Spirometry 101: Comprehending Readings through Patterns


May 11, 2016


This entry was posted on Wednesday, May 11th, 2016 and is filed under Blog by AENT Associates


Spirometry, one of the most commonly advised lung function tests, is used by a number of asthma specialists to diagnose the condition of the patients and the severity of the disorder. This test shows how well you breathe in and out. Lung diseases, such as Chronic Obstructive Pulmonary Disease (COPD), Pulmonary Fibrosis, Asthma, and Cystic Fibrosis, may affect the smooth functioning of the lungs, and in such cases, the physician may prescribe spirometry. Spirometry helps physicians to monitor the severity of these disorders and devise a suitable treatment plan. In this post, we talk about the four major patterns shown by spirometry reading.

1. Normal

Normal spirometry readings change, depending on your age, sex, and size. There is a chart that publishes the range of normal readings. Your doctor refers to this chart at the time of checking your spirometry reading. Interpretations of spirometry results demand a comparison between the measured value of an individual and reference value. These results are considered to be normal if the Forced Vital Capacity (FVC) and the Forced Expiratory Volume-One Second (FEV1) fall within 80 percent of the reference value. The normal value for the FEV1/FVC ratio is 70 percent with 65 percent in those older than 65 years. You should know that a lower measured value relates to a more serious lung abnormality when compared to the reference value.

FVC is a measurement of lung size (in liters); denoting the volume of air that lungs may exhale along with a deep inhalation. While FEV1 is a measure of how much air is exhaled in a second accompanying a deep inhalation.

2. Obstructive

In the case of the obstructive pattern on spirometry, the FVC is frequently normal or near normal. This pattern occurs due to diseases that cause narrowed airways. Asthma and COPD are two main conditions that affect narrowing of the airways and an obstructive pattern on spirometry. In the case of narrowed airways, there is a reduction of air that one can quickly blow out. FEV1, therefore, decreases and the ratio of FEV1/FVC becomes lower than normal. The total capacity of your lungs, however, remains normal or simply undergoes a mild reduction.

3. Restrictive

FVC is less than the expected value for your age, size, and sex, in the case of restrictive spirometry pattern. A spirometry reading shows a restrictive pattern due to conditions that affect the lung tissue or the capacity of the lungs to expand and hold a normal amount of air. Cystic Fibrosis and Scarring of the Lungs also give restrictive patterns on spirometry. The ratio of FEV1/FVC is normal in a restrictive pattern.

4. Obstructive + Restrictive

If spirometry reading displays a combined obstructive and restrictive pattern, the patient may suffer from two conditions at the same time, such as asthma and another type of lung disorder. There are few lung conditions that bear features of both an obstructive and restrictive pattern. One of the examples of such a lung condition is Cystic Fibrosis wherein there is a lot of mucus in the airways, thereby, causing narrowed airways (the obstructive part of the spirometry reading), as well as damage to the lung tissue (resulting in the restrictive component).


Taking a spirometry test is relevant in the world of today, as there is a rapid increase in the cases of respiratory diseases. This widely used lung function test is the method of choice that every Asthma Specialist in Houston or Pearland recommends for a fast and reliable screening of respiratory disorders. If you or someone you know is suffering from asthma or any other lung-related disorder, feel free to get in touch with one of our asthma associates to learn more about possible treatment options.

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This entry was posted in Asthma on May 11, 2016 by AENT Team.

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