Auto-CPAP Vs. Fixed CPAP – What’s The Difference?

Obstructive sleep apnea (OSA) is a condition which, if left untreated, may lead to many adverse effects which include among others, heart disease, increased risk of depression, poor concentration, daytime drowsiness, and irritability. OSA is typically treated by continuous positive airway pressure (CPAP) therapy. CPAP machines come in a wide variety of modalities – the primary types being fixed and auto-CPAP. When you come into Dream Sleep Respiratory for your free sleep test, a Doctor specializing in sleep interprets these results and prescribes a pressure (fixed) or pressure range (auto-titrating) for one of our Respiratory Therapists to program into your machine. One is not necessarily better than the other. It’s all about a unique solution that works best for you and your airways. Let’s talk a bit more about what this actually means.

Fixed CPAP

Traditionally CPAP machines provide a steady or fixed pressure through a mask fitted specially for you at one of our locations. This pressure is based on your sleep study results and is chosen by our Doctor as an optimal pressure prescription to keep your airways open while you sleep, thus preventing any collapse. This in turn keeps your oxygen levels up rather than causing what we call an oxygen desaturation (when your oxygen levels plummet to a dangerous level). Desaturations are caused by airway obstruction (seen in OSA) and place added stress on vital organs like your heart, brain, liver, and kidneys. This puts you at an increased risk of heart disease and even stroke. CPAP prevents this by offering an optimal airway pressure to keep your airways open, which in turn maintains oxygen circulation in your bloodstream. When you come in to Dream Sleep Respiratory for your free follow-up visits with us, we are constantly evaluating if this fixed pressure is still your optimal pressure and we will make any changes deemed necessary.


Also known as APAP, auto-PAP, auto or self-adjusting CPAP, auto-CPAP offers a range of pressure, allowing the machine to titrate to the pressure you need at any given point in time. These machines have a built-in algorithm determining how much pressure is needed for inhalation with each breath you take. The theory here is that your pressure needs may vary on any given night, hour, or minute of sleep. There are a wide variety of scenarios in which this may be the case. Sleeping position is a prime example. In OSA, patients have apneas (brief periods where breathing stops). This is more common when a patient is sleeping on his or her back and this is due to the fact that when we lay flat on our backs, gravity takes over and the jaw and tongue naturally relax and fall back, occluding the airway and causing these apneas. These patients in turn would require higher titrated CPAP pressure while sleeping on their backs, but less once they turn on their side.

CPAP Equipment South West CalgaryPeople suffering from seasonal allergies or nasal conditions like polyps or rhinitis may also need higher pressures for part of the night or even on a seasonal basis. A congested nose brought on by a cold or flu can also cause worsening apneas in those of us diagnosed with OSA, but once you wake up and blow your nose, your pressure needs are less for the time being. People who have a few alcoholic beverages or take sedative drugs before bed may also require increased pressures, as alcohol and sedatives are collectively known to relax the jaw and tongue and increase one’s risk of airway obstruction and associated apneas (known as apneic episodes).  Over the counter cold and flu medications may also have the same effect. In conditions such as these, auto-CPAP can titrate to the pressure you need on a breath-by-breath basis.

Is There a Benefit to One Over the Other?

CPAP Equipment North East Calgary

A systematic review published in Sleep, a medical journal, compared and contrasted twenty-four randomized controlled trials comparing patients on fixed CPAP versus those using auto-CPAP. Both methods of CPAP pressure showed similar improvements in AHI (apnea-hypopnea index; an index our Respiratory Therapists use showing the severity of sleep apnea). Studies also showed no significant difference in blood pressure changes, adverse effects, and most importantly the quality of life, when comparing fixed versus auto-titrating CPAP. All in all, it comes down to your preference and unique lifestyle, as well as our Doctor’s recommendations based on your sleep study results.

CPAP Machines Red Deer

DSR is here to help!

At DSR, we offer the latest and greatest in CPAP technology, whether you are best-suited with a fixed pressure or an auto-CPAP machine. We will work with you and your insurance provider to find the best machine for you and your unique situation. We also offer a wide variety of mask options, offering you the best in value and comfort. We provide a free follow-up program with CPAP purchases from any of our locations and will always go out of our way to ensure your machine and its settings are working well for you. Contact us today if you have any questions!