lung pulse on ultrasound suggest lack of ventilation

Ultrasound of the right lung (Video 2) demonstrates “lung pulse,” which has 93% sensitivity and 100% specificity for apnea or lack of ventilation of the visualized lung. It also indicates that the parietal and visceral pleura are in contact. Among the choices provided, these conditions are most consistent with mucus plugging.

Lung pulse is the term used to describe pulsation of the lung due to the mechanical movement of the heart that is appreciable at the pleural surface via ultrasonography. The rate of lung pulse corresponds to heart rate. For lung pulse to be present, three conditions are necessary: absence of lung sliding; contact between the two surfaces of the pleura; and apnea of the visualized part of the lung.

Lung sliding is the ultrasonographic finding of movement along the pleural line caused by sliding of the parietal and visceral pleura against each other with respiratory motion. Under normal conditions, the prominent sliding movement of the pleura obscures lung pulse at the pleural surface. Absence of lung sliding allows lung pulse to be visible if other essential conditions (discussed below) are also present. Lung sliding can be absent owing to separation of the two surfaces of the pleura (as by air or fluid), inability of the two pleural surfaces to slide against each other (as with pleural adhesions), or lack of respiratory movement of the lung (as in atelectasis or apnea).

Separation of the parietal and visceral pleura by air or fluid dampens transmission of mechanical vibrations of the heart to the surface and mitigates lung pulse. Therefore, the presence of lung pulse implies that the two surfaces of the pleura are in contact and rules out pneumothorax or pleural effusion at that location.

Normal respiratory motion of the lung mitigates transmission of the mechanical movement of the heart to the pleural surface and ameliorates the finding of lung pulse. In addition to the absence of lung sliding, stillness of the lung is essential for vibration of cardiac contractions to be transmitted to the pleural surface. This can happen if the patient is apneic and when something prevents airflow in and out of a lung, such as contralateral mainstem intubation or mucus plug.

Importantly, lung pulse can occasionally be appreciated in ventilated lung between breaths when an inflated lung is still after the end of exhalation and before the beginning of the next breath. In that situation, lung sliding is present during inspiration, and rate of lung pulse is slower than heart rate.

In addition to lung pulse, ultrasound of the right chest (Video 2) also shows B lines (Figure 1). B lines are a type of reverberation artifact generated by thickening of the interstitium of the lung, as from pulmonary edema or interstitial fibrosis. As B lines arise from the interstitium, their presence indicates the absence of air between the surface of the probe and the interstitium of the lung. Hence, B lines are another sonographic sign that rules out pneumothorax even in the absence of lung sliding. Ultrasound of the left lung (Video 1) demonstrates normal aeration pattern with the presence of lung sliding and A lines.1234

Footnotes

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  2. Bhoil R, Ahluwalia A, Chopra R, et al. Signs and lines in lung ultrasound. J Ultrason. 2021;21(86):e225-e233. PubMed ↩

  3. Husain LF, Hagopian L, Wayman D, et al. Sonographic diagnosis of pneumothorax. J Emerg Trauma Shock. 2012;5(1):76-81. PubMed ↩

  4. Lichtenstein DA, Lascols N, Prin S, et al. The “lung pulse”: an early ultrasound sign of complete atelectasis. Intensive Care Med. 2003;29(12):2187-2192. PubMed ↩