I know someone with asthma who has fainted two or three times while laughing. Whenever she finds something hysterically funny, people around her yell: "Breathe!".
LOL! If only it were that easy! At times, especially in the winter if I have a cold and am laughing, I dash outside for a breath of cool air so I can breathe! Crowded and smoky places are also bad, I don't do well in the middle of a crowd. I had to dash outside several times during a night at a comedy club! Lucky for me it was winter! I almost fainted once or twice at Church because I felt suffocated in the middle. I try to find perimeter seats everywhere.