This paper was presented at the International Polio Network's Eighth International Post-Polio and Independent Living Conference in St. Louis, Missouri, June 8-10, 2000.
One could easily imagine why the polio epidemics from the early to mid-part of the 20th century had similar impact on the practice of pulmonary medicine as even the best-known infectious lung disease, tuberculosis. The modern day intensive care units are now primarily staffed by pulmonologists largely due to the huge need from breathing problems created by these two infectious diseases. Since acute polio infection has vanished from the developed world, we presently recognize pulmonary problems from polio as a late complication of residual muscle weakness and/or skeletal deformities such as kyphoscoliosis. During the following review, the initial discussion will note common patient complaints occurring at rest, with increased activity and during sleep. Secondly, there are physical signs and clinical tests that help predict or further define these symptoms that should be explained. Lastly, the appropriate treatment methods can be identified and placed into perspective.
Signs & Symptoms
Up to 6% of polio patients studied in one series required full-time ventilator support but larger percentages present to pulmonary physicians.1 The most common respiratory symptom reported by polio patients is shortness of breath and may come from a variety of causes.2 It is difficult to classify the subtypes of patients because the most profound abnormalities occur in those with severe kyphoscoliosis who invariably have muscle weakness as well. Shortness of breath during activities of daily living is most related to ventilation at polio onset, contracting polio after age 10 or having polio for over 35 years.3 Patients tend to adapt a breathing pattern of more shallow rapid breathing that tends to relieve the shortness of breath.4 Physicians will often further assess this by observing whether the patients worsen when lying flat - so-called `supine dyspnea.' When the diaphragm muscle is severely affected and weak, this can be appreciated further by observing for supine abdominal paradox, where the abdomen will inappropriately collapse inward as the chest expands during inspiration. In those with severe chest wall muscle wasting and intact diaphragms, there may be an exaggerated outward motion of the diaphragm and the chest wall shows a `paradoxical' collapse during inhalation.
Patients may also have sleep related breathing disorders, regardless of whether or not they report disturbances to their sleep. Daytime hypersomnolence is commonly reported, but morning headache and nocturnal awakenings are also present.5 Patients who gain weight tend to have exercise intolerance, but this also predisposes them to more classic obstructive sleep apnea that could be suspected when loud snoring is present.
Traditional pulmonary function testing includes spirometry that assesses expired flows and volumes after a maximal effort. Polio patients classically exhibit restrictive physiology with reduction in lung volumes and a proportionate decrease in flows. Measurements of respiratory muscle strength, identified with maximal inspiratory and expiratory pressures (PiMax, PeMax), may also be reduced.3 Patients from a cohort study of those reporting a history of polio on average, have only a mild reduction in pulmonary function tests but those who specifically reported either respiratory muscle involvement at onset of polio or later developed kyphoscoliosis, have more profound abnormalities including elevated carbon dioxide levels on arterial blood gases, which portends a poorer prognosis.1,6,7 Cardiorespiratory exercise testing is useful in helping to separate out activity limitations from heart or lung impairment versus the often severe deconditioning that also occurs in these patients.8
Overnight oximetry and formal sleep studies (polysomnography or PSG) are used to prove whether polio patients have central hypoventilation, classic obstructive sleep apnea or a mixed disorder.5 Patients with kyphoscoliosis with ill-defined symptoms should be considered for screening overnight oximetry. Those complaining of sleep disordered breathing symptoms as noted above, especially in the presence of moderate restrictive lung disease or daytime hypercapnia, should undergo a PSG study which can reveal profound nocturnal hypoxemia particularly during REM sleep.5,6
The mainstay of treatment for daytime shortness of breath is reconditioning with pulmonary rehabilitation. These programs usually include other helpful techniques such as cough assistance. The same data that suggests increased activity and possibly reduced hospitalizations for COPD patients seems to apply to restrictive lung disease patients.9
Oxygen therapy is generally contraindicated for patients with post-polio problems but ventilatory assistance with non-invasive techniques, primarily nasal nocturnal ventilation has dramatic effects especially in patients with kyphoscoliosis.10,11,12 Corrective surgery to reduce spinal curvature can improve pulmonary performance.13 Careful attention to the cause of ventilatory insufficiency now offers patients marked increases in quality of life.
Peter C. Gay is Associate Professor and Consultant in Pulmonary, Critical Care and Sleep Medicine Mayo Graduate School of Medicine Rochester, MN
Used by Permission. Presented at the Eighth International Post-Polio and Independent Living Conference, June 8-10, 2000, sponsored by Gazette International Networking Institute (GINI). www.post-polio.org; firstname.lastname@example.org
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