What likely causes fluctuating SpO2 in a patient with ketoacidosis receiving oxygen via air-entrainment mask?

Fluctuating SpO2 in a patient with ketoacidosis receiving oxygen via an air-entrainment mask is most likely caused by inadequate total gas flow. When using an air-entrainment mask, the delivery of oxygen is dependent on both the flow of oxygen and the mixing of room air. If total gas flow is insufficient, the mask may not adequately deliver the necessary fraction of inspired oxygen (FiO2), leading to variability in the patient’s oxygen saturation levels.

This situation can manifest as inconsistent oxygenation because the mask is not able to provide a stable and sufficient supply of oxygen to meet the patient's metabolic demands, particularly in the context of metabolic disturbances like ketoacidosis, which can increase the requirement for oxygen. Maintaining an adequate flow is essential to ensure that the patient receives a reliable supply of oxygen, preventing fluctuations in their oxygen saturation levels.

The other factors, while they may influence oxygenation in some scenarios, do not directly account for the primary issue of fluctuating saturation in this context. For instance, a shift in the oxygen dissociation curve would affect how oxygen binds to hemoglobin rather than directly influencing the delivery of oxygen. Unstable blood glucose levels can certainly affect the patient's overall condition and metabolism, but they do not directly