Reading Data

Reading Data

Checking Your CPAP Machine Settings

by Mile High Sleeper

Tips for All PAP Users

Pressure Definition. Machine air pressure is measured in centimeters of water, cm/H2O or cwp, centimeters of water pressure. A pressure of 10 cm/H2O means that if you were drinking water from a 10 centimeter (3.9 inch) straw positioned at the top of the water to your mouth, the suction you create would be 10 centimeters of water pressure. Speech is measured at about 7 cm/H2O pressure past the vocal cords. The average pressure for treating sleep apnea is 10 cm/H2O. Typical pressures for treating obstructive sleep apnea are 6 to 15 cm/H2O. Some people require higher pressures. The air pressure acts as a pneumatic splint to keep the throat open. The pressure is less than a sneeze and rarely causes the ears to pop. Source: TS Johnson MD et al, Sleep Apnea – The Phantom of the Night, p. 92.

Titration is a scientific lab term, meaning to slowly add a little bit more of something until you reach a desired effect. During the sleep study, the sleep technician slowly increases the CPAP machine pressure one centimeter/water at a time until you stop having apneic events (apneas and hypopneas). That and some more calculation lead to a titrated pressure setting. See Reasons Why Your Titrated Pressure May Be Wrong in the peer coaching article CPAP Machine Choices. Research article on the inaccuracies of a one-night titration: http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=14971878&dopt=Citation

Know your titrated pressure from the sleep study. Know the pressure your doctor prescribed. If you don’t know them, ask your doctor’s office for a copy of the sleep study report and doctor’s prescription. Some people start and continue CPAP treatment with the titrated pressure from their sleep study and have continuing good results with no problems. Others still feel tired, or feel tired again after a few months, and need to explore the correctness of their machine pressure setting and pressure prescription, as well as first solving other equipment problems.

Consequences of a wrong pressure setting

Don’t worry; unless you have other serious medical problems, your immediate life is probably not in danger! Long term is another matter if you give up on CPAP therapy. It’s important to know your titrated pressure from a sleep study (if you have been titrated) and pressure prescription, and know that your machine has been set up correctly by the Respiratory Therapist (RT). The prescribed pressure setting on your PAP machine is very important.

If the pressure is too low for you, it won’t eliminate all the apneas or hypopneas and may not clear out all the exhaled carbon dioxide from your mask. Pressure too low may be indicated by snoring, insomnia, feeling starved for air, subtle feelings of suffocation or claustrophobia while on PAP, an AHI (apnea-hypopnea index) above the normal 5 or below events per hour, or still feeling tired or sleepy during the day. Some people find that a setting of 4 or 5 cm/H2O is not high enough to clear the exhaled carbon dioxide, and need a setting of 6, 7, or 8 cm/H2O or more as their lowest setting on an APAP.

Pressure that is too high for you may be indicated by uncomfortable therapy, large mask leaks, mouth breathing, dry mouth and throat even with heated humidification, aerophagia (swallowing air), an AHI above the normal 5 or below events per hour, and still feeling tired or sleepy during the day. Some people have concerns that too high a pressure setting may lead to pressure-induced central apneas (the brain not telling the body to breathe) unless the PAP machine algorithm (operating rules) prevent runaways as in Respironics machines. Pressure settings above 15 cm/H2O are considered high for some people; for others, 18, 19, 20 cm/H2O is high.

If your autopap machine is left at the factory default setting of 4 to 20 cm/H2O, you may experience the problems of both too high and too low. In addition, the APAP machine may have difficulty responding quickly enough with this large range. With pressure too low, too high, or other wrong setting (CPAP or APAP mode, exhalation relief, ramp or settling), your AHI may not be as low as it should be, or you may be more uncomfortable, and you may think the therapy doesn’t work very well and be tempted to give it up. To know your AHI, you need a machine with a smart display or better yet, software. Your AHI should be 5 events per hour or less to be considered in the range of normal sleepers. Many people require an AHI of 2.5 or less to be truly rested and invigorated.

Two measurements of Sleep Disordered Breathing (SDB

Apnea. The Greek word “apnea” means “without breath.” You stop breathing during sleep for ten seconds or longer. Hypopnea. There is airflow through your throat but at a much reduced level, which leads to not getting enough oxygen. It’s abnormally shallow breathing lasting at least ten seconds.

1. AHI, Apnea-Hypopnea Index for sleep apnea: Less than 5 events (apnea or hypopnea) per hour is considered normal. 5 or more events per hour is considered Mild sleep apnea 15+ considered Moderate 30+ considered Severe (from T. S. Johnson MD, Sleep Apnea - The Phantom of the Night, page 211)

Flow limitation or Upper Airway Resistance Syndrome (UARS) is another important, subtle form of SBD. The airflow meets resistance in the nose or mouth, causing the brain to waken the sleeper. The American Academy of Sleep Medicine advocates counting apneas, hypopneas, and flow limitations/UARS for the Respiratory Disturbance Index, RDI.

2. RDI, Respiratory Disturbance Index for sleep apnea: 5 to 20 events per hour is Mild SDB 20 to 40 events is Moderate SDB More than 40 events is Severe SDB (from Barry Krakow, MD, Sound Sleep, Sound Mind, page 245)

Check the accuracy of your machine’s prescribed pressure setting. This is important. Your doctor’s prescription was entered into the PAP machine by a Respiratory Therapist at a DME/home medical equipment company who could make a mistake. The DME company may not have procedures to detect setup errors, so if they made an error, you would never know, unless you had other means to check the settings. (Their follow-up phone call asking “how are you doing?” isn’t precise enough to detect set-up errors.) You are entitled to ask and observe to have the settings checked by a Respiratory Therapist other than the one who set it up, or by a lead respiratory therapist; or minimally, by a slow and careful walk-through demonstration by the same RT who programmed the machine originally. See the end of this article for a sample walk-through of machine set-up. The check could be done when you get the machine, or a few days later if you were overwhelmed by your diagnosis and too much information when you first picked up the machine.

If you run into resistance from the RT about checking your machine setting, is it because they are unwilling or unable? If unable because they are not competent in setting up the machine, there is a greater chance they made an error, and all the more reason to have it checked. If they are unwilling, it may be that, following company policy, they are unwilling to risk your learning how the machine is set so you don’t “tamper” with it. Nevertheless, you are entitled to see if it’s a correct prescription, just as you are entitled to see if the label on a bottled drug prescription or the pill has the right dosage. If you run into resistance, talk with the lead RT or branch manager, or if the DME insists, get a doctor’s prescription to let you observe the correct settings, or get a doctor’s prescription for the clinician’s manual from the DME and check it yourself.

Learn the patient-controlled settings. This is important.

Read the user’s manuals that come with your machine and heated humidifier to learn how to set the features you can control. For example, in a older, classic tank Respironics REMstar autopap, that would be heat/humidity level, C-Flex level, ramp pressure and duration of ramp (if in CPAP mode rather than APAP on an older machine), mask-off alert/auto-off, and button lights. Learn to read the display screens. Use a flashlight and magnifying glass if necessary. If you have trouble pushing buttons, you may want to get someone to help you. Discussion thread on a ramp (settling) pressure setting that was too low: http://www.cpaptalk.com/viewtopic.php?p=134380#134380

Using a clinician’s set-up manual to check the accuracy of your prescribed pressure setting

Personal criteria for using a set-up manual

If you aren’t good with technology, you should probably rely on the respiratory therapist at your local DME to check the prescribed pressure settings; or rely on a family member, friend, or doctor. If you can’t program your VCR, DVR, cell phone, or use most of the features of a digital camera, seek help from others. If you can handle most basic consumer technology, it should be easy for you to use a set-up manual safely and well to check the accuracy of your machine settings. Checking the set-up menu is not much more difficult than changing the time on a digital clock and takes less than a minute, once you know what you are doing.

How to get a clinician’s set-up manual

The clinician’s set-up manual is boxed with the new machine, along with the user’s manual. The local DME/HME company should give you the patient/user’s manual but, fearing liability, will probably withhold the clinician’s manual unless you have a doctor’s prescription for it. When you ask your doctor for a prescription for the manual (before or after you get your machine), tell him/her that without it you can’t check the correctness of your machine settings made by the DME. Discuss your ability to scroll through a menu with your doctor, show him/her the sample dialog at the end of this article if he/she isn’t familiar with a machine’s setup, and show him/her the user’s manual if you already have one. The clinician’s manual isn’t much different; if you can follow the user’s manual, you can follow the clinician’s manual.

If you buy your machine online at https://www.cpap.com, all manuals will be included. Some people buy clinician’s manuals online, but be sure that you get the one for your machine, not another model. Some people ask other experienced users for the simple directions on how to use the buttons to access the set-up menu in the display; you really don’t need the hardcopy set-up manual. For example, see http://www.cpaptalk.com/viewtopic/t15421/How-to-change-settings-on-RemStar-Plus.html and http://www.cpaptalk.com/viewtopic.php?t=11376 and http://www.cpaptalk.com/viewtopic.php?t=10055. Don’t expect support from your local DME in using a set-up manual or machine software.

You do not need machine software to use a set-up manual or instructions to check whether the DME RT set your machine correctly. As you scroll through the settings, write them down for later reference. If you find that the DME set up the machine wrong, not following your doctor’s prescription, inform your doctor and take the machine into your DME for correction by the lead RT or correct it yourself. Report the error to the local DME supervisor/lead respiratory therapist or branch or regional manager, and consider reporting it to the DME branch or regional manager and filing a complaint with The Joint Commission of Accreditation of Healthcare Organizations http://www.jointcommission.org/GeneralPublic/Complaint/oqm.htm so other patients won’t be harmed. The DME needs feedback to improve their quality of service to other patients. See the article on Preventing and Reporting Errors in Your Care.

With a clinician’s manual, you will be able to change the pressure settings beyond the original prescription, but it is inadvisable to do that unless you have supervision from your doctor and software to give you feedback on the results of changes.

To get the machine pressure changed by your doctor and DME, you need to get an appointment or phone your doctor, explain why you think a change is needed, make sure that a prescription was sent to the DME and received, make sure that the DME processed the prescription internally so your local office can make the change, make an appointment at the DME, drive to the local office, wait, have the respiratory therapist make the change, which literally takes about 30 seconds, and drive home. Before you leave, request that another RT check the accuracy of the setting, or get a careful walk-though demonstration from your machine showing correct settings.

An alternative is to team with your doctor to correct or adjust the pressure settings yourself, if you are a suitable candidate for this team effort. See the next article on Changing Your CPAP Pressure Setting.

After you have mastered hose, mask, leaks, comfort, humidity, ramp/settling, exhalation relief, and been stable on PAP for a few weeks or months, borrow an overnight recording pulse oximeter from your doctor or RT, or buy one online. Use it to check your blood oxygen saturation levels at night as another indicator that your PAP is working well.

Even better, get a machine with software to more precisely show how well your therapy is working.

Appendix I

Check the machine accuracy with a manometer

New users, don’t let this scare you. This is rare but important: http://www.cpaptalk.com/viewtopic/t15002/cpap-machine-gone-crazy.html

Rarely, the pressure reading on the machine’s LCD display and actual pressure may be different. You may want to check the actual pressure every six months or annually. An instrument called a manometer will give an accurate reading. A free manometer check may easily be done by your local DME, perhaps before and after AWAKE support group meetings at a sleep lab, or you can make or buy a manometer online. See https://www.cpap.com/ and search. If the pressure is off, some machines have an internal reset feature. If there is no reset, you can change the machine’s pressure setting to match the actual pressure. For example, if you are seeking a prescribed pressure of 9 cm H2O but 9 on your machine isn’t really a pressure of 9, you can bump it up to 10 to get an actual pressure of 9. If you don’t have a manometer and the pressure is off, what really matters is how you feel and your AHI at the actual pressure you do have.

Appendix II

Sample walk-through to check settings on an older Respironics REMstar Auto with C-Flex CPAP (the “classic tank” model)

It takes less than a minute to scroll through the menu, using the buttons on the machine. The respiratory therapist should demonstrate competence and confidence in working with the machine settings. This is a sample dialog that you should hear from the respiratory therapist to confirm correct settings. The dialog for your machine will be different, but the RT should explain each screen.

“Screen 1. Nights at more than 4 hours means the number of nights you used the machine for more than 4 hours. Stop me and ask if you have questions about any of these settings.

Screen 2. AFLE means that the therapy mode is set to Auto CPAP with C-Flex pressure relief, what your doctor prescribed.

Screen 3. Min 9.0 means that your lower pressure is set to 9.0 cm H2O pressure, what your doctor prescribed.

Screen 4. Max. 11.5 means that your higher pressure is set to 11.5 cm H2O. Your machine will automatically adjust up and down between 9 and 11.5 cm H2O, what your doctor prescribed.

Screen 5. C Flex 3 means that your exhalation relief is set to 3, the highest setting offering the most relief. You can change this setting on your own, following the instructions in the user’s manual.

Screen 6. 0:00 ramp means that your ramp (startup) time is set to 0. This means there is no ramp in the APAP mode. Your machine will start at your lowest setting, 9 cm H2O, and adjust upward to 11.5 as you need it. For older REMstar auto machines, the ramp time must be set to zero in the auto mode. If the ramp is set to anything other than 0:00, the machine is set for a split night sleep test, remaining at the lowest pressure for the set number of hours, so you are not getting a full night of therapy. (If your doctor had prescribed CPAP mode instead of APAP, ramp time from 5 to 45 minutes would be available on this older machine. Respironics newer M series autopaps can use ramp while operating in auto mode.)

Screen 7. Alert 1 means that your mask-off alarm beep is turned on. If your hose disconnects or your mask comes off, the machine will beep. It also means that the machine auto-off feature is turned on. You can change this setting on your own.

Screen 8. LED 0 means that the button lights are turned off while the machine is on. You can change this setting on your own.

Screen 1 again means that this is where we came in; we’ve gone through the whole menu and it’s correct.”

Changing Your CPAP Pressure Settings

by Mile High Sleeper (Machine)

This is the second of two articles. See the first article on Checking Your CPAP Machine Setting, sections on Pressure Definition, Titration, and Consequences of a wrong pressure setting.

For Those Who Need and Want to Be More Involved with Their PAP Therapy

Why responsible self-management of PAP therapy? This is important. Most people find that useful information on their optimal pressure settings and PAP therapy in general is elusive. As a result, some people seek information online, buy machine software, and by necessity start to manage their own therapy, because no one else is managing it on a nightly basis. If the quality of information they are able to access is good, if they are discerning, and if they have good medical backup and supervision, this can work well. These people are committed and actively working toward success in a difficult therapy.

Responsible self-management does not mean sole management. Working with a doctor does not have to be an “either-or” process where either the doctor is completely responsible or the patient is completely responsible. Working with a doctor can be a “both-and” process of collaboration. Both the doctor and the patient are managing the therapy. The doctor is managing the medical side and some aspects of the therapy, and the patient is managing his/her nightly therapy and equipment, seeking advice and support from the doctor. The patient is closest to the therapy and best able to notice problems, observe results, and take action to make the treatment work. This may include making gradual changes in pressure settings, in collaboration with the doctor, and trying them long enough to observe results.

Similar to responsible patients with diabetes who test and moderate their blood sugar levels, responsible patients on PAP can be trusted to adjust the many variables of their PAP equipment. CPAP is a safe and live-saving therapy. Not only can the capable PAP user manage the equipment variables; they must manage the variables to be successful.

Know the original pressure setting resulting from your sleep study titration, if you had one. Know the original pressure setting your doctor prescribed. If you have already mastered problems with the hose, mask, leaks, comfort, humidity, ramp/settling, and exhalation relief, and you’ve been on the therapy for several weeks or months and are still not feeling as good as you think you should, or still experiencing sleep apnea symptoms such as nocturia (nighttime urination), you may have a wrong pressure setting. Discussion thread of the inaccuracies of sleep lab titrations and patient at-home experimentation: http://www.cpaptalk.com/viewtopic.php?t=19947&postdays=0&postorder=asc&start=0 Discussion thread on changing your pressure settings: http://www.cpaptalk.com/viewtopic/t25586/New-here--Do-you-change-your-own-pressures.html Discussion thread on why it’s important: http://www.cpaptalk.com/viewtopic/t27856/Why-taking-your-treatment-into-your-own-hands-is-important.html

For people without serious health problems who use machine software in working with their doctor to adjust pressure settings

This is moving up a notch in terms of responsible self management of your therapy. Are you free of serious health conditions such as heart or respiratory trouble, central or complex/mixed sleep apnea, mental health problems, problems with mental acuity, or any other condition that would make your working with pressure settings inadvisable? Are you capable and confident about working with the machine settings and software? Is your physician open to working with you on pressure settings in this manner? See the discussion thread on working with a helpful doctor at http://www.cpaptalk.com/viewtopic/t14847/A-GOOD-doctor-story-for-a-change.html

It is illegal for a DME to change your pressure setting without a doctor’s prescription. It is not illegal for you to work with your doctor in changing your own pressure setting.

Don’t try this at home without software! If you attempt to change pressure settings without software, it’s like shooting at an archery target with your eyes closed. You don’t have enough information to know if your arrow is getting close to the bulls eye. You need to have a machine that is fully data capable, and buy the software (and perhaps a card reader) online at your own expense. Although most software is designed and labeled for the clinician, it is not illegal for you to have it as a patient. One manufacturer, Respironics, wisely offers software designed for the patient. Be aware that your machine’s sensors and software are crude, compared to the sophisticated equipment in a sleep lab. However, they are good enough to be helpful in monitoring and adjusting therapy. Scroll down to see the post by Sleepy-in-AL showing an older Respironics Encore Pro software Daily Details report: http://www.cpaptalk.com/viewtopic.php?t=10245&highlight=puffy Once you have the software, collect some reports to show your doctor, showing your leaks are under control but your AHI (apnea hypopnea index) is still too high. Again visit your doctor and get a written prescription for a new safe pressure or range of pressure, based on your sleep study.

Write down your original pressure and each change you make. Most important, monitor and keep a daily log of how you feel each day, related to the pressure setting and other variables such as mask leak. How you feel is the best indicator of a good pressure setting.

Monitor the software for AHI, flow limitation or UARS, daily events per hour at various pressures, mask leaks, and any other useful data. It’s tempting to overly rely on the software data’s numbers, since they look so precise, but how you feel is more important. It’s necessary to know how to read graphs and charts. If you can’t understand them, get a helper or ask your physician. You will probably need help from a doctor, sleep technician, or other software users to read the first report, if the software doesn’t include definitions of measurements. Although you can ask, your DME RT will probably be prohibited from helping you interpret software reports.

Two measurements of Sleep Disordered Breathing (SDB)

Apnea. The Greek word “apnea” means “without breath.” You stop breathing during sleep for ten seconds or longer. Hypopnea. There is airflow through your throat but at a much reduced level, which leads to not getting enough oxygen. It’s abnormally shallow breathing lasting at least ten seconds.

1. AHI, Apnea-Hypopnea Indexfor sleep apnea: Less than 5 events (apnea or hypopnea) per hour is considered normal. 5 or more events per hour is considered Mild sleep apnea 15+ considered Moderate 30+ considered Severe (from T. S. Johnson MD, Sleep Apnea - The Phantom of the Night, page 211)

Flow limitation or Upper Airway Resistance Syndrome (UARS) is another important, subtle form of SBD. The airflow meets resistance in the nose or mouth, causing the brain to waken the sleeper. The American Academy of Sleep Medicine advocates counting apneas, hypopneas, and flow limitations/UARS for the Respiratory Disturbance Index, RDI, which is more comprehensive than the Apnea-Hypopnea Index.

2. RDI, Respiratory Disturbance Index for sleep apnea: 5 to 20 events per hour is Mild SDB 20 to 40 events is Moderate SDB More than 40 events is Severe SDB (from Barry Krakow, MD, Sound Sleep,Sound Mind, page 245)

Partner with your physician. Show him/her your weekly software printouts and sleep log or diary of how you feel. Use them to plan the next pressure adjustment. For those who were never titrated in a sleep lab, it may take weeks or months to find your optimal pressure or pressure range, but meanwhile, you should be feeling better with each incremental improvement in pressure.

There are no single formulas for success. Try a prescribed setting long enough to know if it works. For most small pressure change adjustments, give them at least week or two. Study your software full details report daily if experiencing any problems, or at least weekly to track and analyze each adjustment. Make small, incremental changes. Change one thing at a time to track the effect and not confuse it with other changes. For example, change only one of the following at a time: mask, mask fitting, humidity level, exhalation relief level (if applicable), ramp time (if applicable), pressure. That’s why it may take months to experiment with all the variables. Most people get their masks and leaks under control, and humidification and exhalation relief, before adjusting pressure settings. (Exception: people who haven’t been titrated and have an APAP initial prescription of 4 to 20 cm/H2O.) For example, you may experiment with masks for a month, getting comfort and leaks under control, while leaving the pressure setting as is. Then you may change the humidifier setting for three days, and then the exhalation relief for four days, leaving the mask and pressure setting unchanged. The following week or two, you may try a new pressure, not changing the mask or other settings. The next week, more refining of the pressure adjustments. Keep a written record of all changes and how you feel, so you don’t get confused and can analyze it later. Discussion thread: http://www.cpaptalk.com/viewtopic/t25791/General-protocol-for-self-pressure-adjustment--Comments.html

Continue to use the detailed software reports and how you feel to track and confirm therapy progress. After you have a correct pressure or range, over time you may want to monitor only monthly or every few months or when you have a problem. When you have a change in masks or weight change, you may want to monitor your software reports and adjust pressures again.

If needed, seek advice from other CPAP users such as http://www.cpaptalk.com/viewtopic.php?t=10357 http://www.cpaptalk.com/viewtopic.php?t=10426 http://www.cpaptalk.com/viewtopic.php?t=16391&postdays=0&postorder=asc&start=0

Once you have a plan

Try if for a week or two, and then, based on your software report and the way you feel, adjust it gradually, narrowing or widening the range or moving it up or down. An AHI of 10 events per hour, which is mild sleep apnea, may mean that your heart is still susceptible to damage. Continue to strive for feeling clear-headed and energized all your waking hours and an AHI of 5 or less. Some people report that an AHI of 2.5 seems to be a marker. With an AHI from 2.5 to 5 they feel tired by the late afternoon or evening, or feel not as good that day. With an AHI under 2.5, they feel great all their waking hours. By comparing how you feel and your AHI figures, you can gauge what your body needs from its PAP therapy. Repeat a pressure or range to be certain that it’s the best for you or a different pressure is needed.

After you have been stable on the same pressure or pressure range for a few weeks or months, borrow an overnight recording pulse oximeter from your doctor or DME, or buy one online. Use it to check your blood oxygen saturation levels at night as another indicator that your PAP is working well.

Ideas for APAP users to discuss with their doctors

With your doctor, discuss a safe range for pressure adjustments in your treatment based on your sleep study, especially the higher pressure. For example, if your titrated pressure is 10 cm/H2O and you have an APAP, how suitable is a range from 7 to 15 cm/H2O for starters? Or does your doctor recommend 9 to 12 cm/H2O? If you haven’t been titrated, is a range from 6 to 16 cm/H2O appropriate for starters or not?

Next, for APAP, some people find a pressure to use as a central number for a range of pressure. If they have a titrated pressure, they use that number. Some people use the median or mean pressure as the central number.

Continuing the above about APAP, some people use their central number and add three points above and below it for a range. For example, if the titrated pressure is 10 cm/H2O, the range is 7 to 13 cm/H2O. Some people start with their titrated setting and go 3 cm/H2O under and 2 cm/H2O above the titrated pressure; for example, 7 to 12 cm/H2O. Some people benefit from an even narrower range, since that may help the machine to respond faster to events; for example, 9 to 11 cm/H2O. Remember, this is tricky business related to your health, throat anatomy, and the capabilities of each machine, so consult a doctor. For example, if you go 2 or 3 above your titrated pressure, is this likely to lead to a pressure-induced central apnea?

Some people on APAP use their titrated pressure as their lowest setting and go up 2 or 3 cm/H2O to catch events. For example, if the titrated pressure is 10 cm/H2O, the range is 10 to 12 or 13 cm/H2O. Again, work with your doctor, based on your titration study and health conditions.

Ideas for straight CPAP users to discuss with their doctors

At some point when they have detected a potentially optimal pressure setting, some people try switching to the straight CPAP mode on their APAP machine, to see if they get better results. Some use their titrated pressure, or 90% pressure, as a straight CPAP setting. If you use the daily events per hour data to find the pressure that gives you the lowest AHI and use that as a straight CPAP setting, it may be too low for events that require a higher pressure setting, and the 90% pressure may be better. Or the opposite, if a 90% pressure is too high and leads to aerophagia or central apneas.

For straight CPAP or autopap users in the CPAP mode, if all this seems too complicated, some start with their titrated pressure or a number just above or below it. For example, with a titrated pressure of 10 cm/H2O, they try that for a week and note how they feel, then try 9 cm/H2O for a week, then try 11 cm/H2O for a week, etc. Once a pressure is found that seems to work, they can fine-tune by going up and down half a cm/H2O from that pressure to see if there is an improvement in the way they feel. For example, trying both 10 and 10.5 cm/H2O.