Increasing duration of smoke exposure induces more severe lung injury in sheep

Eighteen sheep previously prepared for chronic study were divided into three groups of six animals each. These were given graded inhalation injury utilizing smoke obtained from burning cotton-toweling material. Smoke was insufflated into animals with a modified bee smoker at temperatures <40°C. Group H, which received 64 breaths of smoke, showed the most pronounced changes in pulmonary function. The changes consisted mainly of a profound increase in lung lymph flow following a reduced P/F ratio (PO₂ in arterial blood/inspired O₂ fraction) and an elevation in both thermal and gravimetrically measured extravascular lung water. Similar changes were seen in group M (48 breaths of smoke) and group L (32 breaths of smoke). However, the injury was graded based on the changes in gravimetrically measured lung water and lung lymph flow. These were highest in group H and lowest in group L. These studies confirm our ability to accurately quantitate the injury induced by smoke inhalation. In addition, it demonstrates that lung injury associated with the inhalation of smoke can be graded depending on the duration of exposure.