Backpack EKG: An Energy-Autonomous Standalone Three-Lead EKG Platform for Off-Grid Screening Applications

This paper presents Backpack EKG, a standalone, energy-autonomous three-lead electrocardiography (EKG) platform tailored to decentralized cardiovascular screening in offgrid and resource-limited environments. Unlike long-term ambulatory monitors or diagnostic 12-lead systems, the proposed device targets short-duration, repeatable acquisitions within outreach and first-contact workflows, where electrical infrastructure, connectivity, and external computing devices cannot be assumed. The platform integrates biopotential acquisition, embedded real-time processing, on-device waveform visualization, and fully offline data logging in a robust backpack-deployable form factor. A three-lead configuration is obtained from two measured leads plus a digitally derived lead (Einthoven relation), enabling rhythm inspection and heart-rate estimation while reducing hardware complexity and power demand. Energy autonomy is achieved through a rechargeable lithium-ion battery with photovoltaic-assisted charging, supporting up to 10 h of continuous operation and approximately 120 screening acquisitions per charge. Heart-rate estimation was verified using a calibrated patient simulator across 30-320 BPM setpoints, achieving a mean absolute error of 0.19 BPM (mean relative error <0.1 %) under steady-state conditions. Overall, Backpack EKG provides a measurement-oriented, operationally autonomous acquisition platform for screening campaigns where deployment logistics and power availability constrain conventional EKG instrumentation.