Blood Pressure (BP) is a crucial vital sign taken
into consideration for the general assessment of patient’s condition:
patients with hypertension or hypotension are advised
to record their BP routinely. Particularly, hypertension is
emphasized by stress, diabetic neuropathy and coronary heart
diseases and could lead to stroke. Therefore, routine and
long-term monitoring can enable early detection of symptoms
and prevent life-threatening events. The gold standard method
for measuring BP is the use of a stethoscope and sphygmomanometer
to detect systolic and diastolic pressures. However,
only discrete measurements are taken. To enable pervasive
and continuous monitoring of BP, recent methods have been
proposed: pulse arrival time (PAT) or PAT difference (PATD)
between different body parts are based on the combination
of electrocardiogram (ECG) and photoplethysmography (PPG)
sensors. Nevertheless, this technique could be quite obtrusive
as in addition to at least two contacts/electrodes to measure
the differential voltage across the left arm/leg/chest and the
right arm/leg/chest, ECG measurements are easily corrupted
by motion artefacts. Although such devices are small, wearable
and relatively convenient to use, most devices are not designed
for continuous BP measurements. This paper introduces a
novel PPG-based pervasive sensing platform for continuous
measurements of BP. Based on the principle of using PAT to
estimate BP, two PPG sensors are used to measure the PATD
between the earlobe and the wrist to measure BP. The device is
compared with a gold standard PPG sensor and validation of
the concept is conducted with a preliminary study involving 9
healthy subjects. Results show that the mean BP and PATD are
correlated with a 0.3 factor. This preliminary study shows the
feasibility of continuous monitoring of BP using a pair of PPG
placed on the ear lobe and wrist with PATD measurements is
possible.