Bushfire smoke linked with significant FVC drop in asthmatic children

Asthma

By Geir O'Rourke

7 Nov 2022

Average forced vital capacity (FVC) in asthmatic children falls significantly on days of bushfire smoke exposure, data from spirometry during Black Summer of 2019–20 has shown.

Researchers say the FVC% declines may be partially reversible with bronchodilator inhalation but are clinically important, with the worst air pollution days over the period potentially triggering a decrease of 14% in FVC % predicted compared to non-bushfire days.

The modelling also showed the highest mean PM2.5 concentration of 71.6 μg/m3 on bushfire days may result in a decrease of 10% in FEV1 % predicted compared to the lower level of 8.3 μg/m3 on non-bushfire days.

“Our results show for the first time that wildfire exposure around the time of lung function testing is associated with a mean decrease of 5% in FVC % predicted in asthmatic children,” the NSW researchers reported in Pediatric Allergy and Immunology (link here).

“This effect size is considered to be of clinical importance.”

“For instance, specific cystic fibrosis transmembrane conductance regulator modulators have demonstrated a therapeutical effect improvement of around 5% in FEV1 and FVC and their use in CF patients is nowadays accepted standard of care.”

On the other hand, falls in FEV1 were lower and not clinically significant.

The findings were based on 212 lung function tests recorded by 129 asthmatic children who attended Newcastle’s John Hunter Children’s Hospital outpatient department during the 2019-20 bushfires.

These test results were then compared with the daily PM2.5 readings from nearby state government air quality monitoring stations on the days on which the spirometry was performed.

Led by Dr Carla Da Silva Sena of the Hunter Medical Research Institute, the team said it was the first study to demonstrate the effects of the fires with an objective measurement on asthmatic children, while most previous research had been based on ED visits or hospital admissions.

They said their findings were in line with similar studies overseas, although it was impossible to exclude that the true effect on FEV1 was so small that it remained undetected as a result of analysing on a small sample with potentially large variability.

“In either case, our results suggest that bushfire smoke exposure may predominately result in a restrictive lung function limitation while PM2.5 exposure is associated with a mixed, restrictive and obstructive, deficit in asthmatic children,” they wrote.

“Lung volume studies would be required to confirm this hypothesis.”

The authors added: “Mechanistically, the toxic effects of bushfire smoke have been linked to oxidative stress and inflammatory responses highlighting potential preventive and therapeutic strategies to reduce lung function deficits and resultant disease burden caused by wildfire smoke exposure, in particular in susceptible populations such as asthmatics.”

 

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