The studies on dogs are divided into 2 general types: those
employing animals exposed by normal inhalation, and those
using a tracheotomy with insertion of a cannula to form a
tracheostomy. Tracheostomy is clearly extremely invasive
and nonphysiologic , introducing smoke directly into the
trachea and bypassing the nasal passages and the larynx.
Most of the studies involving tracheostomies report
large numbers of deaths, with lung infections also being
very common. Dosimetry data are rare in these papers,
and in most cases only small numbers of animals were
used.