The aim of the present study is to evaluate the accuracy of measuring beat-by-beat diastolic blood pressure from a non-invasive, cuffless and non-obtrusive watch-like optical device worn at the wrist.

Given the prevalence of hypertension in society and the current limitations associated with oscillometric cuffs, the need for a continuous cuffless alternative for blood pressure home monitoring at a global scale is paramount. Such a device would not only improve the global control of blood pressure, but more generally, it could have a larger social impact by improving the comfort and reducing the stress for the clinical management of hypertensive patients.

In the present study the investigators seek to investigate, as a primary purpose, to evaluate the accuracy of non-invasive blood pressure measurements via a watch-like optical sensor and compare these to standard monitoring (arterial line).

Inclusion Criteria:

• Scheduled for cardiac or vascular surgery, with presence of a radial arterial line for perioperative management;
• Willing and able to provide Informed Consent.

Exclusion Criteria:

• (Chronic) pace-maker/ defibrillator in situ at study inclusion;
• Known severe aortic stenosis (mean gradient > 40 mmHg, valve area < 1 cm2);
• Rhythmogenic heart disease (resting heart rate > 120/min) at time of study inclusion;
• Emergency patient (i.e. unscheduled OR).

Consecutive patients scheduled for cardiac or vascular surgery at the Department of Cardiovascular Surgery of Inselspital, Bern.