Certified Respiratory Therapist Practice Exam

A desaturation event in overnight oximetry data is defined as a decrease in SpO2 of what percentage or more?

1. 2%

2. 4%

3. 6%

4. 8%

The correct answer is: 4%

A desaturation event in overnight oximetry data is typically defined by a decrease in SpO2 of 4% or more. This threshold is clinically significant because it indicates a notable drop in oxygen saturation levels, which may reflect respiratory distress or other underlying issues that require further investigation. Monitoring SpO2 is crucial in assessing a patient's oxygenation status, especially during sleep when conditions like obstructive sleep apnea can occur. The choice of 4% is grounded in research and clinical guidelines that have established this cutoff as a marker for a considerable decrease that could potentially impact patient health. This level of desaturation is often associated with episodes where oxygen supply is not meeting the body's demands, prompting evaluation and, if necessary, intervention. Other thresholds, such as 2%, 6%, and 8%, are either too low to be of clinical concern or may indicate more severe desaturation events that are less common in the context of standard overnight monitoring. Thus, the 4% criterion serves as a balanced marker for assessing nocturnal oxygen desaturation.