Faculty Bibliography

Airflow distribution through the tracheobronchial tree is influenced by many factors. In a hollow cast of the central airways, the only factors involved are resistance and inertia of the airflow. Distribution of steady flow during both inhalation and exhalation was measured at different total flow rates in human and canine tracheobronchial casts. The resulting airflow rates in peripheral segments were measured with a sensitive apparatus, which did not disturb the distribution of flow. Inertia of the airflow was found to be small but significant in airways of the human cast and substantially greater in the canine airway cast than in the human cast during inhalation. The influence of airflow inertia during inhalation was largely responsible for the different distributions of flow during inhalation and exhalation through the airway casts. Airflow resistance was found to be considerably greater during exhalation and may have contributed to the redistribution of flow. The forces involved are small but should be considered when modeling the in vivo distribution of airflow

Measurements of flow rates through hollow casts of human and canine tracheobronchial airways, which extend from just below the larynx to airways 1 mm in diameter, show basic similarities in the distribution of air flow and also species differences which must be considered. The distribution of air flow, for both constant and pulsatile inspiratory flow, was measured for minute volumes equivalent to 6, 11, 17 and 22 L min-1 for the human and 3, 6, 8, and 11 L min-1 for the dog. Inertia of air flow (inertance) was found to carry more of the flow to airways of the lower lobes at higher flow rates. Basic differences in airway branching pattern result in a more distinct change in airflow distribution as flow rate changes for the canine cast as compared with the human cast. These differences should contribute to differing patterns of mass transfer of inhaled particles and gases in central airways of the two species

The podiatrist should remain alert to the potential for exposure to hazardous agents such as those discussed in this article. Exposures in the office or hospital may be evaluated by the methods of industrial hygiene. If control is needed, simple measures can frequently effect substantial reduction in exposure and afford protection to the physician, staff, and patient