Introduction

Post-polio syndrome (PPS) is a group of symptoms developed by polio survivors which usually manifest years after recovering from acute paralytic poliomyelitis (polio).¹ It occurs as a result of the polio virus gradually destroying certain nerve cells known as motor neurons and leading to muscle weakness and loss of strength.² Respiratory and breathing problems may eventually result from post-polio syndrome due to the weakening of the respiratory muscles. Although PPS is rarely fatal, its respiratory symptoms can seriously impair a person's capacity for independent living.¹ For instance, weakening in the breathing muscles can lead to difficulty breathing, interfering with daily activities and sleep.

If you had polio in the past, it is important to know about post-polio syndrome and its respiratory issues. This article discusses various aspects of post-polio syndrome, such as its causes, respiratory problems, diagnosis, and management.

Understanding post-polio syndrome

Causes

Post-polio syndrome can only be acquired by those who have had polio, though not all polio survivors will develop it.² PPS is not infectious, unlike polio, and it usually develops many years later, between 15 and 40 years after having polio.² Polio survivors frequently experience a gradual decrease in muscular power in the areas of their bodies that were initially impacted by the polio virus.² While some people may only have mild symptoms, others may see atrophy noticeable weakening and withering away of the muscles.²

The exact causes of PPS are poorly understood. One leading theory proposes a delicate imbalance between chronic denervation and the attempt of the body to rewire neural pathways and maintain muscle function, which is a problem with the way the muscles and nerves communicate.³ Another theory is that a virus that was dormant might suddenly become active again in the nerves that control muscles.³ However, several studies have indicated that certain factors may enhance the likelihood of developing PPS.

Major risk factors for PPS include:

• Normal ageing
• Female sex
• Experiencing more severe motor symptoms during the initial polio infection
• Achieving a lower level of functional recovery after the acute phase (the period of active polio infection)
• Enduring a longer latency period (the time between the acute phase and the onset of recovery) between the acute phase and recovery
• Requiring mechanical ventilation during the acute phase
• Engaging in high levels of physical activity
• Weak immune system
• Muscular overuse and underuse
• Existence of a lifelong disability and serious residual weakness following polio^1,3

Moreover, a history of smoking, obesity, nutritional deficiency, and lung conditions, including bronchitis, emphysema, and asthma, are additional factors that might aggravate the breathing issues of a polio survivor.⁴

Incidence and prevalence

The likelihood of developing PPS is influenced by the intensity and degree of recovery from the original paralytic poliomyelitis-related symptoms. Individuals who experienced more acute symptoms during a polio infection are likely to experience significant PPS symptoms. An estimated 15–20 million people worldwide struggle with polio's aftereffects, and a significant 20%–80% of them will eventually develop post-polio syndrome.⁴

Respiratory issues in post-polio syndromes

Respiratory issues arise due to physical changes in the body, like spinal abnormalities in the skeleton, scoliosis (twisted spines) and resulting thoracic deformity, kyphosis (rounded backs), or degenerative changes in spinal bones; all of these are associated with polio and can aggravate respiratory insufficiency. For those with PPS, these changes can cause problems with breathing, especially if the chest is misshapen and the breathing muscles are weak, leading to difficulty in getting enough air while resting and causing sleep problems.^1,5 Weakened diaphragm and chest muscles make it difficult to breathe deeply and cough, leading to fluid and mucus accumulation in the lungs. These factors contribute to restrictive lung disease (lungs are unable to expand completely) and hypoventilation.^5,6

The most frequent respiratory consequence among polio survivors is pulmonary hypofunction (a reduction in the overall function of the lungs). It causes hypoventilation (underventilation), resulting in not enough air getting to the lungs to properly expand them. Between 27 and 58 % of polio survivors experience respiratory issues such as dyspnea, difficulty in breathing, and snoring.⁵

Recognising the onset of respiratory issues

Common symptoms of PPS include chronic fatigue (extreme weariness), weakening of the muscles, shrinking muscles, muscle and joint pain, and sleep apnea.⁷

In elderly polio survivors, breathing and sleep problems can arise suddenly and often go undiagnosed by the survivors, their families, or their medical professionals. The lungs themselves might not have been affected by the poliovirus's initial destruction, but survivors may have weakened their breathing muscles. Individuals who were dependent on iron lungs throughout the acute stage of the disease have to be more watchful for such issues in the future and educate themselves to identify crucial indicators and symptoms of inadequate breathing, which may escalate into respiratory failure. Even those who did not require ventilatory support initially may still be at risk for breathing and sleep issues, so they should be on the lookout for any warning indications of trouble.⁴

The most common respiratory symptoms include:

• Breathing difficulty due to the weakening of breathing muscles especially during physical activity 
• Interrupted breathing during sleep (sleep apnea)
• Increased susceptibility to chest infections or respiratory illnesses⁸

Common symptoms of hypoventilation include:

• Breathing difficulties while laying flat; wanting to sleep while sitting up (orthopnea)
• Difficulty falling or staying asleep (insomnia)
• Anxiety about falling asleep
• Disturbed, irregular sleep accompanied by frequent awakenings
• Shallow respiration or pauses in breathing
• Arising from sleep with a suffocating sensation
• Nightmares, night sweats, bedwetting, or the desire to pee often
• Excessive drowsiness during the day and morning headaches
• Deteriorating mental health and decreased memory, focus, and cognition
• Fatigue or extreme tiredness after routine tasks
• Feelings of claustrophobia or a sense of poor air quality in enclosed spaces
• Generalised anxiety
• Challenges in speaking for long durations
• Speech with a low volume and fewer words per breath
• Usage of accessory muscles, including those in the neck, to breathe
• Mild cough accompanied by a rise in pneumonia and respiratory infections⁴

If polio survivors exhibit any of the aforementioned symptoms, they should contact a pulmonologist for a respiratory examination.

Diagnosis and assessment

It is critical for people who have recovered from polio, especially those who have been diagnosed with post-polio syndrome, to receive the proper diagnosis, treatment, and testing for respiratory and sleep-related conditions.

Medical history and physical examination

Post-polio syndrome can be challenging to diagnose due to the lack of specific diagnostic tests and the possibility of misdiagnosing symptoms with other illnesses. According to your medical history and the findings of a physical examination, your general practitioner might suspect post-polio syndrome. It could be suspected, for instance, if you previously had polio and, after going for a long time (typically at least 15 years) without experiencing any symptoms, those symptoms have gradually returned.⁹

Pulmonary function tests

Pulmonary function testing can be conducted either at a pulmonary function laboratory. Simpler tests can also be performed at home or in a doctor's office.

The primary objectives of these tests are to identify abnormalities like restricted airflow, reduced lung volume (referred to as restrictive abnormalities), changes in diffusing capacity (as seen in interstitial diseases), and abnormalities in blood gas levels (excessive carbon dioxide or inadequate oxygenation).¹⁰ The tests listed below are frequently carried out.

Spirometry

It measures vital lung capacity. The amount of air that a person can firmly exhale after taking a deep inhale is measured by vital capacity (VC). Vital lung capacities, such as forced expiratory volume in one second (FEV1) and forced vital capacity (FVC), are measured by spirometry and are essential for determining airflow restriction. To prevent airway compression, vital capacity can be measured either slowly (SVC) or fast (FVC). Additionally, peak expiratory flow (PEF) is measured. Weakness in the respiratory muscles may be shown by positional changes during testing.¹⁰

Tests for neuromuscular diaphragmatic function

VC (either seated or laying supine), maximal inspiratory force (MIF), maximum expiratory force (MEF), maximum voluntary ventilation (MVV), and nocturnal oximetry are tests used to assess neuromuscular diaphragmatic function.¹⁰ 

Lung volume testing and diffusing capacity 

The lung volume test measures the amount of air in the lungs following a full exhale and calculates residual volume (RV) and VC. Total lung capacity can be computed from these values. Diffusing capacity evaluates the passage of gas through capillaries and alveolar air sacs before entering the circulation.¹⁰ 

Arterial blood gas measurements

An arterial blood sample is used to assess blood oxygen, carbon dioxide, bicarbonate, and pH. Arterial blood gas measures can be taken while exercising, at rest, or while inhaling oxygen or room air. An oximeter may be used to measure oxygen saturation non-invasively.¹⁰

Sleep studies

To evaluate sleep problems (like sleep apnea or underventilation), sleep tests are often carried out in a sleep laboratory through an overnight examination that records multiple factors at the same time. These investigations comprise muscle measures of the chest and abdomen, oximetry, EEG (brain wave), ECG (electrocardiogram), airflow measurements at the mouth and nose, and frequently a video recording of the subject's movements while they sleep.¹⁰

Management and treatment

Examination to determine the reason for breathing issues is crucial, as it will assist in selecting the best treatment. For instance, scoliosis, weak respiratory muscles, or stiff ribs may be the source of your breathing issues.

Musculoskeletal symptoms could be addressed with physical therapy, however, non-invasive positive pressure ventilation or permanent mechanical ventilation is currently the main treatment available for PPS-related respiratory failure.¹¹

Early implementation of noninvasive respiratory aids such as intermittent positive pressure ventilation as well as biphasic positive pressure ventilators through a mouthpiece or nasal application could stabilise the condition, avoid complications including infections in the chest, additional respiratory decline, the need for an invasive ventilatory aid, and enhance exercise capacity. If you have sleep apnea, using a machine to pressurise your airways while you sleep via a mask can assist prevent them from closing. General interventions such as mobilising secretions (techniques for clear mucus buildup) and providing cough aid are also useful.⁶ 

Furthermore, receiving both the yearly flu vaccination and the pneumococcal vaccination can lower your chance of developing severe chest infections, which may lead to more serious issues.¹²

Healthy living habits

Studies have shown that obesity and smoking make respiratory insufficiency worse. Patients are therefore advised to give up smoking and control their weight.^1,5 Other modifications, like getting enough sleep and eating a well-balanced diet, could also be helpful.²

Respiratory muscle training is beneficial in PPS, much like other muscle training, even for patients who already utilise intermittent noninvasive breathing assistance. You can discover safe and appropriate workouts, for instance, tailored breathing exercises to strengthen your breathing muscles, with the assistance of a respiratory physiotherapist.⁶

Psychological support for coping

Post-polio syndrome symptoms can be upsetting. After contracting the polio virus as a kid, developing post-polio syndrome can lead to tension, anxiety, and social isolation. If you find yourself depressed and unable to find joy in the things you used to like, it is essential to reach out to a medical professional for support and guidance.

Summary

Post-polio syndrome is a phenomenon that some people may develop decades after a polio infection. It is marked by a gradual and permanent weakening or paralysis of the muscles and can lead to respiratory issues. Respiratory problems can develop due to weakened breathing muscles and can lead to restrictive lung disease, pulmonary hypofunction, and hypoventilation, which can cause difficulties in breathing, sleep disturbances, and an increased risk of respiratory infections. It is critical to identify respiratory problems quickly as they arise, especially in older polio survivors and females. Diagnosis involves a combination of medical history, physical examination, and pulmonary function tests. Post-polio syndrome can be effectively managed and treated by determining the underlying cause of respiratory problems. The use of noninvasive respiratory aids, immunisation against diseases, the adoption of healthy lifestyle practices, and respiratory muscle exercise are potential interventions that improve respiratory health and overall well-being. Additionally, psychological support is essential for coping with the emotional impact of the symptoms.