How to choose a PAP machine? Types of PAP machines and myths

February 28, 2025

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Many people have probably heard that there is a “life-saving magic weapon” for patients with sleep apnea, which is the positive airway pressure machine commonly known as the “sleep apnea machine”.

Since obstructive sleep apnea syndrome (OSA) is a disease characterized by apnea and hypopnea, its most direct pathogenesis is the repeated collapse of the upper airway during sleep. Therefore, for most OSA patients, a sleep apnea machine that can achieve positive airway pressure (PAP) is indeed an effective first-line treatment option.

Generally, for patients with sleep apnea whose polysomnography results indicate that AHI (Apnea-Hypopnea Index, i.e. the number of apnea and hypopnea times per hour of sleep) is >15 times/hour, or AHI is >5 times/hour and accompanied by daytime sleepiness, it is often recommended to use home non-invasive positive pressure therapy equipment.

In principle, a sleep apnea machine is connected to the patient through a mask or nasal mask, which delivers a certain pressure of airflow into the patient’s airway. This airflow pressure is strong enough to prevent the upper airway from collapsing during sleep, thereby keeping the airway open. When the airway is open, the patient can breathe normally and avoid apnea. This will prevent the patient from suffering from severe hypoxia due to snoring at night, which will lead to daytime lethargy.

In the past, when people mentioned ventilators, they would think of critically ill patients or ICU wards. However, in recent years, with the improvement of medical knowledge, this prejudice has been alleviated to a certain extent, and more and more people have realized that home ventilators can solve snoring and sleep apnea. In addition, many current sleep apnea machines also have intelligent functions, which can automatically adjust the airflow pressure according to the patient’s breathing pattern and needs to ensure the effectiveness and comfort of the treatment.

Types of PAP (Positive Airway Pressure)

In fact, sleep apnea treatment of OSA is just a verbal name. The scientific name of this therapy is non-invasive positive airway pressure (PAP).

As mentioned earlier, the treatment principle of sleep apnea is to connect the tube to the mask covering the nose or mouth, and pump air into the airway, so that the airway remains open at night to ensure normal breathing.

However, in actual treatment, the PAP process is much more complicated than imagined. For example, for OSA patients who need PAP treatment, their PAP devices need to be titrated to determine the best settings. Common modes include fixed pressure continuous positive airway pressure (CPAP) and auto-titration CPAP (APAP), and occasionally bilevel PAP (BiPAP) is initially selected.

(1) CPAP

CPAP, the full name of which is Continuous Positive Airway Pressure, is also called a single-level sleep apnea machine.

During the use of CPAP, the pressure remains constant. When the patient inhales and exhales, the pressure of the machine’s air supply remains unchanged. It can also be understood as a fixed-gear positive airway pressure device working mode.

CPAP ventilation needs to set the required pressure to completely overcome the airway resistance according to the size of the airway resistance in order to obtain a full therapeutic effect. The airway resistance of different patients varies, and different effective treatment pressures need to be set. Even for the same patient, different sleep stages, different sleeping postures, and changes in lifestyle will cause changes in airway resistance, so the pressure setting should be high enough to avoid the influence of these factors. If the pressure setting is insufficient, apnea and hypopnea cannot be eliminated, which seriously affects the treatment effect.

Usually the fixed CPAP pressure can be determined by polysomnographic (PSG) evaluation in the laboratory, or by the pressure titration process of the APAP technology described below at home.

CPAP can be used for all sleep apnea, and is particularly effective for moderate to severe obstructive sleep apnea, as the ventilation pressure in the airway can be kept very stable during CPAP.

(2) APAP or Auto-CPAP

APAP, the full name is automatic positive airway pressure. As the name implies, the most important feature of the APAP machine is that it can automatically adjust the pressure of the machine according to the needs of the human body. It is very flexible and can automatically help users find the ideal pressure range. Therefore, APAP can be understood as the “automatic gear” of the ventilator, which can automatically adjust the pressure given to the airway during breathing.

For OSA patients or medical staff, APAP is often a very useful mode. APAP is easy to operate, and various parameters are easy to analyze and compare, which is conducive to understanding the treatment effect and changes in the condition. In certain specific cases, the use of APAP can give full play to its automation advantages. For example, when changing body position, after taking sedative hypnotic drugs that can increase the depth of sleep, and after drinking (at this time, the muscles and other soft tissues of the respiratory tract will be further relaxed due to the effect of alcohol), it is best to use APAP, because in these cases, it is necessary to add some additional pressure based on the original pressure. The AfH mode designed specifically for women also belongs to APAP. It has better comfort and treatment effects for patients whose airways are not completely blocked. It is suitable for women and men who pursue comfort.

Of course, for some APAP devices that are not automated or intelligent enough, when the mask leaks, their APAP still has defects in identifying normal breathing patterns and restoring them to reduce output pressure. The number of micro-awakenings of patients may also increase due to the constant changes in pressure.

(3) BiPAP and Auto-BiPAP

BiPAP, the full name is bilevel positive airway pressure. The basic working principle of BiPAP is similar to CPAP and APAP, but it provides two pressures when working. Its working principle is to assist breathing by providing two different airway pressures (i.e., bilevel pressure) in the inspiratory phase and the expiratory phase. When inhaling, the BiPAP ventilator provides a higher pressure to help patients inhale air more easily; when exhaling, the ventilator reduces the pressure so that patients can exhale air more easily.

In short, BiPAP can adjust the inspiratory and expiratory positive pressures separately and synchronize with the patient’s breathing, and can reduce PaCO2 while improving oxygenation, so patients are more comfortable and their compliance is improved. Therefore, it is usually used to treat various diseases such as chronic obstructive pulmonary disease, spinal lateral sclerosis (ALS), obesity hypoventilation, central sleep apnea, neurological diseases, etc.

However, for some BiPAP machines, the pressure setting is relatively complicated. If the inspiratory pressure is too low, it is not enough to overcome the airway resistance, resulting in treatment failure; if it is too high, it will cause a hyperventilation response, and the continuous increase in inspiratory pressure can reduce the patient’s cardiac output. Therefore, BiPAP relies more on professional technicians to set its specific pressure after strict pressure titration, and is more commonly used in medical institutions. Some BiPAPs can adjust the inspiratory pressure and expiratory pressure at the same time according to the airway resistance, which will not cause changes in ventilation and circulation, and the pressure setting is as simple as APAP.

In addition, there is Auto-BiPAP (Auto-bilevel positive airway pressure) based on BiPAP, which can automatically adjust the pressure to adapt to the patient’s breathing pattern and needs.

(4) How to choose among CPAP, APAP, BiPAP, and Auto-BiPAP?

Through the above comparison, we can see that the difference between CPAP, APAP (Auto-CPAP), BiPAP and Auto-BiPAP lies mainly in the pressure change pattern of the airway during treatment.

	Features	Benefits
CPAP	CPAP machines are calibrated to supply a constant stream of pressurized air, which stabilizes the airway and prevents breathing interruptions during sleep.	CPAP is a highly effective treatment for individuals with obstructive sleep apnea (OSA). Known for its straightforward design, CPAP machines are also the most cost-effective option among PAP devices.
APAP	APAP machines go beyond traditional CPAP technology by monitoring your breathing and automatically increasing pressure when needed, ensuring consistent and effective airway support.	APAP machines offer a more adaptive approach by automatically adjusting air pressure based on real-time breathing patterns. This makes them an ideal choice for sleepers whose pressure needs vary throughout the night, providing enhanced comfort and personalized therapy.
BiPAP	BiPAP machines dynamically adapt to your breathing, providing higher-pressure air when you inhale and reducing pressure when you exhale, ensuring a more natural and comfortable experience.	BiPAP machines deliver superior comfort, especially at higher pressure levels, by providing distinct pressure settings for inhalation and exhalation. This advanced therapy is often recommended for individuals with more complex or severe respiratory conditions, ensuring optimal support for challenging breathing issues.

According to clinical experience, in the low-medium pressure range, the treatment effects of CPAP, APAP and BiPAP are often similar. If the treatment effect of CPAP or APAP is still not ideal, you should consider switching to BiPAP. At this time, the comfort of BiPAP will be better than CPAP and APAP. Pressure-sensitive patients can try to use Auto-BiPAP to solve the problem of obstructive sleep apnea.

Considerations when choosing a CPAP

For positive airway pressure devices, we should first pay attention to the performance of the motor and the quality of the humidification function. After all, these are the two aspects that are most related to our experience. The former is related to noise and ventilation volume, as well as the accuracy of adjusting different pressure values during positive airway pressure devices; and for breathing machines that blow directly into the mouth and nose, positive airway pressure devices with pipeline heating and humidification function should be selected as much as possible.

When choosing, it is also best for us to wear and use it after debugging by professionals. The mask needs to be selected according to the size of the patient’s nose, whether there is mouth breathing, and nasal ventilation. Imagine that the mask must be worn on the face every night to ensure smooth breathing. If it does not match you, no matter how good the positive airway pressure device is, it will not work.

In addition, the software and electronic control system of the positive airway pressure devices also directly affect the quality of delayed pressure rise, expiratory pressure release, leakage compensation and other functions, and further determine our experience of use. These often need to be tried to experience.

As for size and portability, I will not go into details here. Many people have no idea about the size of home positive airway pressure devices. They think it is a small one, but when it arrives, they find that it is a huge one and it is difficult to find enough space to place it.

One more thing here. Many people think that positive airway pressure devices can be worn casually after purchase. This is not entirely accurate. Different patients have different types of sleep apnea, different degrees of severity, different sleep states and sensitivity, and the type of ventilator and pressure setting to be selected will be different.

When purchasing a positive airway pressure device, it is best to choose a professional positive airway pressure device fitting center and receive dynamic follow-up services. In the first month of treatment, it is generally necessary to dynamically adjust the relevant parameters of the positive airway pressure devices to debug to the most comfortable and effective treatment state. You should also frequently feedback the problems you encounter during use to the positive airway pressure devices fitting service personnel to obtain professional answers and guidance; or monitor through a home sleep monitoring ring, and then purchase a positive airway pressure device by yourself after obtaining the test report and suggestions from an online doctor.

Myths in Using PAP

In real life, many OSA patients are very afraid of PAP treatment. The reason is that they don’t know enough about the appearance, performance, and significance of PAP, and there are many misunderstandings.

In fact, after understanding how PAP treats OSA and the differences in their working modes, we can summarize the key points to pay attention to when purchasing and using PAP and some misunderstandings we should avoid.

Myth 1: PAP is large and bulky, and inconvenient to carry and use

Many people mistake the positive airway pressure devices used to treat OSA for the large intubation ventilators used in hospitals for rescuing patients or general anesthesia. They are large and inconvenient to use and carry. The size of mainstream home non-invasive positive airway pressure devices has reached the level of a desktop computer host. They are not bulky and can be placed on an ordinary bedside table or desktop at home.

In addition, the ResMed AirMini Portable CPAP, which is ultra-small and ultra-portable and can be used in business travel and travel scenarios, has now been born. Although the ResMed AirMini Portable CPAP is small in size, it has great power. In some core parameters, it is no less than the flagship model.

Myth 2: Positive airway pressure devices are too expensive, cannot solve the problem once and for all, and the cost-effectiveness is too low

In fact, the price of positive airway pressure devices varies, the cheapest is about $500 US dollars, and the more expensive ones are about $2,000 US dollars. Generally, the purchase is based on the patient’s respiratory pressure, financial strength, etc. Expensive machines are not suitable for everyone, and perhaps a very cheap machine can solve the problem.

Myth 3: The positive airway pressure device is too scary, and I don’t want to use it

This may be a personal aesthetic issue. Maybe I personally feel okay, and I can even feel a little cool like a pilot after wearing an oxygen mask. Of course, if you or your family really can’t accept that you wear a positive airway pressure device to sleep, you may need to communicate well and strike a balance between the convenience of treatment and the feelings of your family.

Myth 4: Long-term use of PAP will cause addiction, and you will never be able to get rid of them

For moderate to severe OSA patients, ventilators do need to be worn for life, and wearing them for a period of time can cure snoring. After wearing a PAP for a period of time, it is okay to occasionally not wear it. Even if you don’t wear a positive airway pressure device, you don’t have to worry about addiction. Some patients have a better mental state during the day after wearing a positive airway pressure device, and are more willing to exercise more, adjust their diet, and pay attention to losing weight. After wearing it for a period of time, their weight may drop to normal or even low, and finally achieve complete cure. After wearing a positive airway pressure device for a long time, you may develop a habit. Some patients have the phenomenon that if they do not use a ventilator, they will feel uncomfortable and unable to sleep.

What else should I pay attention to when using PAP?

In addition to using positive airway pressure devices, we can also wear oral appliances, lose weight, and take positional therapy for OSA. Unfortunately, there is no drug to treat sleep apnea. Weight loss has a certain effect on obese OSA patients, and weight loss is beneficial for controlling blood lipids, blood pressure, blood sugar, and many other aspects. From this point of view, weight loss is an ideal treatment method. However, it is difficult for most patients to stick to weight loss, and the long-term success rate of diet + exercise or drug weight loss is limited.

Some mild OSA patients have aggravated sleep apnea in the supine position. Positional therapy is to take the method of forced side/prone sleep to alleviate the condition, such as sewing a tennis ball on the midline of the back of pajamas, so that they cannot sleep supinely, but this method may also cause discomfort, such as hip pain.

OSA can be accompanied by other diseases, such as diabetes, systemic hypertension, pulmonary hypertension, heart failure and ischemic heart disease. After starting OSA-specific treatment, any comorbidities that may be affected by OSA should be closely monitored, and the treatment plan for these comorbidities may need to be adjusted. For example, after successful treatment of OSA, the dosage of antihypertensive drugs may need to be reduced.

However, all of the above is based on sufficient attention and correct treatment of OSA. If snoring is not taken seriously and OSA is not treated until the damage to various systems of the body accumulates to a certain extent, it is likely to miss the stage of early intervention and twice the result with half the effort.

I hope that all patients with problems can pay attention to OSA as early as possible, and use effective treatment methods, such as positive airway pressure therapy, in time to control OSA, to give us a good sleep and a good body.

References

Martínez-García MÁ, Chiner E, Hernández L, et al. Obstructive sleep apnoea in the elderly: role of continuous positive airway pressure treatment. Eur Respir J 2015; 46:142.

McEvoy RD, Antic NA, Heeley E, et al. CPAP for Prevention of Cardiovascular Events in Obstructive Sleep Apnea. N Engl J Med 2016; 375:919.

Kuhn E, Schwarz EI, Bratton DJ, et al. Effects of CPAP and Mandibular Advancement Devices on Health-Related Quality of Life in OSA: A Systematic Review and Meta-analysis. Chest 2017; 151:786.

Schulz R, Bischof F, Galetke W, et al. CPAP therapy improves erectile function in patients with severe obstructive sleep apnea. Sleep Med 2019; 53:189.

Walia HK, Thompson NR, Pascoe M, et al. Effect of Positive Airway Pressure Therapy on Drowsy Driving in a Large Clinic-Based Obstructive Sleep Apnea Cohort. J Clin Sleep Med 2019; 15:1613.

Navarro-Soriano C, Torres G, Barbé F, et al. The HIPARCO-2 study: long-term effect of continuous positive airway pressure on blood pressure in patients with resistant hypertension: a multicenter prospective study. J Hypertens 2021; 39:302.

Tamanna S, Campbell D, Warren R, Ullah MI. Effect of CPAP Therapy on Symptoms of Nocturnal Gastroesophageal Reflux among Patients with Obstructive Sleep Apnea. J Clin Sleep Med 2016; 12:1257.