Point-of-Care Lung Ultrasound in Adults: Image Acquisition

This protocol is a simple, but high yield approach to lung ultrasound image acquisition that evaluates three zones per hemithorax to screen for plural and pulmonary pathology. This technique efficiently samples each of the five lobes of the lung, in contrast to shorter protocols that omit posterior lung zones entirely, or longer protocols that are time consuming. This entire protocol can be performed by busy acute care providers in less than five minutes.

To begin, perform lung POCUS using a linear high-frequency probe. Use a low-frequency ultrasound probe to evaluate anything deeper than the interface of the visceral and parietal pleurae. To preset the machine, select abdomen, select varying depth, then select harmonic imaging disabled, followed by an indicator to the left of the screen.

Perform most of the study in a two-dimensional gray-scale mode called, brightness mode. Perform the studies with the patient sitting up or supine. Divide each hemithorax into three regions reflecting the anatomic segmentation of the lungs.

In the left chest, treat the lingula as the left side analog of the right middle lobe. Apply ultrasound gel to the transducer. Scan the right hemithorax by placing the probe in the mid clavicular line in the first to third intercostal spaces.

Position the probe in the parasagittal orientation, with the indicator mark pointing cranially. Now, click axis"and center the axis on the plural line, so that the cranial and codal rib shadows are visible on the edges of the images. If the dominant pattern is A lines with more than, or equal to, two B lines, decrease the depth so that only a single A line is visible.

If there are three B lines or more, increase the depth until at least two A lines are visible. Next, select the overall gain and adjust the gain until the plural line and A lines are visible as distinctly echogenic lines and the spaces between the plural line and A-lines are hypo-echoic. Then, click on acquire.

To visualize the right-middle lobe, place the probe in the anterior axillary line in the fourth to fifth intercostal space. Position the probe midway between the parasagittal and coronal orientations with the indicator mark pointing cranially. Set the axis, depth and overall gain as demonstrated earlier, and click acquire.

To image the right lower lobe, place the probe in the mid to posterior axillary line, in the fifth to seventh intercostal space. Position the probe in the coronal plane, with the indicator mark pointing cranially. Now, click the axis and center the axis on the diaphragm, such that both the sub-diaphragmatic and super-diaphragmatic structures are visible at the same time.

Click depth"and increase the depth until the subdiaphragmatic spine is visible. Click overall gain"and increase the gain until the liver or spleen appears slightly hyper-echoic. Next, scan the left hemothorax, and image the left upper lobe, by placing the probe in the mid clavicular line in the first to third intercostal space.

Position the probe in the parasagittal orientation with the indicator mark pointing cranially. Set the axis, depth and overall gain as shown previously and acquire the images. To visualize the lingula of the left upper lobe, place the probe in the anterior axillary line in the fourth to fifth intercostal space.

Position the probe midway between the parasagittal and coronal orientations with the indicator mark pointing cranially. Set the axis, depth and overall gain as shown while imaging the right upper lobe and acquire the images. Similarly, visualize the left lower lobe by placing the probe in the mid to posterior axillary line in the fifth to seventh intercostal space, and positioning the probe in the coronal plane with the indicator mark pointing cranially.

Again, set the axis, depth and overall gain as demonstrated while imaging the right lower lobe and acquire the images. The B-mode clip shows a static plural line consistent with a pneumothorax. However, the M-mode tracing shows a barcode intermittently interrupted by a seashore pattern.

This situation occurs commonly when trying to use M-mode to screen for pneumothorax. When a pneumothorax is present, The M-mode findings are often more ambiguous than the B-mode findings. A linear high-frequency transducer shows the L1 view with normal lung sliding and likely B-lines, and the R2 view without any of the following.

No lung sliding, no lung pulse, and no B-lines. The absence of these three findings is highly suggestive of pneumothorax. The only finding that is thought to be pathognomonic for pneumothorax is a lung point.

A lung point refers to the presence of lung sliding entering into, and then retreating completely, from an otherwise static plural line. The static plural line indicates the location of the pneumothorax. One to two thin B-lines per rib interspace are considered within the range of normal.

However, three or more B-lines, or a large confluent B-line occupying most of an interspace is considered pathological. An anechoic or hypo-echoic space between the parietal and visceral pleurae, indicating a plural effusion, is seen. R-3 view obtained in a patient in the setting of pericardiac arrest showed heterogeneous plural effusion with free floating debris.

This was due to acute bleeding into a chronic right plural effusion, creating a right-sided hemothorax. An L3 view showing two signs of lung consolidation shred sign and dynamic air bronchograms. Shred sign refers to the presence of an irregular hyper-echoic line in the middle of the lung parenchyma, from which vertical ring down artifacts propagate.

Dynamic air bronchograms are point-like, round decogenic areas within a consolidation that move during the respiratory cycle. When performing this procedure, it is important to adjust each view until the key expected structures are seen. The key structures for anterior, slash, intra-lateral views, are the plural line and ribs.

For posterior lateral views, the key structures are the following:the diaphragm, the subdiaphragmatic spine, the liver, slash, spleen, and the super diaphragmatic space. This protocol is designed to rapidly narrow the differential diagnosis of acute pulmonary dysfunction. Types of pulmonary dysfunction that would justify this lung ultrasound protocol include any of the following:tachypnea, dyspnea, hypoxemia and or hypercapnia.