Mechanism of bronchoconstriction during inhalation of sulfur dioxide

Inhalation of SO 2 (4–6 ppm) for 10 min decreased airway conductance (increased airway resistance) in seven healthy subjects. Subcutaneous injection of atropine prevented this effect. In anesthetized, paralyzed, artifically ventilated cats, SO 2 increased pulmonary resistance, whether delivered to the upper or to the lower airways. This was prevented by complete cold block of the cervical vagosympathetic nerves or by injecting atropine intravenously before the SO 2 was inhaled. These results establish the reflex nature of bronchoconstriction during inhalation of SO 2 . Note: With the Technical Assistance of Earl H. White reflex bronchoconstriction; airway resistance Submitted on February 18, 1964