A careful history, a comprehensive physical examination, and pulmonary | function tests, should help a physician narrow down your complaints. 1 Make sure to relay all prior episodes of asthma or lung problems, aller - : gies, family history of asthma or allergies, and triggering factors that you < have decoded.
function tests are designed to diagnose various lung diseases. The simplest test involves breathing through a tube into a computerized system. This test, called spirometry, measures the forcefulness of your inhalations and exhalations (9). Spirometry is ; easy to perform, and most doctors who treat asthma have the instru - | ment available in the office. This test generates some numeric values to | rate your forcefulness. It also creates a graph, called a flow-volume loop, which is recorded by the computer. The loop above the vertical axis
represents the exhalation and the loop below represents inhalation. The shape of the loop is specific for various lung diseases. For example, the first loop in 19 shows normal breathing. This shape is also shown for people with asthma when they are not flaring, because their lungs will typically look normal when they are not experiencing an attack.
Spirometry can be performed in two stages: the first stage to diagnose and the second to assess any therapeutic effect of the medications. The second stage is done after medication has been given to dilate the bronchial tubes. If asthma is present, then the loop should return to normal after the treatment. This is shown in the second part of the diagram: The asthmatic loop is superimposed on the normal loop, which shows the response to treatment. If there is a fixed disease like emphysema, there will be no improvement. Remember that you can have a mixed pattern, which makes testing more complicated. The third loop shows changes on the top and bottom of the loop, consistent with COPD, bronchitis, and emphysema.
Pulmonary function tests help diagnose more subtle forms of asthma that occur during exertion only, or as a result of various stimulants. In a subset of bronchial asthma called exercise-induced asthma, spirometry is done after a provocation test either by exercise in a controlled environment or by inhalation of chemical substances known to induce symptoms.
Pulse oximetry can be performed by placing a device on your finger, which is used to measure the arterial oxygen concentration in the blood. During an acute asthmatic attack, as less air flows into the lungs, less oxygen is extracted and circulates within the bloodstream. A low oxygen concentration is very dangerous as it may cause heart attacks, strokes, or respiratory collapse.
Blood tests can also be performed to check the amount of oxygen in your blood. This is called an arterial blood gas. In addition, there are blood tests to determine the level of eosinophils or other white blood cells in your blood. A high count of eosinophils is one of the hallmarks of bronchial asthma, but this elevation is not always present. Allergy testing may also be performed to see if there is an allergic component to the attacks.
Chest X-rays are usually normal between attacks. During an acute attack of asthma, due to excessive trapping of air in the lungs, the appearance is hyperinflated. Chest X-rays can also help exclude pneumonia, which could be the triggering factor of an acute asthma attack.