hyperventilation is the state of breathing faster or deeper (hyper) than necessary, and thereby reducing the carbon dioxide concentration of the blood below normal. This causes various symptoms such as numbness or tingling in the hands, feet and lips, lightheadedness, dizziness, headache, chest pain, slurred speech and sometimes fainting.
The reason it causes the blood pH to increase is because of the levels of carbon dioxide...carbon dioxide gets converted into bicarbonate and hydrogen ions. So basically a decrease in carbon dioxide levels in the blood will increase the pH of blood. The reason is because carbon dioxide breaks up into bicarbonate (H2CO3), which is a buffer used to maintain blood's pH. But if there are not enough carbon dioxide molecules then there will be no dissociation and therefore an increase in pH. Since pH is a measure of the activity of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. pH= pK+Log [HCO3-]/[H2CO3] determines the pH of blood.