In recent years, smart watches and smart bracelets are becoming the most popular wearable devices, these products in the relatively traditional shape of the equipped with a variety of miniaturized devices, portability and direct contact with the human body characteristics, so that it can assume a variety of functions that we could not imagine in the past, one of the more interesting examples is the ability to detect the health status of various wearers such as heart rate, blood oxygen, and ECG.
As a smart watch or bracelet, it obviously should not be a needle in the user when these functions need to be enabled, or we need to manually stick many patch electrodes around the body, if we want to do this, it means that as a smart watch, it also has to meet the specifications as a medical device, and it may also be limited in use, which is a bit of a sacrifice.
Can not use any invasive or sampling detection methods, which means that smart watches need to find another indirect path in the health monitoring function, while tolerating some errors that may be generated by this relatively indirect method, to achieve a balance between usability and functionality. This is also why we can say that the health monitoring values provided by smart watches are for reference only, and timely medical consultation when necessary can protect our physical health to the greatest extent.
Returning to the health monitoring function, the two mainstream technologies equipped with smart watch products are PPG and ECG.
The full name of PPG is photoplethysmography. In principle, it emits a beam of light (usually green light) of a certain wavelength to the skin, and then receives it by a photoelectric receiver by means of transmission or reflection, and processes and displays the periodic light intensity changes detected during this process due to blood circulation, resulting in pulse data. PPG can also be used to measure blood oxygen values, the principle is that the oxygen content of different blood reflectivity is different, the same can be detected by the photoelectric receiver its change, and then through the algorithm to process and estimate, to obtain blood oxygen values.
PPG technology can calculate pulse, blood oxygen and even blood pressure, the advantage is naturally that there is no need for sampling, which is more suitable for normal monitoring. The disadvantage is that it is somewhat too "indirect", the process of collecting transmitted or reflected light signals is easily disturbed by the environment, such as the degree of fit when wearing, the wearer's own movement, body surface sweat and other factors that may affect photoelectric detection, and it still relies more on algorithms to give values, and the "estimated" component is higher.
Therefore, some smart watch products are equipped with small air bags and pressure sensors for specific blood pressure measurement needs, and the more traditional and clinical method of oscilloscopic method is used to accurately measure blood pressure.
Ecg, on the other hand, still refers to electrocardiograms, but when applied to smart watches, there is a big gap in scale from the monitoring methods of large devices and multiple patch electrodes that we commonly see in hospitals. The principle lies in the acquisition of bioelectric signals, and the potential difference and its changes in different parts of the human body can be restored to a variety of values, including heart rate, after being processed by algorithms.
In hospitals, electrocardiograms generally place multiple patch electrodes in the chest and abdomen, etc., in order to read the strongest signal possible far enough from the heart, but the watch is only a device fixed on the wrist, how to achieve this condition? The mainstream solution is to make the non-wearable hand touch the crown of the watch when measuring, that is, to measure the potential difference from the worn wrist to the tip of the non-wearing fingertip.
The measurement method of ecg principle on smart wearable devices is more accurate than PPG, but the coverage is relatively small, and the electrocardiogram itself can reflect a considerable amount of human health data, but the current application on smart watches obviously cannot reach the sensitivity and processing power of hospital professional equipment. Therefore, the data that ECG is more accurate and can be referenced is only heart rate, and how each smart wearable brand integrates the values of PPG and ECG to obtain a health management plan is also determined by the level of their respective algorithms.
In the final analysis, smart wearable devices can not break through the physical limitations of size, in the health monitoring function must rely on algorithm supplements, in our health management status is also based on real-time monitoring and early warning, more prominent all-weather and portability rather than professionalism. However, a variety of smart wearable devices are developing in the direction of actively influencing our lives, for example, today's smart watches can not only carry out health monitoring, but also can link smart homes and other ecological intelligent environmental adjustments according to monitoring data, bringing a futuristic family life scene.