CO2 is actually a remedy for Asthma and Hyperventilation
The Buteyko Breathing Technique is based on the premise that raising blood levels of carbon dioxide through shallow breathing can help people with asthma. Carbon dioxide is believed to dilate the smooth muscles of the airways.
A study involving 60 people with asthma compared the effects of the Buteyko Breathing Technique, a device that mimics pranayama (a yoga breathing technique), and a placebo. Researchers found people using the Buteyko Breathing Technique had a reduction in asthma symptoms.
h/t to Marc Morano