Decompression Sickness in Thailand: Symptoms, Oxygen, Chambers and Flying Home

Decompression sickness, the bends, is what happens when nitrogen your body absorbed under pressure comes out of solution as bubbles after a dive, and in Thailand the two things that matter most are noticing it early and getting oxygen fast. It is rare on ordinary recreational dives, but it is not exotic. In eight years around dive shops on Koh Tao I watched it happen to customers, to instructors, and once to a friend who had done nothing wrong that anyone could point to. Here is what it looks like, what to do in the first hour, where the chambers are, and the flying rule that catches people on their last day.

What decompression sickness is

Decompression sickness is an injury caused by gas bubbles forming in the blood and tissues as the pressure drops on the way up and after the dive. At depth you breathe air at higher pressure, so more nitrogen dissolves into your body. Ascend slowly and it leaves gently through your lungs. Ascend too fast, dive too deep for too long, or stack up enough repetitive dives, and some of it forms bubbles instead, a bit like opening a fizzy drink ¹.

Dive computers and tables exist to keep you inside limits where that is unlikely, and most divers go their whole lives without a problem. But the limits are a model of an average body, not a guarantee for yours. Hard work in a current, dehydration in the heat, a late night before an early dive, and three or four dives a day for a week all push your own risk up. If you are still learning how dive days are structured, the learn to dive on Koh Tao guide covers the training that teaches those limits.

The symptoms, and why people ignore them

The early signs of decompression sickness are usually mild and vague, which is exactly why divers talk themselves out of them. Divers Alert Network lists unusual fatigue, itchy skin, numbness, tingling and paralysis among the symptoms, and a blotchy rash and staggering among the signs someone else might notice ². Add to that the classic aching joint, often a shoulder or elbow, that feels like you slept on it badly.

Timing is the other clue. DAN says symptoms can appear immediately after surfacing or up to 24 hours later, and most often between 15 minutes and 12 hours after the dive ². So the ache that turns up at dinner, or the tingling hand you notice the next morning, still counts.

The trouble is that every one of those symptoms has a boring explanation on a dive trip. Tired? Of course, you did three dives in the sun. Sore shoulder? You carried a tank. Itchy? Sea lice, sunburn, the hostel sheets. My friend on Koh Tao spent an evening rubbing a numb patch on her thigh and blaming a dodgy sun lounger before someone made her call it in. The rule I learned from the instructors I trusted most: any new symptom after diving gets a phone call for advice, not a beer and an early night.

What to do in the first hour

If you suspect decompression sickness, stop diving, get on emergency oxygen straight away, and get medical advice, even if the symptoms seem minor. DAN’s guidance is to provide emergency oxygen right away, at 100 percent or as close to it as the equipment allows, and to give fluids to a diver who is conscious and able to drink ².

In practice that means:

• Tell the dive staff immediately. A decent dive centre has an emergency oxygen kit, staff trained to use it, and an emergency plan they have rehearsed.
• Breathe oxygen for as long as the kit and the advice you are given allow, and do not stop because you feel better.
• Call for help. Use your dive insurer’s emergency line or DAN’s emergency hotline, which exists for exactly this ¹, and call 1669 for an ambulance if symptoms are severe ³.
• Write down your dives: depths, times, surface intervals and any fast ascent. The doctor will want this, and you will not remember it accurately later.

One warning from DAN that is worth underlining: emergency oxygen can make symptoms improve temporarily, only for them to come back later, so a diver should still be assessed even if the symptoms appear to have gone ². Feeling fine after twenty minutes on oxygen is not the end of the story.

If the injury is more general, a fall on a boat, a cut, or something else entirely, the injured in Thailand guide covers hospitals, payment and your insurer.

Chambers in Thailand, and why location matters

Thailand has decompression (hyperbaric) chambers near the main dive hubs, including Koh Tao, Koh Samui and Phuket, but many smaller islands and remote dive sites are hours away from any of them. A study from a navy hyperbaric centre in Bangkok counted about 40 facilities in the country able to treat decompression illness, mostly at navy hospitals, navy facilities and commercial diving facilities ⁴. DAN notes that a diver with severe decompression sickness needs recompression, but is stabilised at a medical facility first and then transferred to a chamber ². That transfer is the slow part, especially from a liveaboard in the Similans or a small Andaman island.

This is why the UK government’s Thailand advice tells divers to check an operator’s credentials, confirm there is oxygen on the boat, and ask whether divers can be transferred to a hyperbaric chamber ⁵. Ask those questions before you book, not on the boat. A good centre answers without hesitation and can tell you exactly who they call. If the person at the desk looks blank, find another shop. The dive regions and their distances from help are set out in the diving in Thailand guide and the best dive sites guide.

The flying rule, and the mountain road

Divers Alert Network recommends at least 12 hours on the surface before flying after a single no-decompression dive, and at least 18 hours after repetitive dives over several days. After any dive that needed decompression stops, the guidance is substantially longer than 18 hours ⁶. A plane’s cabin is not kept at sea level pressure (DAN’s trials simulated a cabin at 8,000 feet), so flying too soon lowers the pressure around you again while there is still extra nitrogen in your body.

On a Thai dive holiday almost everyone is doing repetitive dives over several days, so the 18 hour figure is the one that applies. The easy version: make your last dive day at least a full day before your flight, and use that day for snorkelling, a beach or the ferry. Freedivers mixing breath-hold sessions with scuba should read the same-day caution in the freediving guide.

DAN’s flying guidance is about flights, not roads, but a big climb into the northern mountains is also a drop in pressure. If you are planning one the day after a heavy dive week, ask your dive centre or DAN for advice rather than guessing.

Insurance and what treatment costs you

Chamber treatment is specialised, can run to several sessions, and is only paid for if your insurance covers scuba diving to the depth you were at. In the Bangkok study, about half the divers treated needed two to five chamber sessions ⁴. Standard travel policies often exclude diving or limit the depth, and the UK government’s insurance guidance is blunt about checking exclusion clauses before you travel ⁷. Dive-specific cover such as Divers Alert Network membership is designed for this situation ⁸; whichever route you take, check that your planned depth and your certification level are covered.

The exclusions that catch divers most often, including depth caps and undeclared medical conditions, are set out in the travel insurance for adventure guide. Sort it at home. A dive shop on a small island at nine at night is a bad place to discover what your policy says.

Lowering your risk in the first place

Most of what lowers your decompression risk is unglamorous: shallower, shorter dives, slow ascents, a safety stop every time, plenty of water and a day off. Dive within your computer’s limits and your training, ascend at the rate you were taught, and do your safety stop even when the group is drifting off. Drink water between dives, because Thai heat dehydrates you faster than you notice; the heat and sun safety guide has more on that. Go easy on alcohol the night before. On a long dive week, take a rest day in the middle rather than diving every morning to the end.

None of it is exciting. All of it is what the old hands on Koh Tao actually did, quietly, while the new divemasters chased depth.

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General information, not medical advice or dive training. If you have any symptoms after diving, stop diving, use emergency oxygen if available, and get medical advice through your insurer, DAN or the local emergency services. Follow your training and your dive computer, and confirm your insurance covers scuba diving before you dive.