during intubation sometimes you get confused it tube in stomach or lung , so i propose another method to make sure you are in the trachea, simply if you are not sure it is in trachea , advance the tube more in the lung by default it will advance more in the right lung (anatomically ) , and with just small puffs from ambu not strong puff ,

if it is in esopahgus the sound will increase or remain the same at the stomach (left side ) , but if the tube is in the trachea the sound will decrease at left side (+\- increase at right side of the lung , dependining on the state ot the lung ) , then start to withdraw the tube graduwally till the sound of air is at least entring in both side (not a must equal ) depending on the state of the lung .