Wearable Health Devices-Vital Sign Monitoring, Systems and Technologies

Abstract

Wearable Health Devices (WHDs) are increasingly helping people to better monitor their health status both at an activity/fitness level for self-health tracking and at a medical level providing more data to clinicians with a potential for earlier diagnostic and guidance of treatment. The technology revolution in the miniaturization of electronic devices is enabling to design more reliable and adaptable wearables, contributing for a world-wide change in the health monitoring approach. In this paper we review important aspects in the WHDs area, listing the state-of-the-art of wearable vital signs sensing technologies plus their system architectures and specifications. A focus on vital signs acquired by WHDs is made: first a discussion about the most important vital signs for health assessment using WHDs is presented and then for each vital sign a description is made concerning its origin and effect on heath, monitoring needs, acquisition methods and WHDs and recent scientific developments on the area (electrocardiogram, heart rate, blood pressure, respiration rate, blood oxygen saturation, blood glucose, skin perspiration, capnography, body temperature, motion evaluation, cardiac implantable devices and ambient parameters). A general WHDs system architecture is presented based on the state-of-the-art. After a global review of WHDs, we zoom in into cardiovascular WHDs, analysing commercial devices and their applicability versus quality, extending this subject to smart t-shirts for medical purposes. Furthermore we present a resumed evolution of these devices based on the prototypes developed along the years. Finally we discuss likely market trends and future challenges for the emerging WHDs area.

Keywords: activity; clinical; health; medicine; vital signs; wearable health devices; wearable systems.

Figure 1

Schematic overview of the four main data mining processes (activity, prediction, anomaly detection and diagnose/decision support) in relation to different aspects of wearable sensing in wearable health devices. Filled line- Medical purposes; Traced line: Activity purposes. Adapted from [11].

Figure 2

Number of retrieved scientific papers related with WHDs and a specific physiological sign. The distribution is divided in two time intervals and according to the purpose: medical or activity. (BT—Body Temperature; BP—Blood Pressure; RR—Respiration Rate; BG—Blood Glucose; HR—Heart Rate; SpO2—Blood Oxygen Saturation; ECG—Electrocardiogram).

Figure 3

Generic architecture of wearable health devices system [3,10,81,82,83].

Figure 4

Examples of some wearable health devices. (1)—SensoTRACK ear sensor; (2)—Google Contact Lens; (3)—BioPatch^TM; (4)—Smartwatch Basis PEAK^TM; (5)—QardioCore; (6)—Vital Jacket^® t-shirt; (7)—Moov (activity tracker) [16,92,93,94,95,96].

Figure 5

Heart activity trackers divided by type of WHD on the body (t-shirt, chest strap or adhesive patch) and purpose of usage (fitness/sport to medical/health). The closer to the medical/health side the higher the accuracy and quality of heart activity is. The characteristics chosen for this separation were based on published devices brand specifications [94,95,96,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125].

Figure 6

Horizontal bar graphic showing the total revenue in billions ($) (left axis) from 2015 to 2017, and estimated until 2026. The blue line shows the revenue growth rate in billions ($) (right axis). Adapted from [133].

Figure 7

Horizontal bar graphic showing the trend of global market value of wearable computing devices, in millions, between 2017 and 2019. Adapted from [134].

Figure 8

(A) Connected home medical monitoring devices (in millions) 2011 to 2017 [137]; (B) The world market for telehealth from 2014 divided in the main areas (CHF-congestive heart failures; COPD-chronic obstructive pulmonary disease) [138].