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.
PO2 (partial pressure of oxygen) reflects the amount of oxygen gas dissolved in the blood. It primarily measures the effectiveness of the lungs in pulling oxygen into the blood stream from the atmosphere. CO2 content is a measurement of all the CO2 in the blood. Most of this is in the form of bicarbonate (HCO3), controlled by the kidney. A small amount (5%) of the CO2 is dissolved in the blood, and in the form of soluble carbonic acid (H2CO3). For this reason, changes in CO2 content generally reflect such metabolic issues as renal function and unusual losses (diarrhea).