Ra, the sun, fought the big serpent Apap, as Indra fought Vrittra.
In Egyptian mythology the serpent Apap with an army of monsters strives daily to arrest the course of the boat of the luminous gods.
Well-fitting CPAP masks are critical for property delivery of the air from a CPAP (Continuous Positive Airway Pressure), BiLevel or VPAP (Variable Positive Airway Pressure) or an APAP (Automatic Positive Airway Pressure) machine.
The patient adjusts the traditional Continuous Positive Airway Pressure device whereas the APAP machine's pressure adjusts on its own.
They may be prescribed BiPAP or APAP machines, depending on their specific needs.