Children and adults frequently need a 'breathing tube' when having anesthesia for surgery. The breathing tube is usually inserted after the anesthesia doctor puts a patient to sleep with medicine, so they do not feel the breathing tube. In children, there is often a leak of air between the tube and the windpipe, as the tube is not an exact fit. Anesthesia doctors usually listen for this leak around the tube by listening to the chest with a stethoscope while gently filling the lungs with oxygen from the anesthesia machine. The leak tells them if the tube is the correct size, or too small, or too tight. If it is too small, or too tight, they usually change the tube for a better fit.

The purpose of this study is to see what happens to this leak in the 30 minutes after the tube is placed. No one really knows if the leak gets bigger, smaller, or stays the same. Knowing what happens to the leak will help anesthesia doctors to decide whether to change the breathing tube or not. This is important, as a tube that is too tight can lead to breathing difficulty after removing the tube at the end of surgery, and a tube that is too small may make it difficult for the breathing machine to work effectively for the patient as a result of a large leak of air or oxygen.

Inclusion Criteria:

• Children aged 0-7 years of age
• Surgery with planned endotracheal intubation using an uncuffed ETT.
• ASA 1-3
• Supine position

Exclusion Criteria:

• Lack of parental consent
• Rapid sequence induction with cricoid pressure
• Use of neuromuscular blocking agent/s for intubation.
• Active gastroesophageal reflux disease
• Active upper respiratory tract infection
• Chronic active lung disease requiring frequent treatment such as asthma, or chronic lung disease of prematurity etc.
• Surgery in the lateral or prone position
• Oropharyngeal, neck , laryngeal, or laparoscopic surgery
• Tracheostomy in-situ
• History of previous laryngeal or tracheal surgery
• History of tracheal or laryngeal abnormalities, or stridor of unknown origin.
• History of symptomatic neuromuscular disease or paralysis
• History or features suggestive of a difficult airway on pre-anesthetic evaluation and physical examination.

Pediatric patients undergoing surgical procedures at Oregon Health & Science University