APAP vs CPAP: What are the differences?
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Positive airway pressure (PAP) therapy is the first-line treatment for obstructive sleep apnea (OSA). OSA is characterized by repeated collapse of the upper airway during sleep, leading to apnea or hypoventilation. PAP devices continuously deliver positive pressure airflow through a mask to provide biomechanical support for the upper airway, thereby maintaining airway patency and preventing apnea events during sleep.
Several types of PAP therapy are available for OSA treatment, including single-level PAP and bi-level PAP. Single-level PAP is mainly divided into two modes: CPAP and APAP.
Whether it is a CPAP or APAP machine, its purpose is to transmit air pressure to the collapsed part of the throat through the nostrils or mouth to keep the airway open. The pressure of the breathing machine in CPAP mode needs to be adjusted manually, and ventilation is always performed according to the set pressure value during operation; the APAP machine, that is, a single-level automatic breathing machine, will automatically adjust the pressure within the pre-set pressure range according to the airway obstruction to achieve the best effect.
Differences between CPAP and APAP
In the field of respiratory therapy, continuous positive airway pressure (CPAP) and auto-adjusting positive airway pressure (APAP) are two common treatment methods.
CPAP stands for Continuous Positive Airway Pressure, and its pressure is constant. Once the pressure is set, the ventilator will supply air according to the set pressure. This is currently a popular treatment for sleep apnea. It uses the air pressure generated by the ventilator to be transmitted to the mask through a pipeline, thereby opening the blocked airway.
APAP is a “single-level fully automatic ventilator” whose pressure can change automatically. APAP mode ventilators can monitor the user’s airway in real-time to see if it is unobstructed. When the airway is blocked or unobstructed, the ventilator will actively increase the pressure to support the collapsed or fallen soft tissues to achieve airway patency. When there is no apnea, the pressure of the machine will automatically decrease to improve the user’s comfort.
Although they are all methods used to help patients maintain airway patency and improve sleep quality, there are significant differences in their working principles and application scenarios.
CPAP Overview
Definition: CPAP is a therapy that keeps the airway open by providing a constant flow of air at a pressure higher than atmospheric pressure to the patient’s airway. This constant pressure helps prevent the upper airway from collapsing, ensuring that the patient can breathe smoothly during sleep.
How it works: The CPAP machine generates a continuous flow of air and delivers it to the patient’s airway through a mask or nasal mask. The pressure level of this airflow is adjusted according to a fixed value set by the doctor for the patient.
Application scenarios: CPAP is mainly used to treat obstructive sleep apnea (OSA) and other conditions that require keeping the upper airway open. It is also widely used for breathing assistance in certain types of respiratory failure and high-altitude environments.
APAP Overview
Definition: APAP is a more advanced form of ventilation that automatically adjusts pressure levels based on the patient’s actual breathing needs. This means that the APAP machine can monitor the patient’s breathing pattern in real time and increase or decrease airflow pressure as needed.
How it works: APAP machines have built-in sensors that monitor parameters such as the patient’s breathing rate, depth, and airflow resistance. Based on this data, the machine automatically adjusts the output airflow pressure to ensure that the patient is provided with the most appropriate support at all times.
Application scenario: APAP is more suitable for patients whose conditions may change over time, such as patients with varying degrees of OSA severity, because of its ability to automatically adjust pressure. In addition, APAP is also a better choice for patients who are using CPAP treatment for the first time but have difficulty adapting to fixed pressure levels.
Main Differences
Pressure adjustment: CPAP provides a fixed pressure level, while APAP can dynamically adjust according to the patient’s breathing needs.
Comfort: Because APAP can adjust the pressure according to the patient’s actual situation, it is generally more comfortable than CPAP. This helps to reduce uncomfortable symptoms such as air leaks, dry mouth, and nasal congestion.
Applicability: While both can be used to treat conditions such as OSA, APAP is more suitable for patients with complex and changing conditions due to its flexibility.
Cost: APAP machines are generally more complicated and more expensive than CPAP machines. However, considering its improved comfort and adaptability, it may be worth it for many patients.
| Air pressure level | Target Group | Comfort | Cost | |
|---|---|---|---|---|
|
CPAP |
A constant air pressure level |
More suitable for patients with stable conditions who respond well to specific air pressures |
May feel uncomfortable |
Usually lower priced |
|
APAP |
Automatically adjust the output air pressure |
Suitable for patients who have difficulty determining the optimal fixed air pressure value |
Higher comfort |
Higher price |
In actual use, there are very few users whose airway obstruction conditions remain unchanged. Therefore, if the machine only has CPAP mode, it means that the user’s obstruction condition cannot change too much, and the set constant pressure value needs to be relatively accurate to better solve the snoring problem. At the same time, it is necessary to increase the delayed pressure. After all, the ventilator needs to be worn and turned on before falling asleep. To ensure that the airflow of the ventilator does not affect people’s sleep, a smaller airflow pressure value needs to be given before falling asleep.
The fully automatic mode does not require these operations. When the machine is turned on before going to bed, the respiratory tract is not blocked, and the ventilator intelligently provides a very small airflow, which does not affect falling asleep; after falling asleep, if the blockage is slight, it intelligently provides a suitable smaller airflow, and if the blockage is serious, it intelligently provides a suitable larger airflow, which not only solves the problem but also ensures the comfort and continuity of the entire sleep.
When the APAP machine is not snoring or apnea occurs, the APAP machine will not increase the pressure. When the human body has apnea and snoring, the APAP machine will actively increase the pressure to open the collapsed and blocked upper airway through pressure. When the airway is opened, the APAP machine will automatically reduce the pressure.
What are the advantages of APAP mode?
If needed, APAP can also be used for CPAP. This means it can be set to a single pressure setting to deliver pressurized air. For example, if a patient cannot be treated with APAP, the machine can be set to CPAP mode, eliminating the need to purchase a different type of machine.
APAP devices are able to adjust to different pressure settings depending on your sleep stage. An APAP machine will deliver higher pressure during your REM sleep stage (the deepest, most relaxing sleep when you are most likely to experience apnea events). However, the APAP will then return to a lower pressure during the light sleep stage, making the treatment more comfortable and more effective.
APAP devices can change pressure levels on the fly and adapt to your needs. For example, if you lose weight, you will have a lower risk of apnea events because the fatty tissue in your throat will decrease. Then, if you gain weight, you will most likely need a higher pressure setting because the fatty tissue has become denser/grown and makes it harder to breathe. APAP can even apply these changes basically and adjust them one by one to your needs.
APAP machines use different algorithms and technologies, so not all machines are the same. However, your doctor will help you choose a breathing mode machine that works best for you based on your needs. You may need APAP, but your doctor may also tell you that a fixed-pressure CPAP is sufficient for your situation. APAP machines are also more expensive, but they primarily cater to patients who have more precise and complex requirements for oxygen therapy.
Which is better, CPAP or APAP?
In principle, the APAP mode machine is better than the CPAP mode machine in terms of effect and comfort, because the APAP mode is an automatic pressure-regulating machine.
CPAP machine is a constant pressure ventilator. Once the pressure is set, it cannot be changed during use. For example, if the pressure of the ventilator is set to 10, the machine will blow out air at a pressure of 10 from the beginning to the end of work. Therefore, a pressure measurement must be done before using the CPAP mode machine. Some people do the test in the hospital, and some do the test at the ventilator dealer. Only after the pressure measurement can you know how high the pressure you need at night to avoid snoring and apnea.
Due to its characteristics, the comfort level of the CPAP mode machine is not very high. The reason is that the pressure of the CPAP machine is constant, and this pressure is the highest pressure or 90/95 percentile pressure measured based on snoring and apnea at night, so when you are not asleep, you will feel that the pressure is very high, which makes you feel uncomfortable.
Since the pressure of the CPAP machine is measured based on the patient’s nocturnal airway resistance when the patient has used it for a period of time, it is generally recommended to have regular checkups, because some people may have lower airway resistance over time, while some people may have higher airway resistance, so it is necessary to go to the hospital for regular checkups. It is generally recommended to have a checkup once a year.
APAP mode machine can automatically detect the degree of upper airway obstruction and adjust the pressure according to the degree of airway obstruction, so this machine only needs to set a pressure range, such as 5-15 pressure, which means that the pressure of the ventilator will automatically fluctuate between 5-15. The pressure may be very low at around 5 when it is first used. As sleep deepens, the airway resistance increases and the ventilator pressure will automatically rise at this time. It may rise to around 12 at a certain stage, or it may rise to around 14, but the maximum will not exceed 15. Due to the characteristics of APAP mode, this machine is relatively comfortable.
Generally, when the patient is not asleep, the machine works at a low pressure, which does not affect the patient’s normal sleep. After falling asleep, the machine will automatically adjust the pressure to ensure that snoring and apnea do not occur.
For some patients, CPAP mode is better than APAP mode, such as patients with chronic heart failure and some patients with therapeutic central arrest. For these patients, current studies have shown that CPAP mode machines are better than APAP mode machines. This is mainly because CPAP mode can provide stable ventilation. Unlike APAP mode, the pressure changes automatically, which will cause unstable ventilation. For patients with poor central control ability, it is easy to induce central arrest. Therefore, CPAP is more effective for these patients.
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