It may begin with shortness of breath or perhaps a recurring cough as you inhale. Your ability to take in more air becomes impeded--for any number of reasons. The bottom line is that your body is not receiving the oxygen it requires, and when that happens, your body lets you know it. Exhaustion, depression, lack of focus, and dizziness can all set in, not to mention the organ damage created by a lack of oxygen. Prescription medications or an oxygen...