Can the brain be deprived of oxygen during swimming?

Question
George,

I am a special education teacher.  I was a collegiate athlete (basketball) and coached and taught physical education for over 20 years prior to entering the field of special education 8 years ago.

I have been working with an autistic student in the pool for 8 months. He is seven. In the beginning, he refused to put his face in the water...today he is swimming up to 20 laps, freestyle, including flip turns.

His level of fitness is vastly improving, which is what the parents want. However, the swimmer does not understand the concept of speed.  I am having a difficult time challenging his level of conditioning because he does not understand the concept of speed.  I have begun challenging him by asking him to complete more strokes per breath.  He consistently completes 6 strokes per breath, but is able to complete 10 to 12 before breathing.  I find this challenges his heart lung development and his level of fitness is improving.

Could this be dangerous?  Is there any possibility that this technique would deprive oxygen to the brain and cause damage to my young swimmer?  Do you have any additional suggestions to increase his level of fitness when speed cannot be factored into the equation?

Thank you.  

Answer
Katie--First of all I admire what you are doing.  I spent 5 years working with Special Ed. kids and loved it, I had an incredible sense of joy with every accomplishment we had.  
As long as he isn't holding his breath for long periods(more than 1 lap of the pool), he isn't doing any damage and since you have him breathing every 6th stroke you're just improving is anaerobic conditioning(this is a good thing).  
As for other options, you can try isolating his arms(with a pullbouy)and his legs(kickboard).  As for speed, if he can see you when he swims, have him try to keep pace with you as you walk on the deck.  As he keeps up, try walking quicker.  This is just an idea, I'm not sure if it will work, but worth a try.
Best of luck, I hope this helps,
George