Which of the following statements regarding pulse oximetry is incorrect?

Pulse oximetry is a non-invasive method used to measure the oxygen saturation of a patient's hemoglobin. While it indeed provides a reading regarding the percentage of hemoglobin that is saturated with oxygen, it does not measure the partial pressure of oxygen (PaO2) directly. The measurement is based on the absorption of light by oxygenated and deoxygenated hemoglobin, and consequently, it provides an estimation of oxygen saturation rather than directly reporting partial pressure levels.

In contrast, the other statements accurately describe aspects of pulse oximetry. It can be impacted by excessive surrounding light sources, which can obscure its readings. Significant levels of dysfunctional hemoglobin, such as carboxyhemoglobin or methemoglobin, can lead to erroneous saturation readings. The technology underlying pulse oximetry relies on the differential absorption of light by the different forms of hemoglobin, supporting the idea that the mechanism of measurement is fundamentally tied to how light interacts with these molecules.