Characterisation of Physiological Signal Artifacts in Wearable Biosensors Under Nigerian Tropical Climate Conditions

Wearable biosensors for continuous physiological monitoring in Nigerian tropical climates face unique artifact generation challenges due to high ambient temperature, humidity, and perspiration levels that are underrepresented in existing device validation literature developed under temperate conditions. This study characterises the nature, magnitude, and frequency of physiological signal artifacts generated by wearable biosensors under tropical climate conditions representative of Port Harcourt, Rivers State, using controlled laboratory simulation and field measurement. Three wearable biosensor types were characterized: optical PPG sensors for heart rate monitoring, skin surface EMG sensors for muscle activity monitoring, and skin conductance sensors for stress monitoring. Artifact sources examined include motion artifact from standardized activities of daily living, thermal drift from ambient temperature cycling between 30 and 40 degrees Celsius, sweat-induced electrode impedance changes, and skin displacement from humidity-driven adhesive degradation. Each artifact source was systematically characterized through controlled experimental protocols on thirty volunteers over three-day monitoring periods at a research facility in Port Harcourt. Signal-to-noise ratio measurements quantified artifact magnitudes for each sensor type and artifact source combination. Results show that sweat-induced impedance changes produced significantly larger PPG baseline drift amplitudes than reported in temperate condition validation studies for three of the four sensor models tested. EMG sensors showed significantly elevated noise floor during periods of peak ambient temperature due to thermal drift in high-gain signal conditioning amplifiers. Skin conductance sensor adhesion failure rate was significantly higher above 36 degrees Celsius ambient temperature. Artifact severity showed significant inter-individual variation correlated with sweating rate. Keywords: wearable biosensors, signal artifacts, tropical climate, physiological monitoring, Port Harcourt.