Pulmonary Function Test/ Spirometry Pre & Post

Pulmonary Function Test/ Spirometry Pre & Post

Pulmonary Function Test (PFT) or Spirometry is a commonly used diagnostic tool to evaluate the functioning of the lungs. It measures various parameters of lung function, such as the volume of air you can inhale and exhale, the speed at which you can exhale forcefully, and the amount of air left in your lungs after a complete exhalation.

To perform a PFT or Spirometry, you typically undergo two sets of measurements: pre-test and post-test. Here's what each of these measurements involves:


  • Baseline Measurements: Before starting the test, your height, weight, and age are recorded, as these factors can affect lung function.
  • Instructions: The technician or healthcare professional will provide you with detailed instructions on how to perform the test correctly. It's crucial to understand and follow these instructions for accurate results.
  • Resting Period: You may be asked to rest for a short period to ensure that you're relaxed and prepared for the test.
  • Preparation: You will be given a mouthpiece attached to a spirometer, a device that measures lung function. You will be instructed to sit or stand upright and take a deep breath to fill your lungs completely.
  • Testing Maneuvers: You will be asked to perform several specific maneuvers, including:
    • Forced Vital Capacity (FVC): Take in the deepest breath you can and then exhale forcefully and rapidly until your lungs are completely empty.
    • Forced Expiratory Volume in one second (FEV1): After taking a deep breath, exhale as forcefully and quickly as possible for one second.
    • Other measurements: Additional tests, such as Maximum Voluntary Ventilation (MVV) or Peak Expiratory Flow (PEF), may also be performed depending on the specific requirements of the test or the suspected lung condition.


  • Intervention or Administration: In some cases, you may be asked to inhale specific medications or substances to assess their impact on lung function. This is commonly done in tests assessing bronchodilator response, where a medication is given to see if it improves lung function.
  • Repeat Testing: After the intervention or administration, you will repeat the same set of measurements that were performed during the pre-test.
  • Comparison: The pre-test and post-test results are then compared to evaluate any changes in lung function, especially after the administration of medication.

The pre-test measurements establish a baseline for your lung function, while the post-test measurements help assess the effectiveness of interventions or medications in improving lung function. By comparing the results, healthcare professionals can better understand your lung capacity and identify any abnormalities or respiratory conditions you may have, such as asthma, chronic obstructive pulmonary disease (COPD), or restrictive lung diseases.

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