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Relationship of expired carbon monoxide (CO, ppm) to blood carboxyhemoglobin (COHb, %). The handy conversion table at right can be used for quick reading (Thanks to Bacharach).
Method: The victim inhales ambient air, holds his/her breath for 20 seconds, then expires about 1/2 of his/her breath before inflating the balloon to a diameter of about 5 inches.
Shown at right is the Breath Analyzer Module (BAM) which attaches to the top of a CO monitor. The balloon holding the exhaled breath is in BLUE.
Reading: The CO monitor does not read out blood CO directly - this is done through use of a GRAPH (below, left) or a CHART/TABLE (below, right).
The horizontal scale is in parts per million (ppm) carbon monoxide as measured by the CO monitoring unit in the exhaled air in the balloon. Blood carboxyhemoglobin (COHb) concentration (or saturation) is read from the vertical scale by projecting up from the CO conc. to the heavy oblique line, and then left horizontally to the COHb scale.
For example, 100 ppm CO read from the CO monitoring unit would represent 15%-16% COHb. Normal COHb concentration for non-smokers is usually in the range 0.4% - 1.5%. Smokers usually have higher COHb concentrations depending on when the last cigarette(s) was smoked, etc.
.... Relationship of expired carbon monoxide (CO, ppm) to blood carboxyhemoglobin (COHb, %). The handy conversion table at right can be used for quick reading (Thanks to Bacharach).