Correlation of lung comet score with decreased gas exchange in patients with acute pulmonary edema: a pilot study

Introduction

The aim of this study was to determine the correlation between B+ line score and blood gas analysis (BGA) parameters in patients with acute cardiogenic pulmonary edema (ACPE). The presence of B+ line artifacts on lung US is correlated with increased extravascular lung water. In patients with acute decompensated heart failure the resolution of B+ lines can be used to monitor resolution of pulmonary congestion. A simple nine-point comet score has been proposed to quantify B+ lines and monitor ACPE treatment [1].

Methods

Twenty-one patients with ACPE were submitted to lung US and BGA on presentation at 2 and 24 hours after admission. Lung US was done in nine thoracic areas and scored one point if B+ lines were present. A score of 10 was given for the presence of multiple coalesced comets in all fields (white lung). BGA values were used to calculate PO₂/FiO₂ (P/F) and A-a gradient.

Results

A total of 64 scans were performed with simultaneous BGA. Ninety-eight percent of patients presenting with white lung were severely hypoxic (PO₂ <50 mmHg; P/F <200). Figure 1 illustrates a strong linear correlation between reduction in comet score and improvement in P/F (r = -0.73; P < 0.001). A decrease in comet score of 2 points corresponded to a minimum increase of 20 points in P/F (P < 0.05). The correlation between comet score and A-a gradient was less striking significant (r = -0.51; P = 0.05), perhaps because patients with underlying lung disease were not excluded from this pilot study.

Figure 1

Correlation between reduction in comet score and improvement in P/F.

Conclusions

There is a strong negative correlation between lung comet score and gas exchange in patients with ACPE. In these patients, serial thoracic US may reduce the need for repeated invasive BGA monitoring and further help tailor therapy.