In many countries, PAP machines are only available by prescription. A sleep study at an accredited sleep lab is usually necessary before treatment can start. This is because the pressure settings on the PAP machine must be tailored to a patient's treatment needs.
The pectoralis major muscle also performs internal rotation -- turning your arm in toward your body. This action, also called medial rotation, is important for reaching behind your back to tuck in your shirt and combing your hair on the opposite side of your head.
Your pectoralis minor does do some of the work, as do the biceps, shoulders and other muscles of the back -- but for the most part, the pull-up is a lat exercise. The pectoralis major, the larger of the two pectoral muscles, is not activated much at all by pull-ups.