A response to ‘Auscultation of the chest after tracheal intubation’, Khan A W and Morris S, Anaesthesia 2004; 59: 626–7

We were interested to read a letter by Khan and Morris who described an audit of the frequency of stethoscope utilization after intubation. They found that of 50 consecutive intubations, auscultation was performed on 31 cases. Their letter questions the time-honoured habit of routine chest auscultation after passing the tracheal tube through the glottis. The length of tracheas in ‘normal’ adult patients is usually quoted as approximately 15 cm [1], although previous studies have indicated that the tracheal length is closely related to the height of the patient [2]. In light of this, studies [3, 4] have attempted to provide guidelines for optimal placement of tracheal tubes. Based on the fact that the tube may move ± 2 cm with flexion and extension of the neck, it is recommended that the tip of the tube should be mid-trachea or approximately 5 cm ± 2 cm from the carina [4]. This, however, requires extra procedures such as X-ray or bronchoscopy to confirm the placement. Therefore, manufacturers place black marks on the tracheal tubes to provide a guide to placement. If the tracheal tube can move 2 cm upwards with neck extension and the cuff should be safely placed 1 cm below the vocal cords to avoid compression of the recurrent laryngeal nerve [5], then the black mark should be 3 cm above the cuff. Indeed, when examining commonly available tracheal tubes (e.g. Portex, Mallinckrodt Hi-Lo and Rusch) the distance from the mark (which is recommended to be at the level of the glottis) and the tip of the tube is approximately 9 cm and the distance from the mark to the top of the cuff is frequently 3 cm. It is our recommendation that, in Cormack & Lehane Grade 1 or 2 oral intubations, the tracheal tube is passed through the glottis and the black line is at or less than 2 cm above the glottis (when the head remains in a stationary position). The distance marking on the tube is noted in relation to a fixed point, for example top front incisors,) and the tracheal tube is fixed at this point. Finally, the chest is auscultated in the axillae (being the two points on the chest that are the furthest from each other in the transverse plane). Therefore, the act of auscultation takes its rightful place secondary to optimally placing the tracheal tube under direct vision. Auscultation of the chest after tracheal intubation then plays the following roles: Detection of endobronchial intubation in the patient with a short trachea (< 7 cm). Detection of additional sounds such as crepitations or rhonchi that may indicate pulmonary pathology which may not be detected by other monitors such as airway pressure measurement, capnography and Sao2. In addition, if there are any adverse events, direct laryngoscopy to confirm the correct placement of the tracheal tube may prove to be more informative than chest auscultation. In cases of Cormack & Lehane Grade 3 and 4 intubation, auscultation of the chest has the necessary additional role of detecting oesophageal intubation, as the operator is unable to see the tracheal tube pass through the glottis.