1. Correct Answer: B. There is a left mainstem intubation

Rationale: The M-mode ultrasound in Figure 78.1 shows vertical movement extending from the pleura to the bottom of the screen at regular intervals, representing brief movements of lung tissue. These movements correlate with heartbeats, and this ultrasound pattern is called the lung pulse. The lung pulse confirms the presence of both layers of pleura and excludes pneumothorax at that location. Air between the pleural layers (pneumothorax) would reflect the ultrasound waves, and no cardiac movement could be seen. Normal ventilation should produce a “beach sign” on M-mode. Since this pattern is not seen during ventilation, one should consider the possibility of pneumothorax, or lack of lung movement for other reasons. Because the presence of lung pulse rules out pneumothorax, a lack of ventilation to the right lung is most likely, from esophageal intubation, left-mainstem intubation, or another process obstructing ventilation to the right lung.

1. Lichtenstein D. Lung Ultrasound in the Critically Ill. Springer; 2016, Chapter 31 and 34.

2. Correct Answer: B. The ETT is in the trachea

Rationale: Ultrasound can be a useful adjunct for examination of the upper airway. The ultrasound shown demonstrates a 2D view of the trachea in the long axis (sagittal view), with the left side of the image cephalad, and the right caudad, using a linear transducer. In Figure 78.4, the cricoid cartilage (CC, on the left side) and tracheal cartilages (TC, on the right side of the screen) are visible. Cartilage has an oval hypoechoic appearance. The bright line just below the cartilages represents the air-mucosa (A-M) interface. Reverberations (R, below A-M) represent comet tail artifacts. The ETT is seen as a double line structure, better seen on the right of the screen. Because air does not conduct ultrasound waves well, to make the ETT visible, the cuff was filled here with normal saline. This examination is consistent with endotracheal intubation (choice B is correct). The esophagus and internal jugular veins are not visible in the image (choices A, C are incorrect).

An esophageal intubation will appear lateral to the anterior trachea on a transverse image taken approximately 1 inch above the suprasternal notch (the “double-tract” sign, white arrows, Figure 78.5). The tube diameter visible on the ultrasound is too large for a misplaced NG tube (choice D is incorrect). Also, the well-visible tube segment is due to the cuff filled with saline surrounding the tube, something that would not be possible with an NG tube. In a study by Arya et al., ultrasound identified 100% of tracheal intubations and 83% of esophageal intubations.