THE RATE OF ELIMINATION OF DISSOLVED NITROGEN IN MAN IN RELATION TO THE FAT AND WATER CONTENT OF THE BODY

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Abstract
The inhalation of oxygen results in the elimination of dissolved body nitrogen in equilibrium with pulmonary N. The N content of a young, well developed man weighing 60 kgm. is 840 cc, or 14 cc. per kgm.; 98% of this is eliminated with oxygen breathing over a period of 6 hrs. If it is assumed that the body is 70% water, then 400 cc. of N are dissolved in water and 440 cc. in the body fat and lipids. Dividing 440 by the solubility coefficient of N in fat gives an estimate of 13.2% for the body fat, in contrast with 70% assumed for body water content. The fat from a well nourished dog of 12.2 kgm., extracted with CCl4, comprised 15.4% of the body wt. and the water 59.2%. If these values are multiplied by the respective solubility values of N in fat and water, the N content of the dog per kgm. is 142 cc, or approximately the same as that for man. N elimination follows an exponential type of curve, the slope of which is a function of the cardiac output. The cardiac output in liters can be estimated by dividing the value for N eliminated during the first min. by the quantity of N dissolved per liter of blood. The rate of absorption and the time of elimination of inhalation anesthetics can be estimated from the N elimination curve on the basis of the ratio (solubility in fat) / (solubility in water). During the decompression of divers who have been exposed for short periods (20 min.) to excess pressures, the fat and lipids of the body act as N absorbents and serve as buffers against bubble formation. Under these conditions rapid decompression from relatively high pressures can be safely effected.

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