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Post-Polio Health (ISSN 1066-5331)

Vol. 17, No. 2, Spring 2001

Breathing Problems of Polio Survivors (continued)

What is mechanical ventilation (MV)?

Mechanical ventilation is the use of machines to help people breathe when they are unable to breathe sufficiently on their own. It is most often used for a few days in a hospital setting, when people are recovering from surgery or during a serious illness. However, some people may be unable to breathe on their own after the acute illness is over and may require long-term MV. Other people may have a stable, chronic condition that prevents them from breathing on their own; they may need to use a ventilator only at night or both at night and during the day.

Assisted breathing through mechanical ventilation can help people sleep better and result in improved lung function during the day. MV can restore the gas exchange and prevent respiratory failure.

When is mechanical ventilation an option?

A general guideline, but not a rule, suggests that mechanical ventilation be initiated when there is a 50% decline in VC or a VC of under 1 L. Each symptomatic survivor needs a comprehensive evaluation by a knowledgeable physician to determine when to start MV. This is especially true of the survivors of bulbar poliomyelitis. Mechanical ventilation helps rest the respiratory muscles, resets the sensitivity to CO2 of the controller in the brain, and improves pulmonary mechanics by providing more functional lung expansion.

Is exercise a treatment option?

Chest expansion exercises may help keep the chest wall more elastic and avoid loss of lung volume. There are four ways this can be done: with an Ambu-type resuscitation bag, using a volume ventilator for air stacking, using glossopharyngeal (frog) breathing, or using an IPPB (intermittent positive pressure breathing) machine.

If I need mechanical ventilation, what are the options?

The older technology of negative pressure ventilation, which developed during the polio epidemics to keep respiratory polio survivors alive, has given way to the newer technology of positive pressure ventilation.

Negative pressure ventilators apply intermittent negative pressure (like a vacuum) to the chest and abdomen by means of an iron lung or Porta-Lung, a chest shell (cuirass) or a form of body jacket or wrap. Some polio survivors still use the iron lung, Porta-Lung or cuirass.

The pneumobelt is also still used. It is an inflatable corset around the abdomen which acts by pressing on the abdomen to augment exhalation. Inspiration is not assisted. The pneumobelt can only be used in the upright, seated position and does not work if one is either underweight or overweight.

Positive pressure ventilation uses a bilevel pressure support device or a volume ventilator to deliver air noninvasively via a face mask, nasal mask, nasal pillows, mouthpiece, lipseal or oro-nasal combination, called noninvasive positive pressure ventilation (NPPV). Positive pressure can also be delivered invasively through a tracheostomy tube (TPPV).

What is the difference between a bilevel device and a volume ventilator?

Bilevel pressure devices continuously deliver air, but the inspiratory pressure can be adjusted separately from the expiratory pressure. Bilevel devices are also used with a face or nasal mask or nasal pillows, and, like CPAP, used mainly at night. However, bilevel devices can only deliver a certain amount of pressure that may not be enough for people with respiratory muscle weakness and underventilation. There are many bilevel pressure devices on the market, but the only one that can be truly called BiPAP® is from Respironics.

Compared with volume ventilators, bilevel devices are lightweight, less expensive, easier to use, and adjust better to leaks. However, disadvantages include not being well-suited for tracheostomy ventilation, having no internal battery, not as commonly used with an external battery, may be noisier, and the expiratory pressure is unnecessary for some people and may cause thoracic discomfort. Examples of bilevel devices include Respironics Bi-PAP® S/T and BiPAP® SynchronyT; Puritan Bennett KnightStar 330® and KnightStar 320®; ResMed VPAP® II ST; and BREAS PV102.

Volume ventilators deliver a pre-set volume of air. These machines can deliver much more air than bilevel devices, and thus enable deeper breaths for improved coughing and air stacking. They may be necessary for people with poor lung elasticity, such as those with pulmonary fibrosis, and stiff chest walls, as with kyphoscoliosis, when bilevel is not enough. Volume ventilators, though larger and heavier and more expensive than bilevel units, are quieter, have more alarm features, overcome airway secretions and resistance, have an internal battery, work from battery power easier, can be used for 24 hours, and are well-suited for tracheostomy use.

Examples of volume ventilators include the LP6 Plus, LP10 and Achieva® from Puritan Bennett, PLV®-100 and PLV®-102 from Respironics, TBird® Legacy from Thermo Respiratory Alternate Care and PV501 from BREAS.

A new generation of ventilator technology has produced the LTVT series from Pulmonetic Systems, Inc. These new ventilators are compressorless and run by turbines. They are very small - about the size of a laptop computer - and lightweight, about 13 lbs., but more expensive. They also have the capability to offer both volume and pressure support.

Who decides which equipment to use? How?

The answers to these questions focus on whether there is breathing muscle weakness or whether there are reasonably normal breathing muscles but obstructive sleep apnea (OSA).

If there is nighttime breathing abnormality due to muscle weakness, it is best treated with a machine that assists ventilation, such as the aforementioned bilevel pressure device or volume ventilator.

If the upper airway tends to close off during sleep, OSA occurs. This is often successfully treated by continuous positive airway pressure (CPAP* which delivers a constant flow of air to keep the airway open. 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.

Whether to use a portable volume ventilator or bilevel pressure device is an important decision. Sometimes the choice reflects the experience and training of the pulmonologist or respiratory therapist. Often cost is a factor. In Europe, the costs of the bilevel pressure devices and the volume ventilators are not as disproportionate as they are in the United States.

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.

Where is the best location to start noninvasive positive pressure ventilation (NPPV)?

Generally, NPPV is started in the home by a respiratory therapist from the home health care agency or durable medical equipment (DME) provider, as ordered by the physician (who is not present). However, home health respiratory therapists have limited time, and the home health care agency does not receive reimbursement for the time needed. The therapist usually cannot demonstrate the whole range of equipment and interface options available. Followup is needed repeatedly in the first months to ensure that the equipment and interfaces are comfortable and working properly to achieve optimal benefit.

The use of NPPV can also be initiated as part of hospital discharge, where there should be more time to do it properly. However, many pulmonary critical care physicians are highly ICU-focused, and they and the respiratory therapy staff may not have the experience and interest needed to get optimal results.

When possible, the best approach may be for the individual to visit the home MV unit of a medical center for daytime assessment and for teaching the use of NPPV. The person can try various equipment and interfaces to see which would work best under the guidance of an experienced physician and respiratory therapist. The day visits can be repeated as needed for setup and followup. This is in addition to the home health care/DME company's home visits after the system is selected and ordered.

What does a respiratory therapist do?

Respiratory therapists work under the direction of a physician, usually in hospital settings where they perform intensive care, critical care, and neonatal procedures. Polio survivors usually interact with a respiratory therapist in their physicians' offices and/or in their homes during visits from a therapist hired by a home health agency or a home medical equipment supply company (Apria, Lincare, etc.).

Respiratory therapists perform procedures that are both diagnostic and therapeutic. Some of these activities include: taking arterial blood gas (ABG) specimens and analyzing them to determine levels of oxygen, carbon dioxide, and other gases; measuring the capacity of the lungs to determine if there is impaired function; and studying disruptive sleep patterns. Respiratory therapists help set up and maintain the various equipment (CPAP and bilevel devices, ventilators) to assist breathing, adjust the settings, adjust the mask or other interface, instruct in their use, and monitor compliance.

What is an interface?

An interface connects the tubing from the volume ventilator, bilevel device or CPAP to the person using it. Examples include nasal or facial masks, nasal pillows, lipseal, mouthpiece or tracheostomy. Often the individual is handed only one mask to try by a respiratory therapist from a home health care company, but several different masks may need to be tried in order to find one that fits properly. Many people do best when they can choose at least two (nasal) interfaces that are comfortable and rotate between them. Individuals can use a mouthpiece if they have nasal congestion due to a cold.

Adapting to and making adjustments to an interface is critical and often requires patience and determination. Many users creatively adapt their masks to achieve the best fit.

What is a tracheostomy and when is it necessary?

A tracheostomy is an artificial airway created during a surgical operation called a tracheotomy. A tracheostomy may be necessary for polio survivors who cannot tolerate noninvasive ventilation, for those who can no longer be adequately ventilated noninvasively, and for those who need ventilation more than 20 hours per day. Other considerations include a severely impaired cough and inability to clear secretions, and significant swallowing problems. Some polio survivors who need 24-hour ventilation may prefer to use noninvasive ventilation.

The decision to undergo a tracheotomy is a serious one and should be made by a fully informed individual along with caregivers in consultation with the physician.

How can a polio survivor improve cough?

Retained secretions in people who have impaired coughing ability can turn a common cold into pneumonia. To improve cough, there are two forms of assisted coughing.

Manually assisted coughing involves another person administering a thrust to the chest and abdomen of the individual with neuromuscular disease immediately after that individual takes a big breath.

Mechanically assisted coughing can be performed with the CoughAssist™ by J.H. Emerson Company. The CoughAssist applies positive pressure to provide a deep breath in, then shifts rapidly to negative pressure to create a high flow out, as with a normal cough.

What is cor pulmonale?

Cor pulmonale (right-sided heart failure) can occur in post-polio and in other diagnoses, such as COPD. In both, the low oxygen level causes pulmonary hypertension, liver enlargement, and swollen feet. Cor pulmonale is detected by a careful physician examination, keeping respiratory muscle weakness in mind.

What about oxygen?

Tony Oppenheimer, MD, retired physician in pulmonary and critical care medicine from Southern California Permanente Medical Group (deceased 2005), cautions, "Administering oxygen does not provide assistance to the weakening respiratory muscles, but gives both the patient and the doctor the false impression that appropriate treatment is being provided. Underventilation is mistaken for an oxygen transfer problem. Indeed, administering oxygen can mask the problem.

"Also there is a danger of causing respiratory depression by giving oxygen. It will improve the oxygen saturation, but not the underventilation. It may increase the danger of dying of sudden respiratory failure.

"Some situations may require administering oxygen, such as cor pulmonale or pneumonia due to infection or aspiration. If this occurs in people with respiratory muscle weakness and hypoventilation, then it is important to provide both assisted ventilation and supplemental oxygen, and use ABGs to monitor them."

A useful analogy from Lisa S. Krivickas, MD, Spaulding Rehabilitation Hospital, Boston, in regard to people with respiratory failure from neuromuscular disease is that the lungs are like deflated balloons that are not strong enough to inflate.

To inflate the balloon, mechanical assistance to force air into the balloon is needed. Blowing oxygen across the mouth of the balloon (the equivalent of using supplementary oxygen delivered by nasal cannula) will do nothing to inflate the balloon.

Additional Thoughts from Peter C. Gay, MD
References

American College of Chest Physicians. (1998). Mechanical ventilation beyond the intensive care unit: report of a consensus conference of the American College of Chest Physicians. Chest, 113, Supplement, 289S-344S.

Bach, J.R. (1999). Guide to the evaluation and management of neuromuscular disease. Philadelphia, PA: Hanley & Belfus, Inc.

Bach, J.R. (1996). Pulmonary rehabilitation: The obstructive and paralytic conditions. Philadelphia, PA: Hanley & Belfus, Inc.

Faber, H.K. & Amoss, H.L. (1956). Acute poliomyelitis. In Tice's Practice of Medicine. 335-359.

Fischer, J.R. & Headley, J.L. (1995). Post-polio breathing and sleep problems. IVUN News, 11(4), 2.

Gay, P., & Edmonds, L. (1995). Severe hypercapnia after low-flow oxygen therapy in patients with neuromuscular disease and diaphragmatic dysfunction. Mayo Clinic Proceedings, 70 (4), 327-330.

Hill, N.S. (2001). Long-term mechanical ventilation. New York, NY: Marcel Dekker, Inc.

Hsu, A. & Staats, B. (1998). "Postpolio" sequelae and sleep-related disordered breathing. Mayo Clinic Proceedings, 73, 216-224.

Maynard, F. & Headley, J. (1999). Handbook on the late effects of poliomyelitis for physicians and survivors. Saint Louis, MO: Gazette International Networking Institute.

Oppenheimer, E.A. (2000). Oxygen is NOT for hypoventilation in neuromuscular disease. IVUN News, 14(1), 4-5.

Romaker, A. (1995). New breathing problems in aging polio survivors: respiratory muscle weakness. Polio Network News, 11 (4), 1, 7-8.

Another article about breathing problems of polio survivors that was written by E.A. (Tony) Oppenheimer, MD, FACP, FCCP, can be found at www.skally.net/ppsc/breathe.html. "Assistance for Breathing Problems of Polio Survivors" was first presented by Dr. Oppenheimer to the Rancho Los Amigos Post-Polio Support Group in March of 2001.

Continued ...