Which group is at risk for false readings when using pulse oximetry?

• A. Smokers
• B. COPD patients
• C. Athletes
• D. Children

Answer: (B)

Pulse oximetry estimates oxygen saturation by comparing light absorption of oxyhemoglobin versus deoxyhemoglobin. It assumes normal hemoglobin and cannot distinguish other forms like carboxyhemoglobin or methemoglobin. When abnormal hemoglobin is present, readings can be misleading. COPD patients often have a smoking history, which raises carboxyhemoglobin levels. Carboxyhemoglobin absorbs light similarly to oxyhemoglobin, so the device can overestimate true oxygen saturation, giving a false reading. This makes COPD patients a group at particular risk for misleading SpO2 values. If CO exposure or methemoglobinemia is a concern, more detailed testing such as co-oximetry provides a clearer picture.