What value indicates the need to start oxygen therapy?

Oxygen therapy is typically indicated when a patient's oxygen saturation level falls below 90%. This threshold is significant because levels below 90% can suggest hypoxemia, a condition where there is insufficient oxygen in the blood to maintain normal physiological functions. It is crucial for first responders to recognize when to administer supplemental oxygen to prevent further complications related to inadequate oxygenation, which can lead to serious health issues.

While lower saturation percentages indicate greater severity of hypoxemia, starting oxygen therapy at 95% or above is generally considered unnecessary for most patients. It is only when saturation dips below the 90% mark that the need for intervention becomes more urgent. Thus, the correct answer reflects the standard practice for initiating oxygen therapy in response to low oxygen saturation levels.