Eligibility for Deduction:
If you itemize your deductions on Schedule A (rather than taking the standard deduction), you can claim medical expenses that are not reimbursed by insurance.
These expenses must be incurred primarily to alleviate or prevent a physical or mental disability or illness.
However, there is a floor: Medical expenses are deductible only to the extent that the total exceeds 7.5% of your adjusted gross income (AGI).
unreimbursed out of pocket expenses for a prescribed CPAP are deductible