Respiratory responses to nitrogen dioxide inhalation subtitle: Nitrogen dioxide

Abstract

We investigated the effects of nitrogen dioxide (NO₂), a combustion‐related pollutant reported to depress host resistance to infection, on respiratory patterns in the mouse.

Control mice were exposed to filtered air for 3 days; experimental mice were exposed to 5 ppm NO₂ for the same number of days. After exposure, both control and experimental mice were placed in a respiratory monitor and challenged with clean air (0 ppm NO₂) or 15, 50, or 100 ppm NO₂.

During the challenge with clean air, there were no differences between groups in respiratory rate (RR), tidal volume (TV), or minute volume (MV).

On exposure to NO₂, RR increased, whereas TV and MV decreased in both groups. RR increased significantly more in control mice, whereas TV decreased to the same extent. MV decreased significantly more in the NO₂ mice.

These results indicate 1) that continual exposure to NO₂ for 3 days has no effect on subsequent respiration in clean air, but appears to blunt the irritant response to subsequent exposure to NO₂, and 2) that the depressed host resistance reported earlier is not caused by respiratory changes.

Key words:

• Respiration
• host resistance
• nitrogen dioxide