Respiratory stroke volume changes affect heart rate variability (HRV) mainly by baroreflexes. HRV increases at lower respiratory rates with a maximum at about 0.2 Hz. In 11 migraineurs (M: 9 female, 2 male; 22–49 yrs) and 33 controls (C: 27 f; 6 m; 20–55 yrs) ECG was recorded in supine position while breathing at spontaneous rate (S: 0.25–0.35 Hz) and at 0.2 Hz paced rate (P). FFT spectra of HRV were obtained from RR intervals time series in S and P conditions. Power was assessed in the bands VLF (.02-.04 Hz), LF (.04-.15), HF (.15-.4), TOT (total= .02-.4) LF/HF ratio was calculated.

Results (ms²/Hz; m±se): 

TOT S:C=594.2±72.6 VLF S:C=82.9±9.7 LF S:C=306.3±49.7 HF S:C=204.2±30.8

TOT S:M=364.7±86.5 VLF S:M=51.5±11.5 LF S:M=176.1±50.7 HF S:M=136.1±33.5

TOT P:C=1185.0±224.7 VLF P:C=79.1±11.5 LF P:C=211.1±30.8 HF P:C=743.7±151.1

TOT P:M=421.0±99.2 VLF P:M=60.7±18.4 LF P:M=91.8±18.8 HF P:M=268.6±83.2

LF/HF S:C=2.32±0.46 LF/HF S:M=1.48±0.29

LF/HF P:C=0.49±0.07 LF/HF P:M=0.59±0.13

After 2-ways ANOVA and Bonferroni test TOT P and HF P were greater than TOT S (<.05) and HF S (<.001) in C, but not in M. TOT P and HF P in C were greater than in M (<.05). LF/HF P was lower than LF/HF S in C (<.0001) but not in M. Slowing respiration down to 0.2 Hz increased HRV in C but not in M mainly by increasing vagal control.