title: Respiratory effort-related arousals contribute to sympathetic modulation of heart rate variability.
abstract: OBJECTIVE
  Sympathetic activation induced by sleep-disordered breathing may contribute to cardiovascular morbidity. However, the apnea-hypopnea index (AHI) excludes respiratory effort-related arousals (RERAs) associated with inspiratory flow limitation without oxygen desaturation. We sought to determine whether RERAs are associated with sympathetic activation.
  
  
  METHODS
  Twenty-five adults (12 males, 13 females) with AHI < 10/h and RERA index >5/h were included in this study. Power spectral density analysis was performed on two non-contiguous 10-min segments containing inspiratory flow limitation and arrhythmia-free electrocardiogram during N2 sleep. One segment contained RERA; the other did not, NO-RERA. Spectral power was described in a low-frequency domain (LF; 0.04-0.15 Hz), primarily sympathetic modulation, and a high frequency domain (HF; 0.15-0.4 Hz), parasympathetic modulation.
  
  
  RESULTS
  Analyses of LF and HF powers were made using normalized and absolute values. LF power was greater during RERA compared to NO-RERA (50.3 vs. 30.1 %, p < 0.001) whereas HF power was greater during NO-RERA compared to RERA (69.9 vs. 49.7 %, p < 0.001). The LF/HF ratio was greater during RERA than NO-RERA (1.01 vs. 0.43, p < 0.001). Gender differences emerged using absolute values of power: The percentage increase in LF power during RERA relative to NO-RERA was significantly greater for females than males, 247.6 vs. 31.9 %, respectively (p < 0.02).
  
  
  CONCLUSIONS
  RERAs are associated with a marked increase in cardiac sympathetic modulation, especially in females. Patients with a high RERA index, even in the setting of a low or normal AHI, may be exposed to elevated sympathetic tone during sleep.
authors: Division of Pulmonary, Allergy and Critical Care, Columbia University College of Physicians and Surgeons, New York, NY, USA.
authors: Subani
authors: S
authors: Chandra
authors: Anthony L
authors: AL
authors: Sica
authors: Janice
authors: J
authors: Wang
authors: Viera
authors: V
authors: Lakticova
authors: Harly E
authors: HE
authors: Greenberg
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology*; D001143:Arousal / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D012815:Signal Processing, Computer-Assisted; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*
chemical_list: D010100:Oxygen