Search

This experiment provides an introduction to the fate of nicotine in the body and served as an excellent vehicle to teach some analytical techniques.

Oxygen transport in the lungs from the alveoli to the hemoglobin is affected by a number of resistances: the pulmonary membrane, plasma, the red blood cell membrane, and the paracrystalline material inside the red blood cell (Figure 1). The pulmonary membrane which separates the alveolar gases from the blood stream consists of three parts: a thin alveolar membrane, interstitial fluid, and the capillary wall (44). The thickness of the total membrane is a few microns, and is, essentially, an aqueous medium. Plasma is an aqueous solution containing dissolved proteins, inorganic salts, and solutes of diverse organic compounds other than protein (54). The red blood cell consists of a biological semipermeable membrane surrounding a concentrated hemoglobin solution.

In the consideration of the gaseous diffusion capacities of the pulmonary membrane, the blood plasma, and the red blood cell, it has been calculated that the pulmonary membrane, and, in particular, the blood plasma may be major resistances to the gas transfer from the alveoli of the lungs to the hemoglobin molecules of the red cells. In vitro measurements of the effect of plasma protein concentrations on the diffusivity of oxygen show that the diffusivity can undergo a fivefold change as the plasma protein concentration is varied between the extremes of the normal physiological range. As a result, it appears that the overall gas transfer may be affected and possibly limited by altering the gaseous diffusion coefficient in plasma through changes in the concentration of the plasma proteins.