Lung Ultrasound: A Valuable Tool for Assessing COVID-19 Patients With Different Severity

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Lung Ultrasound: A Valuable Tool for Assessing COVID-19 Patients With Different Severity

The emergence of the coronavirus disease 2019 (COVID-19) pandemic highlighted the urgent need for rapid, non-invasive diagnostic tools to evaluate lung injury and guide clinical management. Lung ultrasound (LUS) has emerged as a promising modality for real-time assessment of pulmonary pathology, particularly in resource-limited settings. This study explores the utility of LUS in characterizing lung abnormalities and predicting disease severity and outcomes in COVID-19 patients, providing critical insights into its clinical application.

Study Design and Patient Population

The single-center retrospective observational study was conducted at Hankou Hospital in Wuhan, China, involving COVID-19 patients admitted to the sixth isolation ward between January 26, 2020, and March 19, 2020. Patients confirmed with COVID-19 via nucleic acid testing who underwent LUS within 24 hours of admission were included. Disease severity was classified according to China’s National Health Commission guidelines: moderate (respiratory symptoms with imaging evidence of pneumonia), severe (respiratory rate ≥30/min, oxygen saturation ≤93%, or PaO2/FiO2 ≤300 mmHg), and critical (respiratory failure requiring mechanical ventilation, shock, or multi-organ dysfunction).

Among 215 hospitalized patients, 55 underwent LUS, with 42 meeting inclusion criteria after exclusions. The cohort had a median age of 62 years (range: 28–86), with equal gender distribution. Clinical classifications included moderate (33.3%, n=14), severe (52.4%, n=22), and critical (14.3%, n=6) cases. Mortality outcomes revealed 37 survivors (88.1%) and 5 non-survivors (11.9%).

Lung Ultrasound Technique and Scoring System

LUS examinations were performed using a GE Healthcare Venue device with linear (5–13 MHz) and convex (2.0–5.5 MHz) probes. A modified 10-region protocol was adopted, covering anterolateral lung fields (8 regions) and posterior areas inferior to the scapulas (2 regions). Each region was scored based on the most severe ultrasound abnormality:

  • 0 points: Normal aeration (A-lines with lung sliding or ≤2 B-lines).
  • 1 point: Mild loss of aeration (≥3 well-spaced B-lines).
  • 2 points: Moderate loss of aeration (coalescent B-lines).
  • 3 points: Severe loss of aeration (lung consolidation).

The global LUS score ranged from 0 to 30, summing scores across all regions. Interobserver reliability was strong (kappa=0.872), ensuring consistency in interpretation.

Key LUS Findings and Patterns

Distinct LUS patterns correlated with disease severity and clinical outcomes:

  1. A-lines and ≤2 B-lines: Predominant in moderate cases (72.9% of regions), indicating preserved lung aeration.
  2. Coalescent B-lines: Increased in severe (25.4%) and critical (76.7%) cases, reflecting interstitial edema and alveolar flooding.
  3. Lung Consolidation: Rare in moderate cases (0.7%) but more frequent in severe (4.1%) and critical (8.3%) groups, signifying advanced parenchymal damage.

Posterior lung regions exhibited greater pathology than anterior zones. For example, coalescent B-lines were observed in 40.5% of posterior regions versus 3.4% anteriorly (P<0.001), consistent with gravity-dependent fluid accumulation in dependent lung areas.

LUS Scores and Disease Severity

Global LUS scores differed significantly across severity groups:

  • Moderate: Median 1.0 (IQR: 0.0–3.0).
  • Severe: Median 9.0 (IQR: 6.0–12.25).
  • Critical: Median 19.5 (IQR: 15.25–21.25; P<0.001).

Non-survivors had higher scores (median 20.0, IQR: 16.0–21.5) compared to survivors (median 6.0, IQR: 1.5–10.5; P<0.001). Regional scores followed similar trends, with posterior zones showing the highest pathology.

Discriminatory and Prognostic Value of LUS

Receiver-operating characteristic (ROC) analysis demonstrated the utility of LUS scores in triaging patients:

  1. Severe/Critical vs. Moderate: AUC=0.948 (95% CI: 0.879–1.016). A cutoff >4.5 distinguished severe/critical cases with 89.3% sensitivity and 92.9% specificity.
  2. Critical vs. Non-Critical: AUC=0.984 (95% CI: 0.947–1.020). A cutoff >15.0 identified critical illness with 83.3% sensitivity and 100% specificity.
  3. Mortality Prediction: AUC=0.975 (95% CI: 0.922–1.028). A score >17.5 predicted death with 80% sensitivity and 100% specificity.

Clinical Implications and Limitations

LUS provides a rapid, radiation-free method to quantify lung injury in COVID-19. The semi-quantitative scoring system aids in early identification of high-risk patients requiring intensive care and predicts mortality. For instance, a global score >15 strongly indicates critical illness, while >17.5 signals poor prognosis, enabling timely escalation of care.

However, the study’s retrospective design and small sample size (n=42) limit generalizability. The modified 10-region protocol, though pragmatic in a pandemic setting, may underestimate posterior pathology compared to comprehensive 12-region examinations. Additionally, operator dependency necessitates training to ensure consistent image acquisition and interpretation.

Conclusion

This study establishes LUS as a critical tool for assessing COVID-19 severity. Characteristic patterns—A-lines, coalescent B-lines, and consolidation—reflect progressive lung injury, while global scores offer prognostic insights. Future studies should validate these findings in larger cohorts and explore longitudinal LUS monitoring to track disease progression and response to therapy.

doi.org/10.1097/CM9.0000000000001921

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