Reasons to Use APAP
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In a forum discussion thread, CPAPtalkers wished for a list of APAP features that they could share with their doctors. This article lists features that CPAPtalkers have discussed. It's part of a longer article, CPAP Machines, which discusses CPAP, APAP, BiPAP, selection criteria and other features. Read that article for a broader perspective.
1. An APAP machine offers a “two-fer.” It can be set to a straight CPAP mode, giving the advantages of a constant pressure plus the other advantages of APAP (such as home titration and a range of pressures), without the disadvantages of CPAP (such as a wrong pressure setting that isn't machine reported or lack of range of pressures to meet various sleep conditions). CPAP therapy needs may differ at various stages of treatment, such as start-up or after other health changes. Some people do better on straight CPAP. Some people do better on APAP. Some people, working with their doctor, use APAP and software to confirm or find their ideal straight CPAP pressure setting.
2. In the APAP mode, the machine automatically adjusts pressure to meet changing pressure needs when you change positions from side to back, are in various sleep stages, are extra tired, have a blocked nose due to a cold or allergy, or have taken alcohol or sedatives. A fixed CPAP setting to handle some of these situations might be too high for comfortable continued use.
3. Without changing the comfort of the baseline lower pressure, the upper range of the APAP pressure setting will respond to the upper range of apnea/hypopnea events (requiring higher pressure), potentially making APAP therapy more effective. A titrated fixed pressure that is too low may miss a sizable number of events on straight CPAP, labeling them as non-responsive, leading to poorer therapy results.
4. APAP automatically adjusts pressure if your pressure need change when you change masks, develop a mask leak, or experiment nightly with various mask fitting adjustments. Theoretically, pressure settings should remain the same with any mask. With APAP and software, the patient can detect and assess the volume of mask leak and test his/her mask adjustments under various pressures. The same holds for the patient’s new mask trials.
5. Some CPAPers trying APAP machines have experienced that they need a lower overall pressure on APAP than their original titrated pressure. A lower pressure may be more comfortable for the patient.
6. Studies have shown that there is better compliance with APAP than with CPAP. Possible reasons may be more comfortable treatment from a lower pressure setting or range, and (with machine display or software) immediate feedback on treatment leading to higher levels of satisfaction and improved treatment.
7. Self-titration. If the patient has a smart card and optional software (or ready access to a DME for printouts) and the requisite skills, willingness, and ability (or a helper), he/she can monitor his/her pressure settings and results and find the optimal pressure setting for straight CPAP, or narrow range of settings for APAP, in consultation with the physician. Research:
American Journal of Respiratory and Critical Care Medicine, Can Patients with Obstructive Sleep Apnea Titrate Their Own Continuous Positive Airway Pressure? http://ajrccm.atsjournals.org/cgi/content/full/167/5/716 Quote: Home self-titration of CPAP is as effective as in-laboratory manual titration in the management of patients with OSA.
Nonattended home automated continuous positive airway pressure titration: Comparison with polysomnography http://www.sleepsolutions.com/clinical_library/Unattended_auto-CPAP.pdf Quote: Nasal APAP titration in this study correctly identified residual apnea equivalent to the use of PSG. This correct identification allows the physician to accurately access the efficacy of treatment.
8. Once optimal pressure settings are found, with software the patient can monitor his/her progress. Software reports provide specific data for the doctor’s analysis.
9. Use of an APAP may reduce the need for sleep doctor visits (and probably DME visits), if the patient is responsibly managing their own therapy and therapy is assisted by APAP capabilities and software.
10. Use of an APAP reduces the need for subsequent expensive sleep tests since the patient is auto-titrating. Working with a doctor and periodically using a pulse oximeter (borrowed, rented, or purchased), the patient can test for oxygen levels at home with the report interpreted by the doctor.
11. Lower APAP pressure settings may do a better job of reducing or eliminating aerophagia (swallowing air) than higher CPAP pressure settings. Others find that aerophagia is reduced by using CPAP rather than APAP, or by using BiPAP.
12. Some of the Respironics CPAP and APAP machines have exhalation relief, called C-Flex, for patient comfort; if more comfortable, it may result in better compliance. (The current ResMed machine does not have EPR exhalation relief in the APAP mode.) C-Flex provides some degree of exhalation relief at a much lower cost than a BiPAP machine, although a BiPAP provides a greater degree of relief for those who require it.
APAP versus CPAP Research
Google APAP vs. CPAP studies. A few research articles:
http://thorax.bmjjournals.com/cgi/content/full/53/suppl_3/S49
Reasons why your titrated pressure may be wrong
The CPAP pressure setting determined in the sleep study may be too high once you settle into therapy.
1. In the sleep lab, you may have experienced more REM sleep (dreaming) for the first time in years, a REM rebound effect requiring a higher pressure. On xPAP therapy after your sleep patterns return to a normal amount of dreaming, your pressure may be too high. 2. Untreated sleep apnea may cause swelling in the mouth and throat, requiring a higher pressure setting in the lab. After xPAP treatment, the swelling may go down, requiring a lower setting. 3. If you had nasal congestion the night of your study due to allergies, a cold, chemical sensitivity, cool air, or air flow from the CPAP machine, a higher pressure setting would be required in the lab than your usual requirements. Source: TS Johnson MD et al, Sleep Apnea – The Phantom of the Night, pages 168 – 169
REM (dream) sleep and sleeping on your back require higher pressure settings because of more apneic events. If you slept poorly and didn’t experience REM or sleep on your back, the technician had to guess what settings you might need. The technician may estimate a pressure that is actually too high or too low.
It’s true that your current titrated setting, if accurate, may not require an APAP. But what about next month or next year? If your weight goes up, you may require a higher setting; if it goes down, a lower one. If you start feeling tired again, you may need a different pressure setting. A sleep study is an expensive and cumbersome way to find your new pressure requirements. With an auto-titrating machine and software in the comfort of your own home, you can determine whether the lab’s titrated pressure is indeed your best pressure, or experiment to find your best single pressure setting (for CPAP mode) or range (for APAP mode), working with your doctor.
Sources: Based on personal experience with obstructive sleep apnea and gleaned from the collective wisdom of cpaptalk.com contributors.
Want more? See the blog http://smart-sleep-apnea.blogspot.com for peer coaching articles on CPAP Machine Choices, CPAP Pressure Settings, and Prescriptions.
Not written by healthcare professionals. The information and opinions offered are not intended or recommended as a substitute for professional medical advice. © Mile High Sleeper, August 2006. Permission to use for free educational purposes.
A Rebuttal - reasons to Use APAP
by CPAPtalk member sleepinginseattle
This rebuttal is offered as a counter-point to the article "Reasons to Use Auto CPAP or APAP". It is my belief that the author's advocacy of auto-adjusting CPAP (APAP) is primarily anecdotal. As such, the author's "Reasons" are a collection to observations drawn from personal experiences and the experiences of others. While this is helpful, it does not provide a thorough investigation of APAP equipment or an accurate picture of its role in the treatment of OSA.
Here is a collection of facts regarding APAP equipment:
1) Some users have reported that an APAP machine may be more comfortable than a conventional CPAP in the treatment of OSA but there is no research that supports this finding conclusively. Compliance is the most important part of the successful treatment of OSA. Research has not shown that you are more (or less) likely to stay compliant with APAP therapy.
2) APAP may offer a two-fer (they can be set to a fixed pressure mode as well as auto-adjusting mode) but the use of auto-adjusting pressure in the treatment of OSA has not been shown to be advantageous.
3) There is no evidence to support a conclusion that wrong pressure settings are or should be a concern for users of conventional CPAP equipment.
4) Many conventional (fixed-pressure) CPAPs offer the same data reporting capability that some APAP machines offer. Data reporting CPAP machines give the same advantages without the added cost or complexity of similar APAP machines.
5) There is no evidence that supports the conclusion that OSA treatment is more effective if the pressure is adjusted based on body position, sleep stage, nasal congestion, fatigue, etc.
6) Disruptors, such as alcohol and sedatives, will mitigate the successful treatment of OSA regardless of your equipment choice.
7) APAP equipment is not intended to be a tool in the fit and sizing of masks. Furthermore, APAP equipment has not been shown to offer any advantages in this area.
8) There is no evidence to suggest that patients, in general, may need a lower pressure than was determined in the PSG titration or that there might be a long-term therapeutic benefit to lower pressure.
9) Self-titration has only been shown to be as effective as conventional sleep lab titration when combined with educational instruction in a laboratory setting.
10) There is no reason to believe that APAP-based therapy will reduce (or should) reduce the number of office visits a patient has. Self-diagnosis, as an approach for managing treatment, has not been proven to be more effective than traditional physician-based treatment. Furthermore, the software available for event reporting is not designed (or intended) to be tool for self-diagnosis.
11) Aerophagia has not been found to be less (or more) likely with APAP equipment.
The author's comments: Reasons why your titrated pressure may be wrong.
The author's comments are a broad advocacy of self-titration versus PSG titration and should be clearly identified as such. There is no evidence to support the author's conclusion that self-titration is more effective than PSG titration.
I suggest that readers do their own research on the subject of self-titration and talk with their doctor.