Wildfire smoke makes pulse oximeters unreliable, misleading COPD patients at home
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COPD and chronic lung disease patients who use home pulse oximeters to monitor their oxygen saturation get falsely reassuring readings during smoke events because carboxyhemoglobin (COHb) from carbon monoxide in wildfire smoke registers as oxyhemoglobin on standard two-wavelength pulse oximeters. A COPD patient in Fresno seeing 95% SpO2 on their home device might actually have an SpO2 of 90% with 5% COHb, which should trigger supplemental oxygen use or an ER visit. They stay home thinking they are fine, and their condition deteriorates. This persists because clinical-grade CO-oximeters that can distinguish COHb cost $3,000-8,000 and are only available in hospitals, while consumer pulse oximeters ($20-50) physically cannot differentiate the two hemoglobin species with only two LED wavelengths.
Evidence
A 2022 study in the Annals of the American Thoracic Society found that wildfire smoke exposure elevated COHb levels to 3-8% in subjects within 10 miles of active fires, enough to cause 3-8 percentage point SpO2 overestimation on standard pulse oximeters. The FDA's 2021 pulse oximeter guidance does not require CO-oximetry capability for consumer devices. Masimo's Rad-57, the only portable CO-oximeter, retails for approximately $3,500 and is not covered by Medicare for home use.