Clinical Definition

T90 represents:

  • Hypoxic Burden: Total time spent with significant hypoxia
  • Physiological Stress: Cumulative impact of oxygen desaturation
  • Cardiovascular Risk: Longer T90 indicates higher risk
  • Treatment Monitoring: Should decrease with effective therapy
  • Severity Assessment: Provides different perspective than frequency measures

T90 is typically expressed as both absolute time (minutes) and percentage of total sleep time, providing information about the duration of hypoxic stress.

Etymology & History

T90 became recognized as an important parameter as clinicians realized that the duration of hypoxia, not just its frequency, was clinically significant for cardiovascular outcomes.

Reference Values & Interpretation

Normal Values

Normal T90 should be <1% of total sleep time. Values <5 minutes of absolute time are generally considered acceptable.

Abnormal Values

T90 >5% of total sleep time indicates significant hypoxic burden. Values >10% suggest severe hypoxemia that may require supplemental oxygen therapy.

How It's Measured

T90 is automatically calculated by sleep study software by summing all time periods when oxygen saturation is below 90% during the sleep study.

Role in Diagnosis

T90 is important for assessing the overall hypoxic burden and may be a better predictor of cardiovascular outcomes than frequency-based measures alone.

Role in Treatment

T90 is used to monitor treatment effectiveness and determine the need for supplemental oxygen therapy. Successful treatment should significantly reduce T90.

Associated Conditions

oxygen-saturation|hypoxic-burden|pulse-oximetry|cardiovascular-risk

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Clinical Guidelines

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Latest Research & Updates

AI-Updated Weekly

Recent research has shown that T90 may be a stronger predictor of cardiovascular outcomes than traditional measures like AHI, highlighting the importance of hypoxic burden assessment.