Comparison of lung ultrasound with transpulmonary thermodilution in assessing extra-vascular lung water

Abstract

Background: Increased extra-vascular lung water (EVLW) is common in critical care and correlates with the severity of acute lung injury, length of intensive care unit stay and mortality. Lung ultrasound (LUS) can assess EVLW by determining the amount of ‘B-lines’: artefacts signifying alveolar-interstitial oedema. This study’s aim was to determine whether EVLW estimation with the help of LUS correlates with the more accurate PiCCO₂^® cardiac output system utilising transpulmonary thermodilution.

Methods: This prospective observational study was undertaken at Universitas Academic Hospital, Bloemfontein. Patients were scanned according to a fixed protocol, followed by transpulmonary thermodilution. The cumulative B-line count was compared with the EVLW index generated by the PiCCO₂^® system.

Results: Four males and six females were enrolled. The mean EVLW index was 9.1 ml/kg/m² (standard deviation 1.45), and the median cumulative B-line count was 14 (interquartile range 6–25). A positive, but not statistically significant, correlation was found (r = 0.40, p = 0.25) between the B-line count and EVLW index.

Conclusion: This study investigated a possible correlation between LUS interpretation and transpulmonary thermodilution in assessing EVLW. Results seem promising, but the small sample could indicate only that LUS might be of use for the assessment of EVLW. Further studies are needed.

Keywords: B-lines,critical care, extra-vascular lung water, lung ultrasound, thermodilution