The Role of Probability. Basic Concepts of Probability. A probability is a number that reflects the chance or likelihood that a particular event will occur. Probabilities can be expressed as proportions that range from 0 to 1, and they can also be expressed as percentages ranging from 0% to 100%.
Thus, when people hypoventilate (i.e. causing an increase in CO2) this causes the pH in your blood to decrease, making it more acidic. (and when hyperventilation occurs, O2 is increased, which causes an increase in pH - making blood more basic).
Alveolar hypoventilation is caused by several disorders that are collectively referred as hypoventilation syndromes. Patients who hypoventilate may develop clinically significant hypoxemia, and the presence of hypoxemia along with hypercapnia aggravates the clinical manifestations seen with hypoventilation syndromes.