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

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Capillary Refill Time; Peripheral Tissue Perfusion

Detailed Description

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.

• Study Type: Observational
• Enrollment (Estimated): 60

Contacts and Locations

• Study Contact: Name: Xavier MONNET, PhD; Phone Number: +33 45213547; Email: xavier.monnet@aphp.fr
• Study Contact Backup: Name: Gwénolé ABGRALL; Email: gwenoleabgrall@gmail.com

Study Locations

• France
  • Le Kremlin-Bicêtre, France
    • CHU Bicetre
    • Contact: Gwénolé ABGRALL; Email: gwenoleabgrall@gmail.com
    • Contact: Xavier MONNET; Phone Number: 0033 45213547; Email: xavier.monnet@aphp.fr

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Adults (≥18 years) admitted to the medical intensive care unit at Hôpital de Bicêtre (AP-HP) for whom a standardized capillary refill time measurement can be performed.

Description

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

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Agreement Between Automated and Clinical Capillary Refill Time Measurement	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.	At inclusion (single assessment)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Inter-Observer Variability of Clinical Capillary Refill Time Measurement	At inclusion (single assessment)	Inter-observer variability of clinically measured capillary refill time assessed by three independent observers, expressed as the coefficient of variation.
Agreement Stratified by Skin Tone	Intraclass correlation coefficient between automated and clinical capillary refill time measurements stratified according to skin tone using the Monk Skin Tone Scale.	At inclusion (single assessment)
Agreement Stratified by Ambient Lighting Conditions	At inclusion (single assessment)	Intraclass correlation coefficient between automated and clinical capillary refill time measurements stratified according to ambient light intensity measured in lux.
Agreement Stratified by Smartphone Model Characteristics	At inclusion (single assessment)	Intraclass correlation coefficient between automated and clinical capillary refill time measurements stratified by smartphone type (iOS or Android) and camera resolution.
Agreement Stratified by Severity of Peripheral Hypoperfusion	At inclusion (single assessment)	Intraclass correlation coefficient between automated and clinical capillary refill time measurements stratified by clinical capillary refill time (< 3 seconds versus ≥ 3 seconds).

Collaborators and Investigators

• Sponsor: Assistance Publique - Hôpitaux de Paris

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): June 1, 2026
• Study Completion (Estimated): June 1, 2027

Study Registration Dates

• First Submitted: March 11, 2026
• First Submitted That Met QC Criteria: March 11, 2026
• First Posted (Actual): March 16, 2026

Study Record Updates

• Last Update Posted (Actual): March 16, 2026
• Last Update Submitted That Met QC Criteria: March 11, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Shock; Critical Illness; Reproducibility of Results; Digital Health; Intensive Care Units; Smartphone Application; Hemodynamic Monitoring; Capillary Refill Time; Observer Variation; Clinical Assessment; Peripheral Tissue Perfusion; Automated Measurement
• Additional Relevant MeSH Terms: Pathologic Processes; Disease Attributes; Pathological Conditions, Signs and Symptoms; Critical Illness; Shock
• Other Study ID Numbers: APHP251601

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No