeter and NIBP will be connected.

Intravenous access will be secured using 22G or 24G IV cannula and IV infusion will be started.

Group-A: ETT tube size will be estimated by using age based formula 

Age/3 + 3.5
In children < 6years -

In children > 6years -  Age/4 + 4.5

Group-B:

ETT tube size will be estimated by measuring the subglottic diameter using high resolution B ultrasonography.

·       Child in supine position with head at neutral position the probe of ultrasonography will be placed in midline.

·       True vocal cords will be localized which can be seen as a pair of hyperechoic linears structure which move along with respiration and swallowing.

·       Then the probe will be moved caudally to visualize the cricoid arch to avoid confusion between the cricoid cartilage and tracheal ring.

·       The measurement of tracheal diameter will be taken as a transverse air column diameter done at cephalic half of the cricoid cartilage which is narrower than the caudal part of cricoid cartilage.

·       Patient will be pre-oxygenated with 100% oxygen for 3 minutes and then premedicated with Inj.Midaz(0.05mg/kg) and Fentanyl (1-2mcg/kg) and induced with Inj.ketamine(1-2mg/kg) and Inj. Scoline(2mg/kg) will be given to achieve skeletal muscle paralysis to facilitate endotracheal intubation.

·       Uncuffed endotracheal tubes will be used.

·       Endo tracheal tube intubation will be done.

The following parameters will be used to assess whether the selected ETT is of an appropriate size :

• ·       ETT passing smoothly through the glottis
•      No audible leak occurs at 10 to 20 cms of H₂O.
•        A square wave capnography on ventilation.