COLIN LAMB wrote:

Question - will the reading of the pulse oximeter discriminate against
carbon monoxide?

Great question Colin. The answer is NO. I had to look it up (from an article in the
medical literature by Neil B. Hampson):

"Presently available pulse oximeters overestimate arterial oxygenation in patients with
severe CO [carbon monoxide] poisoning. An elevated COHb [carbon monoxide bound to
hemoglobin] level falsely elevates the [level of oxygen in the blood] as measured [by]
pulse oximetry, (CHEST 1998; 114:1036-1041)"

What this means is that carbon monoxide, when attached to a hemoglobin molecule (which
carries oxygen within red blood cells) fools pulse oximeters into thinking there is more
oxygen in the blood than there really is. This is not surprising, since oximetry
basically does an analysis of blood color (the redder the blood, the more oxygen it
should be carrying). One way to guess that a patient has carbon monoxide poisoning is
that their skin and lips frequently look very red.

In other words, does the use of a pulse oximeter reduce the need of a carbon
monoxide detector? If carbon monoxide replaces oxygen, then the % of oxygen
would decrease and the oximeter would drop substantially when carbon
monoxide is present? Right?

Wrong. Although carbon monoxide does replace oxygen on the hemoglobin molecule, it fools
the oximeter in thinking there is more oxygen, when there really is less.

Regards,
Jim Skydell