A new study investigated genetic changes that occur in a serious condition affecting scuba divers — ‘the bends’ — and found that inflammatory genes and white blood cell activity are upregulated. The findings could lead to biomarkers that will help doctors to diagnose the condition more precisely.
The bends, more formally known as decompression sickness, is a potentially lethal condition that can affect divers. Symptoms include joint pain, a skin rash, and visual disturbances. In some patients, the condition can be severe, potentially leading to paralysis and death. The bends can also affect people working in submarines, flying in unpressurised aircraft or in spacewalks.
It has been studied for a long time: a 1908 paper correctly hypothesised that it involves bubbles of gas forming in the blood and tissue due to pressure decrease. Yet even after a century the precise mechanisms underlying the condition are not well understood. Animal studies have suggested that inflammatory processes may have a role in decompression sickness, but no-one had studied this in humans.
Nowadays, getting ‘the bends’ is rare as divers have well-established methods to mitigate risk, such as controlled ascents from the depths. Nevertheless, doctors have no means to test for the condition, if they do encounter it, and instead rely on observing symptoms and seeing whether patients respond to hyperbaric oxygen therapy.
To investigate decompression sickness, the researchers sampled the blood of divers who had been diagnosed with decompression sickness and also divers who had completed a dive without it. The blood samples were drawn at two times: within 8 hours of the divers emerging from the water, and 48 hours afterwards, when those divers with decompression sickness had undergone hyperbaric oxygen treatment. RNA sequencing analysis was done to measure gene expression changes in white blood cells.
“We showed that decompression sickness activates genes involved in white blood cell activity, inflammation and the generation of inflammatory proteins called cytokines,” explained Dr Nikolai Pace of the University of Malta, a researcher involved in the study. “Basically, decompression sickness activates some of the most primitive body defense mechanisms that are carried out by certain white blood cells.”
These genetic changes had diminished in samples from 48 hours after the dive, after the patients had been treated with hyperbaric oxygen therapy — an interesting finding. The results provide a first step towards a diagnostic test for decompression sickness, and may also reveal new treatment targets.
“We hope that our findings can aid the development of a blood-based biomarker test for human decompression sickness that can facilitate diagnosis or monitoring of treatment response,” said Prof Ingrid Eftedal of the Norwegian University of Science and Technology, who was also involved in the project. “This will require further evaluation and replication in larger groups of patients.”
Journal information: “Acute effects on the human peripheral blood transcriptome of decompression sickness secondary to scuba diving” Frontiers in Physiology, DOI: 10.3389/fphys.2021.660402