0448 Upper Airway Collapsibility Is Associated with Fluid Shifts in Patients with Sleep Apnea and Diastolic Dysfunction Free

Left ventricular systolic dysfunction contributes to sleep-disordered breathing (SDB) pathophysiology through overnight rostral fluid shifts leading to fluid accumulation in the neck (increasing upper airway collapsibility) and pulmonary vasculature (increasing ventilatory control instability). In contrast to systolic dysfunction, the relationship of left ventricular diastolic dysfunction (LVDD) to overnight fluid shifts and SDB pathophysiology is less well characterized. In an ongoing prospective clinical study of patients with risk factors for or established LVDD and untreated SDB, we are using Phenotyping Using Polysomnography (PUP) analysis to investigate the relationship of overnight fluid shifts to upper airway collapsibility and ventilatory control instability.

Patients are enrolled in the presence of known LVDD or ≥1 risk factor (age ≥55 years, hypertension, diabetes, coronary artery disease, or amyloidosis) and known or suspected SDB with an apnea-hypopnea index (AHI3A) of ≥15 events/hr. Exclusion criteria include ejection fraction (EF) < 40% or factors suspected to interfere with LVDD indices or PUP estimates (e.g. ventricular dyssynchrony, severe lung disease). LVDD is confirmed on transthoracic echocardiography. Patients undergo in-lab polysomnography (PSG) with pre- and post-sleep circumference measurements of the neck and calves (averaged from both calves). PUP estimates of upper airway collapsibility (Vpassive) and ventilatory control instability (loop gain, LG1) are determined for the first and second half of sleep.

14 patients have been enrolled. Complete PSG data is available for 8 patients (age 52.6±10.7 years, 50% female, BMI 36.2±5.0 kg/m^2, AHI3A 28.7±18.4 events/hr, EF 63.0±7.0%). While neck circumference did not significantly change, calf circumference significantly decreased overnight (pre- vs post-sleep median [IQR] 39.4 [37.3-40.5] cm vs 38.6 [25.8-40.2] cm, p = 0.047). Overnight change in Vpassive was inversely correlated with overnight change in neck circumference (R = -0.82, p = 0.023) and positively correlated with overnight change in calf circumference (R = 0.76, p = 0.049). Correlations of overnight changes in LG1 with neck and calf circumferences were not significant.

PUP analysis suggests overnight rostral fluid shift in patients with LVDD contributes to upper airway collapsibility. This preliminary trend will be more fully investigated on reaching the enrollment goal of 30 patients.

AASM PSTA. NIH T32HL160511.