There is a balance that your body regulates in between the Oxygen (O2) and Carbon dioxide (CO2) in your body. You are prone to this hyperventilation if you have emphysema component to your COPD. You can't expel all the CO2 because of lost elasticity in your lungs. When your CO2 levels are high, your brain signals your body for more O2 causing you to feel breathless and that breathlessness causes too shallow of breathing with a panic feeling. Then the O2 level gets too high and the cycle repeats itself. Pursed lip breathing helps you expel the CO2 and also to calm this response. Some folks on here do not describe it quite right so if it is not done right, it does no good. It is simple but must be practiced because it is not the normal way we breathe. Close your mouth and breathe in through your nose to the count of 4 to 6 if you can. Then purse your lips in a tight grimace with a very small opening (like a slit and not an "o") breathe out evenly as you can for double the count. So if you breathe in for 4 counts try breathing out through pursed lips to 6 or 8 if you can manage. The resistance of the breath through the tightened lips helps expel the CO2. Do this when you feel short of breath and it will help regulate your breathing better after about 4 times. Try not to rush through if you are very short of breath because you will be hyperventilating. I found it easier to learn by a respiratory therapist demonstrating it to me and following along with her until I learned it. It won't work if you are puckering up like a whistle, as there is not enough resistance. Hope this helps...looks like I wrote a novel! So breathe in through your nose only counting 1-2-3-4 then out through tight lips, 1-2-3-4-5-6.

HYPOVENTILATION.: is when there is a REDUCED AMOUNT OF AIR entering the Alveoli in the Lungs, resulting in Decreased levels of Oxygen and Increased Levels of Carbon Dioxide in the Blood. .

It is basically... Breathing that is Too Shallow or Too Slow, or to Diminished Lung function.

HYPERVENTILATION is the OPPOSITE.....When Breathing is Too Fast or Too Rapid than Normal.

When we have COPD the lungs appear larger because we aren't expelling all the air. The alveoli get stretched and then cause decreased expiration. I too have hyper ventilation on both lungs; it is better common as COPD progresses. That is the best I can explain my limited knowledge

hypoventilation: n: deficient ventilation of the lungs that results in reduction in the oxygen content or increase in the carbon dioxide content of the blood or both. This came from my medical dictionary.
I did read the above explanation and do agree with pursed lip breathing. Breathe easy my friends.

Hyperventilation is rapid or deep breathing that can occur with anxiety or panic. It is also called overbreathing, and it may leave you feeling breathless