Low alveolar PO2 can be caused by one of two mechanisms. One of them is that the inspired air has low oxygen content. What is the other reason? Low alveolar PO2 can be caused by one of two mechanisms. One of them is that the inspired air has low oxygen content. What is the other reason?a) Hypoventilation b) Low hematocrit c) High altitude d) Low hemoglobin concentration.