[donmoore]

Sebastian,
Was the oximeter connected to the finger? If so you might find this interesting, I asked Kirk Krack about why my SaO2% was falling so much on my pulse/oximeter after I started breathing. He said, “Remember that blood flow is greatly increased to the brain as blood vessels are dilated, while the circulation to the finger is decreased (peripheral shunting).”

So to paraphrase, the brain in the presence of CO2 increases the blood flow to it, but restricts the flow to the fingers and other extremities. When we start breathing it will take longer for new O2 to reach the fingers than the brain due to continued vasoconstriction. Therefore the SaO2% reading drops further than it really is. Actually the SaO2% reading really is that low at the finger, but its higher in the brain. Kirk said that this is less of an issue when connecting to the ear lobe.
don