Care of future mothers amid the <scp>COVID</scp>‐19 outbreak: is there a monitoring role for lung ultrasound?

Health professionals caring for women seek to support their patients as best as they can during the coronavirus disease 2019 (COVID-19) pandemic. Whether by reaching out to patients using telemedicine or spending extra time at the bedside, each moment of interaction can make these difficult times somewhat easier for women. We were interested to read but respectfully disagree with the assertion of Buonsenso et al. that ‘Although chest computed tomography (CT) represents the gold standard to assess lung involvement, with a specificity superior even to that of the nasopharyngeal swab for diagnosis, lung ultrasound examination can be a valid alternative to CT scan, with certain advantages, particularly for pregnant women.’1. The claimed valid and advantageous role of lung ultrasound as an alternative to CT scan is, in our opinion, unsupported and potentially misleading. We have concerns about the use of lung ultrasound for the diagnosis of lung involvement in patients with COVID-19. In their case series, Buonsenso et al. rely on the detection and quantification of B-lines for monitoring women with COVID-19, which they claim to be highly specific indicators of COVID-191. The authors are essentially referring to the use of ultrasound as a ‘stethoscope surrogate’. However, the same ultrasound appearance is seen in interstitial lung disease, heart failure, acute pulmonary edema and even in normal lungs2. Equally misleading is another article by the same authors which describes a training program on using lung ultrasound for the diagnosis and monitoring of COVID-19 pneumonia in pregnant women3. Observation of B-lines and characterization of such ultrasound artifacts, we feel, is unreliable because there is: (1) intra- and interoperator variability in quantifying B-lines, (2) variation in the type and frequency of the probe used and (3) variability in lung appearance depending on the ultrasound scan settings2, 4. The sonographic finding of B-lines in COVID-19 patients is highly non-specific and has considerable overlap with many non-COVID-19-related lung diseases. B-lines are visible even in residual cavities after pneumonectomy and, in our experience, are absent on intraoperative lung ultrasound scans of patients with interstitial lung disease. This is because B-lines are imaging artifacts arising from the difference in acoustic impedance between superficial and deeper structures4. Teaching such a technique to obstetricians3 has no obvious rationale and does not seem to relate to an unmet need. We suggest that clinicians should instead focus on remote monitoring of the respiratory function of pregnant patients, which could be facilitated by the use of a personal pulse oximetry device which future mothers can use at home. In our experience, which is shared with most emergency facilities, such a simple portable and cheap device is of great help in monitoring a worsening status in COVID-19 patients. The use of finger pulse oximeters at home by patients with COVID-19 could pre-empt the precipitous oxygen desaturation that leads to the need for intensive care5. During the COVID-19 pandemic, pseudoimaging approaches2, 4 should be discouraged and diversion of precious human and equipment resources and needless exposure of medical staff to unreliable diagnostic examinations should be avoided.