The effect of sulphur dioxide exposure on indices of heart rate variability in normal and asthmatic adults

Sulphur dioxide (SO2) is an important air pollutant and causes bronchoconstriction in normal and asthmatic adults. This paper has explored the autonomic consequences of SO2 exposure using the spectral anal! sis of heart rate variability. Electrocardiogram recordings were made in 12 normal and 12 asthmatic adults undergoing pollutant exposures, Exposures were of a 1 h duration, double blind, in random order, greater than or equal to2 weeks apart and included air and 200 parts per billion SO2. Spectral analysis of R-R intervals was performed. SO2 exposure was associated with an increase in total power (TP) and high (HF) and low frequency (LF) power in the normal subjects, and a reduction in these indices in the subjects with asthma, The difference in TP with SO2 exposure compared to air was +1730 ms(2) in the normal group and -1021 ms(2) asthmatic group (p<0.003). For HF the respective values mere +964 ms(2) and -539 ms(2) (p=0.02) and for LF, +43 7 ms(2) and -57 2 ms(2) (p=0.01). No change in lung function or symptoms was observed in either group. This suggests that SO2 exposure at concentrations which are frequently encountered during air pollution episodes can influence the autonomic nervous system. This mel; be important in understanding the mechanisms involved in SO2 induced bronchoconstriction, and of the cardiovascular effects of air pollution.