SAPP Saskatchewan Awareness of Post Polio Society Inc.


MASTHEAD

ISSUE #27 DECEMBER 1998


President's Message

I wish you and yours a Happy and Joyful Holiday from all the Board of Directors and their Families.

Well since we last communicated, several things have developed. The major one is the planning of a joint International Post Polio Conference along with Southern Alberta Post Polio Support Society Inc. This Conference will be in celebration of the New Millennium "PPS 2000, The Millennium of Hope" Our planned location is The Temple Gardens Mineral Spa in Moose Jaw, Saskatchewan. We have a number of obstacles to overcome but our confidence and realization is great. For those in the southern part of our three Prairie Provinces and our neighbours in the northern United States, this can be a real opportunity to hear what experts across north America have to offer us as polio survivors.

As for 1999, June the 10th is our tenth year since incorporation, some special events are planned for our Annual General Meeting to take place on Saturday, 10th of April 1999, at Saskatchewan Abilities Council, 1410 Kilburn Avenue, Saskatoon.

Did you realize that as a Registered Charity we can give you an official receipt for all donations, so how about directing some of your charitable contributions toward S.A.P.P.

We are still receiving positive responses to our web site. Any medical questions are redirected to qualified medical persons in the field of Post Polio. Most often these questions are covered in existing articles and are just reinforced by the medical person.

Ron Johnson, President

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The Use of Inspiratory Resistance Training in Post-Polio Syndrome

Part One : Control of Breathing

Breathing muscles require impulses from the brain to make them function. Breathing is largely an automatic process but it may also be controlled voluntarily. That means that most of the time a person breathes without having to think about it. The area of the brain responsible for this automatic breathing is the medulla. The medulla is sometimes called the "bulb", which is a part of the brain stem (the lowest part of the brain). However, when you want to hold your breath or take an extra deep breath, the super computer of the brain (the cerebral cortex) takes over.

Chemical receptors in the chest and in the medulla detect the amount of carbon dioxide, oxygen and hydrogen ions in tile blood. These sensors send input to the medulla which then triggers breathing at the right time. Impulses (like an electric current) travel from the super computer of the brain or the medulla and send messages to the anterior horn cells (motor neurons) of the respiratory muscles. The anterior horn cells of the respiratory muscles are found in the neck (cervical spine) and in the thoracic spine (rib cage area). Firing of these anterior horn cells causes a chemical message to be sent to the breathing muscles. When the muscles get this message, they contract, causing you to breathe.

Respiratory Muscle Anatomy and Function

Inspiratory Muscles

1. The Diaphragm

The diaphragm is shaped like an upside down bowl. It is attached to the lower ribs, the bottom of the breastbone and the front and sides of the lower lumbar vertebrae. The fibers radiate inwards inserting into a central tendon. The zone of apposition (wall of the bowl) is that part of the diaphragm that is apposed to (up against) the inner aspect of the rib cage. The diaphragm muscle fibres are oriented such that when the muscle contracts and is met by counter-pressure of the abdominal contents, the diaphragm fibres pull the rib cage up and out. Thus, on inspiration (breathing in), the diaphragm moves down. The central tendon of the diaphragm meets the resistance of the abdominal contents. The continued contraction of the diaphragm then pulls the rib cage up and out. The downward movement of the diaphragm and the outward movement of the rib cage create a negative pressure within the lungs and air is drawn in.

The abdominal muscles are very important to the efficient action of the diaphragm. The dome shape of the diaphragm and the zone of apposition are maintained by the resting tension of the abdominal muscles and the firm support it provides to the abdominal contents. If the abdominals are weak, you don't get the firm counter-pressure supplied by the abdominal contents. This then lessens the force the diaphragm has to pull the rib cage up and out. In chronic bronchitis and emphysema a person often has a barrel-shaped chest due to hyperinflated lungs. The extra air in the lungs causes the dome of the diaphragm to be flattened. Because the upside down bowl shape of the diaphragm is lost (it resembles a plate instead), the diaphragm fibres pull horizontally (inward) on the ribs rather than upward and outward.

2. The Scalene Muscles

The scalene muscles are located in the sides of the neck and insert on the first and second ribs. They are active on every breath in. They lift and expand the rib cage during inspiration.

3. The Parasternal Muscles

These muscles are attached to the breastbone and run between the rib cartilages in a downward and outward direction. When they contract, the ribs are lifted and the anterior-posterior (front to back) dimension of the rib cage increases.

4. Accessory Muscles of Inspiration

These muscles help out when the person has to work harder to breathe. These include the following:

Sternocleidomastiods - These run from the mastoid process (just below and behind the ear) to insert along the inner third of the collarbone and the top of the breastbone.

External Intercostals - Run between the ribs. These muscles function when you are working harder to breathe, i.e. during exercise.

Expiratory Muscles - Breathing Out

Relaxed expiration (breathing out) is usually passive (not requiring any effort). It happens because of the elastic recoil of the lungs. When you are breathing hard because of exercise, the abdominal muscles may help to push the air out more quickly. The internal intercostals (muscles between the ribs) also work to push the air out when you are working hard.

Therefore, weakness or lack of nerve supply to the abdominals not only hinders the action of the diaphragm on inspiration, but hampers the ability to ventilate at higher than resting levels because these muscles cannot be recruited to help out on expiration (to push the air out quickly).

Post-Polio Syndrome and its Relationship to Respiratory Function

Dalakas defines post-polio syndrome as "the development of new muscle weakness and fatigue in skeletal or bulbar muscles, unrelated to any known cause, that begins 25 - 30 years after an acute attack of paralytic poliomyelitis.

Cashman and Trojan state that the "loss of motor neurons in paralytic polio induces compensatory axonal sprouting of the remaining motor neurons, which markedly increases the number of muscle fibres innervated by the motor neuron." Therefore you get extreme enlargement of the motor unit (up to 7 times the normal size).

The Weichers-Hubble hypothesis states that prominent enlargement of motor units by axonal sprouting is not indefinitely stable and that enlarged units undergo progressive loss of the terminal axon sprouts with time after polio. This notion was based on data that single fiber EMG jitter linearly increased with time after polio. In other words, muscle fibers supplied by the same nerve fibers area getting the message to contract at different times. In normal muscle, two muscle fibers that are innervated (supplied) by the same motor neuron contract at the same time when the nerve sends the signal. To illustrate, when telephone extensions ring in your house, they all ring at the same time. Jitter is when the extensions ring at all different times. Therefore when the nerve fires in a PPS survivor, the muscle fibers may not contract simultaneously. This leads to a weaker muscle contraction. Sometimes, when the nerve fires, the muscle does not receive the message at all. This is called blocking and is analogous to having a phone that doesn't ring at all.

Increased jitter may be due to poor conduction along the ends of the axonal sprouts or to inadequate release of neurotransmitter at the neuromuscular junction. The neurotransmitter is the chemical "spark" that gets the muscle going.

After acute polio, recovery of muscular strength can occur by terminal axonal sprouting of surviving motor neurons, with partial or complete reinnervation of denervated muscle fibers. These enlarged motor units are undergoing a process of continuous remodelling, with constant denervation and reinnervation after acute polio. Thus, the presence of immature terminal sprouts (which are known to have decreased conduction) at all stages following recovery from acute polio, may account, at least partially, for the observed abnormal jitter. Decades after recovery, irreversible degeneration of terminal sprouts without reinnervation may account for the new symptoms of fatigue and weakness observed in PPS.

To sum up;

1. In acute polio some anterior horn cells are lost and the muscle fibers they supply lose their innervation.

2. The surviving anterior horn cells send nerve sprouts to the orphaned muscle fibers.

3. There is a continuous process of remodelling, with some nerve fibers continuing to die off and others beginning to sprout. The baby nerve fibers are not very efficient and neither are the geriatrics. This results in weak muscle contraction because the fibers contract at all different times. This is what is referred to as "jitter".

4. Decades after recovery, a greater proportion of the sprouts may begin to irreversibly degenerate, resulting in new symptoms of fatigue and weakness.

In addition to the metabolic exhaustion of post-polio motor units, neuromuscular junction transmission defects and muscular abnormalities due to overuse occur. In PPS, the transmission defects are believed to be due to poor transmission along the sprouts. The sprouts may not transmit as well as a disease-free motor neuron. Think of how poorly a leaky hose delivers water to a sprinkler. Another cause of poor transmission may be due to limitations in the number or size of packages containing neurotransmitter at the motor nerve terminals. When the water finally gets to the sprinkler, there isn't enough volume to make the water push itself up through the sprinkler holes.

Bulbar Polio

If you have had bulbar polio there are several problems that this causes for breathing. Firstly, because of damage to the respiratory center in the medulla, there may be a lack of drive to breathe, particularly when you are asleep. Secondly, there will likely be problems with the motor nerves that supply the respiratory muscles themselves. In addition, the respiratory muscles may themselves not be strong due to atrophy of some muscle fibers and overuse of others. Sometimes, obstructive apnea due to throat muscle weakness is also a factor.

Conditions that Further Hinder Respiratory Muscle Function

1. Chronic Obstructive Pulmonary Disease (Chronic Bronchitis or Emphysema)

This disease is generally caused by smoking. In chronic bronchitis, secretions in the airways decrease the airway diameter and cause increased airway resistance. To illustrate, if you dip a straw in glue and coat the inside of it, it makes the tube smaller and it is harder for liquids to move through it. In emphysema, the elastic recoil of the lung tissue is lost, hindering expiration and causing air trapping. This causes the person to have hyperinflated lungs. As was said previously hyperinflation causes the diaphragm to flatten. This reduces the zone of apposition of the diaphragm on the ribcage and hinders the mechanical advantage of the diaphragm on inspiration

2. Obesity Because much of the accumulation of excess fat is deposited in close proximity to the chest wall, severe obesity increases respiratory muscle load and markedly impairs pulmonary function.

3. Kyphoscoliosis (Curvature of the Spine) Kyphoscoliosis causes increased work of breathing due to increased stiffness of the chest wall and impaired muscle action due to the altered shape of the ribcage. When you have a situation of inspiratory muscle weakness, the increased work of breathing due to changes in the lung or chest wall may result in a relative overload being imposed on the breathing muscles. This leads to fatigue and possible injury of the inspiratory muscles.

What Can Be Done?

Considerations when Training the lnspiratory Muscles

Respiratory muscles are the same as other skeletal muscles in that they can improve their function in response to training. However, because they must contract repetitively, they have no opportunity to rest and may become fatigued or injured under conditions of overload. Because of the vital fiction of these muscles, care must be taken in progression of exercise because undue fatigue could cause or exacerbate (make worse) respiratory failure.

The danger in post-polio is that because of the precarious nerve supply to the inspiratory muscles and the muscle atrophy already present, those remaining active muscle fibers may be fatigued to the extent that they become damaged and require time to repair. This would further weaken the inspiratory muscles and could potentially result in an increased need for ventilator support.

How Do We Train Respiratory Muscles?

At the Post-Polio Clinic in Edmonton, we have used a device called the P-Flex to do training of the inspiratory muscles of a few patients. The P-Flex looks like a kazoo and has a dial on it so that the diameter of the hole through which you breathe can be changed. It is similar to breathing through straws of progressively smaller diameters. In general, this technique has been known to work well for those individuals who are breathing independently (no ventilator) but become short of breath with exercise.

The general idea is to start at the easiest level on the device. The nose is plugged and the P-flex is placed in the mouth. I have directed the PPS survivor to breathe through it until they BEGIN to feel short of breath. The device is then removed from their mouth. The number of breaths taken and the resistance level recorded. If the person is comfortable taking 50 - 60 breaths at a given resistance level over several exercise sessions they may choose to increase the resistance. Exercise sessions are done a maximum of three times per week with a rest day in between. One mistake we made was that we increased the resistance level too quickly in one gentleman. He found that he had no trouble doing 30 repetitions at a particular level and we therefore increased the resistance factor at the next session. We found that he went from level one to level five over a period of several weeks. However, at level five he was able to take only three breaths. The next session, he pushed himself to do ten breaths. That extra push and the ignoring of his fatigue resulted in a relapse whereby he eventually discontinued using the P-Flex and was placed on oxygen at night. Prior to that time, however he found that he was having less difficulty breathing at night. Perhaps if we hadn't progressed the resistance level has quickly, he might have had better results. I cannot warn you enough to be extremely cautious with the use of a P-Flex. Do this only with the approval of a physician and the supervision of a physiotherapist or respiratory therapist.

Considerations for Use of the P-Flex

1. Use the P-Flex only on the advice of a physician and in consultation with a physiotherapist or a respiratory therapist.

2. Don't use it if you require ventilator support for prolonged periods (more than l 5 minutes) while you are awake.

3. Respiratory function should be measured prior to starting. Bach recommends that resisted breathing training should be done only if Vital Capacity is greater than 30% of predicted normal. Vital Capacity is defined by Sproule as "the greatest amount of air that the subject can expire following a maximal inspiration".

4. Don't use it if you have a cold or chest infection. You are already working against an increased load.

5. Don't use it on a day that you feel totally exhausted.

6. Stop exercise with the device as soon as you BEGIN to feel short of breath.

If you have any questions or comments, I can be reached at:

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Introducing Dr. Evan E. Sampson

Dr. Sampson obtained his BMedSc, MD from the University of Alberta in 1993. In 1998 he gained his FRCPC Physical Medicine & Rehabilitation at the University of Alberta and was the chief resident from 1996-1998.

Dr. Sampson operates a Private Practice Physiatry at Sherwood Park, AB. His special interests include: post-polio syndrome, EMG, acute/chronic musculoskeletal injuries, and interventional pain management.

July 1, 1998, Dr. Sampson took over the role of Director, Post-Polio Clinic formerly run by Dr. Feldman and started seeing patients September 1, 1998. Dr. Sampson's practice is in Sherwood Park. His office address is as follows: #301, 101 Granada Boulevard, Sherwood Park, Alberta, T8A 4W2. Appointments can be made by calling (403) 464-7210 or fax: (403) 449- 5566.

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Polio

Polio [poliomyelitis or infantile paralysis] is not a new disease. In ancient Egypt, there were recorded cases of polio. Prior the to the 20th century, the virus was always present in the environment. This constant exposure to the virus allowed immunity to be built up and passed on to the next generation. A baby would receive antibodies to the polio virus from its mother which provided protection from the virus until the babies own immune system was capable of creating its own antibodies to the virus. Only in people who had absolutely no resistance or natural exposure [self-inoculation from the environment] to polio did the virus cause paralysis.

However at the beginning of the 20th century with the onset of modern sanitation practices and the development of modern plumbing, the polio virus no longer existed in the everyday environment. Exposure to the virus decreased and immunity declined in the general population. Though the polio virus had existed for thousands of years, it had seldom had the opportunity to cause epidemics as was now the case in the early 20th century.

The polio virus is a small RNA [ribonucleic acid] virus that has three different strains. The virus enters the body through the mouth, goes to the stomach and intestines where it begins to reproduce itself. It is then absorbed by the tiny capillaries in the walls of the intestine and from there it is carried by the bloodstream to the spinal cord. Once in the spinal cord, the virus heads directly to its one and only target, the motor neurons. These are the nerve cells that control physical movement. At this point, the viral infection will cause headaches and mild flu-like symptoms. However in those people who have no natural immunity or who have not been vaccinated the virus goes on to infect the entire spinal column and the brain stem which controls breathing. The mild flu-like symptoms now progress to a high fever, intense headache, vomiting, neck and back stiffness and finally paralysis.

People either die from the viral infection or they survive the viral attack [thus the term polio survivor] with varying degrees of loss of motor function. Some of the motor neurons are completely destroyed while others are only partially destroyed and still others are unaffected by the viral attack. Up to 20% of the motor neurons can be totally destroyed before there is any noticeable difference in physical movement to the polio survivor or to a casual observer. It is important to note that the sensory neurons are not affected by the polio virus thus there is no diminishment or loss of feeling even though paralysis has occurred.

One strain or form of the virus tends to concentrate its attack on the brain stem which contains the motor neurons that control breathing. This strain of polio is called bulbar polio. Damage to these neurons often result in paralysis of the respiratory muscles. The polio survivor is placed in an iron lung which physically inhales and exhales air for the polio survivor. To this day there are still polio survivors who must spend their entire day or most of their day in an iron lung or attached to an assistive respiratory machine to stay alive.

The other strain or form of polio centres its attack on the spinal column where it destroys the anterior horn cells which control movement of the trunk and muscle limbs. This strain of polio is called paralytic polio. However all three strains or forms of the polio virus can cause any combination of trunk, limb and respiratory paralysis or loss of function in varying degrees of severity.

After the infection, polio survivors very often regained use of their paralyzed limbs or respiratory muscles through endless exercises designed to strengthen and retrain the muscles to move again. Some polio survivors who left hospitals in wheelchairs were able to regain full use of their limb and trunk muscles. As well, some survivors of bulbar polio regained full use of their respiratory muscles. In other survivors where total loss of motor neurons began to exceed the 50% mark, there was irreversible paralysis in some limbs and a definite diminishment of function in the muscles. Recovery was never complete and many polio survivors experienced radical changes in their lives depending upon their age and situation in life at the time of the infection.

Those survivors who were adults had to undergo severe lifestyle changes due to loss of physical mobility. Some were forced to abandon their careers entirely while others were able to continue in their work areas by learning how to perform tasks in a wheelchair or while using braces and crutches. Others were able to find or create jobs which demanded less physical mobility. Relationships, personal or family, either survived and adapted to the new situation or ended.

Infants, children and teenagers were no less affected than the adults. Most of these returned to their families after hospitalizations but others were placed in foster homes or institutions. Weeks spent in isolation wards and months or even years spent in hospitals or rehabilitation centres had a traumatic emotional effect on the infants, children and teenagers. Children and teens often returned to find that they were no longer members of their peer groups. Infants returned to parents and siblings that they no longer recognized or even remembered.

Polio, though an ancient disease, is not eradicated in the world today nor is it vanquished by modern medicine. There is nothing that can stop or control the destruction of neurons by the polio virus. Nor are there any state of the art, high-tech gadgets that can return loss of motor function. No amount of sophisticated physiotherapy programs or machines will conquer the destructive effects of the polio virus. As in ancient times, one either survives the infection or one dies. Antibiotics no matter how powerful have absolutely no affect on a virus. The only preventative measure is vaccination.

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