As someone with asthma and lowered ability to cycle out CO2, yawning has always helped me restore the “full” feeling and your comment just made everything snap into place.
The primary driver of suffocation panic, pain, and feeling of air starvation isn’t the lack of oxygen but CO2 buildup. It makes sense that yawning on command could then help alleviate the symptoms of CO2 buildup in asthma sufferers.