Strangers in the Night
It’s very important that a mask have a vent to clear exhaled carbon dioxide. Never cover the mask vent with bed covers. Allow it to vent. When you get the mask, ask the technician to show you the vent. Vents may be hard to see. If you don’t know where the vent is, put on the mask, turn on the machine, and feel where air is coming out. Unfortunately, almost all vents are placed to vent forward from your face so air blows on your hand, arm, or bed partner. You can learn to sleep with your arm under a cover or pillow and barricade your partner. You can wear long sleeves and even gloves, if you don’t mind looking like Mickey or Minnie Mouse. Most pharmacies sell soft white cotton gloves, worn for hand ointment, behind the counter. If you have a tolerant and resilient bed partner, you need to find creative options so they don’t get caught in nightly windstorms.
One well designed mask vents straight upward, like a chimney, towards the headboard. It doesn’t vent on your forehead, arm, or partner. It’s a nasal pillow mask, the Headrest Twilight NP. See https://www.cpap.com/productpage/aeiomed-aura-nasal-cpap-interface.html As time goes on, more mask manufacturers may learn to make masks vent less violently.
Leaks are good and bad. A good leak is called the vent flow rate or flush rate, airflow through the vents, purposely designed to flush away exhaled carbon dioxide. Leakage above that rate is a bad leak from a poorly selected, sized, or fitted mask, leaking because it doesn’t rest securely on your face or nostrils. The higher the pressure, the higher the vent flow rate and bad leak rate. Wash your face to remove facial oils before using a mask, and avoid skin moisturizer on your face at night. The mask shouldn’t leak into your eyes (causing conjunctivitis) or anywhere else around its seal. For subtle leaks with nasal pillows, you may not be able to detect leaks by how they feel on your face. Use your hand to feel around the mask for leaks. Another way to detect leaks is by sound. If your mask turns into a sonar device, echoing a new sound off of bed pillows, you have a leak. If your full face mask makes a rude raspberry noise or turns into a wind instrument, you have a large leak.
Some masks are made to “hydroplane” on the face, floating on air for a seal. To adjust it, pull the mask away from your face momentarily so it can inflate and float again. Use sound and hand to detect loose hose connections in your machine around the humidifier connection. If your mask leaks, a very common occurrence, keep experimenting with adjusting it and improvise ways to get a custom fit. If you’ve had the mask for a while and then it begins leaking, check the age of the silicone cushion or nasal pillow. The cushion or nasal pillow (not the whole mask) should be replaced every three months or when worn out. Insurance companies start with Medicare guidelines to design their replacement schedule. See Medicare replacement guidelines at http://www.billmyinsurance.com/cpap-faq/Medicare.html#14
For a discussion thread on interpreting leak rates, see http://www.cpaptalk.com/viewtopic/t14536/Meaning-of-System-Leak-Numbers.html
For a table of vent flow rates of various masks compiled by cpaptalker dsm from other users quoting the manufacturers’ published vent flow rates, see http://www.internetage.com/cpapinfo/leak-rates-1.html. The numbers along the top line of the chart are machine pressure in cm/H2O. This table is useful if you want to compare the necessary vent flow rate with the leak rate shown by your machine software. The difference allows you to assess how badly your mask is leaking due to a poor fit.
It may take several weeks or months of fiddling with your mask and learning to sleep with it, using a data-capable PAP machine with software to track results, before you achieve a satisfactory low level of leaks and AHI (apnea hypopnea index) with a particular mask. You may need to adjust machine pressure up or down for each mask. Learning when to give up, and when to keep trying, only comes from experience. If you give up on a mask, try it again several months later to see if now you can make it work.