From the Guidelines
Pulse oximetry should be interpreted with caution in individuals with darker skin tones, as it may overestimate oxygen saturation levels, potentially masking hypoxemia. This limitation is crucial to consider, especially when readings are in the 90-94% range in dark-skinned patients, as studies have shown that pulse oximeters can overestimate oxygen saturation levels in these patients by up to 3-4% 1. The discrepancy occurs because pulse oximeters work by measuring light absorption through the skin, and melanin can interfere with this measurement.
When monitoring patients with darker skin, clinicians should pay close attention to other signs of respiratory distress, including:
- Respiratory rate
- Work of breathing
- Mental status changes If there's clinical suspicion of hypoxemia despite normal-appearing pulse oximeter readings, additional testing, such as arterial blood gas measurements, should be performed 2. Some newer pulse oximeter models are being developed with algorithms that account for skin pigmentation, though these are not yet widely available in all clinical settings.
Healthcare providers should be aware of the limitations of pulse oximetry in dark-skinned patients, as highlighted in the 2024 American Heart Association and American Red Cross guidelines for first aid 1, which emphasize the importance of considering multiple assessment findings when interpreting pulse oximetry results. The 2023 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations also supports this notion, highlighting the greater discrepancy between oxygen saturation as measured by pulse oximetry and that measured by blood gas in individuals with darker skin tones 2.
From the Research
Oxygen Saturation on Dark Skin Individuals
- The accuracy of pulse oximetry in measuring oxygen saturation can be affected by skin pigmentation, with studies suggesting that pulse oximetry may overestimate oxygen saturation in individuals with dark skin 3, 4.
- A study published in 2007 found that dark skin increased bias at low oxygen saturation levels, with greater bias seen with adhesive/disposable sensors than with clip-on types 3.
- Another study published in 2022 found that pulse oximetry probably overestimates oxygen saturation in people with high levels of skin pigmentation, with a pooled mean bias of 1.11% 4.
- The study also found that the bias of pulse oximetry measurements for people with other levels of skin pigmentation or those from other ethnic groups is either more uncertain or suggests no overestimation 4.
- A study published in 2018 found that body temperature, oximeter model, and skin color were statistically significantly associated with the degree of bias in paired SpO2/SaO2 measurements 5.
Factors Affecting Oxygen Saturation Measurements
- Skin pigmentation is a significant factor affecting oxygen saturation measurements, with darker skin tones leading to increased bias and decreased accuracy 3, 4.
- The type of oximeter sensor used can also affect measurements, with adhesive/disposable sensors showing greater bias than clip-on types 3.
- Other factors such as body temperature, oximeter model, and gender may also influence oxygen saturation measurements 3, 5.
Clinical Implications
- Clinically important bias should be considered when monitoring patients with saturations below 80%, especially those with darkly pigmented skin 3.
- Pulse oximetry measurements should be used cautiously when SaO2 recordings of 4.4% higher or lower than the observed SpO2 would be of concern 5.
- Further study is needed to confirm these observations in relevant populations and to develop more accurate and equitable methods for characterizing skin pigment diversity in research cohorts 6.