A pulmonary function test (PFT) is a comprehensive assessment that evaluates how well your lungs work. These non-invasive tests measure lung function, including how much air your lungs can hold, how quickly you can move air, and how effectively lungs transfer oxygen to your bloodstream. Healthcare providers use PFTs to diagnose conditions like asthma, chronic obstructive pulmonary disease (COPD), or pulmonary fibrosis, monitor disease progression, and assess the impact of environmental factors on lung health. The information gathered from a PFT helps understand your respiratory system and guide medical care.
Pre-Test Preparations
Careful preparation before a pulmonary function test helps ensure accurate results. Wear loose, comfortable clothing that does not restrict your chest or abdomen, allowing for full lung expansion. Avoid heavy meals for at least two hours prior to your appointment, as a full stomach can impede diaphragm movement and make deep breathing uncomfortable. Refrain from alcohol for at least eight hours and strenuous exercise for at least one hour before the test, as these can alter lung function.
Avoid caffeinated beverages like coffee, tea, or certain sodas on the day of the test, as caffeine can cause bronchodilation and potentially skew results. Smoking or vaping should be avoided for at least one hour before the test, as these activities directly affect airway function and oxygen levels. Consult your healthcare provider about specific medication instructions. Depending on the purpose of the test, you may be asked to temporarily stop certain breathing medications to ensure baseline measurements.
Performing the Test
During a pulmonary function test, a technician or respiratory therapist will guide you through various breathing maneuvers. Spirometry is a common component, where you will sit upright with a soft nose clip to ensure all breathing occurs through your mouth. You will then form a tight seal around a disposable mouthpiece connected to a spirometer, a device that measures airflow and lung volume. The technician will provide clear, specific instructions for each step of the test.
For typical spirometry, you will be asked to take a deep breath in, filling your lungs completely, then exhale as forcefully and rapidly as possible until your lungs feel completely empty. This sustained, maximal effort helps obtain accurate measurements of how much air you can exhale (Forced Vital Capacity, FVC) and how much you can expel in the first second (Forced Expiratory Volume in 1 second, FEV1). Multiple attempts are usually required to ensure consistent and reliable readings, and the technician will provide verbal encouragement throughout the process to help you achieve your best effort.
Interpreting Your Results
After completing the pulmonary function test, the collected data will be analyzed by a healthcare professional. They will review the measurements, such as Forced Expiratory Volume in 1 second (FEV1) and Forced Vital Capacity (FVC), and compare them to predicted normal values based on factors like your age, height, gender, and ethnicity. This comparison helps determine if your lung function falls within an expected range or if there are indications of a lung condition.
The FEV1/FVC ratio is an important measurement, indicating whether there is an obstructive pattern, where airflow is reduced, or a restrictive pattern, where lung volume is decreased. A “pass” on a PFT does not imply achieving a perfect score, but rather obtaining accurate and reproducible measurements that reflect your actual lung health. The results provide insights that enable your doctor to understand your lung capacity, identify potential issues, and formulate a treatment plan if necessary. Your healthcare provider will discuss your specific results with you and explain what they mean for your overall respiratory well-being.