Choosing the Right Spirometer

Spirometry is a test designed to assess respiratory function. Spirometry measurements are taken with different types of equipment and technical and human factors can influence the results obtained. A spirometer is a medical device that measures the volume of air inhaled and exhaled during a breathing cycle, as well as inspiratory and expiratory flows. To do this, it uses an integrated pressure transducer. During the test, the patient must fill their lungs with air and then exhale through a plastic tube fitted to the spirometer. With this test, the doctor can establish a diagnosis and, if necessary, prescribe a treatment.

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What are the different types of spirometers?
Spirometers come in both tabletop and hand-held versions. Some models have an integrated pulse oximeter.

MIR hand-held spirometer
- Tabletop or hand-held spirometers: More and more spirometers, especially hand-held ones, are designed for use with a computer, tablet, or smartphone. If so, you need to install a specific program or application. Some models come equipped with Bluetooth technology. Connected spirometers allow test results to be sent directly to the doctor, who can then monitor the patient’s progress more easily.
- Spirometers with pulse oximeters: These offer the possibility of measuring oxygen saturation in the blood with the same device. Oxygen saturation (SpO2) is also a good indicator of respiratory function.
In what applications is spirometry used?
Spirometry has many applications, in clinical practice, sports, and research. These are the main ones:
- Used to diagnose a respiratory condition
- Detects respiratory diseases at an early stage
- Offers the possibility of evaluating the effect of a non-respiratory disease on ventilation
- Often used as a preoperative examination for thoracic or abdominal surgery
- Tabletop spirometers are suitable for office use (for example, in pulmonologists’ offices)
- Hand-held spirometers are ideal for measurements taken outside a hospital environment (for example, in mobile medical emergency units)
- There are spirometers for specific non-clinical uses (e.g. for sports)
- There are also spirometers designed specifically for scientific research
What does a spirometry test consist of?
Spirometry tests can be carried out using slow or forced breathing maneuvers.
- Slow spirometry: The patient inhales and exhales slowly through the mouth via a tube fitted to the spirometer. The patient must fill their lungs completely with air and then empty them completely, without any effort of speed or intensity. This test measures Slow Vital Capacity (SVC).
- Forced spirometry: The patient inhales deeply until the lungs are completely full, then blows the air out as hard and fast as they can. The exhalation should continue for at least 3 seconds, ideally 6 seconds. This is performed three times in a row and measures the Forced Vital Capacity (FVC). The difference between SVC and FVC values is a very useful indicator for the doctor.
Forced spirometry allows other less frequent tests to be carried out and different parameters to be obtained, two examples of which are given here.
- Forced expiratory volume in 1 second (FEV1): As the name suggests, this is the volume of air exhaled in the first second of a forced expiration after a maximum inspiration. It is measured in liters.
- Maximum voluntary ventilation per minute (MVV): To measure maximum ventilation per minute, the patient performs a series of rapid, deep inhalations and exhalations for at least 12 seconds. From this result, the value per minute is calculated.
What technical characteristics should be taken into account when buying a spirometer?
When choosing a spirometer, there are several technical characteristics to take into account, such as the device’s accuracy, the quality of the measurement display, and the type of transducer.
- Accuracy: This characteristic is particularly important if the device is to be used to assess a patient’s respiratory function several times over the course of a day, by repeating the test. The spirometer must be able to accumulate air volume for at least 15 seconds when measuring FVC, and for at least 30 seconds when measuring SVC. However, it is recommended to opt for devices with a storage capacity for longer periods. The device must be able to measure volumes greater than or equal to 8 liters (BTPS) with an accuracy of +/- 3% or +/- 0.050 liters, with flows between 0 and 14 liters per second.
- Display of measurements: The spirometer should allow clear visualization of both the flow-volume and volume-time curves. The doctor graphically sees the progress of each maneuver before moving on to the next to ensure its quality. More precisely, they check that the curves meet the minimum size and resolution requirements described in the device’s recommendations for use.
Medikro transducer
- Transducer: Transducers are generally disposable to avoid the risk of contamination between patients. It is essential to check the accuracy of each transducer.
Technical Characteristics:
- Precision
- Display of measurements
- Transducer
How do you guarantee reliable measurements?
To guarantee the measurements made with a spirometer are reliable, it is strongly recommended that two crucial steps be carried out: validation and quality control.
- Pre-market evaluation/validation: Spirometry systems are evaluated using computer-driven mechanical syringes or other equivalent test systems to test the range of exhalations that are normal to find in the tested population. It should be noted that it is not up to laboratories to test the performance of devices.
- Post-market quality control: Quality control and equipment calibration are part of a laboratory’s good practices. Therefore, it is recommended that you keep records of calibration results, repairs, and other interventions carried out to ensure the device functions properly, as well as the dates of software and hardware updates or changes. When a spirometer is replaced or moved, the quality control and calibration procedures must be carried out again before use.