Ultrasound detection of lymphatic bubbles in a porcine dive model.

Abstract

Ultrasound is currently the optimal imaging modality in the decompression research field for assessing intracorporeal gas. Decompression sickness (DCS) is triggered by excess gas bubble presence in the body; however, the relationship is not well understood. Presently, the decompression physiology field does not have a strong predictive DCS biomarker. In this study, we explore the presence of lymph node decompression bubbles in a porcine model after a provocative hyperbaric exposure. Porcine test subjects (n=37) underwent an aggressive decompression profile as part of a larger study and a subsequent investigation of the left inguinal lymph node was conducted with ultrasound. Ultrasound images were assessed by three trained sonographers for lymph node bubbles. Regional brightness was analyzed after post-hoc phantom calibrated standardization of ultrasound depth and gain settings. Of the 37 animals that we examined for lymph node bubbles, 17 were diagnosed with severe DCS and 14 were identified to have lymph node bubbles. A post mortem dissection was conducted for a few animals, and bubbles could be found streaming from the lymph node corresponding with a severe DCS subject. The brightness assessment of the standardized ultrasound images indicated that DCS cases typically had a decrease in region intensity after the dive with a potential peak sensitivity of 94.1% and specificity of 55% based on receiver operating curve analysis. This study is the first non-invasive detection of lymph node decompression bubbles with confirmation of bubbles by post mortem dissection. A positive correlation between lymph node bubbles and DCS severity was found.