There are four stages of emphysema: at-risk, mild emphysema, moderate emphysema, and severe emphysema. In order to determine if someone has emphysema and which stage he or she is in, the doctor will use a breathing test called spirometry. While the breathing test is normal during the at-risk stage of emphysema, it shows mild airflow limitation during the mild stage, a worsening airflow limitation during the moderate stage, and severe airflow limitation during the severe stage. At the severe phase of emphysema, the worsening symptoms may be life threatening.