I was on the subway this morning when I started to feel a little off. It was too crowded so I felt a little dizzy and wanted to sit down. All of a sudden my vison began to slowly blacken until I couldn t see at all. I felt nauseous and my head hurt and my ears started ringing. I hung on to the handle and waited for it to go away but I began feeling worse and my legs felt like collapsing. The episode lasted for about 10 to 15 minutes and when I came to I had broken out in cold sweat. I felt a little better afterwards but the symptoms started again when more people got on the subway. I got off and sat down and I felt breathless and weak. I m feeling better now but I don t want this to happen again. Have I suddenly developed claustrophobia? Is it lack of sleep?