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.
Edit: SpO2 is the Saturation (peripheral) of Haemoglobin with Oxygen, expressed as a percentage ration compared to fully saturated Haemoglobin (Hb).i.e. when the Haemoglobin (the main oxygen carrying component of blood, found in red blood cells) is fully loaded with oxygen, then is it 100% saturated.t is SpO2, because this is normally measured by placing a probe on the finger which shines red light of two different types through the finger, and a calculation is carried out based on how much of each type of light is absorbed, which tells us how much the Hb is loaded up or saturated.