Ventilator-Assisted Living©

Summer 1998, Vol. 12, No. 2

(continued)

Which Ventilator to Use?

Patricia Folkerth

In the Fall, 1997, issue of IVUN News, I read Dr. E.A. Oppenheimer's article "The American Experience." My name is Patricia Folkerth, and I had bulbar polio in 1950 at the age of 6. I was diagnosed with post-polio syndrome last year. After a sleep study, I was advised to use a CPAP (continuous positive airway pressure) machine, set at "9," which is about average, to correct my sleep apnea. Dr. Oppenheimer's article states that persons with a neuromuscular disease should use "assisted ventilation" rather than CPAP, because CPAP puts a greater burden on respiratory muscles. (I am assuming that by "assisted ventilation" he means a Bi-PAP® S/T system or other bi-level pressure device.)

After several months of using CPAP, I have begun experiencing a heaviness or tightness in my chest, as have some of my friends who are also experiencing the late effects of polio. Does this heaviness mean that we should explore other options for ventilation at night? What kind of test will help us decide which system we should use? I have been hesitant to use a bi-level pressure device because my friends who use them seem to have a great deal of trouble. Is there any other option to support our breathing at night?

Dr. E.A. Oppenheimer responds …

Your questions focus on important issues: whether there is breathing muscle weakness or whether there are reasonably normal breathing muscles but obstructive sleep apnea (OSA).

As one ages with the late effects of polio, respiratory muscle strength may decrease. This may be particularly evident when you lie down, because in this position, the diaphragm has to work harder both to pull air in and also to push the intestines and other abdominal organs which are out of the way when one is upright due to gravity. Thus, night-time breathing abnormality due to muscle weakness is best treated with a device that assists ventilation, such as a small portable bi-level pressure device, e.g. BiPAP® S/T system, or a volume ventilator, e.g. PLV-100, LP6, or LP10.

If the upper airway tends to close off during sleep, OSA episodes occur. These are often successfully treated by continuous positive airway pressure (CPAP) that delivers a constant flow of air to keep the airway open. This requires somewhat more work for the respiratory muscles during the expiratory phase, but the inspiratory phase is assisted by CPAP. It is certainly possible to have weakness in the throat/pharyngeal area that produces OSA, without weakness of the breathing muscles. If this is the case, CPAP is the appropriate treatment.

Pulmonary function tests that show a reduced vital capacity (VC) below 50% of normal and a significant reduction of the maximum inspiratory force (MIF) and maximum expiratory force (MEF) would be indicative of weakened respiratory muscles. It is important to measure the VC in both the supine and upright positions, because with muscle weakness, VC is significantly lower in the supine position. If the tests show significant abnormality indicating weak breathing muscles, then I would consider using a ventilator rather than CPAP.

When there are night-time breathing problems in someone with neuromuscular disease, it is most likely due to respiratory muscle weakness, rather than OSA. However, some individuals may have only OSA or have both neuromuscular weakness and OSA.

Whether to use a portable volume ventilator or bi-level pressure device is an important decision. Sometimes the choice reflects the experience and training of the pulmonary physician or respiratory therapist. Often cost is a factor – in Europe, the costs of the bi-level pressure devices and the volume ventilators are not as disproportionate as they are in the United States. There is a wide range of practice, in some cases questionable, such as using bi-level pressure support for tracheostomy ventilation. Currently, the FDA only authorizes the use of a bi-level pressure support system for not more than 12 hours per day, even though some ventilator users report good experience using it almost 24 hours per day.

The ventilator which is most comfortable for the user and fits his or her individual ventilatory needs best should be the overriding choice. The physician, respiratory therapist, and ventilator user should collaborate on determining the best system, although ventilator users are not often given the opportunity to try different ventilators and systems.

Volume Ventilators

Advantages: 24-hour use, well-suited for tracheostomy ventilation, overcomes airway secretions and resistance, delivers a set volume of air at higher pressure to help cough, easier wheelchair mounting, works off battery power easier, internal battery, external battery can be used also, safety alarms.

Disadvantages: Higher cost, heavier.

Equipment: Nellcor Puritan Bennett LP6, LP10; Respironics PLV-100, PLV-102; Bear 33; Brompton PAC; Breas 501; EV 801; Monnal D, Monnal DCC; Eole 2, Eole 3.

Bi-Level Pressure Devices

Advantages: Lightweight, lower cost, easier to use, adjusts better to leaks.

Disadvantages: Not FDA-approved for more than 12 hours per day, not well-suited for tracheostomy ventilation, no internal battery, not as commonly used with external battery, no safety alarms, noisier, expiratory pressure unnecessary for some patients and may cause thoracic discomfort.

Equipment: Respironics Bi-PAP® S/T, Healthdyne Tranquility PSV model 7700, Nellcor Puritan Bennett Knightstar 335, ResMed VPAP® II ST, Taema DP90, AirSep Remedy.TM

–E.A. Oppenheimer, MD, Pulmonary Medicine (retired), Los Angeles, California

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