A Pulmonary Function Test (PFT) is a non-invasive procedure that measures lung capacity, air volume, and airflow speed. This diagnostic tool identifies respiratory conditions like asthma or Chronic Obstructive Pulmonary Disease (COPD) or monitors treatment effectiveness. Accurate results require careful preparation, and patients frequently ask if they should use their inhaler beforehand. The answer is almost always no, and patients must consult directly with the ordering physician or testing facility for specific instructions.
Understanding the Purpose of the Test
The primary reason for withholding bronchodilator medications is to establish a true, native baseline of lung function. Respiratory conditions narrow the airways, and the PFT measures this specific degree of obstruction. If a patient uses a bronchodilator, which relaxes the airway muscles, the test will incorrectly show an artificially open airway. This interference makes it impossible to measure the underlying severity of the condition.
PFTs often include a “reversibility test.” Initial measurements are taken, followed by the administration of a fast-acting bronchodilator, such as albuterol. Lung function is then measured again to see how much it improves, demonstrating the degree of reversibility. Using an inhaler before the appointment obscures this measurement, potentially leading to an inconclusive test or an incorrect treatment plan.
Specific Inhaler Classes and Required Hold Times
The required cessation period depends entirely on the drug class and its duration of action. Hold times are calibrated to ensure the medication’s effect has completely worn off before testing begins. Following the facility’s specific instructions for your medication is the most important step in preparation.
Short-Acting Beta Agonists (SABAs), often referred to as rescue inhalers, have the shortest required hold time, typically between four and eight hours before the test. Medications like albuterol fall into this category. Since these drugs are designed for quick relief, their bronchodilating effect dissipates relatively quickly.
Longer-acting medications require a significantly longer hold period to wash out of the system. Long-Acting Beta Agonists (LABAs), such as salmeterol, generally require abstinence for 12 to 24 hours prior to the appointment. Similarly, Long-Acting Muscarinic Antagonists (LAMAs), like tiotropium, may need to be withheld for 24 to 48 hours to ensure the airways return to their unmedicated state.
Combination inhalers that mix a LABA or LAMA with an inhaled corticosteroid (ICS) often require the longest hold times, frequently 24 to 48 hours. Because protocols can vary between testing centers and are dependent on the specific drug compound, follow the exact instructions provided by the clinician who ordered the PFT.
Protocols for Emergency Use and Day-of Testing
If you experience severe respiratory symptoms, such as an asthma flare-up, during the cessation period, use your rescue inhaler as medically necessary. If this occurs, immediately contact the testing facility to inform them of the situation. Using the rescue inhaler will invalidate the test results for that day, and the appointment will need to be rescheduled to ensure accurate measurements.
On the day of the test, bring all your inhalers and a complete list of current medications and dosages. This allows the testing staff to confirm which medications were withheld and to administer the bronchodilator during the reversibility portion of the test, if scheduled. It also ensures that your rescue medication is immediately available should you need it after the testing is complete.
While bronchodilators must be withheld, other non-bronchodilator respiratory medications, such as oral and inhaled corticosteroids, are generally continued as usual unless specifically instructed otherwise. These medications do not acutely dilate the airways in the same way bronchodilators do, so they typically do not interfere with the PFT’s primary measurements. Always confirm the status of all your medications with the testing clinic.