A method for measuring nasal and lung uptake of inhaled vapor

This paper describes apparatus and methods for measuring uptake of inhaled vapors in the nose and lungs of dogs. The system allows sampling of air from the trachea at specific times during inspiration and expiration without surgical manipulation of the animal, thus allowing repeated studies in the same animal. During exposure, the dogs are anesthetized and cyclic respiratory patterns are maintained by means of an external respirator. A pneumotachograph installed in the exposure line is connected to a respiratory monitoring system that both monitors the dog's respiratory pattern and triggers sampling at specific times in the respiratory cycle. Air sampling, both at the nose and within the trachea, can be done during the entire breathing cycle or during specific portions of it. Vapors are sampled at a point just external to the dog's nose and from within the trachea through a modified endotracheal tube. To develop and demonstrate the system, three beagle dogs were exposed to 2,4-dimethylpentane and 1.3-dioxolane at nominal vapor concentrations of 500 ppm; vapor sampling was triggered for the entire inspiratory and expiratory portions of the breathing cycle during 10-min exposures. After correcting data to account for vapor that desorbed from the nasal passages during exhalation (after initially being absorbed in the nose during inhalation), net nasal uptake of 2,4-dimethylpentane was 28.3%; net nasal uptake of 1,3-dioxolane was 66.6%. Lung uptake was 14.0% for 2,4-dimethylpentane and 2.1% for 1,3-dioxolane. The system was developed for use with dogs, but it can be adapted for use with any animal species that can be intubated with endotracheal vapor sampling tubes.