the literature from experiments that replicate the rapid changes in CO concentrations measured in armored-vehicle cabins, that is, CO spikes of a few seconds durations. There are also no results reported in the literature from experiments that replicate changes in pulmonary ventilation found in armored-vehicle personnel. Two issues need to be addressed:

  • Do the high CO concentrations found during spikes influence CO uptake, and how can these data be used to obtain a relevant “normalized” inspired CO to plug into the CFK equation?

  • Do increases in workload and ventilation in armored-vehicle personnel augment CO uptake? Previous studies used inspired CO concentrations in excess of those found in armored-vehicle cabins, and data need to be obtained using lower CO concentrations.

The committee recommends that the Army conduct three types of experiments using human subjects to address those issues. Details on methods for each experiment are provided in Appendix C.

  • Experiment 1. Effects of rapid changes in inspired CO concentration at a constant rate of ventilation. This experiment will have one part that addresses the relationship of inspired CO concentrations to CO uptake. The other part will evaluate the CFK equation.

  • Experiment 2. Effects of rapid changes in ventilation at a constant inspired CO concentration.

  • Experiment 3. Effects of simultaneous increases in inspired CO concentration and ventilation on CO uptake, venous blood COHb, and COHb predicted by the CFK equation.

The CFK equation could be evaluated by using animals, such as dogs or cats. However, there are numerous practical arguments against substituting animal data for human data: (1) animal testing would require anesthesia, and the animals could not exercise; (2) animal testing would require development of new approaches. Because experimenters would probably not have previous information in the diffusion capacity and other pertinent variables, they would need to be measured; (3) whereas equipment for conducting experiments using human subjects is already present in pulmonary-function laboratories, such equipment would need to be developed and/or procured for a comparable animal study; (4) the study of effects of increases in ventilation could be performed using animals but would be associated with decreases in arterial oxygen tension and increases in blood pH, which could complicate findings; (5) the results from animal experiments would not be as relevant to the Army’s questions as would results obtained using human subjects; and (6) unlike the case for humans, there is no database from previous animal studies to which to relate results.



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