Exhalation happens if the diaphragm relaxes, returning to its dome form and pushing air out of the lungs. This rhythmic contraction and rest are essential for keeping normal respiratory and making certain suitable oxygen source to your body.Ti?p theo, ki?m tra ??nh k? h? th?ng van c?a b?m c?ng là c?n thi?t. Van có th? b? t?c ngh?n do c?n b?n t? c