Daisy,
After becoming acclimated to altitude and then returning to sea-level, I felt the air was thicker. It didn't rush in and swirl around in my lungs like breathing thinner air. I found myself sort of going - inhale [wait for the molasses like air to flow in], exhale [and have to push harder with my diagram to push it out], but the amount of oxygen in the air more than makes up for any muscle tiredness. I used to suffer a lot on trips going UP until I learned I am lactose intolerant and the MCDs cheese burgers were killing me. The air is most probably A LOT CLEANER in the mountains and the drive home on the freeway exposes yer lungs to all kinds of stuff. I am generally dehydrated too. It always took my body 2-3 days to recover from BPing. Like on Wednesday after coming home on Sunday - but it was all dietary/water related not altitude related.

On a side note - living in Bend at 4,000 feet I can totally kick the rear ends of my friends who live at sealevel. <img src="/forums/images/graemlins/grin.gif" alt="" />
Jim <img src="/forums/images/graemlins/cool.gif" alt="" />