are portable oxygen concentrators allowed as a deduction

Yes, if you purchased this in 2024, it will be reported on the 2024 tax return, but if it was purchased in 2025 it won't be reported until you file your 2025 tax return next year.

The COPD machine is an eligible medical expense.

You can enter the expenses in TurboTax Online here:

• Navigate to Federal > Deductions & Credits > Medical Expenses > Start or Edit
• Enter all the expenses you have as you go through the categories
• On the screen "How much did you spend on insurance premiums?" you can enter the health insurance premiums

Note that in order to claim medical expenses you must itemize deductions and only the expenses over 7.5% of your AGI are deductible.