Just started my cpap treatment, 3 nights now. I'm waking during the night and in the morning with pain in my diaphragm region. Also having a little numbness/tingling in my arms and legs. Any one else experience these types of side effects?

Are you sure it isn't gas that's causing the pain?  One of the problems I face is gas as the machine forces air into my stomach.  If you have a hiatal hernia the flap won't keep the air from building up and thus you get gas.  As for the tingling in the fingers it could be a pinched nerve in your neck or TMJ.  I used to wake up with my thumb, pointer finger and middle finger completely numb.  Sometimes it would take a while for that to go away although I found that if I tipped my chin up (head back) it helped.  Don't know about the tingling in the legs unless you also have sciatica.  It took a full-face mask with the bottom resting on my chin or just under my chin to relieve most of the numbness in my fingers.  Think it was the repositioning of my jaw that did it.  Hope that helps.  There's not much you can do about the gas except for belching and lying on your left side (seems to help bring it up).  The doctors will tell you to raise your head or try all sorts of things but not much will relieve it.  Even Gas-Ex doesn't do much.

it may be from the muscles used for breathing as they adjust to your CPAP, if so have long soaks in hot bath, maybe take painkillers and your muscles should soon adapt

during the day, take deep slow breaths for exercising the muscles


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resmed S6 lightweight, respironics comfort gell mask using CPAP since 1995, no humidifier
during my many years of severe fatigue, no doctor ever asked me if I snored