Don't waste your breath

Our lungs are membrane system that allows the exchange of O ₂, CO ₂, and H ₂O between the body and the air. When air is inhaled, oxygen is transported to the blood by diffusion through the alveolar membrane of the lungs. Carbon dioxide, a waste product produced by cells, is simultaneously removed from the blood by diffusion through this membrane to the air in the lungs, and is then exhaled. During breathing, the air in the lungs becomes saturated with water, and water is therefore removed from the body through respiration. Breathing also plays a role in heat transfer and thermal regulation, since heat transferred to the air in the lungs is removed during exhalation. We have developed a hands-on experiment to introduce freshman engineering students to chemical engineering principles through the exploration of the breathing process. The objectives of this module are (1) to analyze the lungs as a mass transfer device, (2) to use gas analysis to investigate the rate of O ₂ consumption and CO ₂ production, (3) to perform simple mass and energy balances on the lungs, (4) to prepare a simple process flow diagram, and (5) use a process simulator to perform mass and energy balances.