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Alveolar air is
best obtained by asking the person to breath out into a long tube. The air first exhaled
is really coming from the conducting airways, not in contact with capillary blood, and
from a tap in the tube close to the mouth a sample of air is taken toward the end of
exhalation. A more convenient way is to have the person breathe out through a short tube
and capping the tube (both ends) at the end of exhalation. The tube can then be shipped
for analysis. Exhaling into a bag is OK, there is some dilution from the conducting
airways air, i.e., dead space volume. The proper term then is "mixed exhaled
air". See Stewart, R. D., Hake, C. L. and Peterson, J. E. Use of breath analysis to
monitor trichloroethylene exposures. Arch. Environ. Health, 29, 6-13, 1974. |