A surgeon plans a long-acting expansile gas tamponade following vitrectomy for a recurrent retinal detachment. The gas chosen will be delivered at its non-expansile concentration. What is the approximate non-expansile concentration of C3F8?
- A About 14 percent ✓
- B About 5 percent
- C About 30 percent
- D About 60 percent
Correct answer: A. About 14 percent
Explanation
C3F8 expands roughly 4 times its volume over several days, so mixing it to approximately 14 percent makes the final bubble non-expansile while retaining its long intraocular life of up to 6 to 8 weeks. Pure C3F8 would expand dangerously and raise intraocular pressure. SF6, by contrast, doubles in volume and its non-expansile mixture is around 18 to 20 percent, which eliminates option B.
Reference: Kanski's Clinical Ophthalmology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.