Pathophysiology of Decompression (Acute Dysbaric Disorders)
Authors: Klaus Torp
DOI / Source: NOAA training presentation (Mayo Clinic College of Medicine)
Date: None
Reading level: Intermediate
Why This Matters for Freedivers
Freedivers often focus on blackout and barotrauma, but this presentation is a solid reminder that “bubble problems” are real diving medicine—especially when diving becomes repetitive, cumulative, or mixed with hard effort and stress. It also gives you a practical symptom checklist and a clear “don’t wait and see” mindset: if you were fine going in and come out with odd neuro symptoms, think DCI and escalate quickly.
Synopsis
This is a practical, diver-focused presentation on decompression illness (DCI)—the umbrella term that includes decompression sickness (DCS) and arterial gas embolism (AGE)—and why bubbles can cause such a wide range of symptoms.
It starts by building an intuitive foundation: inert gas (mainly nitrogen) dissolves into tissues under pressure, and then has to be eliminated slowly through the lungs on the way back to surface. The “tissue compartments and half-times” idea is introduced to explain why some parts of the body load and unload nitrogen quickly, while others change much more slowly. A great, simple analogy is the soda bottle: pressure keeps gas dissolved, but drop the pressure too fast and bubbles form.
The presentation then explains how bubbles form and why they don’t always cause symptoms. It highlights: - “Silent” bubbles can exist without obvious symptoms. - Bubbles can form in tissues, the venous system, or (more dangerously) the arterial system. - Dive pattern matters: short deep exposures tend to stress “fast” tissues, long shallow exposures can load “slow” tissues, and long deep exposures can stress both.
A key section is the effects of bubbles: they can block blood flow, compress tissues, trigger clotting tendencies, and set off inflammatory reactions. That helps explain why DCI can look like so many different things—pain in joints, tingling, skin changes, extreme fatigue, headache, nausea, balance problems, weakness, confusion, or serious neurological deficits.
It also emphasizes timing: many cases show symptoms early, but delayed onset can happen, and the earlier symptoms appear, the more concerning the case tends to be. The practical message is: “Healthy going into the water, sick coming out, no other explanation — think DCI.”
The presentation covers risk factors (the kind divers actually run into): multiple dives/day, multiple dive days, lots of ascents, dehydration, fatigue, age, and possible anatomical factors (like PFO). It also explores the complicated role of exercise: depending on timing and intensity, exercise may reduce bubble load in some scenarios, but strenuous activity after diving can also be a risk. There’s also discussion of intrapulmonary shunts opening during exercise, which matters because the lungs normally act as a filter for venous bubbles.
Diagnosis is presented as a structured approach: get a clear dive history, track symptom onset and evolution, do a thorough general exam, and (crucially) perform a careful neurological exam—even if the diver feels “mostly fine.”
Finally, treatment is explained in a way that makes sense: hyperbaric oxygen works by (1) shrinking bubbles with pressure, and (2) creating strong gradients that push inert gas out of bubbles while supporting oxygen delivery to tissues. It also outlines pulmonary barotrauma pathways and how lung injuries (like pneumothorax) can overlap with or complicate DCI-like presentations.
Overall, it’s a very usable “big picture” guide: why bubbles happen, what they do, what symptoms to respect, and why early oxygen/recompression is such a powerful tool.
Abstract
This training presentation gives an overview of decompression illness (DCI), including decompression sickness (DCS) and arterial gas embolism (AGE). It explains inert gas uptake and elimination, bubble formation mechanisms, how dive profiles influence where bubbles form, and how bubbles can cause injury through obstruction and inflammatory effects. It outlines common symptoms and their timing, key risk factors (including repetitive exposures and exertion), a practical diagnostic approach, and the rationale for hyperbaric oxygen treatment, while also reviewing pulmonary barotrauma complications.