What are the reasons (indications) for using a bi-level 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 ventilator 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 ventilator assistance requirement (overlap syndrome).

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.

The pressure range of the VPAP is 2 to 25 cm H2O.

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.

 

What is the difference between BIPAP and VPAP?

BiPAP is a registered trademark held by Respironics. 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.

 

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.

 

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.

 

What are central apneas?

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.

 

What is a VPAP device?

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?

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).

 

 

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.

  

How exactly does a bi-level 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.