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Cited by 24Non-Invasive Vital Sign MonitoringECG Monitoring and AnalysisHeart Rate Variability and Autonomic Control

Modeling of artifacts in the wrist photoplethysmogram: Application to the detection of life-threatening arrhythmias

Open access
Paliakaitė, Birutė, Petrėnas, Andrius, Sološenko, Andrius, Marozas, Vaidotas·2021·Biomedical Signal Processing and Control
DOI 10.1016/j.bspc.2021.102421
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Abstract

A model for simulating motion-induced artifacts in the wrist photoplethysmogram (PPG) is proposed for the purpose to improve realism of PPG models. The database of day-long PPGs, acquired during cardiac rehabilitation, is used to extract artifact characteristics, which further serve as a basis for modeling artifacts in simulated PPGs with life-threatening arrhythmias. Depending on the recording, 14–49% of the PPG duration is corrupted by artifacts, mostly due to device displacement, forearm and hand motion. The artifact type influence on the performance of a life-threatening arrhythmia detector shows that the sensitivity drops by 45–48% for extreme bradycardia and by 13–32% for ventricular tachycardia. Poor contact causes 2–4 times more false alarms of ventricular tachycardia compared to the other artifact types under investigation. Simulation of realistic artifacts encountered in activities of daily living allows to comprehensively investigate arrhythmia detectors and understand the artifact types most negatively affecting detection performance. The proposed PPG artifact model is of importance for developing and testing artifact-robust arrhythmia detectors.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper develops a model for simulating motion-induced artifacts in wrist photoplethysmogram (PPG) signals, using artifact characteristics extracted from ambulatory PPGs. It applies the model to show how different artifact types degrade detection of extreme bradycardia and ventricular tachycardia.

Key findings

  • In the ambulatory database, 26.8% of total PPG duration was artifact-corrupted, ranging from 13.6% to 48.6% per recording; day-time artifact burden was 37.0% versus 8.8% at night-time.
  • Artifact classification reached average accuracy of 0.98 with a 4-s minimal artifact duration and thresholds ηu = 0.08 g, ηv = 11, ηw = 0.015.
  • With a quarter of PPG duration contaminated, sensitivity dropped by 45–48% for extreme bradycardia and by 13–32% for ventricular tachycardia; poor contact caused 2–4 times more ventricular tachycardia false alarms than other artifact types.
  • Device displacement produced the largest artifact amplitude, on average 22 times larger than the pulsatile PPG component.

Methods

  • Artifact characteristics were derived from a day-long wrist PPG database collected during cardiac rehabilitation (32 patients, six females, 70.5 ± 9.4 years; 686.1 h total, 21.4 ± 3.4 h per patient) and a standardized artifact database (10 healthy participants, five females, 27.1 ± 2.3 years, BMI 22.3 ± 2.5 kg/m²; 1000 artifacts).
  • Artifacts were identified with a pulse-to-pulse signal quality index, extracted by canceling a modeled pulsatile PPG component, classified into device displacement, forearm motion, hand motion, and poor contact, then characterized by transition probability, duration, spectral slope, and normalized RMS amplitude.
  • The model uses a five-state continuous-time Markov chain and generates artifacts by filtering white noise with a 250th-order FIR filter; it was applied to PhysioNet/CinC Challenge 2015 ECG-derived RR intervals (16 extreme bradycardia and 39 ventricular tachycardia recordings; 227 and 492 episodes, respectively) to simulate 1-h PPGs and test a threshold-based arrhythmia detector.

Limitations

  • Stated: the model is restricted to artifacts mostly caused by movement and device attachment; intrinsic PPG disturbances from physiological processes such as respiration, vasoconstriction due to temperature changes, or stress were not considered.
  • Evident: the ambulatory cohort consisted of post-myocardial-infarction cardiac rehabilitation patients, so artifact characteristics may not generalize to all free-living users.
  • Evident: artifact extraction requires a good-quality reference ECG, and the detector evaluation used a basic threshold-based detector on simulated 1-h PPGs derived from 5-min Challenge recordings.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1016/j.bspc.2021.102421

Cites

60 of 60 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 52 cited sources checked · 0 supported · 0 flagged

  • Findingreasoning

    Poor contact causes 2-4 times more false alarms of ventricular tachycardia compared to the other artifact types under investigation.

    “Poor contact causes 2-4 times more false alarms of ventricular tachycardia compared to the other artifact types under investigation.”
    • Also stated in: § 5.3. Testing of an arrhythmia detector · plain
      “Interestingly, poor contact causes 2-4 times more false alarms compared to the other artifact types.”
    Quote in the paperSubstantial claim
  • Findingown data

    Depending on the recording, 14-49% of the PPG duration is corrupted by artifacts.

    “Depending on the recording, 14-49% of the PPG duration is corrupted by artifacts, mostly due to device displacement, forearm and hand motion.”
    Quote in the paperSubstantial claim
  • Findingown data

    Most artifacts in the ambulatory database were device displacement, forearm motion, and hand motion.

    “mostly due to device displacement, forearm and hand motion.”
    • Also stated in: § 5.2. Artifact characteristics in the ambulatory database · plain
      “Most of the artifacts were identified as device displacement, forearm motion, and hand motion, corrupting 6.4%, 6.2%, and 6.0%, whereas only 1.8% was assigned to poor contact.”
    Quote in the paperSubstantial claim
  • Findingown data

    By inspecting PPGs acquired in free-living activities, high-amplitude artifacts similar to PPG pulses, which exceed the threshold ηc = 0.7, have been observed.

    “By inspecting PPGs acquired in free-living activities, high-amplitude artifacts similar to PPG pulses, which exceed the threshold η c = 0.7, have been observed.”
    Quote in the paperSubstantial claim
  • Findingown data

    Artifact-free intervals prolong during night-time as supported by the decreased rate parameter λ0.

    “Artifact-free intervals prolong during night-time as supported by the decreased rate parameter λ0 .”
    Quote in the paperNot a substantial claim
  • May combine two claims. 22
  • Classified as probably not a substantial claim. 18

  • May combine two claims.

    Findingown data

    The artifact type influences the performance of a life-threatening arrhythmia detector: sensitivity drops by 45-48% for extreme bradycardia and by 13-32% for ventricular tachycardia.

    “The artifact type influence on the performance of a life-threatening arrhythmia detector shows that the sensitivity drops by 45-48% for extreme bradycardia and by 13-32% for ventricular tachycardia.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    Artifacts cause almost no false alarms of extreme bradycardia, resulting in nearly perfect positive predictive value, but adversely affect false alarm rate of ventricular tachycardia.

    “For the same reason, artifacts cause almost no false alarms of extreme bradycardia, resulting in nearly perfect positive predictive value, but adversely affect false alarm rate of ventricular tachycardia.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the ambulatory database, a quarter of the PPG duration was identified as corrupted by artifacts, which is higher than 10.8% reported in [10], but much lower than 44% in [12] and 65.2% in [48].

    “In the ambulatory database, a quarter of the PPG duration was identified as corrupted by artifacts, which is higher than 10.8% reported in [10], but much lower than 44% in [12] and 65.2% in [48].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [10]

      Not checked in the free run.

    • cites [12]

      Not checked in the free run.

    • cites [48] source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    The number of false alarms of ventricular tachycardia reduces markedly and the positive predictive value approaches 1 when applying the SQI.

    “However, the number of false alarms of ventricular tachycardia reduces markedly and the positive predictive value approaches 1.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    37.0% of the total PPG duration is attributed to artifacts for day-time, and 8.8% for night-time.

    “By using such subdivision, 37.0% of the total PPG duration is attributed to artifacts for day-time, and 8.8% for night-time.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    All types of artifacts are less frequent and usually shorter during night-time.

    “This finding coincides with the fact that all types of artifacts are less frequent and usually shorter during nighttime.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Device displacement, on average, causes the largest artifact amplitude which is 22 times larger than that of the pulsatile PPG component.

    “Device displacement, on average, causes the largest artifact amplitude which is 22 times larger than that of the pulsatile PPG component.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    The percentage of the artifact-corrupted PPG markedly increases during day-time, mostly due to device displacement and forearm motion.

    “In line with recent findings [48], our study shows that the percentage of the artifact-corrupted PPG markedly increases during day-time, mostly due to device displacement and forearm motion.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [48] source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    In our study, the sensitivity of ventricular tachycardia detection decreased and the sensitivity of extreme bradycardia detection did not change for an increasing amount of excluded PPGs.

    “Our study shows contradictory results, i.e., the decrease in the sensitivity of ventricular tachycardia detection and no change in the sensitivity of extreme bradycardia detection for the increasing amount of the excluded PPGs.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    Additional pulses often lead to undetected extreme bradycardia, whereas they have little effect on the detection of ventricular tachycardia.

    “For this reason, additional pulses often lead to undetected extreme bradycardia, whereas have little effect on the detection of ventricular tachycardia.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    Device displacement substantially distorts the PPG but is easily identified by the SQI due to its largest amplitude.

    “Although device displacement substantially distorts the PPG, it is easily identified by the SQI due to the largest amplitude.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    Poor contact disturbs the PPG so that additional pulses are produced, making the identification of artifacts problematic.

    “On the other hand, poor contact disturbs the PPG so that additional pulses are produced making the identification of artifacts problematic.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Extreme bradycardia can be a common cause of sudden cardiac death in certain populations, e.g., patients with chronic kidney disease.

    “Also, a recent research shows that extreme bradycardia can be a common cause in certain populations, e.g., in patients with chronic kidney disease [3].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [3]

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Simulation of realistic artifacts encountered in activities of daily living allows comprehensive investigation of arrhythmia detectors and understanding of the artifact types most negatively affecting detection performance.

    “Simulation of realistic artifacts encountered in activities of daily living allows to comprehensively investigate arrhythmia detectors and understand the artifact types most negatively affecting detection performance.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Sudden cardiac death accounts for 15-20% of all deaths.

    “Sudden cardiac death accounts for 15-20% of all deaths [1].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [1]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Patients at risk of sudden cardiac death due to life-threatening arrhythmias could potentially benefit from implantation of a cardiac pacemaker or a cardioverter defibrillator.

    “Patients at risk of sudden cardiac death due to life-threatening arrhythmias could potentially benefit from implantation of a cardiac pacemaker or a cardioverter defibrillator [4].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [4]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Finer hand motions, which do not reflect in biomechanical data, can be dealt with using different PPG wavelengths and a piezoelectric transducer.

    “whereas finer hand motions, which do not reflect in biomechanical data, can be dealt by using different PPG wavelengths and a piezoelectric transducer [22][23][24].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [22][23][24]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Detection of atrial fibrillation in a PPG has demonstrated encouraging results.

    “Recently, detection of atrial fibrillation in a photoplethysmogram (PPG) has demonstrated encouraging results and received wide-scale research attention [9][10][11][12][13].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [9][10][11][12][13]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Signal processing techniques have been invoked for PPG quality estimation and motion artifact reduction.

    “Signal processing techniques have also been invoked for PPG quality estimation [25] and motion artifact reduction [26].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [25]

      Not checked in the free run.

    • cites [26]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Efforts have been made to reduce motion artifacts using accelerometer and gyroscope signals.

    “Efforts have been made to reduce motion artifacts using accelerometer and gyroscope signals [15][16][17][18][19][20][21], whereas finer hand motions, which do not reflect in biomechanical data, can be dealt by using different PPG wavelengths and a piezoelectric transducer [22][23][24].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [15][16][17][18][19][20][21]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    Algorithms cannot claim robustness without considering artifact influence on the performance.

    “Accordingly, such algorithms cannot claim robustness without considering artifact influence on the performance.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Segment removal conceals the true detection performance, but it is not a major problem for atrial fibrillation which often lasts for hours without being dangerous.

    “Although segment removal conceals the true detection performance, it is not a major problem in case of atrial fibrillation which often lasts for hours without being dangerous [31].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [31]

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    To analyze detector performance in long-term PPGs, arrhythmias must be annotated, which is time-consuming and costly.

    “However, to analyze the detector performance in long-term PPGs, arrhythmias must be annotated, which is time-consuming and costly.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    By applying a criterion of successful pulse detection, 42.4% of the total PPG duration was excluded in [13].

    “By applying a criterion of successful pulse detection, 42.4% of the total PPG duration was excluded in [13].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13]

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Artifact-induced additional PPG pulses increase pulse rate and mask episodes of extreme bradycardia, but have less influence on the sensitivity of ventricular tachycardia detection.

    “This can be explained by artifact-induced additional PPG pulses, which increase pulse rate and mask episodes of extreme bradycardia, but have less influence on the sensitivity of ventricular tachycardia detection.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The probabilities of having device displacement and forearm motion artifacts are lower during night-time due to reduced movement, and vice versa during day-time.

    “The probabilities of having the device displacement and forearm motion artifacts are lower during night-time due to reduced movement, and vice versa during day-time.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    The discrepancy between studies on artifact-corrupted PPG percentage possibly arose from different conditions to acquire a PPG and varying signal quality requirements.

    “Possibly, the discrepancy between the studies arose from different conditions to acquire a PPG.Also, varying signal quality requirements, which often depend on the application, may have a substantial impact.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A common practice in PPG artifact identification is to involve an accelerometer.

    “a common practice is to involve an accelerometer for artifact identification [11][12][13][27][28][29][30].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [11] source

      Not checked in the free run.

    • cites [12]

      Not checked in the free run.

    • cites [13]

      Not checked in the free run.

    • Rests on an assumption: The most prevalent PPG artifacts are movement-related.

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationnone given

    Even slight PPG disturbance can be intolerable when PPG morphology is analyzed, but may have a negligible effect on heart rate estimation.

    “Even slight PPG disturbance can be intolerable when PPG morphology is a subject to analysis, but may have a negligible effect on heart rate estimation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The PSDs of hand motion and poor contact are apparently flatter because the spectral power is moved toward high frequencies, suggesting that artifacts are more noise-like.

    “The PSDs of hand motion and poor contact are apparently flatter because the spectral power is moved toward high frequencies, suggesting that artifacts are more noise-like.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The quality of a long-term green-light PPG acquired using a smartwatch was investigated in another study.

    “In another study, the quality of a long-term green-light PPG, acquired using a smartwatch was investigated [48].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [48] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    No artifact type-specific characteristics valuable for the model development were given in that study.

    “Yet, no artifact type-specific characteristics valuable for the model development were given.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [48] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    PPG artifacts have already been studied in the context of finger oximetry and neck photoplethysmography.

    “PPG artifacts have already been studied in a context of finger oximetry and neck photoplethysmography [52,53].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [52]

      Not checked in the free run.

    • cites [53]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The developed model is restricted to simulating artifacts mostly caused by movement and device attachment.

    “A limitation of the present study is that the developed model is restricted to simulating artifacts mostly caused by movement and device attachment.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    In that study, sensitivity increased proportionally to the amount of excluded artifact-corrupted PPG parts.

    “The interesting finding of that study is the increase of the sensitivity proportional to the amount of the excluded artifact-corrupted PPG parts [13].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [13]

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Simulation of realistic artifacts encountered in activities of daily living allows comprehensive investigation of arrhythmia detectors and understanding of artifact types most negatively affecting detection performance.

    “Simulation of realistic artifacts encountered in activities of daily living allows to comprehensively investigate arrhythmia detectors and understand artifact types most negatively affecting detection performance.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Similar artifacts can be encountered in real-life PPGs.

  • Classified as probably not a substantial claim.

    Premisecitation

    Investigation of an atrial fibrillation detector showed that specificity and positive predictive value decrease with an increasing amount of artifacts.

    “Investigation of an atrial fibrillation detector showed that the specificity and the positive predictive value decrease with an increasing amount of artifacts [13].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [13]

      Not checked in the free run.

37 of 37

  • The authors state this as an assumption.

    Adjacent poor-quality pulses, as well as those separated by a single good-quality pulse, constitute a single continuous artifact-corrupted PPG segment.

    “Adjacent poor-quality pulses, as well as those separated by a single goodquality pulse, are assumed to constitute a single continuous artifactcorrupted PPG segment.”

  • The authors state this as an assumption.

    The remaining PPG after removing the slow-changing component consists of heart contraction-related pulsations and artifacts.

    “Then, it is assumed that the remaining PPG consists of heart contraction-related pulsations and artifacts.”

  • The paper relies on this without support.

    Even short episodes of extreme bradycardia and ventricular tachycardia can be life-threatening requiring immediate intervention.

    “In contrast, even short episodes of extreme bradycardia and ventricular tachycardia can be life-threatening requiring immediate intervention.”

  • The authors state this as an assumption.

    Transitions between artifact-free intervals and artifacts can be modeled by a five-state continuous-time Markov chain.

    “The transitions between artifact-free intervals and artifacts are modeled by a five-state continuous-time Markov chain, where the state 0 represents an artifact-free interval and the states from 1 to 4 correspond to ith-type artifacts.”

  • The paper relies on this without support.

    The identification of artifacts in the PPG depends on the chosen approach to PPG quality assessment.

    “The identification of artifacts in the PPG depends on the chosen approach to PPG quality assessment.”

  • The paper relies on this without support.

    The most prevalent PPG artifacts are movement-related.

    “The most prevalent PPG artifacts are movement-related”

  • The paper relies on this without support.

    Green-light PPG is often used in commercial smartwatches to acquire pulse rate.

    “a green-light PPG which is often used in commercial smartwatches to acquire pulse rate”

  • The authors state this as an assumption.

    Similar artifacts can be encountered in real-life PPGs.

    “Therefore, we assume that similar artifacts can be encountered in real-life PPGs.”
8 of 8

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The finding that overall data quality is higher during nighttime in the authors' large cohort is in line with findings in smaller samples specifically for PPG data.

    “This finding in our large cohort is in line with findings in smaller samples specifically for PPG data35,75.”

    From Data quality evaluation in wearable monitoring (2022) · cites this paper as [75]

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Related

Authors
Paliakaitė, B., Petrėnas, A., Sološenko, A., & Marozas, V.
Affiliations
Kaunas University of Technology (LT)
Corresponding author
Paliakaitė, Birutė
ORCID
Venue
Biomedical Signal Processing and Control
Publisher
Elsevier BV
Published
2021-04
Volume
66
Pages
102421
ISSN
1746-8094 (ISSN-L)
DOI
10.1016/j.bspc.2021.102421
OpenAlex
W3126617966
Semantic Scholar
1a5449dbc57ef8cc49c86aec094466f05a844b2b
Cited by
24
References
60
Citations by year
2026: 6 · 2025: 4 · 2024: 3 · 2023: 6 · 2022: 3 · 2021: 2
FWCI
1.06
Type
journal article
Language
en
Open access
Licence
Locations
  • Biomedical Signal Processing and Control (publishedVersion, cc-by)
  • KTUePubl (Repository of Kaunas University of Technology) (submittedVersion, other-oa)
Funders
  • Lietuvos Mokslo Taryba
  • European Regional Development Fund (01.2.2-LMT-K-718-01-0030)
Topics
  • Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › ECG Monitoring and Analysis
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Heart Rate Variability and Autonomic Control
Keywords
motion artifacts, ventricular tachycardia, bradycardia, device displacement, cardiac rehabilitation, activities of daily living, false alarm rate

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