Spirometry tests measure many different parameters in order to diagnose and monitor lots of different respiratory diseases. This is the reason there are 4 different test modes in the SpiroClinic App: Ex-Only, Full Loop, SVC, and MVV. This enables the healthcare professional to measure different parameters for diagnostic purposes.
Ex-only (Exhalation only)
This test involves exhalation only in order to make the necessary measurements. It is, in its essence, measures the maximum amount of air that can be expelled through the lungs after taking the deepest breath possible.
It may help the healthcare team differentiate between obstructive (i.e. asthma, COPD - diseases that make it difficult to exhale) and restrictive (i.e. pulmonary fibrosis) lung diseases. It can also help to assess the progression of the condition and evaluate how effective the treatment is.
In this test, the patient is required to breathe normally 3 times - if tidal start is on - and then inhale fast until they completely fill their lungs. The last part of the test requires the patient to exhale as fast and hard as possible.
This test calculates the following parameters: FVC, FEV0.75, FEV1, FEV3, FEV6, FEV1/FEV6, FEV0.75/FVC, FEV1/FVC, FEV3/FVC, FEV6/FVC, FEV0.75/FEV6, MET25-75, MMEF, FEF25, FEF50, FEF75, FEF25-75, FEF50/FVC, MMEF/FVC, FET, BEV, PEF.
This test necessitates the patient to go through a full loop of inhalation and exhalation in order to complete it. It shows a picture of flow rate vs volume during a full loop of inhaling and exhaling, hence the name.
The results of the test may suggest a restriction in the lungs, a diffuse airflow obstruction, or a lesion that is obstructing the central airways.
In this test, if tidal start is on, the patient is required to breathe normally 3 times, and then inhale fast until they completely fill their lungs. Then they need to exhale as fast and hard as possible, and lastly, to inhale fast until they completely fill their lungs.
This test calculates the following parameters: FVC, FIVC, FEV0.75, FEV1, FEV3, FEV6, PEF, FEV1/FEV6, FEV0.75/FVC, FEV1/FVC, FEV3/FVC, FEV6/FVC, FEV0.75/FEV6, FEV1/FEV6, FEF50/FVC, MMEF, FEF25, FEF50, FEF75, FEF25-75, MET25-75, BEV, MMEF/FVC, FEF50/FVC, PIF, FIV1, FIV1/FIVC, FET.
SVC (Slow vital capacity)
Vital capacity is the most amount of air a person can inhale after exhaling the most amount. Slow vital capacity is the volume of air expired but through an unforced maneuver. The most important function of this test is that it can be used to figure out if there is an airway obstruction.
Another factor in administering lung function tests is obesity, which may affect a forced vital capacity test's results, in which case a test that measures using an unforced maneuver like SVC is a better choice. The same thing goes for elderly patients or patients with neurological conditions who may have difficulties with forced maneuvers.
In this test, the patient is required to breathe normally at least 4 times, inhale completely filling the lungs, and then exhale slowly until the lungs are completely empty. Or, exhale completely emptying the lungs, and then inhale slowly until the lungs are completely full.
This test calculates the following parameters: VC, VCEx, IRV, RF, VCIn, ERV, IC, VT.
MVV (Maximal voluntary ventilation)
MVV measures the largest volume of air that can be moved in and out of the lungs during a 10 to 15 second period with voluntary effort. MVV differs from other ventilatory tests in that it not only reflects the strength of lung muscles, but also the coordination.
The results may be lower in patients showing upper airway obstructions, respiratory muscle weaknesses, or obstructive lung disease.
In this test, the patient is required to inhale and exhale deeply and rapidly, repeatedly and uninterrupted for at least 12 seconds.
This test calculates the following parameters: MVV, MVVTime, MVV6, VT.
- MVV Testing Procedure on Ultima & Elite Plethysmograph, University of Texas Medical Branch Pulmonary Function Clinic, 2014.
- Slow Vital Capacity, Kendig's Disorders of the Respiratory Tract in Children (Seventh Edition), 2006.
- Age-Related Changes in the Respiratory System, Gwyneth A.. Davies, Charlotte E.. Bolton, Brocklehurst's Textbook of Geriatric Medicine and Gerontology (Seventh Edition), 2010.
- What Is Forced Vital Capacity (FVC)?, Deborah Leader, RN. 2022.
- Pulmonary Function Tests for Diagnosing Lung Disease, Eric J. Heckman, MD and George T. O’Connor, MD, MS. JAMA, 2015.
- Pulmonary Function Testing, Scott E.Evans, Paul D.Scanlon, Bruce H.Culver. Clinical Respiratory Medicine (Third Edition), 2008.