Before I explain everything, I want to share a little background on this. I have experienced this problem throughout my life, always due to exercise and only during exercise. I can only compare it to being at high altitude for the first time in your life (like 13,000 feet).
At times, and completely at random, I get the feeling that my trachea/throat is closing/constricting, and causing me to have trouble inhaling and catching my breath. This only happens duing exercise. I was in Breckenridge two years ago, and while my throat did not feel that way, I had the same sensation of a lack of oxygen. After 2 days in Breck, though, I got used to it and was fine skiing.
I am now 35, 6'1", 185 lbs. No personal major history of health issues, other than ADHD, for which I now take adderall, and I didn't as a kid. I also have sleep apnea, so I use a C-PAP. In my teens and 20's I was very athletic, track teams, soccer, skiing, etc. My high school was at high altitude, but I felt the problem when I was at sea level, as well, so I can't only attribute it to the altitude.
Family (dad's side) does have a long history of heart problems, and my grandfather on my mom's side died of cystic fibrosis if I am not mistaken. I smoked for roughly 15 years until I was 31.
Anyway, today I was out running around throwing a softball with two friends. The sprints weren't long, but I was fielding grounders, and some fly balls for roughly about 90 mins. About 60-70 mins in, I started feeling the sensation of my throat getting tight and constricting my airway, making it hard for me to breathe. I had to mentally slow myself down, and try to take in a few deep breaths.
After a few deep breaths, and some water, I felt better. I don't recall if I felt like my chest was heavy, but I did not get the feeling it was. I don't think I was particularly lightheaded. From the running around, though, I was breathing heavy. I have not been physically active for a while, and I am admittedly out of shape. But having had this problem as a teen and in my 20's, I wonder if there might be something to it.