Most of us are aware that a lack of oxygen to the brain results in brain damage. However many do not realise that even low levels or a small period of time of oxygen starvation can cause brain damage.
•    Even though the brain makes up only 2 percent of the average person’s body weight, it consumes 20 percent of its oxygen.
•    For every minute that the body goes without breathing, the risk of permanent brain damage increases greatly.
•    After 5 minutes without oxygen, brain cells begin to die off.
Some lung conditions greatly affect the amount of oxygen that the lungs can absorb from the air we breathe and with low oxygen levels it can lead to the brain being slowly deprived of oxygen and possibly result in minor or major brain damage.  Early symptoms of this can be chronic headaches, hypertension or even a heart attack or stroke. Over time there may only be small changes such as memory loss, confusion, difficulty in walking etc. or more major changes such as blindness, personality changes, speech/communication problems or a reduced ability to think flexibly, work through problems or be able to learn new things.
Sleep Apnea is also a worrying condition, which many people with lung conditions suffer from as during the night you can stop breathing for periods of time, even though maybe only for a short while. However each time it happens the chance of oxygen deprivation to the brain greatly increases and also the risk of brain damage. If you feel that you may be suffering from this condition then visit your doctor and you may be prescribed oxygen to have at night to increase your oxygen levels while you sleep.
For those patients using home oxygen therapy it is very important to ensure that the equipment is working correctly and that the flow rate of the oxygen being supplied by the machine is also correct. It may be only slightly out and not make a noticeable difference to your breathing, however even a slight lowering of oxygen levels over time, if left unchecked, may result in poor health implications on your organs, general health and your brain function, especially if there are other health problems you suffer with that may impact upon your oxygen levels.  This is why it is important to visit your doctor regularly and be monitored as well as to check your equipment at home on a regular basis. Discuss with your doctor or equipment provider about alternative equipment or other accessories or indeed other easy natural ways that you can ensure your oxygen levels remain as high as possible during day and night.
References: http://lunginstitute.com and http://www.braininjury-explanation.com