My wife has been diagnosed with sleep apnea and uses a CPAP machine. It does not seem to help. When she sleeps without the machine and I feel her ribcage, I notice that she holds her abdomen very rigid - almost like a ValSalva maneuver - when she inhales. The degree to which she contracts these muscles makes her sort of "twitch" or "bend in" when she tightens the abdominal muscles. So she is breathing while holding her diaphram and abdominal muscles very rigid. I have felt her doing this for up to 2 hours with no break in the rhythm. Is this a form of sleep apnea? I'm not convinced she has apnea. She has a definite breathing disorder but I can't find any information on one with symptoms like this.