The effects of abdominal breathing on autonomic nervous function in women - The relationship among individual differences in autonomic nervous system activity in a supine position at rest

We analyzed time-domain parameters (%RR50, CVRR, E/I ratio) and frequency-domain parameters (HF, LF, LF/HF, HF/SUM) from R-R interval variability to investigate the differences in autonomic nervous system activity and the effects of abdominal breathing in 20 healthy female subjects (age 48.4 +/-5.5 years). The measurements were taken during spontaneous breathing in a supine position for 20 min and in a sitting position for 20 min, followed by voluntary control of abdominal breathing (expiration to inspiration time ratio was 2 to 1) for 20 min and recovery with spontaneous breathing in a sitting position for 30 min, 100 R-R intervals 16 times for 90 min and also heart rate (BR), blood pressure (BP), respiratory frequency (f) and arterial O-2 and CO2 partial pressure through cutaneous (P-c,O-2, PtcCO2). The subjects were grouped according to the mean values of three autonomic nervous system activity parameters (%RR50, CVRR, E/I ratio) in a supine position. Group 1 (G1) was below average for all three parameters, group 3 (G 3) was above average and group 2 (G 2) was below or above average mixed for the three parameters. A strong correlation (P<0.01, respectively) was observed between %RR50 and HF (0.15<similar to>0.4 Hz) during the following trials : spontaneous breathing in a supine position (r=0.783) and sitting position (r=0.758), voluntary control of abdominal breathing (r=0.597), and recovery with spontaneous breathing in a sitting position (r=0.756). With regard to the characteristics of each group, the following were observed : G1 showed an accelerated trend of sympathetic nervous system activity and the approximate mean value was indicated in measurements of respiratory-circulatory system activity (HR, f, BP). G2 showed an unstable trend in which either sympathetic or parasymathetic nervous system activities were accelerated, blood pressure was higher and many respiratory frequencies were observed among the three groups. G3 showed an accelerated trend in parasympathetic nervous system activity; and both blood pressure and respiratory frequency were consistently low in the three groups. These results indicated that there were natural differences in each subject in autonomic nervous system activity and physiological function in a supine position at rest. It was found that voluntary control of abdominal breathing enhanced the vagal modulation of the heart rate in subjects who showed an accelerated trend of sympathetic nervous system activity