Intraocular Gas Calculator: SF6, C2F6 and C3F8 Concentrations, Duration and Safe-to-Fly Date
Last updated: November 2026
Gas tamponade is used in vitrectomy for retinal detachment and macular hole, and in pneumatic retinopexy. Each gas has its own non-expansile concentration, expansion if injected pure, and lifetime in the eye. This tool gives the mix for your syringe, the expected duration, and the earliest date the patient can fly or have nitrous oxide anaesthesia.
The gases at a glance
| Gas | Non-expansile concentration | If injected pure | Typical duration | Common use |
|---|---|---|---|---|
| Air | 100% | No expansion | About 5–7 days | Simple detachments, fluid-air exchange, short tamponade |
| SF6 | About 18–20% | Doubles in volume, peak at 24–48 hours | About 2 weeks | Macular hole, superior breaks, pneumatic retinopexy (0.3–0.5 mL pure) |
| C2F6 | About 15–16% | About 3 times, peak at 36–60 hours | About 4–6 weeks | Intermediate tamponade |
| C3F8 | About 12–14% | About 4 times, peak at 72–96 hours | About 6–8 weeks | Inferior breaks, PVR, longer tamponade (pneumatic: 0.3 mL pure) |
Safety rules for every gas patient: no air travel, no travel over mountain passes or high-altitude roads, and no nitrous oxide anaesthesia until the gas has gone (a gas-warning wristband helps). Nitrous oxide diffuses into the bubble and can raise IOP enough to occlude the central retinal artery. Check that the bubble has gone before clearing the patient: the dates below are estimates.
For learning and quick checks only. Confirm any result that changes treatment against your own measurements, the device manufacturer's guidance and current local protocols.
Related: Retina, Retinal Detachment Surgery: Vitrectomy, Gas Bubble and Head Positioning, Proliferative Vitreoretinopathy, Macular Hole Staging: Gass vs IVTS Classification. See all eye calculators and tools.
Key sources
- American Academy of Ophthalmology. Basic and Clinical Science Course, Section 12: Retina and Vitreous (current edition), chapter on vitreoretinal surgery
- Thompson JT. Kinetics of intraocular gases: disappearance of air, sulfur hexafluoride, and perfluoropropane after pars plana vitrectomy. Arch Ophthalmol. 1989;107:687-691
- Values vary slightly between sources; the ranges shown reflect common practice. Check your unit's protocol and the gas supplier's instructions
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