Smartphone Camera Measurement of Breathing-Related Heart Rate Variability Compared With ECG in Healthy Adults
NCT07922161, Not applicable, Not yet recruiting, BELL Therapeutics Inc.
Trial 10
As registered on ClinicalTrials.gov, in the graph's capture of the registry.
| Field | Value | Source |
|---|---|---|
| Title | Smartphone Camera Measurement of Breathing-Related Heart Rate Variability Compared With ECG in Healthy Adults | ClinicalTrials.gov |
| NCT number | NCT07922161 | ClinicalTrials.gov |
| Status | Not yet recruiting | ClinicalTrials.gov |
| Phases | Not applicable | ClinicalTrials.gov |
| Enrollment | 36 participants, estimated | ClinicalTrials.gov |
| Lead sponsor | BELL Therapeutics Inc. | ClinicalTrials.gov |
| Conditions | Respiratory Sinus Arrhythmia, Heart Rate Variability, Healthy Volunteers | ClinicalTrials.gov |
| Interventions | Smartphone simultaneous facial and fingertip photoplethysmography (research app), Audio-guided paced breathing | ClinicalTrials.gov |
| First posted | 2026-11-06 | ClinicalTrials.gov |
| Last updated | 2026-11-06 | ClinicalTrials.gov |
Registered outcomes 25
Each outcome the trial registered, primary first, in ClinicalTrials.gov's words.
| List | Outcome | Time frame | Description | Source |
|---|---|---|---|---|
| Primary | Log Ratio of Facial Remote Photoplethysmography to ECG Respiratory Heart Rate Variability Amplitude During Slow Paced Breathing | Seven slow paced-breathing conditions (3 minutes each; 6.0 breaths/min 5 minutes) during a single study visit (Day 1) | ln(A\_pp face / A\_pp ECG) for each slow paced-breathing condition (4.0, 4.5, 5.0, 5.5, 6.0, 6.5 and 7.0 breaths/min). A\_pp is the peak-to-peak amplitude (ms) of the first harmonic of inter-beat intervals at the guided breathing frequency, estimated separately for the face and the ECG within the same window (60-180 s after the start of each 3-minute condition and 60-300 s for the 5-minute 6.0 breaths/min condition). Unit: natural-log ratio (unitless; 0 means no difference); +0.1 means a facial amplitude about 10% larger than the ECG amplitude. The reported value is the bias, the mean log ratio pooled across participants and the seven rates, with repeated-measures 95% limits of agreement and participant-level confidence intervals. Conditions without a valid facial estimate are counted in the facial measurement failure outcome. | ClinicalTrials.gov |
| Secondary | Log Ratio of Fingertip Contact Photoplethysmography to ECG Respiratory Heart Rate Variability Amplitude During Slow Paced Breathing | Seven slow paced-breathing conditions during a single study visit (Day 1) | ln(A\_pp fingertip / A\_pp ECG), with A\_pp, analysis windows and summary defined as in the primary outcome: the bias pooled across participants and the seven slow rates, with repeated-measures 95% limits of agreement and participant-level confidence intervals. Unit: natural-log ratio (unitless; 0 means no difference). Conditions without a valid fingertip estimate are counted in the fingertip measurement failure outcome. | ClinicalTrials.gov |
| Secondary | Within-Participant Difference Between Facial-to-ECG and Fingertip-to-ECG Absolute Log Ratios of Respiratory Heart Rate Variability Amplitude During Slow Paced Breathing | Seven slow paced-breathing conditions during a single study visit (Day 1) | For each participant, \|ln(A\_pp face / A\_pp ECG)\| minus \|ln(A\_pp fingertip / A\_pp ECG)\| in the same window, averaged over the slow paced-breathing conditions in which both sensors give a valid estimate. Unit: natural-log ratio (unitless); positive values mean a larger facial error. The reported value is the mean across participants with a participant-level 95% confidence interval. Each sensor is also compared with the ECG separately, because agreement between face and fingertip does not imply agreement with the ECG. | ClinicalTrials.gov |
| Secondary | Percentage of Attempted Conditions Without a Valid Facial Estimate | All nine conditions during a single study visit (Day 1) | Percentage of all originally attempted breathing conditions, pooled across participants, in which the facial pathway yields no valid estimate under the quality rules fixed before evaluation data are analyzed. The denominator is every attempted condition, including conditions whose ECG is unsuitable as a reference. Failed conditions are not removed, and the reason for each failure is reported. | ClinicalTrials.gov |
| Secondary | Percentage of Attempted Conditions Without a Valid Fingertip Estimate | All nine conditions during a single study visit (Day 1) | Percentage of all originally attempted breathing conditions, pooled across participants, in which the fingertip pathway yields no valid estimate under the quality rules fixed before evaluation data are analyzed. The denominator is every attempted condition, including conditions whose ECG is unsuitable as a reference. Failed conditions are not removed, and the reason for each failure is reported. | ClinicalTrials.gov |
| Secondary | Percentage of ECG Beats Without a Matching Facial Pulse Beat (Missed Beats) | Analysis windows of all nine conditions during a single study visit (Day 1) | Percentage of ECG beats (R peaks) in the analysis windows of all originally attempted conditions, including conditions counted as measurement failures, for which no facial pulse beat is detected within 150 ms of the R peak after the median delay between the ECG and the pulse signal in that condition is subtracted, with each beat matched at most once; a pulse beat detected but displaced beyond this tolerance leaves its ECG beat unmatched. Results at tolerances of 100 ms and 200 ms are reported as a sensitivity analysis. ECG segments unsuitable as a reference are excluded from the denominator and reported separately. The reported value is the mean of participant-level percentages with a 95% confidence interval. Errors computed only from matched beats do not show missed beats. | ClinicalTrials.gov |
| Secondary | Percentage of ECG Beats Without a Matching Fingertip Pulse Beat (Missed Beats) | Analysis windows of all nine conditions during a single study visit (Day 1) | Percentage of ECG beats (R peaks) in the analysis windows of all originally attempted conditions, including conditions counted as measurement failures, for which no fingertip pulse beat is detected within 150 ms of the R peak after the median delay between the ECG and the pulse signal in that condition is subtracted, with each beat matched at most once; a pulse beat detected but displaced beyond this tolerance leaves its ECG beat unmatched. Results at tolerances of 100 ms and 200 ms are reported as a sensitivity analysis. ECG segments unsuitable as a reference are excluded from the denominator and reported separately. The reported value is the mean of participant-level percentages with a 95% confidence interval. Errors computed only from matched beats do not show missed beats. | ClinicalTrials.gov |
| Secondary | Percentage of Facial Pulse Beats Without a Matching ECG Beat (Extra Beats) | Analysis windows of all nine conditions during a single study visit (Day 1) | Percentage of facial pulse beats detected in the analysis windows of all originally attempted conditions that have no matching ECG beat (spurious beats), using the same one-to-one matching as for missed beats: within 150 ms of the R peak after the median delay between the ECG and the pulse signal in that condition is subtracted, with each beat matched at most once. A beat displaced beyond this tolerance from its ECG beat also counts as unmatched. Results at tolerances of 100 ms and 200 ms are reported as a sensitivity analysis. Beats in ECG segments unsuitable as a reference are excluded and reported separately. The reported value is the mean of participant-level percentages with a 95% confidence interval. | ClinicalTrials.gov |
| Secondary | Percentage of Fingertip Pulse Beats Without a Matching ECG Beat (Extra Beats) | Analysis windows of all nine conditions during a single study visit (Day 1) | Percentage of fingertip pulse beats detected in the analysis windows of all originally attempted conditions that have no matching ECG beat (spurious beats), using the same one-to-one matching as for missed beats: within 150 ms of the R peak after the median delay between the ECG and the pulse signal in that condition is subtracted, with each beat matched at most once. A beat displaced beyond this tolerance from its ECG beat also counts as unmatched. Results at tolerances of 100 ms and 200 ms are reported as a sensitivity analysis. Beats in ECG segments unsuitable as a reference are excluded and reported separately. The reported value is the mean of participant-level percentages with a 95% confidence interval. | ClinicalTrials.gov |
| Secondary | Log Ratio of Facial to ECG Root Mean Square of Successive Differences (RMSSD) During Free Breathing | 5-minute free-breathing condition (60-300 s window, and 60-180 s window for the 3-minute comparison) during a single study visit (Day 1) | ln(RMSSD face / RMSSD ECG). RMSSD (ms) is computed from facial pulse intervals and from ECG RR intervals in the same window, using only consecutive valid interval pairs. Unit: natural-log ratio (unitless; 0 means no difference). The reported value is the bias (mean across participants) with 95% limits of agreement, for the primary 60-300 s window and, to indicate whether free breathing could be shortened to 3 minutes, for the 60-180 s window of the same recording. | ClinicalTrials.gov |
| Secondary | Log Ratio of Fingertip to ECG Root Mean Square of Successive Differences (RMSSD) During Free Breathing | 5-minute free-breathing condition (60-300 s window, and 60-180 s window for the 3-minute comparison) during a single study visit (Day 1) | ln(RMSSD fingertip / RMSSD ECG). RMSSD (ms) is computed from fingertip pulse intervals and from ECG RR intervals in the same window, using only consecutive valid interval pairs. Unit: natural-log ratio (unitless; 0 means no difference). The reported value is the bias (mean across participants) with 95% limits of agreement, for the primary 60-300 s window and, to indicate whether free breathing could be shortened to 3 minutes, for the 60-180 s window of the same recording. | ClinicalTrials.gov |
| Secondary | Log Ratio of Facial to ECG Standard Deviation of Normal-to-Normal Intervals (SDNN) During Free Breathing | 5-minute free-breathing condition (60-300 s window, and 60-180 s window for the 3-minute comparison) during a single study visit (Day 1) | ln(SDNN face / SDNN ECG). SDNN (ms) is computed from facial pulse intervals and from ECG RR intervals in the same window, using only valid intervals. Unit: natural-log ratio (unitless; 0 means no difference). The reported value is the bias (mean across participants) with 95% limits of agreement, for the primary 60-300 s window and, to indicate whether free breathing could be shortened to 3 minutes, for the 60-180 s window of the same recording. | ClinicalTrials.gov |
| Secondary | Log Ratio of Fingertip to ECG Standard Deviation of Normal-to-Normal Intervals (SDNN) During Free Breathing | 5-minute free-breathing condition (60-300 s window, and 60-180 s window for the 3-minute comparison) during a single study visit (Day 1) | ln(SDNN fingertip / SDNN ECG). SDNN (ms) is computed from fingertip pulse intervals and from ECG RR intervals in the same window, using only valid intervals. Unit: natural-log ratio (unitless; 0 means no difference). The reported value is the bias (mean across participants) with 95% limits of agreement, for the primary 60-300 s window and, to indicate whether free breathing could be shortened to 3 minutes, for the 60-180 s window of the same recording. | ClinicalTrials.gov |
| Secondary | Log Ratio of Facial to ECG Respiratory Heart Rate Variability Amplitude at 15 Breaths/Min | 3-minute 15 breaths/min condition during a single study visit (Day 1) | ln(A\_pp face / A\_pp ECG) in the 60-180 s window of the 15 breaths/min condition, with A\_pp defined as in the primary outcome. Unit: natural-log ratio (unitless; 0 means no difference). The reported value is the bias (mean across participants) with 95% limits of agreement. | ClinicalTrials.gov |
| Secondary | Log Ratio of Fingertip to ECG Respiratory Heart Rate Variability Amplitude at 15 Breaths/Min | 3-minute 15 breaths/min condition during a single study visit (Day 1) | ln(A\_pp fingertip / A\_pp ECG) in the 60-180 s window of the 15 breaths/min condition, with A\_pp defined as in the primary outcome. Unit: natural-log ratio (unitless; 0 means no difference). The reported value is the bias (mean across participants) with 95% limits of agreement. | ClinicalTrials.gov |
| Secondary | Log Ratio of Facial to ECG Respiratory Heart Rate Variability Amplitude With a Shorter Settling Period or Shorter Recording (Exploratory) | 0-180, 15-180 and 30-180 s windows and 120-second windows starting at 0, 15, 30 and 60 s, in the first 3 minutes of the seven slow paced-breathing conditions during a single study visit (Day 1) | The primary measure, the bias of ln(A\_pp face / A\_pp ECG) pooled across participants and the seven slow rates, recomputed with less of the start excluded (from 0, 15 or 30 seconds instead of 60 seconds to the end of the third minute) and with fixed 120-second windows starting at 0, 15, 30 and 60 seconds, which correspond to conditions of 2, 2.25, 2.5 and 3 minutes (60-180 s is the primary window). For 6.0 breaths/min the first 3 minutes of the 5-minute recording are used. This separates the effect of the excluded settling period from that of analysis length. Unit: natural-log ratio (unitless; 0 means no difference). Overlapping windows are not treated as independent samples, and a shorter recording is not called sufficient without pre-specified agreement limits. | ClinicalTrials.gov |
| Secondary | Log Ratio of Facial to ECG Respiratory Heart Rate Variability Amplitude at 6.0 Breaths/Min: 3-Minute and 5-Minute Windows | 5-minute 6.0 breaths/min condition (60-180 s and 60-300 s windows) during a single study visit (Day 1) | Bias of ln(A\_pp face / A\_pp ECG) (mean across participants, with 95% limits of agreement) at 6.0 breaths/min from the 60-180 s window, as in a 3-minute condition, and from the 60-300 s primary window of the same recording, to indicate whether this condition could be shortened to 3 minutes. Unit: natural-log ratio (unitless; 0 means no difference). The 3-minute comparison is limited to this condition and to free breathing (RMSSD and SDNN outcomes) and is not extended to the other rates. | ClinicalTrials.gov |
| Other | Percentage of Participants Whose Facial and ECG Estimates Give the Same Breathing Rate With Maximal Respiratory Heart Rate Variability Amplitude (Exploratory) | Seven slow paced-breathing conditions during a single study visit (Day 1) | For each participant, the rate between 4.0 and 7.0 breaths/min with the largest A\_pp is identified separately from the face and from the ECG. The outcome is the percentage of participants for whom the two rates are the same, among participants with valid estimates at all seven rates from both sources. A maximum at 4.0 or 7.0 breaths/min is flagged as a grid boundary. This rate is not treated as a physiological resonance frequency or an optimal treatment rate. | ClinicalTrials.gov |
| Other | Percentage of Participants Whose Fingertip and ECG Estimates Give the Same Breathing Rate With Maximal Respiratory Heart Rate Variability Amplitude (Exploratory) | Seven slow paced-breathing conditions during a single study visit (Day 1) | For each participant, the rate between 4.0 and 7.0 breaths/min with the largest A\_pp is identified separately from the fingertip and from the ECG. The outcome is the percentage of participants for whom the two rates are the same, among participants with valid estimates at all seven rates from both sources. A maximum at 4.0 or 7.0 breaths/min is flagged as a grid boundary. This rate is not treated as a physiological resonance frequency or an optimal treatment rate. | ClinicalTrials.gov |
| Other | Absolute Difference Between Belt-Measured and Target Breathing Rate During Paced Breathing | All eight paced conditions during a single study visit (Day 1) | Absolute difference (breaths/min) between the breathing rate measured by the respiratory belt and the target rate, averaged over the eight paced conditions for each participant and summarized as the mean across participants. Values for each target rate are supplementary. | ClinicalTrials.gov |
Outcomes 0
Each outcome the trial posted results for, in ClinicalTrials.gov's words.
| Type | Outcome | Time frame | Population | Units | Measured as | Source |
|---|
Results by group 0
Each measurement the trial posted, group by group, in the words and numbers it posted.
| Outcome | Group | Category | Value | Spread | Units | Source |
|---|
Participant flow 0
How many started, completed or left each group, period by period.
| Period | Milestone | Group | Participants | Units counted | Source |
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Adverse events 0
Each adverse event the trial posted, group by group: the participants affected out of those at risk.
| Type | Event | Organ system | Group | Affected | At risk | Events | Source |
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Adverse event totals 0
The totals the trial posted for each group.
| Total | Group | Affected | At risk | Source |
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Papers 0
The papers the trial lists on ClinicalTrials.gov.
| PMID | Listed as | Source |
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Grants 0
The grants NIH RePORTER links to the trial, newest funded first: NIH's, and some of AHRQ's, CDC's, FDA's and VA's. Each shows its title, principal investigators, organization and funder in its newest year.
| Project | Title | Principal investigators | Organization | Funder | Fiscal years | Source |
|---|
Trial comparisons 0
Comparisons of the trial's two groups, calculated by ConductScience from the counts it posted.
| Comparison | Source |
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Tests 0
The ConductCognition tests this trial's registered outcomes name, as ScienceGraph matched them in trial-tests-2026-11-12-0.2.1.
| Test | Named as | Source |
|---|
Source 5
| Field | Value | Source |
|---|---|---|
| Release | trials-2026-11-12-0.4.0 | ClinicalTrials.gov |
| Release manifest SHA-256 | 0f4a8d8c48aee2a7573ae0fa94ecbeab70c1adbe449bbc95c424bc7d3e97b9d4 | ClinicalTrials.gov |
| Registry capture | 2026-11-12 | ClinicalTrials.gov |
| Results copy, AACT | 2026-03-23 | ClinicalTrials.gov |
| NIH clinical studies file | 2026-11-13 | ClinicalTrials.gov |
Release trials-2026-11-12-0.4.0
ClinicalTrials.gov's posted results, through CTTI's AACT: ClinicalTrials.gov data via Aggregate Analysis of ClinicalTrials.gov (AACT), CTTI. CTTI makes its materials freely available and requests acknowledgement. https://aact.ctti-clinicaltrials.org/documentation/299 ClinicalTrials.gov's data carry an international copyright outside the United States: https://clinicaltrials.gov/about-site/terms-conditions.
ClinicalTrials.gov: none stated ClinicalTrials.gov's data carry an international copyright outside the United States: https://clinicaltrials.gov/about-site/terms-conditions.
NIH RePORTER's clinical studies and project files: Public domain (NIH RePORTER)