Lung ultrasound in a Singapore COVID-19 intensive care unit patient and a review of its potential clinical utility in pandemic

On 31 December 2019, China informed the World Health Organization (WHO) of a novel viral pneumonia in the city of Wuhan (Hubei). The WHO declared the COVID-19 outbreak a public health emergency of international concern (PHEIC) on 30 January 2020. Subsequently, on 12 March 2020, the World Health Organization declared COVID-19 a pandemic⁽¹⁾.

Point-of-care lung ultrasound is performed at the patient’s bedside, and offers the trained clinician a rapid imaging adjunct to the chest X-ray and the CT (computed tomography) scanner. This is the first report describing the clinical features and lung ultrasound images of a patient with COVID-19 infection admitted to an intensive care unit in a Singapore regional general hospital. In addition, we provide a brief review of the potential clinical utility, and address the challenges associated with lung ultrasound in the current COVID-19 pandemic.

We present the case of a healthy 39-year-old female who complained of 4 days of coughing, exertional dyspnea and fever after returning from Malaysia a week prior. There was no history of travel to China or contacts with any confirmed COVID-19 cases.

The patient was admitted because of tachypnea and hypoxemia (PF(Pa02/Fi02) ratio 185). There were bilateral lower lobe consolidations on chest X-ray (CXR) (Fig. 1).

Fig. 1.

On day 4 of admission (D8 illness), because of escalating oxygen requirements, she was intubated and transferred to the intensive care unit (ICU) for further management with lung protective ventilation.

Point-of-care lung ultrasound was performed daily by either one of 2 identified lung ultrasound trained intensivists, using the ultrasound machine (GE Logiq E) curvilinear transducer with the abdominal pre-set in the ICU with a pre-determined protocol.

Three points on each side of the lung were identified for ultrasound imaging⁽²⁾. These were the upper BLUE point, the lower BLUE point, and the PLAPS points. The BLUE points corresponded to the midclavicular line, anterior-axillary, and posterior-axillary lines that were estimated locations of the upper lobe, middle lobe and lower lobes of each lung, as described by Daniel A. Lichtenstein.

Findings from multiple lung fields using the abdominal pre-set captured from the curvilinear probe were recorded for documentation purposes, and compared between the 2 trained intensivists.

Progress was assessed by the identification of areas of increased involvement and assessment of more or less B-lines. Areas of interest were further examined with the phase array and linear probe, if needed.

B-lines were the predominant feature in the reported case (Fig. 2 B). An increasing density and distribution of B-lines were associated with deteriorating oxygenation (Fig. 3). The “white lung” ultrasound feature (Fig. 2 A) was frequently found at the peak of clinical deterioration during days 10–12, and associated with the lowest P/F ratio.

Fig. 2.

Fig. 3.

Decreasing density and distribution of B-lines were associated with clinical improvement (Fig. 3). The coalescing and reduction of B-lines appear to reflect more closely clinical progression then serial chest X-ray imaging.

There were fragmented pleural lines associated with diffuse sub-pleural consolidations which projected B-lines (Fig. 4). The COVID-19 virus had a predisposition to the peripheral locations of the lung. Small peripheral consolidations with features of dynamic air bronchogram (Fig. 2 D), hepatization, and the sonographic “shred sign” (Fig. 2 C) were found early after the ICU admission of the patient which resolved first upon recovery before improvement with B-lines.

Fig. 4.

Our report illustrates the clinical features and point-of-care lung ultrasound images in a COVID-19 patient admitted to the ICU.

The main cause of mortality and morbidity in COVID-19 is respiratory failure⁽¹⁾. The role of point-of-care lung ultrasound in evaluating the causes of respiratory failure is well established in literature, and continues to be relevant in the evaluation of respiratory failure in COVID-19 patients^(3–5).

In our case report, lung ultrasound features of diffuse and bilateral B-lines with patchy involvement, pleural disruption, fine subpleural consolidations, and white lung features found in our experience are similar to those reported in other limited case studies^(6,7). These ultrasound features show good correlation with CT thorax performed in COVID-19 patients^(2,8).

Based on our observations and a literature review, there are 4 potential additional roles of point-of-care lung ultrasound in the current COVID-19 crisis.

Firstly, lung ultrasound can protect healthcare workers by reducing the usage of chest X-ray and CT scanning⁽⁹⁾. A significant percentage (3 to 10%) of COVID-19 patients are healthcare workers^(10,11). The ability of an operator to use lung ultrasound in place of chest X-ray/CT to simultaneously examine, acquire and interpret findings at the patient’s bedside prevents unnecessary transfers, and reduces the risk of contamination of the facility and exposure of other healthcare workers to COVID-19 patients.

Secondly, lung ultrasound can assist in the triage and assessment of clinical progression. An increasing density of B-lines and involvement of more lung fields have been shown to be correlated with clinical progress, peaking at days 10–12^(2,7,8). This finding has been incorporated in the triage protocol in Italian hospitals to assist physicians in identifying ill COVID-19 patients who may benefit from the escalation of care^(12,13). Lung ultrasound also shows good correlation in the early identification and assessment of morbidity and mortality in the management of acute respiratory distress syndrome^(14,15). The Kigali Modification of the Berlin Criteria for the diagnosis of acute respiratory distress syndrome that utilizes lung ultrasound has been shown to improve the diagnosis of acute respiratory distress syndrome in resource-limited settings^(16,17). In the context of ARDS secondary to COVID-19, the quantification of lung ultrasound via the lung ultrasound score is associated with increased severity and mortality from ARDS⁽¹⁸⁾.

Thirdly, the Surviving Sepsis Campaign Guidelines on the Management of Critically Ill Adults with Coronavirus Disease 2019 (COVID-19) give a strong recommendation for the early initiation of proning for severe hypoxia in COVID-19 pulmonary infection⁽¹⁹⁾. Early proning is associated with a reduction in intubation, and an improvement in mortality in COVID-19 patients, as suggested by a multicenter cohort study by the Chinese, and should ideally be performed in patients with bibasal/posterior involvement of the lung^(20–23). Detection of B-lines in the bilateral posterior/basal aspects of the lung may allow physicians to select patients (both awake and intubated) who will benefit most from proning.

Fourthly, a recommendation for the management of critically ill COVID-19 patients is the early use of moderate to high PEEP for lung recruitment, though this needs to be individualized in view of the risk of barotrauma and hemodynamic instability. Reaeration visualized on lung ultrasound can be used as a bedside adjunct to determine PEEP-induced lung recruitment⁽²⁴⁾.

Our case report also highlights challenges associated with the widespread use of lung ultrasound in the management of COVID-19 patients.

Firstly, the features of B-lines that may be representative of ground glass changes or interstitial syndrome associated with subpleural consolidations are non-specific. This feature can also be seen in other viral infections such as measles, influenza, and respiratory syncytial virus infection^(25–27). Hence, there is insufficient evidence to rely solely on this lung ultrasound finding for the diagnosis of COVID-19.

Secondly, the application of point-of-care ultrasound is operator-dependent, and requires basic training. Even so, learners have found that it is not difficult to acquire basic lung ultrasound skills over a short period of time, with a minimum required number of 25 supervised scans⁽²⁸⁾.

Thirdly, the precise lung ultrasound protocol best suited to COVID-19 patients has not been established. The BLUE protocol achieves the imaging of a total of 6 lung fields⁽⁴⁾. It was chosen, as they were in areas most accessible in our critically ill patients. A disadvantage is that since involvement is patchy, areas of involvement may be missed. Some physicians have used more lung ultrasound fields in patients who are less ill and more ambulatory. A proposed standardized lung ultrasound score by Soldati et al. comprising 14 sites with a standardized lung score may be better suited^(12,13).

Fourthly, there is no standardized protocol for the disinfection of ultrasound units. This could be overcome by the use of hand-held ultrasound devices that are cheaper and easier to disinfect. However, further research is required on this aspect.

Our report illustrates the ultrasound findings observed in a COVID-19 patient, and the potential use and challenges associated with lung ultrasound for physicians who need a diagnostic adjunct for non-specific respiratory symptoms in patients during the current COVID-10 pandemic. Point-of-care lung ultrasound can be considered an alternative imaging modality, replacing chest X-ray and CT scanning, in the triage and ongoing management of patients to protect healthcare workers in resources-constrained settings in the COVID-19 pandemic.