BiPAP vs. CPAP

Key Takeaways

• While CPAP delivers a constant level of air pressure to keep the airway open, BiPAP provides two pressure levels: one for breathing in and one for breathing out.
• BiPAP may be beneficial for people who have difficulty exhaling against CPAP pressure, those needing higher pressure settings, or people with central sleep apnea or another respiratory condition.
• Your doctor will help you find the appropriate PAP therapy based on your condition and needs.

The Difference Between CPAP and BiPAP

CPAP is typically the initial treatment for obstructive sleep apnea (OSA), which is the most common type of sleep apnea. However, BiPAP may be prescribed to certain people who have OSA, central sleep apnea (CSA), or another sleep-related breathing problem.

Both provided treatment using a bedside machine that pressurizes air and pumps it through an attached hose. At the other end of the hose is a mask that is worn over the nose or the nose and mouth. Air flows through the hose and mask and into the upper airway that leads to the lungs. This airflow keeps the airway clear of obstruction to prevent lapses in breathing, snoring, and sleep disruptions.

However, there are a few key differences between CPAP and BiPAP, which we'll break down below.

Pressure Levels

The key difference between BiPAP and CPAP is that a BiPAP machine provides different air pressure levels for inhalation and exhalation. In contrast, a CPAP machine uses the same amount of air pressure whether the sleeper using the machine is breathing in or out.

Conditions Treated

Research had found similar results for both CPAP and BiPAP as treatments for OSA. CPAP is initially recommended because of its simplicity and extensive track record. However, there are circumstances in which BiPAP therapy may be more effective than CPAP.

BiPAP machines are typically best for people who have complex sleep-related breathing problems or who have struggled with CPAP therapy. BiPAP therapy is most often used in two specific circumstances:

• If high pressure is required: Some sleepers need very high levels of air pressure when they inhale in order to prevent breathing disruptions. A BiPAP machine delivers this higher air pressure, then reduces the pressure level during exhalation. 
• If initial CPAP therapy is ineffective: While CPAP helps many people with obstructive sleep apnea, it isn't effective for everyone, and some people are bothered by the air pressure provided by the CPAP device when they exhale.

BiPAP is also often the best treatment option for people who have complicated breathing disorders like CSA, which is caused by improper signaling between the brain and the muscles that control breathing.

Cost and Insurance Coverage

In most cases, a BiPAP machine is more expensive than a CPAP machine. However, the actual out-of-pocket cost depends on your health insurance coverage, including whether you have required copays or deductibles.

Growing Similarities

In many ways, though, the differences between BiPAP and CPAP machines are growing smaller. Often, contemporary CPAP devices are able to provide more than one level of air pressure. For example, a pressure relief setting on many CPAP devices allows for a minor reduction in air pressure during exhalation.

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How BiPAP Works

BiPAP stands for bilevel positive airway pressure. When the BiPAP machine is turned on, it releases air at two different pressure levels.

• Inspiratory positive airway pressure (IPAP) refers to the level of air pressure delivered when a sleeper is breathing in.
• Expiratory positive airway pressure (EPAP) refers to the level of air pressure delivered when a sleeper is breathing out.

A BiPAP machine generally delivers higher air pressure while the sleeper is breathing in and lower air pressure while they are breathing out. The type of BiPAP machine a sleeper has also impacts the air pressure they receive while asleep. There are two main types:

• Fixed BiPAP: In these machines, two fixed air pressure levels — one for breathing in and one for breathing out — are determined by a doctor and programmed into the device. These two levels don't change during the night. 
• Auto-adjusting BiPAP: Auto-adjusting BiPAP devices can modify pressure levels in response to a sleeper’s breathing. While these BiPAP machines start with programmed base levels of pressure for breathing in and out, they use sensors to monitor breathing and an algorithm to alter pressure levels as needed.

How BiPAP Pressure Levels Are Determined

The air pressure settings on a BiPAP machine are calibrated carefully to try to make the BiPAP treatment as effective as possible. Experts recommend establishing BiPAP settings during a sleep study conducted in a specialized sleep lab. During the study, a technician can closely monitor breathing, oxygen levels, and brain activity. With this data, they can identify optimal BiPAP pressure levels.

Alternatively, some BiPAP machines have built-in sensors that are designed to automatically adjust pressure levels to avoid breathing disruptions. These machines can also be used to determine the initial pressure levels. However, experts still recommend initially determining optimal pressure levels in a sleep study.

Benefits of BiPAP

For people with obstructive sleep apnea, a major benefit of a BiPAP machine is that it may be more comfortable to use than a CPAP machine, because of the lower air pressure level it delivers during exhales.

People who require high levels of air pressure while inhaling may especially benefit from using a BiPAP machine. High air pressure might be difficult to tolerate while breathing out. By providing lower pressure during exhalation, a BiPAP machine may encourage nightly use, which is important for treating sleep apnea.

BiPAP machines can be programmed to operate in one of three different modes depending on what is needed to resolve breathing problems. Because a BiPAP machine can be programmed with a timer, BiPAP therapy can also offer benefits to people with health conditions that cause slowed or irregular breathing, including central sleep apnea. In these cases, BiPAP can help regulate breathing and enable better sleep.

Drawbacks of BiPAP

When used for obstructive sleep apnea, the main concerns of using a BiPAP machine are the potential for insufficient pressure and higher costs.

By design, a BiPAP device lowers the level of air pressure during exhalation. For some people, it's possible that the pressure will be too low to keep the airway open and successfully treat OSA.

Another potential drawback is that BiPAP machines can be more expensive than CPAP machines. People whose devices are covered by insurance may not notice a big price difference, but BiPAP therapy may have a larger financial impact on those who have to pay for their machine out of pocket.

How to Decide Between CPAP and BiPAP

Since PAP machines are only available by prescription, the decision about whether to use BiPAP, CPAP, or another type of PAP therapy must be made by a doctor or sleep specialist. Your provider will review the results of your sleep study, consider any underlying health conditions, and evaluate how well you tolerate different pressure settings.

CPAP might be right for you if:

• You’ve been diagnosed with obstructive sleep apnea and don't require unusually high pressure settings.
• You can comfortably tolerate continuous, steady air pressure while breathing.
  
• You prefer a PAP machine that is simple to use, widely available, and typically more affordable.
• You don't have coexisting respiratory conditions that make exhaling against pressure difficult.

BiPAP might be right for you if:

• You have central sleep apnea or a combination of obstructive and central events (also known as complex sleep apnea).
• You need higher pressure settings than CPAP can comfortably or effectively deliver.
• You struggle to exhale against continuous pressure and benefit from a lower exhalation pressure.
• You have certain medical conditions—such as COPD, neuromuscular disorders, or obesity hypoventilation syndrome—that require more advanced pressure support.
• You tried CPAP but could not tolerate it despite adjustments to mask fit, pressure settings, or comfort features.

Your doctor can help explain the benefits of each approach and guide you toward the therapy that offers the best comfort, safety, and long-term results.

Work with your provider to find the right mask. Ask for a refit before asking for a new one altogether.

Frequently Asked Questions