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The different between Auto CPAP and BiLevel CPAP

Have you ever wondered what the different is between CPAP, AutoCPAP and BiLevel devices? How do you know which one is the best for your treatment? Great questions and although the answers can be complex, it’s a good place to start your patient education after the sleep apnea diagnosis. All 3 are referred to as flow generators and are FDA controlled medical devices, which requires dispensing by prescription.
如你對以上二種呼吸機感到疑惑, 不知道它們的分別或那一款才適合自己, 那這裡或許可解開你的疑慮。

This is the most basic flow generator and the device most often prescribed first, because it costs less and most patients do well with it. If challenges arise, then AutoCPAP or BiLevel are then prescribed.
CPAP stands for Continuous Positive Airway Pressure, a constant and continuous flow of air that the patient must inhale and then exhale over. One of the biggest challenges adjusting to CPAP is the overwhelming feeling of that continuous flow of air pressure upon exhalation. Most manufactures offer a resolution to this challenge by sensing and / or reaching the machine pressure upon exhalation. Depending on the manufacturer, this feature has different names. The Philips Respironics features are known as it CFLEX, AFLEX or BiFLEX. ResMed refers to it as EPR (expiratory pressure relief) and Fisher & Paykel Healthcare offers the uniquely different SensAwake. These comfort features have the ability to reduce or self adjust the machine pressure up to 3cmH2O.

固名思義是一種持續提供正氣壓的機器, 這是最經濟的一款呼吸機, 同時成效也非常好。 但最大問題是, 這呼吸機只會提供一樣氣壓供用者吸氣和呼氣,很多用者會感到呼氣時比較困難, 因為呼氣時必須用力呼出比呼吸機提供的更高的氣壓。 為解決呼氣困難高個問題,很多廠商加入一種呼氣減壓的技術,這種技術有很多名稱, 如飛利浦偉康(Philips Respironics)叫CFLEX, AFLEX 或 BiFLEX. RESMED則叫EPR, Fisher & Paykel 則叫Sensewake. 這種呼氣減壓技術能夠最多減3cmH2O幫助你更易呼氣。

Your CPAP pressure is 10. You have no problem inhaling that delivery of air, but when you begin to exhale while the air is still being delivered, you may feel overwhelmed, claustrophobic or even experience a choking sensation. So if our machine is set with EPR 3, you would receive 10 at inhalation and then the machine reduces to 7 to make it easier for you to exhale.

當呼吸機提供10cmH2O, 吸氣時沒有問題, 但當你呼氣時你便會感到困難, 因為呼吸機同時提供10cmH2O給你,若你沒有比它更大力度你便覺得呼氣困難。 所以如果呼吸機上有呼氣減壓功能時, 可設定最大值為3cmH20, 當你吸氣時呼吸機提供10cmH2O, 吸氣時就會減低3cmH2O, 即呼氣時只提供7cmH2O, 這樣呼氣時就更易。

AutoCPAP - Automatic titrating (measuring and adjusting) continuous positive airway pressure
This machine is also know as APAP. Unlike CPAP which is set to deliver one continuous pressure, APAP is set within a high and low pressure range for the purpose of varying inhalation needs. The range is predetermined by your prescribing physician. APAP has sensitive algorithm technology that allows the machine to detect how much inhalation pressure you need with each breath.
The theory of providing a range is that one’s pressure needs may vary during any given night or hour of sleep. One example is sleeping position; most of us have more apnea episodes and of longer duration when we sleep on our backs vs. side or stomach sleeping. Think “gravity” as when we lay flat on our back, the jaw and tongue naturally relax and fall back, thus blocking the airway and causing apnea episodes. Some of us may have nasal conditions or seasonal allergies that require higher pressures during part of the night or seasonally. Even a slightly stuffy nose may cause worsening apnea episodes. We may need higher pressures on occasions when we are under the influence of alcohol too close to bed time (yes, with your doctors approval it is ok to have a glass of wine or alcoholic beverage). Some of us require sedate medication for pain causing effect. On those nights, APAP should provide the proper inhalation pressure we need on a breath by breath basis.
In theory, an AutoCPAP should work set at the lowest pressure of 4 and the highest of 20, however some experts believe APAP is more effective if the range is tightened a bit closer to the average know cpap pressure needed by each patient. If APAP is challenging for you, bring this to the attention of your prescribing physician.

它不像持續正氣壓呼吸機(CPAP)般只會提供固定氣壓, 它可以設定一個最低和最高氣壓,APAP內置感應器去偵測你當時情況而自動調節不同吸入氣壓.
每個人每晚的睡眠情況都會有所改變,另外由於地心吸力的關係,不同的睡眠姿勢都會影響你需要的吸入氣壓,例如你昂睡時, 下巴和舌頭放鬆後會向下王,氣管受的壓力會最大, 但當側睡時所受的壓力就相對變小。每晚睡眠時會不斷轉換睡眠姿勢,導致你的每一個呼吸都有可能需要不同氣壓另氣管擴張。又例如你睡覺前喝了大量酒精飲品導致你當晚睡覺時有可能需要更大氣壓去解決窒息,這時全自動氣壓調節呼吸機便可發揮它的功用,適當地提供足夠氣壓。
全自動機基本上會提供由最低4cmH2O到最高20cmH2O, 但有些醫生會認為把氣壓範圍盡量調節到靠近你的平均最高氣壓效果更理想。如用全自動機後發覺氣壓不太理想,請尋求你的專科醫生意見。

BiLevel - indicates a flow generator that delivers 2 distinct pressures, one for inhalation and the second for exhalation.
The most complex device, it is also the most expensive and typically reserved for special needs. Most Bilevel devices offer a high setting range of 25cmH2O vs CPAP and APAP which typically top out at 20. Since exhaling over a constant pressure is one of the most challenging aspects of adjustment for the patient, BiLevel best serves those who require mid to high range inhalation pressure needs. Since high inhalation pressures are extremely difficult to exhale over, this device is set at 2 distinct and constant pressures, one for inhalation and one for exhalation. Remember that CFLEX, EPR only have the ability to reduce points lower, so when a patient requires an inhalation pressure of 20 for example, lowering to 17 is still extremely challenging, so BiLevel can be set at any pressure from its minimum of 4cmH2O.
AutoBiLevel are now available and have similar feature as the APAP regarding the inhalation and exhalation pressure variables.

Since BiLevel works similarly to a ventilator, it is commonly used for patients with other disorders such as ALS, Parkinson’s or other diseases with patients who need assistance with breathing. It is also frequently prescribed for patients who have central sleep apnea, although many with central apnea do quite well with CPAP or APAP.

高低雙壓呼吸機 (BiLevel / BiPAP)
定壓機(CPAP)及全自動機(APAP)的呼氣減壓功能只能減掉3cmH2O, 即當你吸入20cmH2O時,呼氣時可減到17cmH2O, 但請留意就算減到17cmH2O時,氣壓仍非常大,呼氣時仍相當困難,這時候就更需要高低雙壓機(BiPAP)。高低雙壓機可調節到無論你吸入多大氣壓,呼氣時都可以減到最低氣壓即4cmH2O,這樣呼氣時就沒有問題了。

Having these options for treating your sleep apnea is useful knowledge. If you have tried and failed on CPAP, discuss APAP or BiLevel or AutoBilevel with your prescribing physician. Each flow generator has different features and benefits, so finding the one that best suits you needs is very important to your successful therapy.

以上說明了三類睡眠呼吸機(CPAP, APAP, BiPAP)的分別,如果你試了定壓機(CPAP)而效果不太滿意,請跟你的醫生討論是否應轉用自動機(APAP)或高低雙壓機(BiPAP), 每一種呼吸機發揮到不同作用,適合不同需要人士使用,請小心選擇那一款才適合你的呼吸。

**the information included on this site is for educational purposes only. It is not intended nor implied to be a substitute for professional medical advice. Contact your physician or health care provider when you have health related questions. Never disregard or delay medical advice because of information you have obtained on this site. **

by Tracy R. Nasca
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