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Table 1 Summary of novel sensors to detect heart rate in newborn babies

From: Non-invasive sensor methods used in monitoring newborn babies after birth, a clinical perspective

Name (References)

Skin contact (SC)

Non-Contact (NC)

Method

Limitations

Advantages

Reflectance Photoplethysmography (rPPG) [36,37,38,39]

SC

Optical measurement of the back reflected transmitted light incident on a photodiode to detect variation in blood volume

• Sensor displacement

• Motion artefacts

• Studies only on stable newborns not in need of resuscitation

• Forehead perfusion better than peripheries

• Easier placement of sensors

• Less interference with resuscitation

Dry ECG electrodes NeoBeat [26,27,28,29]

SC

Light skin contact potential sensing

• Influence of environmental factors was not determined

• Most studies on stable term babies not in resuscitation condition

• Small sample size

• Quick to be placed and display the HR measurement

• Easy to use

• No need of skin preparation

• Placement on upper abdomen should not interfere with chest compressions

• Reported high correlation with reference conventional ECG monitor

• Not influenced by motion

• Suitable device for HR monitoring in both high- and low resource settings

Handheld Doppler ultrasound (HhDU) [40,41,42]

SC

Detection of blood flow velocity through reflectance measurement of ultrasound

• Additional staff required to perform reading

• Interference with resuscitation efforts

• Not tested on preterm babies

• Whole team can hear heart rate

• ECG does not always imply cardiac output whereas audible Doppler sounds do.

• Quick takes 3 s and more accurate than auscultation and palpation HR

• Equipment readily available in childbirth facilities in primary care

• No financial implications

Digital stethoscope (DS) [43,44,45]

SC

Digital recording & analysis of the acoustic waves of the heart

• Loss of sensor contact with precordium

• Environmental noise

• Accuracy of DS HR is greater than chest auscultation and umbilical cord palpation

Video Photoplethysmography (VPG) [34, 46,47,48]

NC

Video recording of skin to detect blood volume changes

• Motion artefact

• Poor illumination

• Not tested in low light environment

• Not affected by high frequency oscillation ventilation, gentle rocking movement

• Non-obtrusive no discomfort, stress, pain, or epidermal stripping

• No interference with X-rays

• No impact on parent-child bonding

Capacitive sensors [35, 49, 50]

NC

Non-contact electric potential sensing of the ECG

• Susceptible to power line interference

• Movement artefacts

• Reduce the likelihood of irritation, allergy, or discomfort

• Increased comfort

• It has promise for introduction to bedding

Piezoceramic sensors [51]

NC

Measurement of heart vibration through the piezoceramic effect

• Limited study to a single subject

• Susceptibility to movement artefacts

• Non-contact so reduces the risk of skin disorders

• No restriction of babies’ movement

• Decreased mechanical and painful stimuli

Laser Doppler vibrometer [48, 52]

NC

Optical based technique used to record the doppler frequency shift of a laser beam scattered from the chest wall through an interferometric based measurement

• Size

• Complexity

• Cost of equipment

• No contact

• Continuous monitoring

• Can be used in MRI

• Reduced biohazards and risk of contamination

• Reports simultaneously HR and RR

• Can be used for prolonged monitoring