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.
The decrease in barometric pressure with increasing altitude reduces PAO 2. PAO 2 decreases from 103 mm Hg at sea level to 81 mm Hg in Denver, Colorado (5280 ft [1609 m]) and to 48 mm Hg at the top of Pikes Peak (14,110 ft [4301 m]).s the altitude increases, barometric pressure decreases. This decrease in barometric pressure affects the partial pressure of alveolar oxygen (PAO 2). The percentage of oxygen remains stable at about 21%.