Take a look at the following two videos. The First Lady to the United States; Michelle Obama has changed from mouth breathing to nasal breathing as illustrated by the following two videos:

As Mrs Michelle Obama demonstrates, breathing through the nose is imperative for good heath, alertness and productivity. Conversely, mouth breathing has the opposite effect often resulting in stress, fatigue, respiratory complaints and poor concentration. Mouth breathing causes a disturbance of blood gases resulting in less oxygen been delivered to the brain. The first step of the Buteyko Breathing Method is to learn how to unblock the nose and switch to nasal breathing on a permanent basis.