Respiratory Dead Space Increase Following Atropine in Man, and Atropine, Vagal or Ganglionic Blockade and Hypothermia in Dogs

Abstract

Tracheal and bronchial muscles in normal man have a significant degree of tone. The usual preoperative dose of atropine in man blocks this tone and enlarges the anatomic dead space (Fowler''s technique) by about 40 ml or 30% (in 6 subjects). The dog dead space (using articicial respiration) was increased 50-90% by any of the following: atropine, hexamethonium, Arfonad, vagotomy, and immersion hypothermia to 24[degree]C. It was shown that anatomic dead space could be increased by broncho-dilatation simultaneously with terminal bronchiolar constriction produced by histamine released by Arfonad in dogs. The physiological dead space determined from arterial CO2 tension was also somewhat increased by these drugs. The size of the anatomic dead space provides a good index of bronchial constriction.