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Vance Wilson, Senior Product Manager, Bilevel and VPAP® Devices, began his healthcare career as a registered respiratory therapist (RRT) working in the hospital and in adult, neonatal, and pediatric intensive care. After several years, he became a sales representative then product manager in the respiratory device industry. Vance has been with ResMed for over three years.
Are these devices rented or purchased generally?
I don't know how it breaks out, but they are both rented and purchased. My conversations with home care dealers lead me to believe that they are often rented and then converted to purchases several months after making sure the therapy will be continued. Some dealers offer a long-term rental option that assures that any maintenance or repairs are handled without added expense to the patient.
What are the reasons (indications) for using a bilevel device?
Bilevel devices are often used for patients that cannot tolerate fixed pressure CPAP at higher pressure prescriptions. The higher pressure is still required to relieve upper airway obstruction; however, the expiratory pressure may be lowered to increase comfort over a fixed higher pressure level. Bilevel is also used with patients who need some ventilatory assistance. The types of patients that fit in this category are those with neuromuscular disorders (i.e. ALS, post-polio), patients with chronic lung disease, those who have chest wall deformities, and those who are being treated for central apnea. Central apnea is characterized by lack of any respiratory effort during sleep for prolonged periods as opposed to obstructive apnea where there is respiratory effort, but the airway is obstructed. Central apnea patients need a backup rate that guarantees a minimum respiratory rate during these apneic periods. And lastly, some patients have both obstructive sleep apnea and a ventilatory assistance requirement (overlap syndrome).
Are there many different bilevel devices out there?
There are four main manufacturers marketing bilevel devices. No doubt, there will be at least one more player in the market in the coming year.
Could you elaborate on the concept some have that mouth leaks are more common with bilevel, and if that is so, does the VPAP series deal with that?
Mouth leak is more common in bilevel treatment primarily due to the higher inspiratory pressure commonly used for failed CPAP and ventilatory assistance patients. The other reason that mouth leak is such a big issue with bilevels is the fact that they have to track the patient's respiratory pattern in order to stay in sync. The fastest way to make a bilevel patient not use their device is to let the device get out of sync with the patient's respiratory pattern. VPAP uses the combination of the software algorithm Vsync™ and some unique setting parameters called TiCONTROL™. TiCONTROL allows the clinician to fine-tune minimum and maximum inspiratory time limit parameters. In other words, VPAP can be set to prevent premature termination of inspiratory pressure (before an effective volume of air is delivered) or it can be set to prevent prolonged inspiratory pressure. During a mouth leak, a bilevel device can no longer accurately track the transition from inspiration to exhalation. Consequently, the unit gets stuck at the inspiratory pressure for 3 seconds (maximum limit). With VPAP, the clinician can set a maximum inspiratory time that is tailored to the patient's inspiratory time. These features are very effective in the management of various diseases for which many patients are prescribed bilevel therapy. No other device has this flexibility. Vsync is our patented control algorithm for the management of leak and the reliable performance of patient/device synchrony. Vsync tracks the changing mask and mouth leaks and constantly readjusts the baseline and breath trigger thresholds to remain in synchrony with the patient.
I have a tendency to breathe through my mouth at night. I have used your VPAP for a few years now, and found the only effective way to control my mouth breathing at night is to tape my mouth shut with surgical tape (to my doctor's dismay). I understand you now make a full face mask to alleviate this problem. Please expand on this option.
Certainly, the easiest way to handle a mouth leak is to use a full face mask. Our sales of full face mask vs. nasal masks continue to grow. The Mirage full face mask is surprisingly comfortable to wear. I believe that this option would be favorable over taping your mouth shut. Give it a try. Also, I would mention that the IPAP Max setting on your VPAP may need to be adjusted if you are having problems with prolonged inspiration (unit not shutting off when you are exhaling) as a direct result of mouth breathing.
I would like to know the range of pressure changes that are handled by the VPAP machine. I am presently using a pressure of six but could possibly be needing eight at times. Six keeps the mouth breathing to a minimum but does not eliminate it. Thanks!
The pressure range of the VPAP is 2 to 25 cm H2O.
Your AutoSet technology is superior to others on the market. What features does your VPAP have that set you apart from other brands?
As is the case with our AutoSet T™[since this chat, ResMed has released another autotitration device, the AutoSet Spirit™], we do some pretty unique and useful things with our VPAPs. The most important VPAP features are called TiCONTROL and Vsync. TiCONTROL allows the clinician to fine-tune minimum and maximum inspiratory time limit parameters. In other words, VPAP can be set to prevent premature termination of inspiratory pressure (before an effective volume of air is delivered) or it can be set to prevent prolonged inspiratory pressure (often caused by mouth leak). These features are very effective in the management of various diseases for which many patients are prescribed bilevel therapy. No other device has this flexibility. Vsync is our patented control algorithm for the management of leak and the reliable performance of patient/device synchrony. Vsync tracks the changing mask and mouth leaks and constantly readjusts the baseline and breath trigger thresholds to remain in synchrony with the patient.
Is it true that Central apnea is best treated by bilevel?
Yes. A bilevel is better than CPAP for central apneas because it assists spontaneous respiratory effort, as opposed to merely keeping the upper airway open. With a central apnea, you actually stop making an effort to breathe, so an obstructed airway is not the problem, and a constant pressure wouldn't assist ventilation. The two pressure levels of a bilevel device assist ventilation during these periods of apnea. I would also mention that fixed CPAP pressures above 10 cm H2O have been known to actually increase or cause central apnea in some cases.
Is bilevel only used by patients who fail on CPAP?
No. Bilevel is also used with patients who need some ventilatory assistance. The types of patient that fit in this category are those with neuromuscular disorders (i.e. ALS, post-polio), patients with chronic lung disease, those who have chest wall deformities, and those who are being treated for central apnea. Central apnea is characterized by lack of any respiratory effort during sleep for prolonged periods (>10 seconds) as opposed to obstructive apnea where there is respiratory effort, but the airway is obstructed. Central apnea patients need a backup rate that guarantees a minimum respiratory rate during these apneic periods.
Is VPAP noisier than CPAP? Bigger?
The VPAP is similar in sound output to our ResMed S6 CPAP when in the CPAP mode. However, VPAP is not usually used in the CPAP mode, except in a sleep lab, so we must measure the sound output in a bilevel mode and compare it to other units on the market. Although VPAP is the quietest unit we have tested, patients that are accustomed to CPAP may find the sound more noticeable. This is because the unit is cycling between two different pressures, which is accomplished by changing the motor speed to push more or less air into the circuit. Sometimes a louder yet constant sound is less noticeable.
Are there certain pressure requirement minimums for bilevel use? I have difficulty with CPAP on a pressure of 9 cm H2O, but my doc says that's too low a pressure for him to prescribe a bilevel for me. He tells me to just keep trying!
There is no standard that clearly states when you should consider trying bilevel over CPAP. What exactly is your trouble with CPAP? Do you have difficulty breathing against the CPAP pressure? Have you tried to use the delay feature in order to give yourself a chance to fall asleep before the unit reaches full pressure?
Someone in the Talk About Sleep chat rooms said they got a bilevel issued as soon as they were diagnosed. Yet, I am fighting with my doctor for one. Why?
Not sure, but I can only guess that the diagnosis was other than pure obstructive sleep apnea. For instance, if you have a neuromuscular disorder (i.e. ALS) it's quite easy to qualify for a bilevel device without first failing on a CPAP. The other possibility is the prescribed pressure may have been high enough in addition to inability to tolerate this high CPAP pressure during the sleep lab titration. This may have been adequate for the physician to justify a bilevel unit. Perhaps this patient has an overlap syndrome (OSA + need for ventilatory assistance).
I was recently hospitalized overnight for a minor surgery. The hospital would not let me bring and use my own bilevel. They insisted on using one of theirs. Are hospital machines different in some way?
This is a common practice for hospitals, and I believe it is related to liability. Hospitals require all devices to have a hospital-grade, grounded electrical plug. They also require that all the equipment used in the hospital is electrically tested at least once/year. We have had problems selling to some hospitals that have not yet caught up to current standards. Our devices are electrically isolated (double insulated, double isolated) from the patient and therefore are not required to be grounded. In fact, they are not permitted to be grounded, as this would defeat the electrical safety design. So, I'm not sure what the reason is in your particular case, but if you ask them why and they say it's just policy, then it's a liability issue with untested equipment. If they say it's because the unit does not have a three-pronged plug, then they are ignorant of the fact that double insulated, and isolated (class II) devices are a suitable substitute for three-prong grounding. Don't feel picked on, we also have to fight this battle now and again.
I know that not all masks and nasal pillows may work with AutoPAP, but how about bilevel. Are there any known masks or nasal pillows that may not work with your VPAP?
Most masks and other interfaces can be used with VPAP; however, there are some features that may be affected and therefore may create problems. I can't speak for all bilevels, but in the case of VPAP, features such as Smart Start/Stop, mask alarm, and breath triggering may be affected by certain interfaces that possess vastly different flow resistance characteristics. In other words, the mask alarm may not sound when the mask falls off or the Smart Stop feature may not work due to the higher resistance of nasal prongs.
What is the difference between BIPAP and VPAP?
BiPAP is a registered trademark held by Respironics. Since they were first to market before ResMed and others entered the market, the name BiPAP stuck as the generic term for any and all bilevel devices such as VPAP. It's similar to Kleenex or Band-Aid, which are both brand trademarks.
Does your VPAP download any info for patient or doctor?
Yes. It downloads basic compliance data (hours of usage per session).
Thanks for having these moderated chats, I have learned more here than anywhere! Does VPAP have any bells and whistles not found in other brands of bilevel machines?
The most important VPAP features are called TiCONTROL and Vsync. TiCONTROL allows the clinician to fine-tune minimum and maximum inspiratory time limit parameters. In other words, VPAP can be set to prevent premature termination of inspiratory pressure (before an effective volume of air is delivered) or it can be set to prevent prolonged inspiratory pressure. The most common cause of prolonged inspiration is mouth leak. These features are very effective in the management of various diseases for which many patients are prescribed bilevel therapy. No other device has this flexibility. Vsync is our patented control algorithm for the management of leak and the reliable performance of patient/device synchrony. Vsync tracks the changing mask and mouth leaks and constantly readjusts the baseline and breath trigger thresholds to remain in synchrony with the patient.
How high does the VPAP go? I am now on 20 and will probably need an increase soon?
The maximum pressure is 25 cm H2O. Higher pressure may exceed the esophageal sphincter opening pressure, which may result in air entering your stomach.
What is "back-up rate" and how does it work?
A back up rate is only available on certain bilevel devices that include an S/T mode. The T stands for timed. The clinician sets a minimum respiratory rate for certain patients that have inconsistent respiratory efforts and thus don't have a reliable respiratory rate. When this occurs, the "timed" back up rate kicks in to guarantee this minimum rate. As soon as the patient breathes faster than the back up rate, they again can control the rate. In the case of VPAP, even when a timed breath is triggered, the patient still has control of when the breath is terminated. This feature helps keep the patient in synchrony even if they don't trigger the breath initially. They often will participate in determining when they want the breath to end.
How does VPAP know when to give inhalation pressure? Or is it a timed delivery of pressure?
VPAP is flow-triggered, meaning it responds to the patient's inspiratory airflow. In order to do this, it must subtract the flow that exits the bleed ports in the mask (which is a known constant factor at a given pressure) and flow that leaks around the mask/mouth. This requires a rather complicated software algorithm to sort all this out, but it is very effective. Based on the isolated patient flow, VPAP is looking for a minimum rate of flow (approximately 25 milliliters/second) to determine that the patient has initiated a new breath. In a mode called S/T (spontaneous/timed), if the patient does not initiate a breath before a maximum period (based on the back-up rate) has elapsed, a time-triggered breath is machine initiated. VPAP also has a Timed mode whereby the patient's respiratory activity is ignored and the breaths are strictly delivered at regular timed intervals. Not too many clinicians use the timed mode and thankfully so. You didn't ask, but the algorithm and threshold are also used to determine when the patient has begun exhaling, which is just as important in keeping in sync with the patient's breathing pattern.
I read on your web site that a CPAP is not considered a ventilator, but a bilevel is. Please explain!
Let's take a quick look at Webster's definition for ventilate: "To cause fresh air to circulate in." The only conventional way to cause fresh air to circulate, in this case to allow carbon dioxide to be expelled from the pulmonary system, you must create a pressure differential. Just as in the weather, wind is created by differences in barometric pressure from one area to an adjacent area. Bilevel provides two pressure levels that are cycled between during each breath. The higher pressure is delivered during inspiration to cause airflow to move or circulate into the lungs. The lower pressure is provided during the expiratory phase to allow air to move out of the lungs carrying the body's gaseous byproduct carbon dioxide. Conversely, CPAP only provides one pressure level and thus does not promote the movement of air in and out of the lungs. In this case, the patient must provide the pressure changes from within the pulmonary system in order to ventilate. The primary instrument that normally creates the necessary pressure differential is the diaphragm.
I am an MS patient and wonder if VPAP would benefit my constant daytime sleepiness. I have had a sleep study and do not have apnea, but my doctor mentioned the possibility of bilevel use.
I'm afraid I don't have much information on MS in relation to bilevel treatment. I did a quick review of some literature and it seems that the disease is quite variable in its clinical presentation. It could be that the fatigue symptom could be related to periods of under ventilation or frequent arousals during sleep. A simple nocturnal oximetry study (monitoring of oxygen saturation during sleep) could tell a lot about your sleep quality. Also, a short trial using a bilevel device would be relatively easy to perform and you should be able to see a difference within a week if it is effective. Since your doctor has already mentioned it, you should be able to justify a trial to see if it helps.
Why would a person have a high carbon dioxide level? Is this common with sleep apnea? Why would VPAP help with this?
Carbon dioxide is the marker for the quality of ventilation. If carbon dioxide is elevated then there is something wrong with the cardio-pulmonary system. Some common causes are chronic obstructive lung disease, e.g. emphysema, asthma (during an attack only), central apnea (during periods of apnea), and neuromuscular diseases that cause weakness in the muscles of respiration (diaphragm). Slightly elevated carbon dioxide levels during periods of obstructive or central apnea are common, but they are completely reversible once the apnea ceases. Bilevel is used to normalize carbon dioxide during these apneic periods. For patients that have chronic carbon dioxide elevation, VPAP is used to assist ventilation during sleep and sometimes even during the day to help normalize carbon dioxide and even oxygen saturation during these episodes. In this patient group, the effect of normalizing carbon dioxide during sleep has a sustaining effect of lowering the carbon dioxide levels even during the day when the patient is not receiving bilevel therapy. It resets their ventilation rheostat.
I have a high number of hypopneas and was diagnosed with UARS last week. My doctor says UARS is treated with CPAP, but should I be asking about your VPAP?
VPAP is not usually indicated for pure UARS unless there are other overlapping diseases that would necessitate assisted ventilation, i.e. emphysema. If, however, the pressure required to treat the disorder is too high for you to tolerate, then possibly a bilevel unit would improve comfort by providing a lower expiratory pressure and using the higher inspiratory pressure to relieve the UARS.
I know that the high level of VPAP is determined in the sleep lab to stop apneas, but how is the exhalation pressure determined?
Frankly, there seems to be much controversy regarding the use of bilevel for the treatment of non-tolerated fixed CPAP. In this case, the protocol for setting the two pressures are similar to setting CPAP, but by using two pressures that are typically 4-7 cm H2O apart. Once that is established, if the patient also needs ventilatory assistance, the upper pressure would be increased until oxygen desaturations are obliterated or carbon dioxide is normalized (if this is monitored). Basically, the exhalation pressure is lowered enough to improve comfort, but not so much that the upper airway is allowed to close.
I was told I have mixed apnea, both obstructive and centrals. I will be buying a bilevel soon, as recommended by my doctor. I have no insurance and these machines are so much more than CPAP. Why won't CPAP work? What does VPAP do different and better for the centrals?
CPAP would work fine for your obstructive apneas, but central apneas mean you sometimes stop trying to breathe during sleep. CPAP above 10 cm H2O has been shown to increase or cause central apneas. Bilevel, in particular units that have an S/T mode, is required to provide the back up ventilation necessary to maintain normal oxygen and carbon dioxide exchange during these central apneas. The key to good bilevel performance is that it synchronizes with your respiratory efforts when you are breathing normally so as not to disturb your sleep. VPAP has an algorithm (Vsync) that maintains good synchronization even when the mask or mouth has intermittent leaks. There are also unique inspiratory time control features (TiCONTROL) that allow your clinician to fine-tune the inspiratory time window to your normal breathing pattern.
What are central apneas? I was just told I have apnea, how do I find out if I have central apnea?
Central apnea is cessation of respiratory effort for greater than 10 seconds. During an obstructive apnea, you are prevented from drawing air into your lungs despite respiratory effort, but during a central apnea, you stop trying to breathe. You need to have a sleep study to make the diagnosis. Sometimes this can be done in a home environment, but most payers will require an attended, in-lab study.
Your ResMed Sullivan Comfort automatically adjusts pressure for mask leaks. Does this mean it is an AUTO-bilevel?
This just means that the unit measures the hose pressure relative to the set pressure(s) and adjusts the flow to maintain the set pressure(s). Without this feature, the mask pressure could fall to a sub-therapeutic level in the event of a leak around the mask cushion or through the mouth.
Your Web site says that "Recent studies show that all patients on bilevel therapy experience mouth leaks" why is that? I wanted to try a bilevel, but now am not sure. Did I misunderstand?
This comment has just been changed to clarify that patients with "nasal masks" experience mouth leaks. The studies that the comment refers to showed that sometime during the night in virtually all the patients in the study, mouth leak was noted. In fact, this is a true statement for a high percentage of CPAP patients as well, but it is more of an issue with bilevel due to the need for a bilevel unit to know what breath phase the patient is in at all times. If there is a significant mouth leak, bilevel units are unable to accurately track whether the patient is inhaling or exhaling. The result is the patient can get out of sync with the unit. Don't be alarmed; there are a few ways to deal with this potential problem. First, there are chin straps, but these are often ineffective. Then there are full face masks, which sound worse than they are, especially if you get a Mirage full face mask. And lastly, there are features in VPAP that prevent the inspiratory time from getting out of control, which is the main manifestation of this problem as it relates to bilevel units.
I am considering bilevel because my pressure keeps needing to be increased. I love the ramp feature on my CPAP, does your VPAP have a ramp feature?
Yes, VPAP has the same ramp feature as our ResMed S6 CPAP line. I would suggest considering the AutoSet T as well, although reimbursement may be a bit tougher. The AutoSet T automatically adjusts pressure in response to several measurements that are related to your obstruction at that particular moment. In your case, since your fixed pressure prescription keeps climbing, you obviously have some anatomical dynamics that are causing this increase in pressure. No matter what it is, the AutoSet T will simply maintain the correct therapeutic pressure breath-to-breath and night-to-night.
Is the danger of CO2 re-breathing more prevalent on bilevel or at certain pressures?
CO2 rebreathing is a very complex factor. There are many parameters that can increase or decrease the risk. The one absolute is that lower pressures increase the risk of CO2 rebreathing. Our bilevel units start at 2 cm H2O due to the fact that our masks have been designed to minimize this effect by reduced volume inside the mask and higher intentional bleed flows that are strategically placed in the mask frame or inlet elbow. Other factors that are much more difficult to access are respiratory rate, breathing pattern, existing lung disease, and level of leak. In general, the risk is not nearly as high today as newer mask technologies have tended to address the issue for most applications. Unless you have chronic lung disease, breathe at an accelerated rate, or use a poor mask design and the expiratory pressure is quite low, you don't need to worr
I notice you have several different bilevel products, can you simply explain the basic difference between them? I am looking to purchase and want to understand which is best suited for my needs. Thanks in advance for your answer! I have loved all of my ResMed masks and currently use your CPAP.
The Sullivan Comfort is your basic bilevel, which is well suited to treat garden variety OSA, as long as compliance downloading is not required and a pressure difference of 7 cm H2O or less (between inspiratory and expiratory pressure) is needed. The VPAP II is often chosen as it offers a bit more flexibility for the clinician to fine-tune the breath flow and inspiratory time. It has an LCD to make changes very easy and can download compliance information (hours of use/night). The VPAP II ST-A is only needed if you require a back up rate (S/T mode) and integral alarms, but it doesn't sound as though this is what you need. Of course, the cost goes up as you go from the Comfort, to VPAP II, to VPAP II ST-A.
My home health care company told me flat out that my insurance will not pay for a bilevel machine, even though my doctor said I could choose between CPAP or bilevel. Is it simply a money issue or what? The Home Health care would not explain and my doctor is no help either. Insurance company never has anyone available for me to talk to when I call. Very mad!
Basically, there is no standard that clearly states when you should consider trying bilevel over CPAP. In fact, to my knowledge, there aren't even any studies that show that bilevel improves patient tolerance of high fixed pressure CPAP in treating OSA. However, lack of clinical data doesn't diminish the overwhelming industry standard that when the patient is unable to tolerate fixed CPAP, and therefore will not comply with the treatment, a bilevel unit is an alternative treatment. It all boils down to you giving CPAP a good try, using the ramp or delay feature to progressively increase pressure as you sleep and then still not being able to tolerate the treatment. The physician should then be able to justify the additional cost of a bilevel unit. Payers certainly recognize that paying a little more today offsets paying lots more in the long run for the complications associated with untreated OSA. If we could only get more of them to realize the more logical device progression is from CPAP to AutoSet T. The AutoSet T (automatically adjusting CPAP) would address the non-compliance issue more effectively at a lower cost.
VPAP is the ResMed product line of bilevel positive airway pressure devices. It stands for Variable Positive Airway Pressure.
What are the differences between VPAP, BiPAP, and bilevel devices?
Good question. VPAP and BiPAP are both trademarked names for bilevel devices. Many people call bilevel devices BiPAPs, but this is simply due to the fact that BiPAP was first into the market. Just like Kleenex and Band-Aid, this trademark name has been used as a generic term for all bilevel ventilators.
How does a bilevel device work?
Bilevel devices work by cycling between two pressures, a higher pressure for inspiration and a lower pressure for expiration. Most bilevel devices "decide" when to cycle by monitoring the respiratory effort (inspiratory flow) of the user. Many bilevel devices also have a backup rate, basically a timer that ensures a minimum respiratory rate is maintained.
How does a bilevel device differ from a CPAP machine?
A CPAP delivers one constant level of positive pressure while a bilevel device alternates between two pressures, one for when you inhale and one for when you exhale. They treat different conditions.
When should a VPAP or bilevel device be used?
Bilevel devices are often used for patients that cannot tolerate fixed pressure CPAP at higher pressure prescriptions. The higher pressure is still required to relieve upper airway obstruction, however the expiratory pressure may be lowered to increase comfort over a fixed higher pressure level. Bilevel is also used with patients who need some ventilatory assistance. The types of patients that fit in this category are those with neuromuscular disorders (i.e. ALS, post-polio), patients with chronic lung disease, those who have chest wall deformities, and those who are being treated for central apnea. Central apnea is characterized by lack of any respiratory effort during sleep for prolonged periods as opposed to obstructive apnea where there is respiratory effort, but the airway is obstructed. Central apnea patients need a backup rate that guarantees a minimum respiratory rate during these apneic periods. And lastly, some patients have both obstructive sleep apnea and a ventilatory assistance requirement (overlap syndrome).
Is the VPAP device the same cost of a CPAP or the AutoSet T?
No. The price continuum for these products starts with CPAP being the least expensive, then AutoSet, and the most expensive is VPAP. Of course, there are models within both CPAP and VPAP with different prices, but the product categories still fall this way on the price continuum. The added cost for AutoSet is in components to detect snoring, flattening, etc. as well as the LCD screen and memory for data acquisition and downloading. The VPAP has a more aggressive blower/impeller, flow measuring components, a larger LCD, and integral alarms.
How does the VPAP differ from the BiPAP?
The major differences that our customers see is the philosophy of breath control design and noise output. Our philosophy in implementing methods to handle the various conditions and disease states that the VPAP will encounter differ dramatically from the BiPAP. For instance, the BiPAP relies heavily on several software algorithms in order to manage mouth leak and synchronization challenges, which are very common in this treatment. These algorithms do work well with many common conditions but sometimes fail to address many others. On the other hand, VPAP does have an algorithm to manage breath trigger thresholds in the face of changing leak, but instead of trying to handle all other conditions with more imperfect algorithms, we give the clinician a few additional manual settings that provide them the control they need to deal with so many other conditions that today aren't addressed with software. The second major difference is the lower noise output of VPAP. You just have to listen for yourself to appreciate. Many of our reps show the VPAP with it turned on while talking about its features. Then when the customer says, "Okay, could you turn it on so I can hear how quiet it is," they say, "It's been on all this time." They are amazed.
Is a bilevel device louder than a CPAP?
It really depends on the pressure setting. For some, even if the pressure setting is similar to CPAP, the fact that the pressure is changing between inspiratory and expiratory pressure levels is more noticeable than a constant sound.
Can a bilevel device use humidification like a CPAP machine can?
Absolutely.
Can a bilevel machine be used with a full face mask?
Absolutely. In fact, since the pressure changes breath-to-breath and many bilevel patients are on higher inspiratory pressure due to their disease, more full face masks are used on bilevel units vs. CPAP.
Does the VPAP machine work with a Breeze mask?
It can, but some of the features may be affected. The Breeze system has a very small inlet hose, which creates very high resistance to flow. This high resistance can cause the mask alarm, Smart/Start/Stop feature, and compliance data functions to be compromised. The treatment pressure (at the mask) may also be slightly less. If none of these features are important to the user or clinician, then the effect is unimportant.
Does a VPAP machine work with a Fisher & Paykel humidifier?
Yes.
I use oxygen all the time, and I have been told that I might have to use a VPAP machine to help me breath better during sleep. Can I use this machine with oxygen and humidification?
Absolutely. You can use up to 15 liters/minute of oxygen and approved humidifiers with no issues.
Can a bilevel machine be used if I am already on oxygen?
Yes. You can use a VPAP with up to 15 liters/minute O2. The oxygen can be bled into the circuit instead of through a nasal cannula. You will likely need to try different oxygen flow and monitor a pulse oximeter to get the right flow while on a bilevel. Oxygen delivery through a bilevel and mask is a bit more touchy than through a nasal cannula alone. Just keep in mind that if you change the mask, the treatment pressure, or where you bleed the oxygen into the circuit, then the result may change even if the oxygen flow is constant.
How many conditions beside sleep apnea can a bilevel device be used for?
Since a bilevel is essentially a ventilator, it is often used to provide assisted ventilation for many diseases: ALS, post-polio, chest wall deformity, chronic lung disease, and central apnea disorders. In the acute care environment, bilevels are often used for short-term ventilation when placing a tube in the patient's trachea is either impossible or undesirable.
In the sleep lab, is it harder or easier to titrate an apnea patient with the VPAP?
I guess it might be slightly harder, but not much. You just need to pick an EPAP pressure that helps the patient cope with the treatment, typically 3-7 cm H2O lower than the inspiratory pressure. The inspiratory pressure is determined just as you would a CPAP pressure.
If during a CPAP titration, a patient has no further apneas or hypopneas on a pressure of 15, but is intolerant to the constant pressure, what bilevel pressures would you suggest be started in this case?
Unfortunately, the protocols that I have at my disposal don't describe the titration process starting with a final, fixed pressure. Let me describe the protocol that I have; hopefully, you can modify this to work for your scenario. First, start at IPAP 8, EPAP 4. Then, increase both pressures together (1-2 cm increments) until you have obliterated airway obstruction, verified by absence of snore and no failed attempts to trigger the device into IPAP despite respiratory effort. Then, if the patient has overlap syndrome, you may need to continue to increase the IPAP alone (1 cm increments) to provide the necessary ventilatory assistance to obliterate non-apneic oxygen desaturations. Ideally, transcutaneous CO2 is also monitored to help fine-tune the IPAP pressure.
What actually triggers the change in the two pressures from Inspiratory to Expiratory in a bilevel device, change in flow or change in pressure?
Flow triggering is used for most bilevel devices as well as ICU ventilators today. Some devices still pressure or volume trigger. In the case of VPAP, the device is looking for a threshold of approximately 25-50 ml/sec flow.
What are the advantages of each triggering mechanism?
Sorry, I don't have studies to site to substantiate any claims, but I do know that in ICU ventilators flow triggering was shown to provide the shortest delay time under most conditions. Flow triggering definitely performs better in obstructive patients that exhibit autoPEEP as it is easier to meet the flow-trigger threshold than to draw the autoPEEP level down to the pressure threshold.
Is one triggering mechanism better in severe restrictive lung disease with chronic carbon dioxide retention?
I'm not aware of any data to support a bias toward one trigger mechanism; however, a recent abstract presented at 2001 ATS meeting showed that flow-triggered pressure support devices tended to shorten the inspiratory time when connected to a restrictive lung model. Conversely, inspiratory time was prolonged when connected to an obstructive lung model, the worst thing to do for these patients. We hear from restrictive patients who complain of waking up short of breath and feeling suffocated. VPAP has a unique setting called IPAP Min that allows clinicians to set a minimum inspiratory time for these patients. The IPAP Min feature is active for both spontaneous and timed breaths (for S/T mode). Other devices have a timed inspiration setting, but this is for timed breaths only. IPAP Min has been very useful in restrictive patients in helping to assure consistent volume delivery even in deep stages of sleep.
During the day I use two liters per minute of oxygen, which is fed directly to my nose using a portable Helios tank. My question deals with the use of an oxygen concentrator during sleep to produce the same amount of oxygen. The oxygen from the concentrator is fed through a connector hose to my ResMed VPAP II (Sullivan VPAP II). I question whether the oxygen concentrator is really needed since the air from the VPAP system will dilute the oxygen being delivered. Maybe the VPAP system is sufficient to do the job. I use an IPAP of 16 and an EPAP of 13, and the flow goes into an HC300 glass, which holds distilled water and is heated by a HC100 Fisher & Paykel heater. At the exit vent, there is a connector that takes the hose from the oxygen concentrator. I am using a Mirage mask and headgear.
Your observations are sound. It is true that the 2 L/min of oxygen bled into the VPAP circuit is significantly diluted with room air. However, this is also the case with oxygen delivered through a nasal cannula. Although the concentrator releases nearly 100% oxygen, the concentration actually received through a cannula is roughly 24-26% (room air is 20.9%). This is due to the mixing of room air, regardless of whether you breathe through your nose or mouth. We have done some testing on the estimated oxygen concentration of various masks and have found that they are all different under identical conditions. Some deliver higher or more stable oxygen concentration if connected directly to the mask. Others deliver higher or more stable oxygen concentration when bled into the circuit. It important to note that leaks have a major effect on oxygen delivery as do your breath-to-breath volume and pressure setting.
With all that said, we tested our disposable nasal mask at similar pressures, using 2 L/min oxygen with and without leak, and we tested it using an average adult breath volume. We found that the oxygen delivery was pretty consistent, around 23%-25%. This is not the mask you're using, but at this low oxygen flow the concentration doesn't appear to vary that much between masks. I think you're pretty close, but an oximeter and how you feel are the best ways to affirm this.
How exactly does a bilevel machine help us to get rid of carbon dioxide build-up if we are retainers? All pressure seems to be while we inhale.
First, I should point out that there is pressure applied while you exhale as well as when you inhale. Carbon dioxide (CO2) retention (or hypercapnia) is a consequence of the cardio pulmonary system's inability to adequately blow off the CO2 that the body produces. For instance, someone with chronic obstructive pulmonary disease (COPD), due to damage to both airways and lung air sacs, has a very difficult time ventilating (moving a sufficient volume of air in and out of the vast lung fields to "blow off" enough CO2 to normal levels). If they work harder to ventilate, they produce more CO2; it becomes a vicious cycle. A bilevel device is a ventilator that augments your spontaneous effort to help blow off CO2 by increasing the volume of air per breath without you increasing effort. In fact, depending on the settings, you may not have to work nearly as hard to maintain as without the therapy. It was once thought that using a bilevel machine would improve CO2 at night when the bilevel device would improve rest by reducing the ventilatory effort of the patient, but they would probably worsen during the day. Since those early days of speculation, it has been well documented that nocturnal ventilation, which can normalize CO2 during the treatment, has a sustaining effect of reducing CO2 during the day as well. The physiology is very complicated, but suffice to say that the body's threshold for CO2 is reset to a lower level. Therefore, the body is no longer targeting the higher CO2 level it had before treatment. The fact that the patient gets a better night's sleep likely helps them maintain more consistent ventilation during the day. The increased breath volume may also help to improve ventilation in areas of the lungs that tend to collapse and improve lung secretion mobilization. Oftentimes, the result is increased quality of life and increased activities of daily living due to higher energy levels.
I believe you have an AutoSet CS bilevel device in clinical trials for CSR within the USA. Can you please provide an update on the status of these trials and why your VPAP II is not used, i.e., is the VPAP II more for OSA patients, with possibly heart failure? What type of patients are best indicated for your VPAP II Bi-Level device?
Sorry to be vague on this issue, but since this a new device in a clinical trial for FDA clearance, I cannot give very complete information, except to say that the AutoSet CS is not, strictly speaking, a bilevel device. The trial is proceeding as expected. We are selling this device in other parts of the world, so we are quite confident of the outcome at the conclusion of the trial. Bilevel and CPAP devices have been used for the treatment of Cheyne-Stokes respirations. However, we believe the AutoSet CS is even better for these patients. To answer your second question, the types of patients that are indicated for the use of bilevel are patients that have problems tolerating fixed CPAP pressure (usually higher than 10 cm H2O), and patients that need ventilatory assistance either due to central apneas (lack of respiratory effort for at least 10 seconds), respiratory insufficiency and respiratory failure.
View the VPAP and other ResMed products in the Talk About Sleep Equipment Fair.
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