Can Your Smartphone Take Your Blood Pressure?

Cardiovascular disease is the leading cause of death in North America, so it’s no wonder patients are looking for new ways to monitor their health conveniently. Recently, claims across social media platforms have advertised the use of smartphone applications to accurately monitor blood pressure, detect changes in mental health status, and even alert the user of an abnormal heart rate.

Although the claims seem interesting, healthcare clinicians are not convinced this is a reliable way to monitor one’s health.

What is blood pressure?

Blood pressure (BP) measures the pressure of circulating blood within the blood vessels sent from the heart, known as arteries. Blood pressure is usually characterized in two terms: systolic pressure and diastolic pressure. Systolic pressure is expressed when the heart contracts and diastolic pressure is when the heart relaxes. These two numbers are measured and presented in a reading, systolic being the upper number and diastolic being the lower number. A normal blood pressure reading is 120/80 or less; however, these readings vary from person to person.

Clinicians generally look for two things when monitoring a patient’s blood pressure:

1. Hypertension. This is a clinical term to describe a higher-than-normal blood pressure reading.
2. Hypotension. This is the opposite and is used to describe low blood pressure readings.

Combined with oxygen levels, respiratory rate, and temperature, healthcare providers can effectively monitor the patient’s overall health and notice signs of potential problems.

Standard methods of taking blood pressure

Generally, healthcare providers take a patient’s blood pressure using one of two currently approved methods:

1. Manual blood pressure monitoring. The traditional, non-invasive method involves placing a blood pressure cuff over a patient’s arm and positioning the stethoscope over the artery. The blood pressure cuff is manually pumped to provide pressure against the artery until no pulse can be heard. As the pressure is released, the mercury tube sphygmomanometer is observed. When the pulse appears and disappears, readings at these points give you the diastolic and systolic measures. With proper technique, this method provides an accurate blood pressure reading.
2. Automatic blood pressure cuff. The second and most convenient way is using an automatic blood pressure cuff at home or in a clinical setting. In this case, the cuff is inflated (pumped), and as the cuff deflates, the blood flow in the artery is detected by the monitor and displayed digitally. This allows the patient to get an accurate reading from the comfort of their home or allows clinicians a reliable and fast way of checking blood pressure in clinical settings.

How apps monitor blood pressure

Currently, dozens of phone apps are advertised on social media platforms that promise reliable and accurate blood pressure data. These apps, however, are not approved by the Food and Drug Administration (FDA) and are not recommended as a reliable source of monitoring by clinicians.

The most commonly advertised types of smartphone applications offering blood pressure monitoring are:

1. Photoplethysmography (PPG) signals. PPG signals are the most commonly marketed tools to monitor blood pressure via a smartphone application. These downloadable applications claim to take a photo of the artery using the camera and flash of a phone to capture a 30-second report from the user’s finger. This data is commonly used to report pulse; however, it is not known to be an accurate assessment of blood pressure monitoring. A study on PPG signals found that the participant’s blood pressure was overestimated and inaccurate. The study found the applications using this method to be beneficial only to complement traditional blood pressure monitoring and not a substitution due to the inaccuracy of readings.
2. Transdermal optical imaging. This technology uses videos or a 'selfie' to look for blood flow changes in the arteries in the face. The applications then use machine learning, called artificial intelligence (AI), to determine blood pressure based on changes in the rate of flow seen in the face. This method uses patient history data to build a profile (database) for reference.

Although one study did find data that correlates closely to blood pressure readings taken with a standard manual cuff, and another noted that the use of transdermal optical imaging could estimate blood pressure, estimation is not accurate enough when it comes to a patient’s health.

Are blood pressure monitoring apps safe?

Although taking blood pressure on a smartphone seems convenient, relying on this method alone is unsafe and can give patients inaccurate data. One study found a considerable disagreement between blood pressure readings taken with standard methods versus those done with phone applications and concluded that some phone applications even masked hypertension completely.

Some applications, such as transdermal optical imaging, rely on the user to manually input past blood pressure readings from an automatic or manual cuff before comparing this data to the applications. This data is then compared, and, using AI, a blood pressure estimation is given to the patient. Unfortunately, this patient-given data can be inaccurate and give false readings to the user.

Currently, there are no FDA-approved smartphone applications for blood pressure monitoring.

Ways to improve health with a smartphone

Although the current applications available are not considered accurate, there are many ways your smartphone can help you with your day-to-day healthcare needs. These include the following:

• Store the results of your blood pressure
• Monitor your pulse
• Tracking your activity, including steps
• Record your weight

The future of blood pressure monitoring

Although the current methods of blood pressure monitoring from a phone are not approved or reliable, there is a future for blood pressure monitoring from the comfort of a smartphone.

Photoplethysmography signals and transdermal optical imaging are getting more and more accurate with better technology and AI. Another option may soon hit the market as a reliable source of blood pressure monitoring by using a small 'cuff-like' object placed around the finger and a smartphone camera to detect the pressure in the artery.

There is a future for a more convenient way for patients to monitor blood pressure readings at home with a smartphone. Until then, the best way is to use an FDA-approved home monitoring system or see your doctor for an accurate blood pressure reading.