How come breathing in during inspiration is not affected by bronchoconstriction (asthma/copd)?

Negative pressure: When you breathe in, your chest wall and diaphragm expand and create decreased pressure in your lungs. Because the bronchoconstriction is also inside your lungs, the negative pressure causes the airway to expand as well, and air flows in easily. When you breathe out, the chest wall and diaphragm relax, and pressure in the lungs increases. This snaps the airways closed again, like a valve.