Didgeridoo playing as alternative treatment for obstructive sleep apnoea (2006)
https://pmc.ncbi.nlm.nih.gov/articles/PMC1360393/It worked
It took me 1-2 years to learn circular breathing, but even just learning to play for 15 seconds on one breath can give the "oxygen high" from breathing so much.
"Participants received a standardised acrylic plastic didgeridoo that was developed by the instructor in collaboration with Creacryl GmbH (Ebmatingen, Zurich, Switzerland, and costs €80 (£43; $94), fig 1). The didgeridoo is 130 cm long with a diameter of 4 cm and an elliptical embouchure with a diameter of 2.8-3.2 mm. Acrylic didgeridoos are easier for beginners to learn on than conventional wooden didgeridoos."
Check out the papers on Inspiratory Muscle Training (IMT) and bridge swallowing.
Original paper: https://www.bmj.com/content/332/7536/266
https://www.youtube.com/watch?v=wNscQ3bGxNk
...along with various other videos on that person's youtube channel (he's an NHS Sleep and Ear Surgeon).
Of course, there are lots of underlying causes of sleep apnea that vary between people, so what helps one person may or may not be relevant for others. Seeing a doctor in the field should be your first step if you suspect you are suffering from sleep apnea.
Oh, did you make use of the central telephone service did you? You didn't send the list by carrier pigeons?