My lung doctor said I will have to be on O2 for the rest of my life. Need to get portable oxygen. Doctor said setting 3 at home on stationary concentrator and 5 when out walking. Can that be pulse or does it have to be continuous. At the time I didnt know the difference so I didn't ask. Trying to find the right portable. My lung doctor is had to get hold of so I thought maybe someone here might know. Thank you.