LAUSR

Introduction: Periodic Breathing (PB) is common in heart failure (HF). The loop gain (LG) reflects the amount of instability of the respiratory control system. The LG can be quantified by a mathematical model based on the cyclic respiratory pattern. We investigated the intra- and interindividual variability of the LG and its dependency on sleep stage and body position. Methods: Polysomnographies (PSG) of untreated patients with LVEF>45%, central AHI>15/h and predominant PB were analysed retrospectively. Single PB cycles were quantified by duty ratio („DR“=ventilation duration/cycle duration) and LG=2π/(2π*DR – sin (2π*DR)). LG was evaluated according to sleep stage and body position. Results: 12 PSG with 1224 PB apneas in total were analyzed (12 men, 73±5 y, BMI 28±4 kg/m2, LVEF 30±8%). LG showed high interindividual variability (mean LG 1.6±0.5) and revealed different characteristical LG subgroups: 7 patients showed significant LG differences between sleep stages with lower values in slow wave sleep (N1:1.6±0.7 vs. N3:1.3±0.3; p Conclusion: The high intra- and interindividual LG variability LG and differences in sleep stage and body position dependency in this group of patients suggests the existence of different definable phenotypes of disturbed respiratory control. Therefore, a single LG value per patient is no reliable measure. Individual characteristics of PB have to be considered.