With a metal straw, you solve collapse, but you don't solve restrictive airflow. I'd just buy a breathing trainer with adjustable resistance (start low, set a

With a metal straw, you solve collapse, but you don't solve restrictive airflow. I'd just buy a breathing trainer with adjustable resistance (start low, set a time goal (e.g. 15 minutes once a day), and increase it one level every session until you fail, then move back one, do a few sessions, then try to move up, repeat).