Are you in the US? Does he have primary or secondary l/e? You may need to talk to both the orthopods and his Lymphoedema management team for advice as there will be post operative oedema - and with the complication of A fib, he may not benefit from use of the IPC. He may also have retention bandages on, which will require changing frequently for the first few days, plus either staples/stitches on the wound with possible drains attached.

My knee is being replaced this very morning!!!!! I'm trying to keep distracted!!!

There is a helpful, very recent post, on the facebook page of the Lymphoedema Support Network (surgery on lymphoedema affected limbs).

Hi Lycoming - has your husband had his op yet? Can you ask his medical team and nurses/therapists about this? For an uncomplicated knee replacement, using the IPC device should be fine (assuming good wound healing, no signs of infection or DVT, good sensation etc, good circulation to the foot etc). But best to check with his medical team to be sure. Also, you can ask the people who provided you with the IPC - they should have some guidelines too. The pressures might need to be adjusted too.