Blood Pressure Measurement in Low-Resource Settings

Group 38Members: Satish Chandrasekhar, Karthik Krishnan, Matt Everett

Client: Dr. Donald ElbertSeptember 22, 2014

Background and Need for Blood Pressure Measurement

Blood PressureClassification Systolic BP (mmHg) Diastolic BP

(mmHg)Need

Both/Either?

Hypotension <90 <60 Either

Normal (Normotension)

90-120 60-80 Both

Prehypertension 120-139 80-89 Either

Stage 1 Hypertension 140-159 90-99 Either

Stage 2 Hypertension >159 >99 Either

Table 1. NIH Guidelines for Hypotension and Hypertension Diagnosis

Problems with Hypertension/Hypotension

• Hypertension is a precursor to cardiac disease• Myocardial Infarction• Stroke• Chronic Heart Failure

• Hypotension•Dizziness

• Fainting

Demographics of Hypertension

Country Adults w/ hypertension

(%)

USA 33

India (urban, 30% of population)

40.6

India (rural, 70% of population)

17

India (total) 25

• 2009 – Contributed to 348,000 deaths

• 170 million cases in India• 77.9 million cases in the United

States

Need for Blood Pressure Measurement

• Approximately 20% of adults with hypertension in US unaware that they have disorder

• 16% of all adults in India undiagnosed

• Limitations:• Cost• Training

Measurement Techniquesand Existing Technologies

Auscultatory Method

• Widely used in clinic by doctors

• Inflate and deflate cuff while listening to sounds in sphygmomanometer

Use of Korotkoff sounds in BP measurement. Shaded region of curve represents region in which sounds can be distinguished [14] .

Aneroid Sphygmomanometer• Used in conjunction with stethoscope

• Uses auscultatory method

• Cost: $10 - $60• Accuracy within 0.4kPa (3 mm Hg)

•Measured by trained clinicians• Medical training required to

distinguish soundsAneroid sphygmomanometer [15]

Oscillometric Method

• Measures pressure waves• Can measure mean arterial

pressure accurately• Not as good of estimates

for systolic and diastolic pressure

http://tensoval.com/oscillometric-measurement-devices.php

Wrist Monitors

• Uses oscillometric method

• Requires little to no training to use

• Cost: $30 - $90• Susceptible to changes in body

positionOmron Wrist Monitor [34]

LionsGate Mobile BP Monitor

• Also uses oscillometric method

• Outputs results to mobile smartphone

• Currently not on market for sale

Pulse Wave Velocity

• Measure pulse at two points on body, and amount of time needed for pulse to reach each point

• Velocity = Distance/Time• Not as accurate• Susceptible to motion artifacts and

variations due to body position• Needs to be calibrated with other BP

measurement technique http://content.onlinejacc.org/article.aspx?articleid=1144323

SOMNOtouch by SOMNOmedics

• Uses Pulse Wave Velocity Method

• Outputs data to wrist monitor

• Also not available for sale in US, pending FDA approval

Invasive Cannulation

• Insert cannula into artery to measure blood pressure changes

• Most accurate method

• Drawbacks:• Invasive/inconvenient• Training required to perform procedure

Cannulation of Radial Artery [33]

Patents

•Patch Sensor

•Optical Methods•Emission, reflection, sensing•Calibrate using BP measurements

Patch Sensor

Project Scope and Design Specifications

Design SpecificationsParameter Specification

Cost Less than $25 (Rs. 1500)

Training Required to Operate Literate individuals with no medical training

Rapid Results within 30 seconds of set-up

Accurate Within 0.67kPa (5 mmHg) of current methods

Reusable All components must be reusable

Safe Must not cause harm to user

Measurement Non-continuous, as a screening tool

Non-invasive Must not require surgical procedure to measure

Preliminary Design Scheduleand Team Responsibilities

Tentative Design Schedule

Team Responsibilities

• All 3 members have input in all parts of design process• Would also collaborate to learn unfamiliar material

• Strengths/Focus:• Matt – Software• Satish & Karthik – Electronics/Circuits

• All 3 members will work to schedule meetings with client (Dr. Elbert) and mentors

Questions?

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14. Janusz Kaczorowski, PhD, Martin Dawes, MB, BS, MD, FRCGP, Mark Gelfer, MD. Measurement of blood pressure: New developments and challenges. BCMJ, Vol. 54, No. 8, October, 2012, page(s) 399-403 — Articles.

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