A Novel Smartphone App for the Measurement of Ultra-Short-Term and Short-Term Heart Rate Variability: Validity and...

Area of Science:

• Cardiology and Exercise Physiology
• Biomedical Engineering
• Wearable Technology

Background:

• Smartphone applications for heart rate variability (HRV) measurement are prevalent.
• Ultra-short-term HRV recordings from wearable devices remain under-examined.

Purpose of the Study:

• To assess the validity and reliability of ultra-short-term HRV measurements using the Pulse Express Pro (PEP) smartphone app.
• To compare PEP's HRV assessments against electrocardiogram (ECG) standards.

Main Methods:

• 60 healthy adults underwent 5-minute resting HRV measurements using both ECG and the PEP app.
• Analyzed time-domain (SDNN, RMSSD, pNN50) and frequency-domain (nVLF, nLF, nHF) HRV variables across various short recording durations (1-5 minutes).
• Employed standardized differences, ICC, Spearman correlation, and Bland-Altman analysis for validity and agreement assessment.

Main Results:

• Time-domain HRV indices (SDNN, RMSSD, pNN50) demonstrated high validity and reliability with trivial effect sizes and near-perfect correlations, even in 1-minute recordings.
• Frequency-domain indices (nLF, nHF) showed moderate to near-perfect agreement, with acceptable limits of agreement achieved after 3-minute recordings.
• Bland-Altman analysis indicated good agreement between ECG and PEP for SDNN, RMSSD, and pNN50 after 1-minute recordings.

Conclusions:

• The PEP app is suitable for 1-minute ultra-short-term HRV recordings for time-domain indices (SDNN, RMSSD, pNN50) to assess autonomic function.
• A minimum of 3 minutes of recording is recommended for accurate frequency-domain HRV indices (nLF, nHF) using the PEP app.