It is difficult to determine the adequate depth of endotracheal tube placement in infants and young children. It is usually determined by an equation according to the patient's age (12 + age/2, cm) or auscultation method. The auscultation method is to intentionally place the tip of the endotracheal tube into the right main stem bronchus and then withdraw it until breath sounds are equal. The tube is fixed 1 or 2 cm proximal to the point where breath sounds become equal. However, in small children or infant, as the breadth sound in unilateral lung transmits the contralateral lung field and is often difficult to listen in a noisy operation room, it is often difficult to determine the depth by auscultation method. Pleural sliding sign, or sliding lung sign is a ultrasonographic finding that the visceral pleura moves against the parietal pleura. It is used to identify whether the lung is ventilated by ultrasound. The investigators are trying to use this pleural sliding sign to determine the depth of endotracheal tube, and compare this method with auscultation method.
The investigators are trying to evaluate the efficacy of ultrasonographic determination of depth of endotracheal tube placement in infants and young children by using the pleural sliding sign.