Traveling Senior

My uncle and grandfather are traveling to the US next month.  Lolo's (grandfather) doctor says, although he is on a pacemaker, he is fit to travel.  He is 86 and a US veteran.  He wants to see his other children and grandchildren in the States and lolo is very excited because it's been more that 15 years since he last visited. Mom wants to make sure though, she's been asking around if respironics oxygen concentrators are okay to use.  She wants to get one for lolo just in case.  I'd like to find out too so I'll be checking it out in a bit after I'm done with my tasks.