Therefore, your PR interval may or may not be short and I wouldn't worry until you receive a full report. The PR interval is short in children and lengthens as we get older. A normal value in adults is 120 to 200 milliseconds. It is however shorter than 120ms in approximately 2 to 4% of the adult population.
It is SaO2 that measures oxygen saturation of hemoglobin, and it should be clear that it depends on the partial pressure of arterial oxygen. If PaO2 drops, there's less dissolved oxygen, and therefore less saturation of hemoglobin with oxygen.
SpO2 and SaO2 are two very different values. Sure, in some patients you can use SpO2 as a guide, but it doesn't always reflect what's actually going on in the blood, such as in cases of patients with septic shock. A good guide to help understand this is the oxyhemoglobin saturation curve.aO2 is an invasive measure of the % of Oxyhemoglobin (oxygen saturated hemoglobin) in the blood using lab tests on arterial blood. SpO2 noninvasive measure the % of saturated hemoglobin in the capillary bed and does not identify what is saturating the hemaglobin.