Continuous positive airway pressure (CPAP) machines are used to maintain an open airway in patients diagnosed with obstructive sleep apnea. The machine functions by blowing pressurized air into the airway via mask at a setting determined by sleep study and prescribed by a physician.
Only around 180 impact craters have ever been discovered on Earth and around 30 per cent of them contain important natural resources of minerals or oil and gas. The largest and oldest known crater prior to this study, the 300 kilometre wide Vredefort crater in South Africa, is 2 billion years in age and heavily eroded.
The largest volcano on Earth is Mauna Loa, Hawaii, with an  area of 5271 km2, more than half of the big island of Hawaii. It  is also the largest in volume, at more than 7â¦5,000 km3. The Mauna  Loa (long island) ridge extends for more than 120 km, but at  a slightly lower elevation than Mauna Kea to the north.    The largest volcanic crater in the continental US is the  Yellowstone supervolcano in Yellowstone National Park, in NW  Wyoming in the US.