Contactless Radar Blood Pressure Validation

High blood pressure is the biggest risk factor for heart attacks and strokes. There are several machines available for measuring blood pressure, but most of them need to contact the skin causing discomfort from the inflatable cuff or risking the transmission of infections from reusing cuffs. There are also situations where the cuff machines are inaccurate, such as in older people or during exercise. Therefore, the investigators are trying to develop an accurate contactless system for measuring blood pressure.

The investigators have used advanced but safe radar to create a small machine with a camera that can measure blood pressure from a distance without the need to contact the participant's skin anywhere. It works by detecting tiny movements and changes on the skin produced from the heartbeat and pulse that cannot be seen with the human eye. The investigators want to study how accurate our radar blood pressure machine is by comparing it to other traditional methods of measuring blood pressure.

Firstly, radar blood pressure will be compared to auscultatory blood pressure (a blood pressure system using a cuff) in a group of 25 participants at rest attending a specialist blood pressure clinic. This is currently the internationally recommended method for validating new blood pressure devices.

Then radar blood pressure will be compared with invasive blood pressure (measured inside the arteries by a small tube) in 50 participants undergoing clinically-indicated cardiac catheterisation at the Royal Free Hospital.

Next a radar device capable of measuring blood pressure in participants lying inside the cardiovascular magnetic resonance (CMR) scanner will be developed. The radar blood pressure derived in the CMR scanner will be compared to oscillometric blood pressure in 25 participants (a cuff-based BP system that is currently used in patients being scanned). Finally, radar-BP will be compared with oscillometric BP in 50 participants during exercise including sit-to-stand movements and using a bike ergometer.

Inclusion criteria

Group 1:

• Age > 18 years old
• under the care of the complex hypertension clinic
• able to take auscultatory blood pressure from right arm

Group 2:

• Age >18
• has been selected to undergo invasive coronary angiogram by a consultant cardiologist

Group 3:

• Age >18
• willing to undergo a cardiac MRI scan

Group 4:

• Age > 18

Exclusion criteria

Group 1

• anyone unable to consent
• inaudible Korotkoff K1/K5 sounds
• systolic BP difference >12 mmHg and/or diastolic >8 mmHg in any of the auscultatory measurements during the validation study
• contraindication to cuff-based BP measurement e.g. lymph node clearance on right side

Group 2:

• anyone unable to consent
• anyone in whom right radial arterial access cannot be obtained (e.g. severe skin abnormality such as scleroderma)
• known arterio-venous malformation or fistulas in right arm
• any contraindication to an invasive angiogram such as severe frailty

Group 3:

• anyone unable to consent
• anyone with a classical contraindication to an MRI study such as known metal fragments allergy to used contrast
• high degree heart block
• asthma

Group 4:

• anyone unable to consent
• anyone with exertional chest pain or known uncontrolled angina
• anyone with a known positive cardiac stress test.