Bends and Low Altitude
That is correct. The bends has different forms but is basically a problem with nitrogen which has bubbled out of the tissues or blood rather than being returned to the lungs and expired normally.
This will have occurred with a reduction in ambient pressure as the diver ascends from depth. Ambient pressure is further reduced (at an additional 1mb per 27ft agl) which could permit the offending nitrogen bubbles to further grow and therefore cause further damage.
Thus, it is preferable when transporting bends victims to fly them at the minimum altitude that the flight can be still be conducted safely thereby minimising bubble growth.