Agreement between ultrasonic bubble grades using a handheld self-positioning Doppler product and 2D cardiac ultrasound

Abstract

Introduction: Intravascular bubble load after decompression can be detected and scored using ultrasound techniques that measure venous gas emboli (VGE). The aim of this study was to analyse the agreement between ultrasonic bubble grades from a handheld self-positioning product, the O’DiveTM, and cardiac 2D ultrasound after decompression. Methods: VGE were graded with both bilateral subclavian vein Doppler ultrasound (modified Spencer scale) and 2D cardiac images (Eftedal Brubakk scale). Agreement was analysed using weighted kappa (Kw). Analysis with Kw was made for all paired grades, including measurements with and without zero grades, and for each method’s highest grades after each dive. Results: A total of 152 dives yielded 1,113 paired measurements. The Kw agreement between ultrasound VGE grades produced by cardiac 2D images and those from the O’Dive was ‘fair’; when zero grades were excluded the agreement was ‘poor’. The O’Dive was found to have a lower sensitivity to detect VGE compared to 2D cardiac image scoring. Conclusions: Compared to 2D cardiac image ultrasound, the O’Dive yielded generally lower VGE grades, which resulted in a low level of agreement (fair to poor) with Kw.