I have obstruction in my nose much of the time, so bugs, beware (eecchh, cough, cough!!), but I noticed two things that are pertinent to this thread the last sunday when I took a long uphill ride...

1)when I am too tired to continue, it is better to stop altogether and rest two minutes than to walk the bike. I recover, and then can get back on with renewed strength.

2)forcing several all muscle (diagphram plus chest muscles) inhale hard breaths can clear some of the CO2 and lactic acid, allowing me a few more strokes before I have to quit. I can ignore the exhale, it is sufficient, but forcing a deep inhale invigorates me.

I totally agree that yoga helps develop a better breathing pattern for biking.. and living.