Asthma Medicines

Besides simple spirometry, the physician may perform other pulmonary function tests to better assess and define a patient’s condition. Patients with a variety of illnesses may have reduced capacities and flow rates and further testing may be needed. These tests include measurement of lung volume in which the different divisions or “compartments” of the lungs are measured. These divisions represent quantities of air that are distributed throughout the lung. One example would be the quantity of air that remains in the lung at all times to keep it expanded.

Measuring of lung volumes may be performed by two methods. A common technique requires inhaling a special gas mixture containing helium that the patient breathes for several minutes. Analyzing the amount of helium exhaled allows the physician to calculate how the air was distributed in the different air divisions of the lung. Another technique for measuring lung volumes requires an airtight box called a body plethysmograph. In this technique the patient sits in a clear box that resembles a phone booth and breathes against a mouthpiece. By analyzing pressure changes in the box as the patient breathes it is possible to determine the volume of gas in the lungs.

Another important pulmonary function test is known as a diffusion capacity. This is a sensitive test for the loss of gas exchanging units of the lung as in emphysema. In this test the patient again breathes a special gas mixture and an amount of exhaled gas is collected. By determining how fast the inhaled gas has disappeared, it is possible to determine whether the air sacs are exchanging gases normally.

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