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 bronchoconst riction in normal and asthmatic adults. This paper has explored the autonom ic 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 b lind, in random order, greater than or equal to2 weeks apart and included a ir and 200 parts per billion SO2. Spectral analysis of R-R intervals was performed. SO2 exposure was ass ociated with an increase in total power (TP) and high (HF) and low frequenc y (LF) power in the normal subjects, and a reduction in these indices in th e 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 funct ion or symptoms was observed in either group. This suggests that SO2 exposure at concentrations which are frequently enco untered during air pollution episodes can influence the autonomic nervous s ystem. This mel; be important in understanding the mechanisms involved in S O2 induced bronchoconstriction, and of the cardiovascular effects of air po llution.