Since I graduated from anesthesia school, I have given up the time-honored habit of routine chest auscultation after passing the tracheal tube through the glottis. This is another practice that we have been taught in school as one of the best ways to confirm tube placement. I still remembered the first time I was asked to auscultate after the tube was in, I wasn’t sure whether the tube was in with all the background noises in the OR. The failure to hearing good lung sounds made me look into buying an electronic stethoscope. Fortunately, I didn’t spend $300-$400 on an expensive stethoscope. I realized that a bigger tidal volume and auscultation of midaxillary lines of the chest can help hear the lung sounds better upon auscultation in the OR. So if you just start out in the OR, you are questioning yourself why you can’t hear the lung sounds well to confirm tube placement, you are not alone.
Should we still honor the habit of auscultation in the elective case OR setting? This study shown above suggested otherwise. The reasons are as below: first of all, the reliability of auscultation is related to a tidal volume, sites of auscultation, and presence of gastric distension, . A bigger tidal volume, auscultation of midaxillary lines of the chest, and absence of gastric distension may improve sensitivity, whereas auscultation of the epigastrium may improve specificity. Secondly, it is subject to the examiner’s experience. In the study shown above, 55% of first year residents missed endobronchial intubation by auscultation in 55% of cases and performed significantly worse than experienced anaesthetists. Hence the interpretation of auscultation of the lung sounds is very subjective. In addition, Chest auscultation requires interruption of chest compressions during CPR. So it is really practical in the real emergency situation.
This study suggests that less experienced clinicians should rely more on tube insertion depth than on auscultation to detect inadvertent endobronchial intubation. Tube insertion length to 20-21 cm in women and 22-23 cm in men is important to avoid the endobronchial intubation, especially when high ambient noise precludes accurate auscultation. However, it fails to recognize the value of peak pressure as a useful tool to confirm tube placement immediately after insertion. If the length of the tube is correctly placed, and patient doesn’t have significant pulmonary diseases, airway peak pressure shouldn’t be significantly high. The peak pressure and ETCO2 waveform are usually adequate to confirm the endotracheal intubation.
Does it mean that it doesn’t warrant the need to auscultate after intubation? No, it doesn’t mean that. This blog is not meant to discredit the merit of auscultation, but rather we shouldn’t do it for the sake of doing it. We improve our practice based on the clinical evidence but based on the habit or “this is how we were taught”. If you have Cormack & Lehane Grade 3 and 4 intubation, auscultation of the chest has the necessary additional role of detecting esophageal intubation, as the practitioner is unable to see the tracheal tube pass through the glottis.In addition, if you are intubating someone on the floor where you don’t have access to the anesthesia machine (ETCO2, and Peak pressure), auscultation is still a confirmatory step to ensure the proper placement of the endotracheal tube.
Well, let me know what your thoughts are on this subject! Send me some comments!