Important Gear
Technical divers are usually meticulous – or, at least I hope they are. We should analyze and label every cylinder, research relevant topics, and reduce risk as much as is reasonable. Regulators should be taken care of and serviced routinely. The same goes for CCRs, lights, and exposure protection. The most important piece of equipment isn’t purchased or serviced at the dive shop – it’s our body.
Your cardiovascular system – your heart, lungs, and circulation – underpins every dive you do. If it performs poorly, every part of the dive carries more risk. And unlike a regulator or scrubber, you can’t swap it out mid-dive. But, for some reason, this isn’t a focus point for many divers.
Cardiovascular Fitness and DCS Risk
We spend time discussing decompression algorithms and tweaking Gradient Factors – 70/85?! No way, I use 75/80! – as if decompression risk lives entirely in software. That is a myopic view. Decompression doesn’t happen in a dive computer.
Good cardiovascular health supports:
- Lower DCS Risk
- Diving Is More Fun – Climbing a ladder in doubles with stages or deco bottles shouldn’t feel like a survival event. Carrying gear to the water shouldn’t be the hardest part of the dive. Being fit makes hard diving feel easier.
- You May Need to Tow or Rescue a Buddy – Could you tow a stressed diver on the surface? Could you manage an unconscious teammate? Could you assist in a long extraction while breathing hard yourself?
- When Things Go Pear-Shaped – Bad situations often demand sudden effort. Cardiovascular reserve buys options.
Poor cardiovascular fitness can work in the opposite direction.
Obviously, fitness doesn’t make anyone immune to DCS. But treating decompression risk as only a function of gradient factors while ignoring the physiology doing the actual off-gassing misses a huge part of the picture.
If you care about reducing DCS risk, fitness should lead the conversation.
Take this experiment, for example:
Wisløff, U., Richardson, R. S., & Brubakk, A. O. (2004). Exercise and nitric oxide prevent bubble formation: A novel approach to the prevention of decompression sickness? The Journal of Physiology, 555(3), 825–829. https://doi.org/10.1113/jphysiol.2003.055467
Rats were exposed to hyperbaric conditions with varying times of exercise. Some before, some after. A sedentary group was used in each timetable as well. The rats that exercised 20 hours before the dive had the greatest survival rate. Survival rate is a bit of a misnomer; rats in other groups died within minutes of the dive from DCS. The rats in the 20-hour group lived for an hour and were killed.
Grocery Store Fallacy
A diver suffers a cardiac event during a dive, and their friends say, “Well, it could have happened in the grocery store, who could have known?”
Cardiac issues are a leading cause of fatality for divers, according to the 2018 DAN annual report. These events during a dive are not always chance events, though. First off, you aren’t typically exerting yourself at the grocery store like you are underwater, especially the static lung loading experienced on a CCR or with high gas density. Secondly, the availability of care in a public space is higher than underwater inside a cave or shipwreck.
Risk Mitigation
Technical diving is built around reducing risk through preparation, redundancy, and margin. So if a diver knowingly ignores a controllable factor that improves survival, decompression resilience, emergency response, and buddy support… what is that, if not poor risk mitigation?
Skipping regular cardiovascular exercise while obsessing over minor equipment details or algorithms is delusional. Any technical diver, and especially an instructor, should be exercising their heart weekly.
I’m not a doctor, but regular cardiovascular exercise matters. It’s the same as maintaining your gear – routine maintenance.
Your heart is doing more to keep you alive on a deep dive than your deco computer. If your dive buddy wants to dive with failing gear, they’re putting you at risk. The same logic applies to poor health.