How to determine your CPAP pressure setting

If you’ve been treated with continuous positive airway pressure (CPAP) for obstructive sleep apnea, you may be wondering: Is the severity of sleep apnea as measured by the Apnea Hypopnea Index (AHI) the same as what is needed for effective treatment? CPAP pressure related?

Learn how prescribed CPAP settings relate to the underlying degree of sleep apnea and what other factors may be involved in determining your best treatment, including anatomy, sleep position, and sleep stage.

This article discusses the sometimes inverse relationship between the severity of sleep apnea and the pressure setting on the CPAP machine. It also explains the key factors in determining the correct setup. In the end, it should make sense for a pressure setting to be recommended by a board-certified sleep physician.

sleep apnea severity

It is natural to assume that there is a relationship between the degree of obstructive sleep apnea and the prescribed CPAP pressure setting being treated. Consider an analogy: If you need a blood pressure medication, a higher dose will have a greater effect. Unfortunately, when it comes to treating sleep apnea, this relationship is not so straightforward.

Obstructive sleep apnea (OSA) is diagnosed by a nighttime sleep study or home sleep apnea test, which assesses the number of times per hour the upper airway collapses, causing a drop in blood oxygen levels or waking from sleep.

If the airway collapses completely, it is called apnea. If it partially collapses, it is called hypopnea. The total number of these events per hour of sleep is called the Apnea Hypopnea Index (AHI).

You might think that severe OSA requires a higher CPAP pressure setting to treat it. In practice, this is not always the case, as multiple factors are involved in determining the desired settings. Typically, therapy starts at a low setting and increases gradually to address all apnea and hypopnea events as well as snoring.

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The lowest setting on a CPAP machine might be 4 to 5 centimeters of water pressure (abbreviated as cm of H2O or CWP). Most people need more pressure than this low setting. The maximum setting varies by machine type, but can be as high as 25 or 30 CWP. The average setting is usually somewhere in between these two extremes.

Understanding AHI Ratings

The AHI values ​​and corresponding ratings are:

  • Less than 5 (<5): normal, meaning no sleep apnea
  • 5 to 15 years: mild sleep apnea
  • 15 to 30 years: Moderate sleep apnea
  • Over 30 (>30): severe sleep apnea

Determining the desired CPAP pressure

If CPAP settings are determined to be part of an overnight titration study in a sleep lab, then polysomnography The technician will watch your breathing pattern while you sleep and adjust the settings upwards. This is done remotely from another room so you won’t be disturbed.

The goal is to eliminate sleep apnea and snoring, and observe deep sleep, including rapid eye movement (REM) sleep. This setting should also be optimized during supine (supine) sleep, when sleep apnea typically worsens.

Some people go home with an auto-adjusting CPAP machine, sometimes called AutoCPAP or APAP. In this case, the prescribing doctor recommends a range of pressures. The machine will start from a low position and adjust upward based on the measured airway resistance (indicating continued soft tissue collapse, such as the base of the tongue or soft palate into the throat).

CPAP provides intermittent pulses of additional air pressure to assess resistance and, in turn, upper airway collapse. If the airway is open at the CPAP setting provided, keep that setting.

People with more severe sleep apnea often require higher CPAP pressures or even bilevel therapy, which provides varying degrees of stress. Children may require similar pressure levels as adults, despite their smaller overall size and smaller airway size.

Settings can violate assumptions

The required CPAP pressure is not always directly related to the severity of sleep apnea. Some people with mild OSA need high pressure, while some people with severe OSA need relatively moderate pressure.

Factors Affecting Pressure Settings

The anatomy of the upper airway and the nature of airway obstruction play the largest role in determining the desired CPAP pressure setting. If sleep apnea is due to allergies or a deviated septum (off-center nasal passage), a collapsed soft palate, or the tongue falling back into the airway, a different amount of air is needed to push these tissues out of the way.

Also, being overweight or obese may affect the settings. In fact, when people lose about 10% of their body weight, they may need to be adjusted by turning down CPAP settings.

Alcohol, drugs that relax your airway muscles (such as benzodiazepines), and sleeping on your back may all temporarily increase your stress needs. Finally, morning REM sleep may relax muscles and exacerbate sleep apnea.

Anatomical Effects Settings

Biggest impact on CPAP settings? The anatomy of the upper airway and the nature of airway obstruction.

Doctor knows best

Given these factors, it’s not always easy to determine how much CPAP pressure might be needed to treat sleep apnea. It can also be different at night, depending on your sleeping position and sleep stage.

If the pressure is too low, you may experience five or more episodes of sleep apnea and other symptoms, such as snoring or waking up gasping for air. If the pressure is too high, you may experience side effects such as gas swallowing and intermittent sleep.

So while it should help you understand the science behind CPAP settings, the final decision should be made by an expert. In other words, it is Proper setup of the CPAP machine by a board-certified sleep physician is essential. A doctor can ensure the best experience and maximum benefit from the machine.

remember the mask

Don’t overlook the importance of a CPAP mask, which delivers air through the nose or mouth. The choice is up to you (are you a nose respirator or a mouth respirator?), but the mask has to fit. “There is no difference in efficacy for a large number of mask types. The best mask is the one you feel comfortable and wear regularly.”


It makes sense to assume that severe OSA requires a higher CPAP pressure setting to treat it, while mild apnea requires a lower setting. Reality may draw very different conclusions. In fact, there may be an inverse relationship between the severity of sleep apnea and the pressure setting on the CPAP machine. This is because multiple factors are involved in determining the best settings. Most important are the anatomy of the upper airway and the nature of the airway obstruction. Finally, pressure settings should be determined by a board-certified sleep physician.

VigorTip words

Unlike some other conditions, sleep apnea is treatable.Eliminating it from your life promises to boost your mental health and well-being, Department of Sleep Medicine
Harvard Medical School said. If you’re having a hard time imagining enjoying a good night’s sleep, try to imagine seven — and then seven more. In other words, quality sleep may be more than you can dream of. For the first time in your life, it can be a viable part of your life. Now that you’ve taken your first steps with a CPAP machine, you have every reason to be optimistic about the results.