Authors’ contributions
LV and DO concept, design and drafting the manuscript. TB, FB, EB, FB,
GF critical revision of the manuscript for important intellectual
content. RK and DL critical review and editing the manuscript. All
authors read and approved the final manuscript.
Lung ultrasound
During this ongoing battle against the novel COVID-19, LU has quickly
been recognized as a tool for diagnosis and monitoring of lung
involvement severity (1).
A normal LU demonstrates what are termed A lines. These are a repetition
of the pleural line at the same distance from skin to the pleural line.
This is indicative of air below the pleural line, corresponding to the
parietal pleura. Lines may be complete or partial (Figure 1, Movie 1).
Demonstration of B lines are described as hyperechoic laser-like
artifacts that resemble a “comet tail” (Figure 2). These arise from
the pleural line and move in concert with a sliding lung. The A lines
are generally not present. B1 lines are associated with an interstitial
syndrome and diminished lung aeration. B2 lines are confluent lines
appearing as a “white lung” (called also glass-rockets), equivalent to
computed tomography (CT) ground-glass opacities. This suggests a more
severe loss of lung aeration (Movies 2 and 3).
Lung consolidations (C) are associated with hepatization of lung
parenchyma with or without air bronchograms, and suggest major loss of
lung aeration (atelectasis vs. pneumonia) (Movie 4).
We have not identified an ultrasound appearance that would be
pathognomonic of COVID-19 (4).
Lung ultrasound score
The lung ultrasound score (LUS) has been shown to be a useful tool in
intensive care (ICU) patients with adult respiratory distress syndrome
(ARDS). We feel this has been of value in assessing severity of lung
involvement with COVID-19 (2-3).
One may perform a topographic analysis of the underlying lung regions
daily without moving the patient. A scan of the three different areas of
the thorax: anterior, lateral, and posterior, and then superior and
inferior segments are performed. Thus, six specific regions for each
lung are defined and categorized by one of four different aeration
patterns.
A point scoring system is employed by region and ultrasound pattern as:
A = 0 point, B1 = 1 point, B2 = 2 points, C = 3 points. Thus, a LUS of 0
is normal, and 36 would be the worst.
LUS score can be used to follow the clinical patient trajectory in which
an increased score means decreased lung aeration, while on the contrary,
a decrease in score means an increase in lung aeration limiting the need
of chest x-ray and CT scan (4).
An experienced sonographer can do this examination within 5 minutes,
while brief training and about 25 supervised exams seem to be sufficient
to achieve a basic ability to perform the study (5). A prior study
showed the impact of LU to affect clinical decisions in up to 50% of
intensive care unit patients (6).
Clinical context
Although a patient’s clinical context allows for an improved pre-test
estimate of COVID-19 lung involvement, it appears that LU may serve as a
bedside tool to improve evaluation of lung involvement, and also reduce
the use of chest x-rays and CT (7). In addition, several intensive care
units following central venous line positioning with ultrasound, have
not been routinely obtaining post insertion chest x-rays (8-9).
While the ability of a chest x-ray to discriminate a bacterial pneumonia
from a non-bacterial infection is no more than 60% (10), LU has a
higher sensitivity (80%) (11). Specific comparison studies in
critically ill patients regarding viral pneumonia, however, are few
(12).
Conclusion
During this pandemic we have used LU in patients suspected or diagnosed
with COVID-19. Application of LUS has allowed for identification of
patients with lung involvement and severity. In addition, serial studies
help us follow for progression or regression of disease.
With the application of LU we have had a noted reduction in use of chest
x-rays and CT scans during this pandemic, helping make care and
management of our patients a little more efficient.
REFERENCES
- Peng QY, Wang XT, Zhang LN, Chinese Critical Care Ultrasound Study
Group (CCUSG). Finding of lung ultrasonography of novel coronavirus
pneumonia during the 2019-2020 epidemic. Intensive Care Med 2020 Mar
12. doi: 10.1007/s00134-020-05996-6.
- Man MA, Dantes E, Domokos Hancu B, Bondor CI, Ruscovan A, Parau A,
Motoc NS, Marc M. Correlation between transthoracic lung ultrasound
score and HRCT features in patients with interstitial lung diseases. J
Clin Med 2019; 8 (8). pii: E1199. doi: 10.3390/jcm8081199.
- Zhao Z, Jiang L, Xi X, Jiang Q, Zhu B, Wang M, Xing J, Zhang D.
Prognostic value of extravascular lung water assessed with lung
ultrasound score by chest sonography in patients with acute
respiratory distress syndrome. BMC Pulm Med. 2015;15: 98. doi:
10.1186/s12890-015-0091-2.
- Bouhemad B, Mongodi S, Via Gabriele, Rouquette I. Ultrasound for
“Lung Monitoring” of ventilation patients. Anesthesiology 2015;122:
437-47. doi: 10.1097/ALN.0000000000000558.
- Rouby JJ, Arbelot C, Gao Y, et al. Training for Lung Ultrasound Score
Measurement in Critically Ill Patients. Am J Respir Crit Care Med
2018. [Epub ahead of print].
- Xirouchaki N, Kondili E, Prinianakis G, et al. Impact of lung
ultrasound on clinical decision making in critically ill patients.
Intensive Care Med 2014;40:57-65.
- Brogi E, Bignami E, Sidoti A, Shawae M, Gargani L, Vetrugno L, et al.
Could the use of bedside lung ultrasound reduce the number of chest
x-rays in the intensive care unit? Cardiovasc Ultrasound 2017; 15:23.
doi: 10.1186/s12947-017-0113-8.
- Smit JM, Haaksma ME, Lim EHT, Steenvoorden TS, Blans MJ, Bosch. FH et
al. Ultrasound to detect central venous catheter placement associated
complications: a multicenter diagnostic accuracy study. Anesthesiology
2020; 132:781-94. Doi: 10.1097/ALN.0000000000003126.
- Vetrugno L, Bove T, Orso D, Flabio B, Boero E, Ferrari G. Lung
ultrasound and COVID-19 “pattern”: not all that glitters today is
gold tomorrow. J Ultrasound in Med. (Accepted for publication)
- Courtoy I, Lande AE, Turner RB. Accuracy of radiographic
differentiation of bacterial from nonbacterial pneumonia. Clin Pediatr
(Phila) 1989; 28(6): 261-264.
- Berce V, Tomazin M, Gorenjak M, Berce T, Lovrenčič B. The usefulness
of lung ultrasound for the aetiological diagnosis of
community-acquired pneumonia in children. Sci Rep 2019; 9(1): 17957.
- Testa A, Soldati G, Copetti R, Giannuzzi R, Portale G, Gentiloni
Silveri N. Early recognition of the 2009 pandemic influenza A (H1N1)
pneumonia by chest ultrasound. Crit Care 2012; 16(1): R30.
Figures
Figure 1. Lung ultrasound of normal aerated lung. A lines are visible:
they are a repetition of the pleural line at the same distance from skin
to pleural line. This indicates the presence of air below the pleural
line (which corresponds to the parietal pleura). A lines can be complete
or partial (as in this image);
Figure 2. Lung ultrasound of interstitial syndrome, characterized by the
presence of three or more B lines between two ribs. B lines are
hyperechoic laser-like artifacts that resemble a comet tail, arise from
the pleural line and move in concert with lung sliding. A lines are
wiped out.
Supplemental information
Movie1: Anterior region with A lines.
Movie 2: Posterior region with coalescent B lines.
Movie 3: A thickened and disrupted pleural line with B lines.
Movie 4: A subpleural consolidation disappearing with inspiration.