Influence of Contact Forces on Wrist Photo plethysmography – Prestudy for a Wearable Patient Monitor / Einfluß von Kontaktkräften auf die photoplethysmografische Pulsmessung am Handgelenk – Vorstudie zu einem tragbaren Patientenmonitor

Rafolt, D.; Gallasch, Eugen

doi:10.1515/bmt.2004.005

Cited by 15 publications

(19 citation statements)

References 9 publications

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“…By increasing the pressure placed upon the sensor, the DR values showed an increasing trend. This result matches that seen when a reflective sensor was placed on the radial artery [24]. The most significant changes in terms of DR improvement occurred between 24 mmHg and 98 mmHg with a mean increase of 38.6% (p < 0.05).…”

Section: Discussionsupporting

confidence: 83%

“…The contact pressure of the PPG sensor has been shown to affect the SNR value of the PPG signal [24]. To provide an estimate of the pressure, a force sensor was used to measure the orthogonal force vector applied to the surface of the skin by the reflective PPG sensor (FS20-0000-1500-G, Measurement Specialties, Hampton, Virginia).…”

Section: Methodsmentioning

confidence: 99%

“…For PPG measurements, a light source and a photo-detector are placed on the skin: while part of the emitted light is absorbed into the tissue, a portion of the light reaches the photo-detector [23]. Depending on the placement, the photo-detector either detects the reflected light off the tissue or the transmitted light through the tissue [24]. The DC portion of the signal is correlated to stagnant components such as tissue and bone.…”

Section: Introductionmentioning

confidence: 99%

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Robust Sensing of Distal Pulse Waveforms on a Modified Weighing Scale for Ubiquitous Pulse Transit Time Measurement

Carek

Inan

2017

IEEE Trans. Biomed. Circuits Syst.

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The measurement of aortic pulse transit time (PTT), the time for the arterial pulse wave to travel from the carotid to the femoral artery, can provide valuable insight into cardiovascular health, specifically regarding arterial stiffness and blood pressure, BP. To measure aortic PTT, both proximal and distal arterial pulse timings are required. Recently, our group has demonstrated that the ballistocardiogram (BCG) signal measured on a modified weighing scale can provide an unobtrusive, yet accurate, means of obtaining a proximal timing reference; however, there are no convenient, reliable methods to extract the distal timing from a subject standing on the modified weighing scale. It is common to use a photoplethysmograph (PPG) attached to a toe to measure this distal pulse, but we discovered that this signal is greatly deteriorated as the subject stands on the scale. In this paper, we propose a novel method to measure the distal pulse using a custom reflective PPG array attached to the dorsum side of the foot (D-PPG). Twelve subjects of varying skin tones were recruited to assess the preliminary validation of this approach. Pulse measurements using the D-PPG were taken from seated and standing subjects, and the commercially available PPG were measured for facilitating comparison of timing measurements. We show that the D-PPG was the only sensor to retain the high detection rate of feasible timing values. To further test and optimize the system, various factors such as applied pressure, measurement location, and LED/photodiode configuration were tested.

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Section: Discussionsupporting

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Robust Sensing of Distal Pulse Waveforms on a Modified Weighing Scale for Ubiquitous Pulse Transit Time Measurement

Carek

Inan

2017

IEEE Trans. Biomed. Circuits Syst.

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“…Second, we show that HR accuracy as measured by these activity monitors is acceptable during low-intensity activities and high-intensity activities with repetitive wrist motion but that HR accuracy is poorer when there is no repetitive wrist motion and when any activity is at a high intensity (ie, ≥70% of maximal aerobic capacity). Prior research has suggested that PPG sensors used to measure the HR are liable to poor accuracy during activities with increased physical exertion or activities involving repetitive contractions of forearm skeletal muscles [36-38]. It has been suggested that during activities involving sustained muscle contractions or higher intensity exercises, the contact between the device’s PPG sensor and skin is decreased, leading to a disruption in the signal quality and causing poor quality data [36,37].…”

Section: Discussionmentioning

confidence: 99%

Accuracy of Wrist-Worn Activity Monitors During Common Daily Physical Activities and Types of Structured Exercise: Evaluation Study

Reddy¹,

Pooni²,

Zaharieva³

et al. 2018

JMIR Mhealth Uhealth

138

123

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BackgroundWrist-worn activity monitors are often used to monitor heart rate (HR) and energy expenditure (EE) in a variety of settings including more recently in medical applications. The use of real-time physiological signals to inform medical systems including drug delivery systems and decision support systems will depend on the accuracy of the signals being measured, including accuracy of HR and EE. Prior studies assessed accuracy of wearables only during steady-state aerobic exercise.ObjectiveThe objective of this study was to validate the accuracy of both HR and EE for 2 common wrist-worn devices during a variety of dynamic activities that represent various physical activities associated with daily living including structured exercise.MethodsWe assessed the accuracy of both HR and EE for two common wrist-worn devices (Fitbit Charge 2 and Garmin vívosmart HR+) during dynamic activities. Over a 2-day period, 20 healthy adults (age: mean 27.5 [SD 6.0] years; body mass index: mean 22.5 [SD 2.3] kg/m2; 11 females) performed a maximal oxygen uptake test, free-weight resistance circuit, interval training session, and activities of daily living. Validity was assessed using an HR chest strap (Polar) and portable indirect calorimetry (Cosmed). Accuracy of the commercial wearables versus research-grade standards was determined using Bland-Altman analysis, correlational analysis, and error bias.ResultsFitbit and Garmin were reasonably accurate at measuring HR but with an overall negative bias. There was more error observed during high-intensity activities when there was a lack of repetitive wrist motion and when the exercise mode indicator was not used. The Garmin estimated HR with a mean relative error (RE, %) of −3.3% (SD 16.7), whereas Fitbit estimated HR with an RE of −4.7% (SD 19.6) across all activities. The highest error was observed during high-intensity intervals on bike (Fitbit: −11.4% [SD 35.7]; Garmin: −14.3% [SD 20.5]) and lowest error during high-intensity intervals on treadmill (Fitbit: −1.7% [SD 11.5]; Garmin: −0.5% [SD 9.4]). Fitbit and Garmin EE estimates differed significantly, with Garmin having less negative bias (Fitbit: −19.3% [SD 28.9], Garmin: −1.6% [SD 30.6], P<.001) across all activities, and with both correlating poorly with indirect calorimetry measures.ConclusionsTwo common wrist-worn devices (Fitbit Charge 2 and Garmin vívosmart HR+) show good HR accuracy, with a small negative bias, and reasonable EE estimates during low to moderate-intensity exercise and during a variety of common daily activities and exercise. Accuracy was compromised markedly when the activity indicator was not used on the watch or when activities involving less wrist motion such as cycle ergometry were done.

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“…Poor performance of the devices could be a function of peripheral circulation in distal extremities, but since peripheral pulses were not assessed during our study, this remains speculative. Previous studies have suggested that changes in contact force between photoplethysmographic sensors, such as the one used by Fitbit Charge HR devices, and skin can affect the quality of blood flow, causing artifacts in heart rate measurement [32]. Improper positioning of the device, such as within a skin fold, or the presence of hair or sweat can interrupt signal transduction [33].…”

Section: Discussionmentioning

confidence: 99%

Validation of a Self‐Monitoring Tool for Use in Exercise Therapy

Powierza

Clark

Hughes

et al. 2017

PM&R

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Background Aerobic exercise at a sub-symptom heart rate has been recommended as therapy for Post-Concussion Syndrome (PCS). Assessing adherence with an accurate heart rate monitoring instrument is difficult limiting the proliferation of large-scale randomized controlled trials. Objective To evaluate the validity of the Fitbit Charge HR against electrocardiogram (EKG) to monitor heart rate during a treadmill-based exercise protocol. Design A methods comparison study. Setting Sports medicine research center within a tertiary care institution. Participants A convenience sample of 22 healthy participants (12 female) aged 18–26 years (mean age: 22 ± 2 years). Methods Fitbit Charge HR heart rate measurements were compared to EKG data concurrently collected while participants completed the Buffalo Concussion Treadmill Test (BCTT). Main Outcome Measures Agreement between Fitbit Charge HR and EKG was assessed by intraclass correlation coefficients (ICC3,1), Bland-Altman limits of agreement, and percent error. Results We observed a strong single-measure absolute agreement between Fitbit Charge HR and EKG (ICC3,1 = 0.83; 95% CI: 0.67 – 0.90). Fitbit Charge HR underestimated heart rate compared to EKG (mean difference = −6.04 beats per min (bpm); SD = 10.40 bpm; Bland-Altman 95% limits of agreement = −26.42 to 14.35 bpm). 69.9% of Fitbit heart rate measurements were within 10% error compared to EKG, and 91.5% of all heart rate measurements were within 20% error. Conclusions While the mean bias in measuring heart rate was relatively small, the limits of agreement between the Fitbit Charge HR and EKG were broad. Thus, the Fitbit Charge HR would not be a suitable option for monitoring heart rate within a narrow range. For the purposes of post-concussion exercise therapy, the relatively inexpensive cost, easy implementation, and low maintenance make Fitbit Charge HR a viable option for assessing adherence to an exercise program when expensive clinical equipment is unavailable.

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Influence of Contact Forces on Wrist Photo plethysmography – Prestudy for a Wearable Patient Monitor / Einfluß von Kontaktkräften auf die photoplethysmografische Pulsmessung am Handgelenk – Vorstudie zu einem tragbaren Patientenmonitor

Cited by 15 publications

References 9 publications

Robust Sensing of Distal Pulse Waveforms on a Modified Weighing Scale for Ubiquitous Pulse Transit Time Measurement

Robust Sensing of Distal Pulse Waveforms on a Modified Weighing Scale for Ubiquitous Pulse Transit Time Measurement

Accuracy of Wrist-Worn Activity Monitors During Common Daily Physical Activities and Types of Structured Exercise: Evaluation Study

Validation of a Self‐Monitoring Tool for Use in Exercise Therapy

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