The sleep medicine industry uses compliant long term cpap patients as the denominator in order to conclude it’s “extremely effective”. If you stop cpap therapy after a year (or even years!) of it not working, they will blame patient compliance not the machine. The machine manufacturers (who incidentally happen to fund most sleep research) have made a variety of machines and settings, and thus there is always another setting to adjust or device to try before concluding cpap won’t help. The assumption is that it’s “extremely effective” and thus, all failures are attributed to compliance. “You just need to find a better doctor to help with the titration”, or “you need a different type of mask”, or “turn off the autoset and up the pressure”, or “it can takes years to adapt to the machine and see improvement”, or my favorite “you may feel much worse and get very little sleep but the science says you need cpap, even if it’s not helping the apnea and maybe even making it worse.” Indeed, the research literature show cpap is potentially iatrogenic, inducing or increasing (central) sleep apnea in some patients. The solution the industry has marketed, a different type of cpap device for CSA called asv, about twice the cost of a regular cpap, actually increased mortality in a major trial iirc. So yeah, if you don’t give up after years and dozens of machines and doctors and weekly titration appointments and none of that helping at all and maybe even making the apnea worse or even killing you (if you have HF, the main cause of CSA, then yes, cpap is “extremely effective” or there wouldn’t be a multibillion dollar business behind it propped up by insurers who can presumably use cpap patient non-compliance to deny future insurance claims related to the cardiovascular system or metabolic dysfunction.