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| REVIEW ARTICLE |
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| Year : 2020 | Volume
: 30
| Issue : 6 | Page : 6-10 |
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Lung ultrasound in the COVID-19 pandemic
Vito Cianci1, Mirko Zanatta2
1 Department of Emergency, University of Padova, Italy
2 Department of Emergency, Arzignano Hospital, Vicenza, Italy
| Date of Submission | 18-May-2020 |
| Date of Decision | 03-Oct-2020 |
| Date of Acceptance | 31-Aug-2020 |
| Date of Web Publication | 26-Oct-2020 |
Correspondence Address:
Mirko Zanatta
Department of Emergency, Arzignano Hospital, AULSS 8 Berica, Via Parco 1, Arzignano, Vicenza 36071
Italy
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jcecho.jcecho_50_20
Lung ultrasound (LUS) is one of the most important and innovative applications in emergency and critical care medicine for the management of critically ill patients. Ultrasound has been widely used in the COVID-19 pandemic as an extremely reliable technique and has proved to have a key role in the diagnosis and monitoring of patients with acute respiratory failure. The diagnostic accuracy of LUS is higher than chest X-ray and similar to computed tomography, which is considered the gold standard. COVID-19 pneumonia has some distinctive ultrasonographic signs but not pathognomonic, and LUS significantly improves the management of COVID-19 patients speeding up the diagnostic path. The examination is bedside; reduces the risk of contamination, avoiding mobilization of the patients; cuts down the amount of radioactive exposure; and gives real-time answers to many diagnostic and therapeutic doubts. Finally, the instruments are small and the scanner and the probes can be protected from contamination easily.
Keywords: COVID-19, lung ultrasound, pandemic, pneumonia
How to cite this article:
Cianci V, Zanatta M. Lung ultrasound in the COVID-19 pandemic. J Cardiovasc Echography 2020;30, Suppl S2:6-10 |
| Introduction | |  |
Lung ultrasound (LUS) is one of the most important and innovative applications in emergency and critical care medicine, and its use has significantly changed the management of critically ill patients.[1],[2],[3],[4]
Ultrasound has grown more relevant in the last years with the availability of new, small, handheld machines that can be carried to patients' beds and installed in different settings, both in hospital departments (emergency medicine, cardiology, internal medicine, pneumology, geriatric, infectious disease, surgery, and intensive care unit) and out of hospital on ambulances or helicopters.
Ultrasound has been widely used in the COVID-19 pandemic as an extremely reliable technique.[5],[6],[7],[8],[9] It can be adapted to all settings where patients are managed, gives rapid and clear answers, and is safe and cost-effective.
It reduces the amount of radioactive exposure, permits to monitor the lung lesions, gives real-time answers to specific clinical questions and an important feedback about the effects of pharmacological treatment and ventilation. In addition, the possibility to perform the examination bedside without moving the patient reduces the risk of contamination.
Hence, LUS is considered suitable for an extensive use in the COVID-19 pandemic, according to the original meaning of critical ultrasound: “when there is a dangerous performance gap between the patient status and the resources available for an appropriate decision-making and problem-solving.”[2],[10]
| Methods | | |
The technique could be extremely different according to the clinical conditions, which range from patients without any symptoms to those with severe respiratory insufficiency, and to the setting (emergency department, medical department, and intensive care unit).[1],[3]
Patients with a suspected or confirmed COVID-19 infection are usually placed in a supine position or seated on the bed in order to examine the posterior and basal areas of the lungs.[11],[12]
Those with severe respiratory distress syndrome or treated with continuous positive airway pressure (CPAP) or a noninvasive ventilation (NIV) are usually placed in a supine position with an elevation of the chest of 30°–45°, reducing the possibility to scan the posterior regions. Collaborative patients can be slightly turned on the right and left sides using a pillow or a rolled-up blanket.
On the other side, the anterior areas are hidden when “the prone swimmer position,” is used for prone position ventilation. The elevation of the shoulder with a pillow, as described by Uglade, forms a space to put the transducer and opens an important window toward the anterior parts of the chest.[13]
In terms of choosing the probe, LUS is usually performed with a 3.5 MHz convex transducer for the identification of the lung profile (A: dry; B: wet [14]), consolidations, and pleural effusions, with a high-frequency linear probe (7.5–12 MHz) for a more precise and accurate evaluation of the pleural line, lung sliding, and subpleural consolidations. Color Doppler function is sometimes useful for better characterization of lung consolidations.[12]
A suitable presetting of the scanner is mandatory, selecting the appropriate lung preset and gain, for the best visualization of the pleura and B-lines. If a lung preset is not available, the abdomen preset should be chosen.
The most comprehensive examination, in a patient with a suspected or confirmed COVID-19 infection, includes the 12-regions technique, which also permits to scan the posterior areas of the lungs [Figure 1].[3],[11],[12] | Figure 1: The 12-regions technique in patients with suspected COVID-19 pneumonia
Click here to view |
One of the methods that has been recently established worldwide [11],[12] suggests to divide each lung into six regions, which are generated by the intersections of the parasternal line (PSL), anterior axillary line (AAL), posterior axillary line (PAL), and paravertebral line (PVL) with the horizontal intermammillary line: regions 1 and 2 denote the anterior superior and anterior inferior areas; regions 3 and 4 represent the lateral superior and lateral inferior areas; and regions 5 and 6 represent the posterior superior and inferior areas.
The examination usually starts from the PSL searching for the lung sliding longitudinally, moves downward and laterally toward the AAL, PAL, and PVL; then, it is necessary to complete the scan with transversal and oblique scans, to prevent the posterior shadowing of the ribs. This panoramic examination of the chest is called “the lawn mower technique” [Figure 2].[11],[12]
The operator must pay attention to protect himself/herself from the risk of contamination during the bedside examination of patients with suspected COVID-19 infection: an appropriate separation from the face of the patient must be guaranteed to prevent accidental contact with the infectious droplets that come from sneezes, cough, nebulizer, CPAP, and NIV; the use of individual protection devices is mandatory. Intubated patients might slightly reduce the risk of contamination because the airways are sealed by the endotracheal tube.
Finally, the ultrasound must be adequately prepared by covering both the machine and the probes with disposable protections and cleaned with an appropriate cleanser at the end of the examination.
| Semeiotics | | |
COVID-19 pneumonia has some distinctive ultrasonographic patterns but not pathognomonic; these patterns can also be found in many other bacterial or viral pneumonia and in acute respiratory distress syndrome (ARDS) [Table 1].[14],[15],[16] | Table 1: The ultrasonographic and computed tomography characteristics of COVID-19 pneumonia
Click here to view |
The most important features can be sought in three lung landmarks:
- Pleural line
- Subpleural area
- Costophrenic angle.
The most important finding in the COVID-19 pneumonia is the “B-line,” which may appear as isolated and nonhomogeneous vertical artifacts or as a storm of aggregated and fused lines in the “white lung” pattern; in the middle, there are all the intermediate clinical pictures of the interstitial syndrome [Figure 3].[4],[14],[15]
They start from the pleural line or from lung consolidations, in a way that resembles other interstitial pneumonia. Nevertheless, in COVID-19 pneumonia, a wide and bright B-line has been often observed, which looks like a “light beam” that switches on and off when the patient breaths.[9] Areas of a normal lung are usually next to pathological findings, and the “light beam” sign represents an early manifestation of a lung lesion [Figure 4].
Pleural line is often irregular and thickened, and even short interruptions of the line are observed in correspondence with lung consolidations [Figure 5] and [Figure 6]. The distribution of these findings is irregular, patchy, and not homogeneous, and they should be scanned and studied with a high-frequency linear probe.[4],[14],[15] | Figure 6: Interstitial syndrome with multiple B-lines, irregular pleural line, and subpleural mini-consolidations
Click here to view |
Subpleural consolidations are another important pathological feature of COVID-19 pneumonia: they are mainly small, hypoechoic consolidations, located under the pleural line; they are usually identified in both lungs, have different shapes (triangular, circular, and stretched), and do not have any color-Doppler echo [Figure 5], [Figure 6], [Figure 7].[4],[14],[15]
Larger consolidations are the ultrasonographic sign of pneumonia, which are often observed in the posterior areas, in severe and advanced lung disease, and caused by the high local inflammation. These lesions have nonhomogeneous echogenicity, B-line artifacts at the far-field margin, and both air and fluid bronchograms [Figure 8] and [Figure 9].[4],[15],[17] | Figure 9: Thickened and irregular pleural line with small subpleural consolidation
Click here to view |
Small and thin pleural effusions can be found next to the lung consolidations, whereas either moderate or severe pleural effusions are not usually observed in COVID-19 pneumonia [Figure 10].[4],[14],[15],[17]
| Diagnosis, Monitoring, and Stratification | | |
LUS is an important and adaptable tool, and it represents the first step of the instrumental evaluation in a patient suspected of having COVID-19 infection. The triad of COVID-19's diagnostic pathway involves chest X-ray, computed tomography (CT) scan, and ultrasound.
LUS has demonstrated to be relevant and unique to rule in or rule out an interstitial syndrome; it has a high sensitivity and a moderate specificity, and the global accuracy is higher than that of the chest X-ray.[12]
The performance of ultrasound in COVID-19 infection resembles, in many situations and settings, a CT scan of the chest, which is considered the gold standard.
Although COVID-19 infection does not have a pathognomonic lung pattern, resembling other bacterial or viral pneumonia and ARDS, many studies have already demonstrated the capability of ultrasound to identify some typical lung features of COVID-19 pneumonia. The ultrasonographic and CT characteristics of COVID-19 pneumonia are described in [Table 1].[14],[15],[16]
On the other hand, COVID-19 has some lung characteristics that are completely different from those observed in a cardiogenic pulmonary edema, and the differences are summarized in [Table 2].[12] | Table 2: Lung ultrasound differences between cardiogenic pulmonary edema and COVID-19 pneumonia
Click here to view |
In addition, a new interesting role of ultrasound is gaining importance: the monitoring of patients and the estimation of prognosis. It can estimate short-term prognosis effectively; in particular, it has a high negative predictive value and it can identify early pleural and lung lesions and can predict worsening of clinical conditions.
When LUS is performed together with point-of-care echocardiography combined with the evaluation of inferior vena cava, it can also be used to monitor patients with COIVD-19 pneumonia in a step-by-step manner. It enables physicians to evaluate the effect of pharmacological and fluid therapy; to set CPAP, NIV, and ventilator properly; to monitor the effect of ventilation on alveolar recruitment; and to guide weaning from mechanical ventilator. This new trend is in tune with the guidelines published by the most important international scientific societies, which consider critical ultrasound a useful diagnostic tool and an efficient instrument for monitoring and guiding the management of critically ill patients.[3],[18],[19]
In all these settings and situations, LUS maintains a high predictive value when it is strictly connected with all the other information that come from the patient's history, in particular the time related to the onset of the disease, physical examination, and laboratory and radiological findings.
| Conclusions | | |
LUS has all the features that make it a perfect, reliable, and adaptable instrument during the COVID-19 pandemic:
- Cost-effective
- High sensitivity
- Good specificity
- No radioactive exposure
- Bedside
- Reduced diagnostic time
- Reduced patient movements, thereby lowering the risk of contamination
- Prognostic capabilities
- Bedside monitoring.
LUS has become a modern and effective operative example that can be exploited in the management of a major global emergency, like the COVID-19 pandemic, where there is a gap between the current needs and the available resources.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
[Table 1], [Table 2]
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