Dyshemoglobins and Pulse Oximetry: How COHb and MetHb Influence Measurement Accuracy   Pulse oximetry has become central to physiological monitoring across wearables, medical devices, and clinical research studies. Yet even the most advanced sensor architectures face fundamental challenges when hemoglobin exists in altered forms—known as dyshemoglobins . Carboxyhemoglobin (COHb) and methemoglobin (MetHb) change light absorption in ways that directly influence SpO₂ readings an