Improving spirometer precision to aid lung condition diagnosis

Spirometry is a frequently used medical office test to evaluate how well a patient’s lungs work by looking at how much air they inhale and exhale, as well as the speed at which they exhale.

Improving spirometer precision to aid lung condition diagnosis

Image Credit: Superior Sensor Technology

Spirometers are thought to be the most suitable method for testing and diagnosing a number of lung conditions that affect breathing, including:

  • Asthma
  • COPD
  • Chronic bronchitis
  • Emphysema
  • Pulmonary fibrosis

If a patient has previously been diagnosed with a chronic lung disorder, spirometry may also be used periodically to monitor the effectiveness of medications and whether breathing problems are in check.

Further, spirometry may be necessary before a planned surgery to check lung function and that the patient is fit for the rigors of an operation. Finally, spirometry may be utilized to screen for occupational-related lung disorders.

Spirometry measures lung capacity and volume under a range of test conditions. Some of the most frequently applied measurements are:

  1. Forced Vital Capacity (FVC): The largest amount of air that a patient can exhale after taking their deepest breath is measured. A less than normal FVC reading signals restricted breathing.
  2. Forced Expiratory Volume (FEV1): The amount of air exhaled during the first second of exhalation is measured. This reading evaluates the extent of the breathing problem – the lower the FEV1, the more severe the obstruction.
  3. Maximum Voluntary Ventilation (MVV): The maximum amount of air that can be inhaled and exhaled within one minute is measured.
  4. Forced Expiratory Flow (FEF): The speed or flow of air that the lungs exhale during the middle portion of the breath.
  5. Peak Expiratory Flow (PEF): The maximum level of flow or speed of air the lungs exhale during the entire exhalation.
  6. Tidal Volume (TV): The volume of air inhaled or exhaled when in a resting condition.
  7. Total Lung Capacity (TLC): The maximum volume of air present in the lungs when inhaling.

The FEV1/FVC Ratio is a key measure. Healthy adults should have an FEV1/FVC Ratio of around 70 – 80%, but it does decline with age.

In obstructive diseases (asthma, COPD, chronic bronchitis, emphysema), FEV1 is reduced as the airways display an increased resistance when exhaling; the FVC may also be reduced due to the premature closure of the airway during expiration, just not in the same amount as FEV1.

This produces a reduced value (less than 70%, often as low as 45%). In restrictive diseases (such as pulmonary fibrosis), the FEV1 and FVC are both proportionally reduced. The value may be displayed as normal or even increased due to decreased lung compliance.

Improving spirometer precision to aid lung condition diagnosis

Figure 1. Spirometer Example. Image Credit: Superior Sensor Technology

The role of differential pressure sensors in spirometers

While there are a number of types of flow sensing spirometers, such as turbine, thermal and ultrasonic, the focus here is on differential pressure-based spirometers. This class of spirometers is extremely common and offers precise measurements.

A differential pressure sensor transforms the pneumatic pressure values into proportional electrical signals. The pressure sensor generally includes a thin diaphragm. The diaphragm is the most crucial part for the measurement of the pressure and is fitted with strain-sensitive and compression-sensitive resistance structures.

When a patient inhales and exhales into the spirometer, the diaphragm is deflected by air pressure. These deflections are then translated into electrical signals (analog output voltages) that are relative to the applied differential pressure on the sensor as measured by the diaphragm.

However, several external factors can impact pressure sensors due to their sensitivity. These include factors such as noise, humidity, temperature, atmospheric pressure and the physical positioning/orientation of the device.

Differential pressure sensors also face a challenge when measuring low-pressure air flow and may require recalibration, as they have a tendency to drift from their zero reading over time.

Differential pressure sensors that can cancel out the impact of noise and are not vulnerable to changes from position/orientation, offer a stable, consistent zero value, allowing health professionals to improve their diagnoses of lung performance and enable spirometers to deliver the most accurate readings.

Superior Sensor’s technology advantage

Superior Sensors’ proprietary NimbleSenseTM architecture is the first System-in-a-Sensor integrated platform in the industry.

Integrating both a highly differentiated advanced pressure sensing system with the capacity to incorporate optional building blocks allows Superior Sensors to fuse the highest levels of accuracy and reliability with spirometry-specific exclusive features.

With unique technology used in the SP Series of differential pressure sensors, Superior’s products provide several advantages for spirometry and critical care medical devices.

Z-TrackTM auto zero

Superior’s proprietary Z-Track technology practically eradicates zero drift by preserving minimal zero-point deviation with stable results regardless of elapsed time. For additional details on Z-Track technology, read the Z-Track blog post.

Position insensitivity

Superior’s innovative dual-die implementation with the SP210 sensor preserves consistent and extremely precise handheld readings irrespective of the physical orientation of the spirometry device.

With respect to position insensitivity, the SP210 is an industry leader, with a positional sensitivity within 0.25 Pa.

Highest levels of accuracy

Sensor accuracy is absolutely key, as the difference between an effective and ineffective treatment plan can rest on the accuracy of the diagnosis. A small deviation in measurements can lead to changes in the dosage or even the type of medication a patient is prescribed.

Superior’s SP Series spirometry sensors can boast the best accuracy in the industry, as close as within 0.05% of the selected pressure range.

Fastest warm-up and response times

For time-restricted applications, the warm-up time of the spirometer is vital. The SP Series effectively eliminates warm-up time as the device is operational in just 60 milliseconds.

Moreover, the time it takes the pressure sensor to update its measurement data is just as important.

The quicker updated pressure measurements are received, the more accurate the spirometry readings. While user-configurable, Superior’s sensors can facilitate update rates as fast as 2 milliseconds.

Lowest noise floor

As previously mentioned, external noise can negatively impact the accuracy and performance of spirometers.

Utilizing Superior’s built-in advanced digital filtering technology, Superior’s pressure sensors cancel out the noise these factors create before they reach the sensor sub-system. Thus, the noise is removed before it becomes an error signal that can lead to erroneous lung measurements.

Low power consumption

As many spirometers are self-contained handheld devices or connected to a computing device via a USB port, power consumption is another critical factor in the device’s overall performance.

With power consumption as little as 5 mA, the SP Series will not adversely impact the battery life of even the most sophisticated, complex spirometry equipment.

Improving spirometer precision to aid lung condition diagnosis

Figure 2. Handheld Spirometer Example. Image Credit: Superior Sensor Technology


A spirometer is an essential tool used in the diagnosis and treatment of numerous types of lung diseases. Spirometry products demand high-performance differential pressure sensors to diagnose a patient’s lung functions accurately.

Moreover, these handheld units must offer extremely accurate readings irrespective of how the unit is positioned when it is in use.

Superior Sensor’s innovative differential pressure sensor technology, based on the proprietary NimbleSense architecture, offers a number of differentiating features that help medical device makers set their products apart from the rest in a competitive marketplace.

For more detailed information about Spirometry solutions, please visit Superior Sensor’s product page.

About Superior Sensor Technology


Superior Sensor Technology is an innovative, high technology company is revolutionizing the high performance, cost driven pressure sensor market by developing integrative, highly intelligent solutions for industrial, HVAC and medical applications.

Our proprietary pressure sensor technology with advanced programmable software features enables customers to develop higher performing, more reliable equipment.

Sponsored Content Policy: publishes articles and related content that may be derived from sources where we have existing commercial relationships, provided such content adds value to the core editorial ethos of News-Medical.Net which is to educate and inform site visitors interested in medical research, science, medical devices and treatments.

Last updated: Feb 11, 2022 at 3:10 AM


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