Normally, air enters the body through the mouth and nose. Fresh air, high in oxygen, flows through the windpipe into all the airways, until it reaches the tiny air sacs in the lungs, where oxygen and carbon dioxide are exchanged. The air that's breathed out is stale, meaning it's high in carbon dioxide, the body's waste gas. All of this blocks the flow of air. People with asthma often feel that if they could just cough up enough mucus, their symptoms would subside, but rarely is it possible to clear the airways completely.
Asthma attacks can strike without warning and last from minutes to days.
People experiencing an attack feel as though they can't get enough air into their lungs. But what's really happening is their airways are too constricted to let stale air out of their lungs. This trapped air blocks fresh air from entering the lungs. During a severe asthma attack, emergency room doctors will take a blood sample to check on the blood's oxygen and carbon dioxide levels. Fortunately, this doesn't happen too often, but as asthma cases are rising, the number of asthma deaths are rising as well.