Phenotyping Using Polysomnography Attributes Reduced Respiratory Events after Continuous Positive Airway Pressure...

Area of Science:

• Sleep Medicine
• Respiratory Physiology
• Cardiovascular Health

Background:

• Continuous positive airway pressure (CPAP) is a primary treatment for obstructive sleep apnea (OSA).
• The apnea-hypopnea index (AHI) may decrease after CPAP treatment, but the underlying mechanisms require further elucidation.
• Phenotyping Using Polysomnography (PUP) offers a method to assess OSA pathophysiology using routine polysomnography (PSG).

Purpose of the Study:

• To investigate whether changes in AHI after CPAP therapy are mainly associated with improved ventilatory control stability or other PUP-estimated pathophysiologic mechanisms.
• To compare changes in loop gain with a 1-minute cycle time (LG1), arousal threshold, and upper airway collapsibility (Vpassive) with AHI changes.

Main Methods:

• PUP analyses were conducted on existing PSG data from participants before and after CPAP therapy.
• Participants underwent baseline PSG, CPAP treatment for approximately 4.4 months, and repeat PSG after CPAP withdrawal.
• Mixed-effects models were used to determine which PUP estimate best explained changes in AHI.

Main Results:

• While overall AHI decreased after CPAP, the change was not statistically significant. However, a significant AHI decrease was observed in patients with severe OSA.
• For severe OSA patients, decreases in LG1 and increases in Vpassive exceeded test-retest limits.
• Increased Vpassive, decreased LG1, and decreased arousal threshold predicted decreased AHI. Vpassive demonstrated the most significant effect on AHI.

Conclusions:

• PUP estimates suggest that improvements in upper airway collapsibility (Vpassive) are the primary driver of AHI reduction after several months of CPAP therapy in OSA patients.
• While ventilatory control (LG1) also plays a role, Vpassive appears to be the dominant factor influencing AHI changes.