CPAP is rarely used by people with mild or moderate OSA because the benefits of the treatment are less than for those with severe OSA, but the hassle, cost and difficulty to tolerate remain the same. The only time CPAP would be recommended for someone with mild OSA is if they have significant daytime sleepiness, hypertension, heart palpitations or other OSA-related symptom and need to completely rid themselves of their sleep apnea.
Many CPAP machines now have comfort features to aid treatment adherence. Heated tubing keeps the air inside the tube from condensing against the sides of the tube and making gargling noises or spitting water into the user’s face. Condensation in a CPAP tube occurs when the relatively warm air inside the tube meets the walls of the tube which are cooled by the room air, especially on colder nights. The second main comfort feature commonly found in modern CPAP machines is pressure relief, which lowers the pressure by between 1cmH2O and 3cmH2O during exhalation. This makes it easier to breathe against the pressure and helps sleep onset.
A variant of CPAP is an automatic device known as APAP. An APAP machine can be set to a minimum and maximum pressure which allows the algorithm programmed in the machine to adjust the given air pressure depending on real time breathing patterns. This is especially useful for people whose sleep apnea varies greatly between different sleep stages or positions. The user can fall asleep with a relatively low pressure and only when the machine detects obstructed breathing will it increase the pressure until breathing becomes regular again.
BiPAP stands for Bi-level Positive Airway Pressure and is usually reserved for when CPAP is not able to adequately treat sleep apnea. BiPAP gives a higher pressure when the user breathes in than when they breathe out which aids comfort if a high pressure is needed and can force the body to breathe at a normal rate. It is effectively a more extreme version of pressure relief. Where the inhalation/exhalation pressure difference for CPAP pressure relief is between 1cmH2O and 3cmH2O, BiPAP’s pressure difference is between 4cmH2O and 10cmH2O. It is not the same as a ventilator, because although it has a lower pressure to breathe against, there is still a positive pressure coming from the machine. BiPAP is used when someone is intolerant of high CPAP pressures or if a high CPAP pressure is still unable to adequately treat sleep apnea.