Background: Endotracheal intubation has become a well established standard in protecting the airway during surgical procedures, and in emergency situations. Serious complications can occur from the incorrect placement of an endotracheal tube in a mainstem bronchus. If unrecognized it can lead to hypoxemia secondary to atelectasis of the unventilated lung and hyperinflation of the intubated lung, which can result in barotrauma. As bedside method the golden standard to verify the correct endotracheal tube placement is bilateral ausculation of the chest. However this is not always satisfactory, as breath sounds can be transmitted to the opposite side of the chest in spite of endobronchial intubation. Therefore other clinical tests to verify the correct endotracheal tube placement have become part of daily clinical practice, like observation of symmetric chest movements, and use of the cm markings printed on the endotracheal tube. However so far no study investigated which of these bedside clinical methods works best in detecting an inadvertently placed endobronchial tube in adults. We therefore designed a study to compare three different bedside methods to verify endotracheal or endobronchial tube placement.

Objective: To determine which of four commonly used bedside methods of detecting inadvertent endobronchial intubation in adults has the highest sensitivity and specificity.

Design: Prospective randomized, blinded study. Setting: Tertiary, academic hospital, department of anaesthesia. Participants: 160 consecutive ASA I or II patients, aged 19-75 years, scheduled for elective gynaecological or urological surgery.

Interventions: Patients were randomly assigned to eight study groups. In four groups, an endotracheal tube (ETT) was fiberoptically positioned 2.5-4.0 cm above the carina, whereas in the other four groups the tube was positioned in the right mainstem bronchus. The four groups differed in the bedside test used to verify the position of the endotracheal tube. First-year residents and experienced anaesthesiologists independently performed one of the following randomly assigned bedside tests in each patient in an effort to determine whether the tube was properly positioned in the trachea: 1) bilateral auscultation of the chest (Auscultation); 2) observation and palpation of symmetric chest movements (Observation); 3) estimating the position of the ETT by the insertion depth (Tube Depth); and, 4) a combination of all three mentioned tests (All Three).

Main outcome measures: Correct and incorrect judgements of endotracheal tube (ETT) position as independently assessed by first-year anaesthesia residents and experienced anaesthesiologists with each of the four bedside tests.

Inclusion Criteria:

ASA I or II patients, aged 19-75 years, scheduled for elective gynaecological or urological surgery that needs endotracheal intubation.

Exclusion Criteria:

• Pre-existing lung disease, pleural effusion, anticipated difficult airway, known endobronchial or tracheal lesions, or patients at risk for aspiration of gastric contents.