Diagnosing disease is mostly a process of knowing what is "normal" and recognizing what is not. A doctor recognizes a disease by seeing a pattern formed by symptoms and findings during a physical examination. Laboratory tests can confirm these opinions or findings. Advances in technology have led to a flood of diagnostic methods for imaging the body.
Bronchoscopy
A bronchoscopy uses an endoscope, an optical instrument, that visually examines the structures inside the lung. A powerful light shines down one bundle of optical fibers to illuminate the airway and lung tissue. The image reflects back up the tube along another bundle of fibers, magnifying it through a lens into the eyepiece. This device, when attached to a computer, can record images for further examination. According to the U.S. National Library of Medicine, a bronchoscopy helps the doctor identify and sometimes treat problems such as coughing up blood, identifying a tumor or foreign object or removing fluid or mucus from the airway. Using a bronchoscope to extract samples of lung tissue will help identify signs of cancer or lung infection.
Arterial Blood Gas
The function of the lungs is to supply the body with oxygen and to release carbon dioxide. According to the American Association for Clinical Chemistry, an arterial blood gas, or ABG, measures the amount of oxygen and carbon dioxide in the blood using a fresh sample of blood obtained from an artery. During episodes of respiratory distress, such as an asthma attack, the blood oxygen level may be low and the carbon dioxide level is high. Blood gas evaluation is fundamental to diagnosing and managing many heart and lung disorders and is an extremely effective diagnostic tool.
Pulmonary Function Tests
Spirometry, one of several pulmonary function tests, is a valuable tool in diagnosing lung disorders. A person breathes into a spirometer, which records the total volume of exhaled air, called the forced vital capacity or FVC. The test also measures the volume of air exhaled in one second, called the forced expiratory volume in one second or FEV1. If the ratio of FEV1 to FVC is less than normal, the person may have an obstructive lung disease such as asthma. Asthma causes the airways to narrow, resulting in a slower than normal expiratory rate. A reduction in both of these measurements often means the person may have a restrictive lung disease such as pulmonary fibrosis.
