Whether your patient has trouble getting air in or getting it out, a basic diagnostic tool is pulmonary function testing, which typically consists of three tests measuring airflow, lung volumes, and diffusion. Three tests The most frequently performed test is basic spirometry, which can be done at the bedside. This test assesses expiratory airflow by having the patient put on a nose clip, take a deep breath, then blow forcefully and fully into a mouthpiece connected to a spirometer. Sometimes a bronchodilator is administered after the first spirometry test to determine if the drug improves airflow. The spirometry test is the only PFT that involves postbronchodilator values because only spirometry values can be affected by bronchodilator use.
Lung volumes testing, the second component of pulmonary function testing, is performed in a PFT lab.
For this test, the patient sits in a closed glass box slightly larger than a telephone booth. Wearing a nose clip, she breathes and pants several times into a mouthpiece. The therapist performing the test communicates with the patient through an intercom. Test results help determine airway dynamics inside and outside the thoracic cavity. Carbon monoxide is used because it readily travels across the alveolocapillary membrane and binds with hemoglobin over 200 times more easily than oxygen.