Feasibility of a New Lung Ultrasound Protocol to Determine the Extent of Lung Injury in COVID-19 Pneumonia

Abstract

Background: Lung ultrasound (LUS) scanning is useful to diagnose and assess the severity of pulmonary lesions during COVID-19-related ARDS (CoARDS). A conventional LUS score is proposed to measure the loss of aeration during CoARDS. However, this score was validated during the pre-COVID-19 era in patients with ARDS in the ICU and does not consider the differences with CoARDS. An alternative LUS method is based on grading the percentage of extension of the typical signs of COVID-19 pneumonia on the lung surface (LUSext).

Research question: Is LUSext feasible in patients with COVID-19 at the onset of disease, and does it correlate with the volumetric measure of severity of COVID-19 pneumonia lesions at CT scan (CTvol)?

Study design and methods: This observational study enrolled a convenience sampling of patients in the ED with confirmed COVID-19 whose condition demonstrated pneumonia at bedside LUS and CT scan. LUSext was visually quantified. All CT scan studies were analyzed retrospectively by a specifically designed software to calculate the CTvol. The correlation between LUSext and CTvol, and the correlations of each score with Pao₂/Fio₂ ratio were calculated.

Results: We analyzed data from 179 patients. Feasibility of LUSext was 100%. Time to perform LUS scan was 5 ± 1.5 mins. LUSext and CTvol were correlated positively (R = 0.67; P < .0001). Both LUSext and CTvol showed negative correlation with Pao₂/Fio₂ ratio (R = -0.66 and R = -0.54; P < .0001, respectively).

Interpretation: LUSext is a valid measure of the severity of the lesions when compared with the CT scan. Not only are LUSext and CTvol correlated, but they also have similar inverse correlation with the severity of respiratory failure. LUSext is a practical and simple bedside measure of the severity of pneumonia in CoARDS, whose clinical and prognostic impact need to be investigated further.

Keywords: ARDS; COVID-19 pneumonia; CT volumetry; interstitial pneumonia; lung ultrasound; lung ultrasound scoring.

Figure 1

A and B, The four chest areas that were examined to assess the extension of the pulmonary lesions in patients with COVID-19 pneumonia. A, Patient is first placed in the supine position: area 1 is scanned longitudinally between the sternum and the anterior axillary line; area 2 is scanned longitudinally between the anterior axillary line and the posterior axillary line. B, Patient is then turned in the lateral decubitus: area 3 is scanned longitudinally between the spine and the medial margin of the scapula; area 4 is scanned in oblique (along the intercostal spaces) below the inferior margin of the scapula. The same procedure is then repeated on the other side.

Figure 2

The scheme for collection of the data on the visual extension in percentage of the COVID-19 pulmonary lesions, visible by lung ultrasound examination on the chest wall. Each area is examined, and a percentage of 0-25-50-75-100% is assigned visually. The final score in percentage is given by the sum of the percentage of each area divided for the total of eight scans.

Figure 3

The flow diagram shows the flow of participants to our study. In the group of 98 patients who did not perform lung ultrasound extension scoring, six patients had an alternative lung ultrasound diagnosis. LUS = lung ultrasound scan; LUSext = lung ultrasound extension score.

Figure 4

A-D, Correlations between A, lung ultrasound extension score and the CT scan volumetry of pulmonary lesions; B, lung ultrasound extension score and Pao₂/Fio₂ ratio; and C, CT scan volumetry of pulmonary lesions and Pao₂/Fio₂ ratio, in 179 patients with COVID-19 pneumonia. D, Correlations between lung ultrasound extension score and the CT scan volumetry of pulmonary lesions in a subgroup of 114 patients with Pao₂/Fio₂ ratio <300 mm Hg at presentation. CTvol = CT scan volumetry; LUSext = lung ultrasound extension score; P/F = Pao₂/Fio₂ ratio.