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Table 3 Heart rate variability and urine catecholamine: patients with and without CPAP treatment

From: Nocturnal CPAP improves walking capacity in COPD patients with obstructive sleep apnoea

Heart rate variability Overlap syndrome n = 18#   COPD  
n = 20@
  Baseline With CPAP p Baseline With CPAP p
LF (nu) 46.6 ± 16.1 31.3 ± 16.7 0.001 31.8 ± 10.8* 28.7 ± 20.4 0.401
HF (nu) 32.2 ± 12.0 43.1 ± 19.1 0.029 41.9 ± 12.1* 43.6 ± 19.3 0.287
LF/HF 1.8 ± 1.2 0.9 ± 0.7 0.003 0.9 ± 0.6* 1.2 ± 1.9 0.514
Urine catecholamines Overlap syndrome n = 12 $   COPD  
n = 12 $
  Baseline With CPAP   Baseline With CPAP  
Norepinephrine, ug 17.0 ± 8.4 10.4 ± 6.4 0.003 11.1 ± 5.3* 11.9 ± 7.5 0.485
Epinephrine, ug 2.4 ± 0.9 1.4 ± 0.7 0.025 1.5 ± 0.6* 1.8 ± 0.8 0.374
  1. *P < 0.05; when compared with baseline overlap syndrome group.
  2. P values represent comparisons between before and after CPAP in each corresponding group.
  3. LF low frequency, HF high frequency nu normalized unit.