What factor determines the need for oxygen therapy in hypoxemic patients?

The need for oxygen therapy in hypoxemic patients is primarily determined by oxygen saturation levels. Oxygen saturation refers to the percentage of hemoglobin molecules in the blood that are bound with oxygen. In conditions of hypoxemia, where there is a deficiency of oxygen in the blood, monitoring oxygen saturation is crucial to assess the severity of the patient's condition and to guide treatment decisions.

When the oxygen saturation levels fall below a certain threshold, typically around 90%, this indicates that the body's tissues may not be receiving enough oxygen to function effectively. Therefore, healthcare providers often use pulse oximetry to measure these levels and determine if supplemental oxygen is needed to help restore adequate oxygenation.

While the presence of symptoms can provide additional context about a patient’s respiratory status, it is the actual measurements of oxygen saturation that lead to the decision to initiate oxygen therapy. Other factors like a patient's age and the cost of oxygen supplies do not directly influence the medical necessity for oxygen therapy but may affect other considerations in treatment planning. Thus, oxygen saturation levels are the key determining factor in identifying the need for oxygen therapy in hypoxemic patients.