Hyperventilation

Hyperventilation is breathing in excess of what the body means blowing off too much CO2 thereby LOWERING the CO2 level beneath 35 mmhg. Hyperventilation is breathing that is deeper and more rapid than normal. It causes a decrease in the amount of a gas in the blood (called carbon dioxide, or CO2). This decrease will cause a patient to be lightheaded, have a rapid heartbeat, and be short of breath. It also can lead to numbness or tingling in your hands or feet, anxiety, fainting, muscles spasms and cramping, and sore chest muscles.Hyperventilation causes the carbon dioxide level in the blood to decrease. This lower level of carbon dioxide reduces blood flow to the brain, which may result in the following nervous system and emotional symptoms.

• Weakness
• Fainting
• Dizziness
• Confusion
• Agitation
• A feeling of being outside yourself
• Seeing images that aren't there
• Feeling as if you can't breathe

Overbreathing can also cause the calcium levels to drop in your blood, which may result in the following nervous system symptoms:

• Numbness and tingling (usually in both arms or around the mouth)
• Spasms or cramps of the hands and feet

(Carpal Pedal syndrome....Hand or foot spasms: MedlinePlus Medical Encyclopedia)

• Muscle twitching

Many different factors can cause chest symptoms with hyperventilation syndrome. Normally, breathing is relaxed. If a person over breathes, the lungs become overinflated. Without thinking about it, the person might use the chest muscles to expand the rib cage. This extra muscle work will feel like shortness of breath, and the person will have difficulty taking a deep breath. The chest muscles will become tired, just like the legs tire after a long run. The lowered carbon dioxide levels in the blood can cause squeezing of the airways, which then results in wheezing.
Hyperventilation Causes, Symptoms, Treatment - Hyperventilation Symptoms on eMedicineHealth

When you are breathing too fast or taking frequent deep breaths you blow off too much C02 there fore DECREASING CO2 levels dropping them below 35 mmhg. 
Medscape: Medscape Access Hyperventilation Syndrome requires registration but it's free and a great resource.

HYPOVENTILATION
The respiratory system serves a dual purpose: delivering oxygen to the pulmonary capillary bed from the environment and eliminating carbon dioxide from the blood stream by removing it from the pulmonary capillary bed. Metabolic production of carbon dioxide occurs rapidly. Thus, a failure of ventilation promptly increases the levels of carbon dioxide measured by arterial blood gas analysis (PaCO₂) greater than 45mmHg.Medscape: Medscape Access
Hypoventilation Syndromes Alveolar hypoventilation is defined as insufficient ventilation leading to an increase in PaCO₂ (ie, hypercapnia). 

hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate(hypo means "below") to perform needed gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapnia) and respiratory acidosis