Most people have a shallow breathing pattern. It’s alot to do with 21st living – day to day stresses/anxieties. This means the breathing will mainly take place in the upper part of the chest, while the rest will not be used. This is very inefficient as vital capacity will be reduced, and more breaths per minute will be used, along with more energy too.
A better breathing cycle begins much lower – in the belly, and gradually fills the thorax in a 3-D action[/i].
This means expansion is outward to the sides as well as upward and forward. This will massively increase vital capacity, produce a slower breathing rate, and mean you can climb faster and for longer.
To the OP – your mild asthma means you can breath in OK, but you may have more difficulty breathing out occasionally. Diaphragmatic breathing may be beneficial in your case. Focus on the movement – filling out to the sides etc at the level of your lower ribs…
Have fun experimenting and see the difference