Blood pressure is one of the most important indicators of cardiovascular health. Today, some smartwatches claim to measure or estimate blood pressure using photoplethysmography, commonly known as PPG. Although PPG is convenient and valuable for tracking pulse-related signals, a smartwatch with an inflatable airbag generally provides a more direct and potentially more reliable method of measuring blood pressure.
How does an airbag-based watch measure blood pressure?
An airbag-based blood pressure watch uses the oscillometric principle—the same fundamental method used by most automatic upper-arm blood pressure monitors.
During a measurement, a miniature airbag inside the watch strap gently inflates and applies controlled pressure to the wrist artery. As the airbag pressure changes, the watch detects small pressure oscillations created by blood flowing through the artery. Its algorithm analyzes these oscillations to calculate systolic and diastolic blood pressure.
Because the device applies known physical pressure and directly observes the arterial response, it is measuring a physiological effect closely related to blood pressure rather than relying entirely on an indirect estimate.
How does PPG estimate blood pressure?
PPG uses LED light and an optical sensor to observe changes in blood volume beneath the skin with each heartbeat. It works very well for measuring heart rate and can also support blood-oxygen, sleep and cardiovascular-trend analysis.
However, PPG does not directly measure the pressure inside an artery. To estimate blood pressure, a PPG-based device must use an algorithm to infer pressure from characteristics such as pulse-wave shape, timing and amplitude.
These optical signals can be influenced by many factors, including:
- Skin contact and strap tightness
- Wrist movement
- Skin temperature
- Sensor position
- Blood-vessel stiffness
- Stress, exercise and body posture
- Medication and physiological changes
- Differences among individual users
For this reason, many cuffless systems require initial and periodic calibration using a traditional cuff-based monitor. According to the American Heart Association, the accuracy of many cuffless devices depends heavily on the quality and frequency of this calibration.
Why is the inflatable-airbag method generally more reliable?
The main difference is direct measurement versus algorithmic estimation.
An inflatable airbag produces a controlled pressure around the wrist and detects the artery's physical response. PPG alone records an optical pulse signal and then predicts what the corresponding blood pressure may be.
A properly designed and clinically validated airbag-based watch therefore offers several important advantages:
A more direct measurement principle
Oscillometric measurement is already widely used in home and clinical blood pressure monitors.
Less dependence on personal calibration
A cuffless PPG algorithm may lose accuracy as a user's vascular condition, medication, temperature or activity changes. An oscillometric airbag measurement does not depend entirely on a previously calibrated relationship between PPG signals and blood pressure.
Better detection of absolute blood pressure values
PPG can be helpful for observing patterns, but translating an optical waveform into exact systolic and diastolic values is technically difficult. An airbag measurement captures pressure oscillations under known cuff pressure.
A stronger reference for AI analysis
Airbag-based readings can provide higher-quality reference data for training a personalized AI model. PPG and other sensor signals can then be used between airbag measurements to identify trends and support more comfortable monitoring.
The best approach may combine both technologies
Airbag and PPG technologies do not need to compete. They can complement each other.
The inflatable airbag can provide periodic reference measurements, while PPG can collect pulse-wave information more frequently and with less interruption. Artificial intelligence can analyze these measurements together with heart rate, activity, sleep and other relevant signals.
This hybrid approach combines the measurement strength of an inflatable airbag with the convenience of optical monitoring. It can offer users a more complete view of how their blood pressure changes throughout the day and night.
Proper technique and clinical validation still matter
No wrist device is automatically accurate simply because it contains an airbag. Accuracy also depends on the watch's design, airbag size, sensor quality, algorithms, wrist position, user technique and clinical validation.
During an airbag measurement, the user should remain still, keep the wrist near heart level and follow the manufacturer's instructions. Consumers should also confirm that a device has the appropriate regulatory authorization for its intended market.
A smartwatch should not be used to change medication or make urgent medical decisions without consulting a qualified healthcare professional.
Conclusion
PPG is an excellent technology for convenient, frequent pulse monitoring, but estimating blood pressure from light-based signals alone remains challenging. An inflatable-airbag watch uses the established oscillometric principle and measures the artery's response to controlled pressure, making it a more direct foundation for determining systolic and diastolic blood pressure.
By combining airbag-based measurements, PPG sensing and personalized AI analysis, wearable blood pressure technology can provide both greater convenience and more meaningful cardiovascular insights.