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NCT Number: NCT07473869

Smartphone Application for Automated Measurement of Capillary Refill Time (CRT)

This prospective, monocenter observational study aims to validate a smartphone application (CRTApp) that automatically measures capillary refill time (CRT) from a short video of a standardized finger compression. Sixty adult intensive care unit (ICU) patients will undergo a CRT measurement recorded with a professional Android smartphone. Clinical CRT will be determined from the video by three blinded observers (reference = median of the three measurements). The application will analyze the same video locally to provide an automated CRT measurement. Agreement between automated and clinical reference CRT will be assessed, and predefined subgroup analyses will explore performance across skin tone, ambient lighting, smartphone characteristics, and severity of peripheral hypoperfusion.

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Key information

Conditions

Capillary Refill Time Critical Illness Disease Attributes Pathologic Processes Pathological Conditions, Signs and Symptoms Peripheral Tissue Perfusion Shock

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

About this study

Capillary refill time (CRT) is a bedside indicator of peripheral perfusion, but visual assessment is prone to inter-observer variability. In this study, CRT is measured using a standardized method (10-second finger compression with a glass slide). A video of the fingertip is captured without audio; framing is strictly limited to the fingers. Files are pseudonymized at acquisition. Videos are transferred via USB to an AP-HP workstation and stored on an AP-HP server; no cloud or messaging is used, and videos are deleted from the smartphone after import. Automated CRT is computed locally from the video by CRTApp without network transmission and without retaining the video. Statistical analyses will include intraclass correlation coefficient and Bland-Altman analysis for agreement. Secondary analyses will evaluate agreement stratified by skin tone (Monk scale / ITA), ambient lighting (lux), smartphone characteristics, and severity of peripheral hypoperfusion.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age ≥ 18 years
  • Adult patients hospitalized in an intensive care unit
  • Clinical indication for capillary refill time assessment (hemodynamic monitoring, suspected peripheral hypoperfusion, or therapeutic evaluation)
  • No objection from the patient or legal representative

Exclusion criteria

  • Skin lesions at the measurement site
  • Known severe peripheral vascular disease
  • Finger amputation
  • Presence of distinctive skin marks on fingers (tattoos, significant scars, or prominent moles) that may interfere with measurement or increase the risk of patient re-identification

Treatment and study plan

Primary outcomes

  1. Agreement Between Automated and Clinical Capillary Refill Time Measurement

    Time frame: At inclusion (single assessment)

    Agreement between capillary refill time measured by the smartphone application and the clinical reference measurement performed by expert clinicians using the standardized method (10-second glass slide compression). Agreement is assessed using the intraclass correlation coefficient between the automated measurement and the median of three blinded observers.

Secondary outcomes

  1. Inter-Observer Variability of Clinical Capillary Refill Time Measurement

    Time frame: Inter-observer variability of clinically measured capillary refill time assessed by three independent observers, expressed as the coefficient of variation.

    At inclusion (single assessment)

  2. Agreement Stratified by Skin Tone

    Time frame: At inclusion (single assessment)

    Intraclass correlation coefficient between automated and clinical capillary refill time measurements stratified according to skin tone using the Monk Skin Tone Scale.

  3. Agreement Stratified by Ambient Lighting Conditions

    Time frame: Intraclass correlation coefficient between automated and clinical capillary refill time measurements stratified according to ambient light intensity measured in lux.

    At inclusion (single assessment)

  4. Agreement Stratified by Smartphone Model Characteristics

    Time frame: Intraclass correlation coefficient between automated and clinical capillary refill time measurements stratified by smartphone type (iOS or Android) and camera resolution.

    At inclusion (single assessment)

  5. Agreement Stratified by Severity of Peripheral Hypoperfusion

    Time frame: Intraclass correlation coefficient between automated and clinical capillary refill time measurements stratified by clinical capillary refill time (< 3 seconds versus ≥ 3 seconds).

    At inclusion (single assessment)

Study contacts

Contact information is provided by the study sponsor or research team.

Gwénolé ABGRALL

CONTACT

[email protected]

Xavier MONNET, PhD

CONTACT

[email protected]

45213547 ext. +33

Sponsors and collaborators

Lead sponsor

Assistance Publique - Hôpitaux de Paris

Other

Registry information

Acronym: CRTApp

Important dates

Study start
2026
Primary completion
2026
Study completion
2027
First posted
Mar 16, 2026
Registry last updated
Mar 16, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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