Cardiovascular metrics can now be measured from the upper arm without precise sensor positioning, with testing demonstrating clinical-grade accuracy. A knitted sleeve combining electrocardiography and impedance plethysmography recorded blood pressure, stroke volume and vascular resistance in real time. The device sustained signal fidelity under motion and repeated wear, addressing a persistent limitation of optical consumer wearables in a field where cardiovascular diseases remain the leading global cause of mortality.
- The sleeve integrates silver-coated conductive yarn into a breathable, stretchable fabric housing two ECG and four IPG electrodes arranged around the upper arm.
- It captures cardiac electrical activity and blood-flow impedance changes simultaneously, enabling extraction of parameters including stroke volume and systemic vascular resistance.
- Experiments demonstrated stable signal-to-noise ratios across dry, wet, stretched and motion conditions, outperforming conventional optical approaches reliant on arterial alignment.
- The study was published in Microsystems & Nanoengineering by researchers from the Chinese University of Hong Kong and collaborating institutes.
THE STUDY: Researchers developed a textile-based alignment-free electrophysiological sensing sleeve. The work evaluated continuous haemodynamic monitoring from the upper arm using integrated electrocardiography and impedance plethysmography, targeting metrics such as stroke volume and systemic vascular resistance that are rarely accessible outside clinical settings. Trials involving 10 participants assessed performance across breathing tasks and daily activity.
- The system was published with a DOI reference and detailed experimental validation of simultaneous ECG and IPG waveform capture.
- Researchers measured blood pressure, stroke volume, cardiac output, heart rate and systemic vascular resistance using synchronised electrical and impedance signals.
- The study examined performance under dry, wet, stretched and motion states to simulate daily wear conditions.
- Controlled breathing protocols evaluated beat-by-beat variation in recorded haemodynamic parameters.
PERFORMANCE BENCHMARKS: Blood-pressure prediction errors remained within clinically relevant ranges across varied wear conditions, with systolic and diastolic root mean square errors recorded at 7.05 mmHg and 5.93 mmHg. The textile sleeve also maintained a mean absolute error of approximately 4 mmHg after re-wearing. Signal stability persisted during motion, rotation and axial displacement.
- Experiments confirmed robust ECG and IPG signal-to-noise ratios across dry, wet, stretched and movement scenarios.
- Beat-by-beat measurements captured dynamic variation in core haemodynamic parameters during controlled testing.
- Comparative testing showed performance surpassing pulse-wave-velocity and zero-baseline estimation approaches.
- Accuracy remained consistent even when the sleeve was removed and worn again, demonstrating insensitivity to re-positioning.
DESIGN AND DEPLOYMENT: The sleeve is engineered with silver-coated conductive yarn seamlessly knitted into a breathable, stretchable textile architecture. The electrodes are arranged circumferentially around the upper arm to capture cardiac electrical activity and blood-flow-driven impedance changes. The porous fabric structure supports sweat permeability of 37.5 mg·cm⁻²·h⁻¹ and elasticity exceeding 45 per cent, exceeding comparable commercial electrode materials in these properties.
- The alignment-free configuration maintains consistent signal capture during typical upper-arm movement and repositioning.
- Synchronous ECG–IPG waveforms enable extraction of parameters such as RR interval, QTc, pulse transit time and dZ/dt.
- The textile outperformed commercial electrodes in heat dissipation and stretch resilience.
- Researchers identified applications in long-term home monitoring, chronic disease management, integration into smart clothing systems and scalable, low-cost deployment beyond clinical environments.
- The dual-modal physiological modelling also supports arrhythmia detection, vascular stiffness assessment and recovery tracking in heart-failure patients.
WHAT THEY SAID
Our work demonstrates that precise cardiovascular monitoring no longer requires rigid hardware or perfect sensor positioning. By integrating ECG and impedance plethysmography into a soft knitted sleeve, we enable accurate measurement of blood pressure and haemodynamic parameters even during movement, sweating, or re-wearing.
— Ni Zhao (corresponding author)
Department of Electronic Engineering
The Chinese University of Hong Kong
