To the Editor:
I read with interest the article by Ramsingh et al.1 regarding point-of-care ultrasound verification of endotracheal tube (ETT) insertion depth. Numerous tests had been previously utilized to prevent and/or detect inadvertent endobronchial (main stem) intubation.2 Each one of these tests has its own advantages and limitations. Undoubtedly, the use of point-of-care ultrasonography is a welcome addition, but it should not be forgotten that like any other confirmatory test, it has its own limitations. For example, deflation and reinflation of the ETT cuff to detect tracheal widening may not be safe when there is a high risk of aspiration as in trauma or obstetric patients. Applying cricoid pressure in rapid sequence induction situations may limit the area of transducer movement or distort the image. Ultrasound verification cannot be used when there is a neck collar in place unless the collar is released. Furthermore, the lung pleural sliding sign can be absent in patients with pleurisy, pneumothorax, pneumonia, or pulmonary consolidation3 in spite of correct ETT position (false positive) and artifacts may mimic pleural sliding after pneumonectomy even with main stem intubation4 (false negative). Since the displacement of a properly positioned ETT may occur with changes in the head, neck, and body positions,5 it has been recommended to periodically check the ETT position both intraoperatively and in ventilated patients in the critical care setting. The use of ultrasound may be difficult or impossible for intraoperative periodic assessment during surgery on the anterior or posterior neck, as well as during esophageal, thoracic, and trauma surgery where the surgical field may extend from the neck down. In all of these situations, other tests may be needed to verify proper positioning of the ETT. For early detection and correction of inadvertent endobronchial intubation, it is prudent to understand the limitations of ultrasound verification and to combine multiple confirmatory tests.
The author declares no competing interests.