Protocol and Guidelines for Point-of-Care Lung Ultrasound in Diagnosing Neonatal Pulmonary Diseases Based on International Expert Consensus

The ultrasound has been successfully used for neonatal lung disease diagnosis, but only three hospitals have mastered this technique. This protocol is helpful for shortening the learning curve. Compared with chest x-rays, the ultrasound is more accurate for diagnosing lung diseases and it is easy to learn, can be performed at the bedside, and is safe for neonates and the medical staff.

Ultrasound is not only used for lung disease diagnosis, but also can be used to guide or assist the treatment and nursing of neonatal lung disease with many benefits. Lung ultrasound is a new application field and a new technology. Visual demonstration shows how to perform the technique intuitively for new learners.

Disinfect a high-frequency linear probe for point-of-care lung ultrasound before and after each patient examination to avoid nosocomial infection and cross-contamination. To optimize the image for lung scanning, select one type of small parts preset and adjust the depth to four to five centimeters. Click Focus Zone to select one to two focuses and adjust the focus position to near the level of the plural line.

Turn on Speckle Reduction Imaging and select level two to three to reduce the speckle noise. Turn on the crossbeam and select level two to improve the contrast resolution. Then, activate the harmonics to improve the signal-noise ratio, or select the fundamental frequency for sharper A or B lines.

When the scanning perimeters have been set, apply a layer of pre-warmed gel on the transducer. Then, place the infant in the appropriate position for the first part of the exam. For lung portioning by the six-region method, use the anterior axillary line and the posterior axillary line as boundaries, and divide each lung into one anterior, lateral, and posterior lung region to achieve a total of six regions for scanning.

For lung portioning by the 12-region method, in addition to dividing each lung into three regions as demonstrated, and use the line that connects the nipples to divide each lung into upper and lower lung fields, for a total of 12 regions. When the lung has been portioned, place the transducer on the top region of the left or right chest, and press the appropriate button on the instrument interface to scan in B-mode. For perpendicular scanning, adjust the transducer so that it is perpendicular to the ribs, and slide the transducer from the midline to the lateral side along the wide axis.

Then, move the transducer down to the next region, keeping the transducer perpendicular to the ribs as just demonstrated. Take care to always keep the transducer perpendicular to the ribs to obtain accurate and reliable results while performing perpendicular scanning. When all of the regions have been scanned in perpendicular, return the probe to the top left region and rotate the transducer 90 degrees, so that it is parallel to the ribs.

Then, slide the probe along the narrow axis to obtain a scan of the first region, and repeat the parallel scan for the rest of the lung portions. After the anterior chest has been imaged, move the transducer to the subaxillary region to scan the lateral chest. After lateral chest scanning has been finished, place the transducer below the xiphoid and angle the transducer from side to side to scan the diaphragm and the bottom of the lungs via the liver as the acoustic window.

When the transdiaphragmatic scanning finishes, change the neonatal position to the prone or lateral position to scan the posterior chest or other subaxillary region. The neonatal normal lung field appears hypoechoic on a B-mode ultrasound. Plural lines and A-lines are smooth, regular and parallel, forming a bamboo-like appearance called the bamboo sign, whereas in M-mode imaging, the lines appear as the seashore sign.

Respiratory distress syndrome mainly manifests as lung consolidation with significant air bronchograms, as well as abnormal plural line and absent A-lines. Mild transient tachypnea can be assessed by lung ultrasound and mainly manifests as alveolar interstitial syndrome and a double lung point. Severe transient tachypnea in the acute period mainly manifests as a compact B-line, white lung, or severe alveolar interstitial syndrome.

Mild and severe transient tachypnea are also characterized by plural line abnormalities, A-line disappearance, and different degrees of plural effusion in one or both sides of the chest. Pneumonia is characterized by lung consolidations accompanied by air bronchograms. The size of the consolidation in severe pneumonia is usually large with irregular or jagged boundaries.

Lung consolidation is the most important sonogram characteristic of meconium aspiration syndrome, and the size of the consolidation is related to the degree of the disease. The plural and A-lines and disappearance of lung sliding are the most important ultrasonic indicators of pneumothorax. Selecting a high-frequency linear probe and choosing a lung ultrasound preset, and scanning perpendicular to the ribs are critical to the success of this technique.