Loop Gain in Apnea vs. Hypopnea Predominant Sleep Apnea

Definitions and Diagnostic Considerations

• Apnea is defined as the complete cessation of airflow for ≥10 seconds, according to the American Academy of Sleep Medicine 1, 2
• Hypopnea is defined as a partial reduction in airflow (≥30% drop from baseline) for ≥10 seconds associated with either ≥3% oxygen desaturation or an arousal, as stated by the American Academy of Sleep Medicine 1, 2
• The American Academy of Sleep Medicine recommends scoring both apneas and hypopneas to calculate the Apnea-Hypopnea Index (AHI) 3, 2
• Polysomnography remains the gold standard for distinguishing between apnea and hypopnea events, as noted by the American Thoracic Society and the European Sleep Research Society 5, 6

Clinical Implications and Pathophysiology

• The relative proportion of apneas versus hypopneas may provide insight into underlying pathophysiological mechanisms, including loop gain, according to the American Academy of Sleep Medicine 1, 4