---
title: "Predisposing Factors for Decompression Sickness"
description: "Why the same dive bends one diver and not another: PFO, sex, dehydration, cold, exertion, and the DCS risk factors no computer can see."
canonical: "https://donarundas.com/depth-notes/safety/predisposing-factors-for-decompression-sickness"
author: "Donarun Das — TDI Trimix Instructor, KISS Sidewinder CCR Instructor"
category: "safety"
published: "2025-06-03"
tags: ["dcs", "risk-factors"]
disclaimer: "Dive theory published by a working instructor for education. It is not medical advice and not a substitute for training. Decompression, gas, and depth decisions belong with your own training, your dive computer, and a dive medical officer."
license: "© Donarun Das. Quote with attribution and a link to the canonical URL."
---

# Predisposing Factors for Decompression Sickness

## It's not just the dive profile

Two divers can run the identical profile on the same day and walk away with completely different outcomes: one fine, one bent. [Decompression sickness](https://donarundas.com/depth-notes/safety/decompression-sickness) (DCS, "the bends") is what happens when dissolved nitrogen comes out of solution as bubbles faster than your body can clear it, the same way a capped bottle of soda fizzes over the moment you crack it open. How likely that is for *you*, on *this* dive, is not decided by your computer alone.

Across more than four decades of dive-medicine literature, DCS is treated as a multifactorial condition shaped by external exposure variables (depth, duration, ascent profile, conditions, post-dive behaviour) and intrinsic biological factors (age, body composition, vascular and endothelial function, sex, and how readily you form venous gas emboli, the small bubbles that ride your veins back toward the lungs). This article is about those personal modifiers, the things that shift your risk beyond what the algorithm permits.

For the underlying mechanism, see [decompression sickness, what it is and why it happens](https://donarundas.com/depth-notes/safety/decompression-sickness).

Roughly in order of how much they pay off, biggest and most controllable first:

1. **Never skip or shorten your stops, and never rush the ascent.** Profile violations show up in a large share of DCS cases (42% in one DAN report, 69% in the Adelaide series). This is the single most controllable factor you have.
2. **Ease off on repetitive and multi-day diving.** Residual nitrogen and bubble nuclei carry over, so lengthen your surface intervals and dive more conservatively as the days stack up.
3. **Arrive hydrated, and skip the alcohol the night before.**
4. **Manage temperature and exertion.** Avoid hard work at depth, and skip the heavy lifting and the hot shower right after a dive.
5. **Respect the flying-after-diving intervals** above.
6. **Know your fixed factors.** Age, a significant PFO, prior DCS, and lower fitness have no dial you can turn on the day, so they tell you how much extra conservatism to build in. If you have ever had unexplained neurological DCS, ask a dive physician about a bubble study.

> **If you suspect DCS**
>
> Treat it as an emergency. Put the diver on 100% oxygen, keep them lying flat and hydrated, and call your local emergency number and a diving emergency hotline (DAN: +1-919-684-9111). Recompression is the definitive treatment and earlier is better. Do not wait to "see if it passes."
>
> This article is education, not medical advice. If you have a heart, lung, or other relevant condition, or a history of DCS, get a proper dive-medicine evaluation before you dive.

## References

- Marroni A, Kot J, Pieri M, Pelliccia R, Balestra C. Identification of DCS risk factors in recreational diving: multifactorial model based on the DAN DSL Database 2024. *International Maritime Health* 2026;77(1):1–12. doi:10.5603/imh.108038
- Lautridou J, Dugrenot E, Amérand A, et al. Physiological characteristics associated with increased resistance to decompression sickness in male and female rats. *J Appl Physiol* 2020;129(3):612–625. doi:10.1152/japplphysiol.00324.2020
- Germonpré P, Lafère P, Portier W, et al. Increased risk of decompression sickness when diving with a right-to-left shunt. *Front Physiol* 2021;12:763408. doi:10.3389/fphys.2021.763408
- Gempp E, Blatteau JE, Pontier JM, et al. Preventive effect of pre-dive hydration on bubble formation in divers. *Br J Sports Med* 2009;43(3):224–228. doi:10.1136/bjsm.2007.043240
- Daubresse L, Vallée N, Druelle A, et al. Effects of CO₂ on the occurrence of decompression sickness: a review of the literature. *Diving and Hyperbaric Medicine* 2024;54(2):110–119. doi:10.28920/dhm54.2.110-119
- McKenzie B (1984). Epidemiology of decompression sickness (cited across DAN case-series reviews).
- Gorman DF (1988). Decompression sickness: the Adelaide series.
- Knight R (1988). Decompression sickness in recreational divers (DAN report).
- Weinmann M (1991). Decompression sickness risk factors in recreational diving.
- McIver RG (1991). Recurrent decompression sickness (US Navy series).
- Gawthrope IC (2015). Venous gas emboli and prior decompression sickness.
- Dugrenot E (2022). Endothelial function and decompression susceptibility.
- Blake DF (2018). Temperature, bubble growth, and decompression risk.
- Denoble PJ, Holm JR (eds) (2015). *Patent Foramen Ovale and Fitness to Dive: Consensus Workshop Proceedings.* DAN/UHMS.
- Denoble PJ, Marroni A (eds) (2019). *Differential Diagnosis of Decompression Illness Workshop Proceedings.* DAN/UHMS.

## Related posts in the series

- [Decompression Sickness: What It Is and Why It Happens](https://donarundas.com/depth-notes/safety/decompression-sickness)

- [Thermal Stress in Diving](https://donarundas.com/depth-notes/physiology/thermal-stress-in-diving)

- [Immune Suppression and Diving](https://donarundas.com/depth-notes/physiology/immune-suppression-and-diving)

- [Pulmonary Barotrauma and AGE](https://donarundas.com/depth-notes/safety/pulmonary-barotrauma-a-g-e)

- [Fitness to Dive: Managing Chronic Conditions](https://donarundas.com/depth-notes/safety/fit-to-dive)

- [Post-Dive Fatigue](https://donarundas.com/depth-notes/physiology/post-dive-fatigue)

### Train with me

Predisposing DCS risk factors come up in every technical decompression course I teach: knowing your own risk profile changes how you plan. [Enquire about training →](https://donarundas.com/contact)

## Common questions

### What increases your risk of decompression sickness?

Beyond the dive profile itself, the main modifiers are missed or shortened stops and fast ascents, repetitive and multi-day diving, dehydration, cold, hard exertion, a PFO, prior DCS, and on recent data female sex. The most controllable factor is ascent discipline.

### Does a PFO mean you cannot dive?

No. A patent foramen ovale is a normal variant in roughly a quarter of adults and is not an automatic disqualification. Divers with a significant PFO are advised to dive more conservatively and discuss it with a dive physician; closure is reserved for recurrent unexplained neurological DCS.

### How long should you wait to fly after diving?

DAN advises at least 12 hours after a single no-stop dive, 18 hours after repetitive no-stop dives, and 24 hours after decompression diving. Treat 24 hours as a floor for technical dives.

---

**Source:** [https://donarundas.com/depth-notes/safety/predisposing-factors-for-decompression-sickness](https://donarundas.com/depth-notes/safety/predisposing-factors-for-decompression-sickness)

**About the author:** Donarun Das is a TDI Trimix and KISS Sidewinder CCR instructor teaching technical and rebreather diving in the Maldives, Sri Lanka, and India. He holds the deepest verified civilian dive in India (103 m, open-circuit trimix, Lakshadweep, March 2026). Courses: https://donarundas.com/courses — enquiries: https://donarundas.com/contact

> Dive theory published by a working instructor for education. It is not medical advice and not a substitute for training. Decompression, gas, and depth decisions belong with your own training, your dive computer, and a dive medical officer.

## Sitemap

See the full [sitemap](https://donarundas.com/sitemap.md) for all pages available as Markdown.