The Use of M-Mode Ultrasonography to Differentiate the Causes of B Lines

The presence of B lines on lung ultrasonography is a characteristic feature of both cardiogenic pulmonary edema (CPE) and noncardiogenic alveolar interstitial syndrome (NCAIS), so their presence does not allow the clinician to differentiate between the two entities. Our study used M-mode ultrasonography of the pleura to differentiate CPE from NCAIS.

A total of 43 subjects were enrolled in the study, and based on history, physical examination, and chart review, the patients were divided into three groups: an NCAIS group, a CPE group, and a control group. Three distinct pleural line morphologic categories were identified: a continuous pleural line, a fragmented pleural line, and a sinusoidal pleural line. In addition, two separate subpleural patterns were independently identified by the investigators: a horizontal pattern and a vertical pattern. These pleural and subpleural patterns were correlated with subject diagnoses.

A fragmented pleural line and a vertical subpleural pattern on M-mode ultrasonography is associated with patients who have NCAIS. Most patients with CPE have a continuous pleural line and a vertical subpleural pattern on M-mode ultrasonography. A sinusoidal pleural line on M-mode ultrasonography is suggestive of the presence of a pleural effusion.

Our results indicate that M-mode ultrasonography is useful to distinguish CPE from NCAIS based on the pleural and the subpleural morphologic features.