You need to go through this with your health persons.we dont know your daily rates, your high levels after or how soon they raise etc...
We cannot advise you whether your levels etc would handle a unit before changeover or whether a tbr after would be best or a combination.
You must do this with your health people if you haven't got the confidence to sort out by yourself..
For example.. one person above mentioned tbr for 2hrs whilst I was needing 250% for 5 hours....
A please and thankyou would be appreciated....