Table 2.

A simplified description of where in the COVID‐19 patient care pathway lung ultrasound is of most use

Severity of COVID‐19–related lung injury	Typical sonographic characteristics	Typical clinical characteristics
Pre‐disease to moderate	Development of B‐lines which begin to increase in number and distribution. The pleural line begins to become irregular. Areas with B‐lines are adjacent to normal areas of lung sliding and A‐lines. These are ‘skip lesions’ or ‘spared areas’. Small (~1 cm) consolidations.	Respiratory rate > 30 min−1. Oxygen saturations ≤93% on room air. The need for supplemental oxygen. Lung tissue begins to lose aeration.
Severe	B‐lines continue to increase in number and distribution, and begin to affect the upper and anterior areas of the lungs. B‐lines become coalescent/confluent. Small consolidations increase in number and size.	Oxygen saturations ≤ 93% on supplementary oxygen. Clinical signs of respiratory distress. The need for additional supplemental oxygen or respiratory support. Lung tissue is becoming progressively de‐aerated.
Critical	Extensive coalescent B‐lines affect the upper and anterior areas of the lungs. Significant small consolidations affect the upper and anterior areas of the lungs. Posterio‐basal sections of the lungs have significant bilateral alveolar interstitial syndrome progressing to consolidation with or without air bronchograms. Pleural effusions are small or rare unless the patient's fluid balance is high.	Likely to be or require invasive mechanical ventilation. The need for a high fraction of inspired oxygen. Dependent areas of lung tissue have becoming non‐aerated.