Relationship of lung ultrasound score with oxygenation and pulmonary mechanics in mechanically ventilated patients: An observational study.

Background and aims: Less than three B-lines indicate normal lung aeration, whereas multiple B-lines indicate moderate-to-severe loss of aeration. This study aimed to find a correlation between lung ultrasound score (LUSS) with oxygenation [ratio of arterial oxygen partial pressure (PaO₂ in mmHg) to fractional inspired oxygen (FiO₂)] and respiratory mechanics (compliance and resistance).

Methods: In total, 101 lung ultrasounds were performed in 50 patients aged 18-60 years, requiring mechanical ventilation for at least 24 hours. Twelve region methods was used, the number of B-lines were counted in each intercostal space, and LUSS was calculated. In addition, ventilator and arterial blood gas (ABG) parameters were noted. The correlation between these variables with LUSS was evaluated using Spearman's coefficient. A receiver operating curve analysis was performed to find the cut-off value of LUSS to predict a PaO₂/FiO₂ ratio of <200.

Results: LUSS showed a negative correlation with PaO₂/FiO₂ ratio (ρ = 0.827, P < 0.001) and lung compliance (ρ = 0.634, P < 0.001) but a positive linear correlation with lung resistance (ρ = 0.735, P < 0.001). LUSS > 12 predicts a PaO₂/FiO₂ ratio of <200 with a specificity of 85.7% and a sensitivity of 97.37% (P < 0.001).

Conclusion: LUSS is an easy and effective bedside tool for measuring lung parameters in mechanically ventilated patients. It correlates moderately with oxygenation, lung compliance, and resistance.