Early lung ultrasound assessment for the prognosis of patients hospitalized for COVID-19 pneumonia. A pilot study

Sensitivity of Lung Point-of-Care Ultrasound (POCUS) to Predict Oxygen Requirements in Emerging Viral Infections

OBJECTIVES

The prognostic characteristics of lung point-of-care ultrasound (L-POCUS) to predict respiratory decompensation in patients with emerging infections remains unstudied. Our objective was to examine whether scored lung ultrasounds predict hypoxia among a nonhypoxic, ambulatory population of patients with COVID-19.

METHODS

This was a diagnostic case-control study. Three academic emergency departments across the United States collected a convenience sample of nonhypoxic subjects with COVID-19, scored subjects' hemithorax at 7 locations using lung ultrasound, and followed outcomes for 40 days. We defined cases as hypoxia (≤91% by pulse oxygenation) from 2 hours after index presentation to day 40. Follow-up was by telephone plus home pulse oximeter and by chart review. We conducted a logistic regression to test the association between L-POCUS scores and hypoxia. To evaluate lung ultrasound score prediction of a hypoxic event, we calculated sensitivity and specificity at optimal cut off scores and report receiver operating characteristic curve and area under the curve.

RESULTS

We enrolled 163 subjects but excluded 15 (3 duplicate entries; 12 lost to follow up). Median age was 41 years (interquartile range [IQR] 31-56); 83 (56%) were female, and median body mass index was 29 (IQR 25-35). We classified 47 of 148 as hypoxic cases (32%, 95% confidence interval [CI]: 25-40), leaving 101 controls. L-POCUS scores associated with hypoxia by logistic regression (odds ratio = 1.05, 95% CI: 1.02-1.08), with a 5% increase in odds of hypoxia for each 1-unit increase in L-POCUS score. The optimal cut-off score was 15 (sensitivity, 0.60; specificity, 0.73) and the area under the curve was 0·66 (95% CI 0·58-0·75). The correctly classified proportion was 69% (95% CI: 61-76).

CONCLUSIONS

Among nonhypoxic COVID-19 patients, higher L-POCUS rubric scores were associated with hypoxia but no scoring threshold strongly predicts hypoxia at 40 days.

Lung Aeration in COVID-19 Pneumonia by Ultrasonography and Computed Tomography

We conducted a prospective single-center observational study to determine lung ultrasound reliability in assessing global lung aeration in 38 hospitalized patients with non-critical COVID-19. On admission, fixed chest CT scans using visual (CTv) and software-based (CTs) analyses along with lung ultrasound imaging protocols and scoring systems were applied. The primary endpoint was the correlation between global chest CTs score and global lung ultrasound score. The secondary endpoint was the association between radiographic features and clinical disease classification or laboratory indices of inflammation. Bland−Altman analysis between chest CT scores obtained visually (CTv) or using software (CTs) indicated that only 1 of the 38 paired measures was outside the 95% limits of agreement (−4 to +4 score). Global lung ultrasound score was highly and positively correlated with global software-based CTs score (r = 0.74, CI = 0.55−0.86; p < 0.0001). Significantly higher median CTs score (p = 0.01) and lung ultrasound score (p = 0.02) were found in severe compared to moderate COVID-19. Furthermore, we identified significantly lower (p < 0.05) lung ultrasound and CTs scores in those patients with a more severe clinical condition manifested by SpO2 < 92% and C-reactive protein > 58 mg/L. We concluded that lung ultrasound is a reliable bedside clinical tool to assess global lung aeration in hospitalized non-critical care patients with COVID-19 pneumonia.