Protective effect of respiratory devices in farmers with occupational asthma.

To the authors' knowledge there have been no previous reports on the protection afforded by powered filtering respirators in farmers with occupational asthma attributed to the inhalation of organic dust. In order to investigate this question, 26 farmers with occupational asthma were challenged with an exposure to work-related dusts for up to 60 min. This resulted in highly significant increases in airway resistance (Raw), thoracic gas volume (TGV) and specific airway resistance (sRaw) compared to baseline values. After a mean period of 21 weeks the farmers were subjected to a second challenge, this time wearing a protective respiratory device (RD) with a P2 filter. Significant increases in Raw, TGV and sRaw were again observed, but on average these were 50-80% smaller than the increases seen when RDs were not worn. These differences were found to be statistically significant. This shows that the use of a respiratory device in farmers suffering from occupational asthma reduces the development of bronchial obstruction but does not prevent it. The use of this kind of respiratory device cannot substitute for the proper management of asthma since the devices do not offer complete protection.