Tissue tension, nitrogen

If we assume that all tissues have the same susceptibility to bubble formation, their inert gas tissue tension should be the same as the best experimental line for the PB data. By this method we can calculate back to determine what the time constant of these faster tissues would be in order to acquire this level of inert gas tension. When this is done, the tissue time constant is 6.3 minutes for the two-minute bottom time experiments. While this is significantly faster than the 25.5-minute constant measured for the slow tissues, it is still significantly greater than the slowest time constant measured in the nitrogen washout studies (Figure 12). Thus, it is assumed that the well-perfused tissues of the body would never be the sites of bubble formation for dives greater than two minutes. These data also confirm experimentally the generally held notion that there is a spectrum of response time for the body tissues. 

There are various factors that predispose to decompression sickness. Some of these are obesity, age, exercise, and CO2 accumulation. In general, older individuals are more susceptible to decompression sickness than younger persons this is apparently related to the status of the circulatory system. Increased physical activity results in more rapid saturation of the tissues per unit time than in a resting individual. This increased rate of tissue saturation is due to the increased rate of ventilation and circulation resulting in more rapid transport of nitrogen to the tissues. Due to their very rapid circulation and ventilation, small animals are more resistant than man to decompression sickness. Blinks et al. (B28) found that increased CO2 tension in the tissues lowers the threshold for bubble formation. Although the mechanism of this phenomenon is not known, there is reason to suspect that it may be due to the high solubility and diffusibility of carbon dioxide (H5). 

Figure 17. Effect of oxygen tension on concentrations of mobile phosphates in root tips. 145.7 MHz P-NMR spectra of maize root tips perfused with oxygen- or nitrogen-saturated 50 mM Glc/0.1 mM CaSO. The inset is an expansion of the ATP region of the spectrum showing very high ATP/ADP ratios in aerobic tissue. The concentration of cytoplasmic P, increases greatly in hypoxia. Reproduced, with permission, from [15], 1984, Annual Reviews Inc.

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