A comparative evaluation of accuracy and response time in ear and finger pulse oximetry during repeated maximal breath-holding: implications for safety

• Measurement site significantly influences temporal dynamics and magnitude of SpO 2 decline during maximal and repeated breath-holds. • Ear-derived oximetry exhibited faster response kinetics and lower SpO 2 at breakpoint and nadir compared with finger measurements. • Finger oximetry demonstrated temporal lag and systematic underestimation of hypoxemia, with discrepancies increasing with breath-hold duration. • Centrally perfused sites, such as the earlobe, should be preferentially used to improve timely risk recognition and reduce hypoxic blackout risk.