MODEL RELEASED. Lung function test. Female patient breathes into a spirometer to assess her lung health. The spirometer is formed of a bag (upper right) which fills with her exhaled air. The bag is connected to machinery which draws a graph of her rate of exhalation. Spirometry is used to diagnose lung diseases such as asthma and bronchitis. These diseases cause narrowing of the airways in the lungs. This can be detected by spirometry as the initial rate of exhalation falls dramatically. Treatment of minor lung disorders includes inhalation of bronchodilator drugs, which widen the airways. Major problems, such as emphysema, may require a heart-lung transplant.