trouble walking

hi, ive only been to a handful of citys, but i would believe that having walking/breathing issues will limiting. London & Paris has great subways and buses. I would say the Subway is out of the question for you since you have to traverse stairs both up and down and then if you have any transfers, there more to get to the other platforms. Buses or taxis maybe the best bet or if you can arrange some type of shuttle/van service? good luck and happy trails.

Paris has a good bus system, better then Romes in my opinion. Most people with elderly, mobility impairment, or small kids prefer the buses in Paris, including elderly relatives of mine who used the metro well into their 70s then switched to buses, and yes, an occasional taxi. an If your friend is agreeable to it I suggest in large musuems you take advantage of using the wheelchairs some may have ,, save their walking strength for when they have to go between sites. Some sites are going to be difficult, some impossible ( no going up the Towers of Notre Dame for example) but many will be doable . For the Eiffel Tower do make sure you reserve a timed slot entry ahead of your visit, I think you can book 30-60 days out, standing in line can be just as tiring as walking sometimes. Use a museum pass to skip lines for some sites. Pace each day so that you cover one "big" site in morning perhaps when traveller is feeling least tired, then an afternoon of something easier,, a boat cruise is fun. In the scheme of things ,, allow some money for taxis, the trip is worth thousands , so what if you have to spend 200 dollars for taxi fares ..
Taxis in Paris are metered and there are taxi stands all over the place, it is harder to street hail a taxi, they are not allowed to stop for a street call if you are within a certain distance of a taxi stand, so sometimes it seems like they are ignoring you but you may not be aware that a taxi stand is near by. There are maps of taxi stand locations out there in google land, I have seen them. Find them and print one out . Assume your group will have to split up now and then.

I can address some of your concerns about Italy, in addition to Pat's advice which is good anywhere. Most train stations in large cities have elevators specifically for use by travelers with diasabilities, in some places they require station staff to unlock them, so leave time for getting to the track. There are reserved seats for travelers with disabilities on buses, trains and metro (metro stations often have escalators as well as some elevators). These seats are usually closest to the door. At museums, call ahead or ask your hotel to call ahead to reserve a wheelchair, or to see if one is available. I've seen people of all fitness levels using Nordic walking sticks, about $100/set. Another option would be to take along a 3-footed walking cane with a seat attached - very useful for outdoor sites where the terrain is not level enough for a wheelchair and where the site is expansive (Roman Forum comes to mind). As an example of an easy city, Bologna - compact city center, train station with elevators, great food and sights. Also covered galleries on most strrets so a slow pace in hot weather is easy. Venice, on the other hand, has what seems like a thousand bridges with short staircases at each end - might make travel slower but probably not impossible, especially with a cane or walking stick(s). There are some websites for travelers with disabilities, check those out as well.

This is a duplicate question. Answers have been given in the "To The Boot" area.

I know there are travel websites specific to your situation. I also thought London would be worth checking into. From planning my trip there, I remember their Trip Planner on the TFL (Transport for London) site allows you to plot your path with accessibility options (some subway stations have escalators; others elevators; some only stairs) plus there's a whole section in Visit London for accessibility issues. I learned a lot from the top of a Hop on Hop off bus - the route is a minimum of 2 hours (?) and the ticket is good for all day. I would think that the flat parks of London and other historic sites would lend themselves to either a wheelchair or a scooter? The downside of London - and other candidates - would be rain. Tough enough to maneuver without getting drenched if you don't have mobility issues. I would consider that in my plans.
It can be done - happy planning!

I think there is a section on the Grafitti Wall that covers this topic. You may want to look at it.

Rick used to have a book called Accessible Europe. It's out of print, but you can probably get a used copy. It had chapters on the "biggies" like London, Paris, and Rome. I agree that forgetting about metros, and focusing on buses, and planning to take more taxis than other visitors, is a good idea. In France and Italy, if you call for a taxi instead of getting it at a taxi stand, the meter starts when they driver gets your call, which adds a few euros to the fare. But if you're at a place with no taxi stand out front (hotel, restaurant, smaller museum) it's worth having them call for a taxi if anyone is tired.

Michelle, has this person already made arrangements for his/her oxygen? How about for your flight? Would s/he consider a folding wheelchair that you could bring from the States? Some even come with a carrying case when not being used. It would really save their energy and your itinerary.