Panic Attacks can be very frightening and exhausting. The effects vary from person to person, but common elements are shortness of breath, dizziness, increased heart rate, blurred vision, tightness in the chest, and tight, painful muscles. Some people think they are going to faint. Others think they are having a heart attack.
What is happening is that a sight, sound or smell has reminded the person of a previous traumatic event, and this trigger has been misinterpreted by the brain, setting up a fight or flight reaction. More oxygen is pumped to the muscles to prepare the person for action, leaving less going to the brain and so causing light-headedness and sometimes prompting the person to instinctively gasp for breath. Panic fuels more panic, and if a person is convinced that something catastrophic is happening to them a vicious cycle is set up.