Post-Polio Health (ISSN 1066-5331)
Vol. 17, No. 2, Spring 2001
How did acute poliomyelitis affect breathing? What is bulbar polio? What is spinal polio?
The poliovirus affected, in many different patterns, the nerve cells in the lower brain (bulbar) and spinal cord that control the muscles of the body. Poliovirus does not damage the lung tissue or the nerves to the airway muscle.
When the bulbar nerves were destroyed (bulbar polio), the muscles of the throat were weakened. This resulted in choking during eating and a diminished ability to cough.
When the spinal nerves were affected (spinal polio), muscles of the arms and legs, and trunk muscles needed for breathing and for taking a deep breath for coughing were weakened. Polio survivors may have had some combination of bulbar and spinal polio, so there may be corresponding throat muscle and limb/respiratory muscle weakness. Involvement of the upper part of the spinal cord weakened the key breathing muscles – the diaphragm and chest musculature.
How does respiratory muscle weakness affect breathing?
The diaphragm is the key muscle for inspiration (breathing in). When it is weakened by polio, the work of breathing becomes harder, especially when a person is lying down. With each breath, the abdominal contents have to be pushed down, but when sitting upright, gravity assists the diaphragm by pulling the contents down. Polio survivors, especially those with scoliosis, compensate by breathing faster but more shallowly because they lack the muscle strength to stretch a stiff rib cage. They may also have smaller lung volumes that further reduce respiratory muscle efficiency and drastically increase the work of breathing. This can lead to underventilation and respiratory failure.
How does respiratory muscle weakness affect sleep?
Respiratory muscle weakness contributes to sleep-disordered breathing. During REM (rapid eye movement) sleep, relaxation of many voluntary muscles, including the shoulder, chest and abdominal muscles, often occurs. And, these muscles are used to assist breathing when the diaphragm is weak. Consequently, a weak diaphragm has difficulty sustaining adequate breathing, especially when lying down. This leads to a decreased level of oxygen in the blood, or SaO2 desaturation. SaO2 desaturations can extend into non-REM sleep and contribute to arousals, inducing sleep fragmentation, and decreasing the amount of time in REM sleep. The quality of sleep deteriorates.
A polio survivor experiencing a combination of any signs and symptoms in the following list should immediately seek a respiratory evaluation, preferably by a pulmonary physician (pulmonologist) with experience in neuromuscular disease.
- Shortness of breath on exertion (dyspnea)
- Need to sleep sitting up (orthopnea)
- Retention of carbon dioxide (CO2):
– morning headaches;
– poor concentration and impaired intellectual function
- Sleep disturbances:
– not feeling rested in the morning;
– sleepiness during the day;
– dreams of being smothered and/or nightmares;
– restless and/or interrupted sleep;
– fatigue or exhaustion from normal activities; snoring
- Claustrophobia and/or feeling that the air in the room is somehow bad
- Difficulty in speaking for more than a short time
- Quiet speech with fewer words per breath
- Use of accessory muscles to breathe
- Weak cough with increased susceptibility to respiratory infections and pneumonias
Are all polio survivors at risk for breathing problems?
No. Individuals who used an iron lung, or barely escaped one, during the acute phase should be aware of potential problems. Those survivors who did not need ventilatory assistance during the acute phase, but who had high spinal polio resulting in upper body weakness and/or diaphragm weakness, and those with scoliosis (sometimes referred to as chest wall deformity) may also be at risk.
Other factors contributing to breathing problems are asthma, COPD, smoking, obesity and sleep apnea: either central, obstructive or mixed.
Another compounding factor is diminished vital capacity (VC), which happens to everyone as they age.
Why do these problems often go unnoticed?
The reasons are varied and can be complex. The onset of respiratory problems is insidious, and this gives an individual time to become accustomed to each decrease in function. Thus, one is not immediately aware that anything is wrong, and a treating physician may not recognize the signs or be familiar with the option of home mechanical ventilation. The person's spouse or family should be questioned about signs and symptoms, changes in activity levels and breathlessness and sleeping patterns.
Additionally, facing breathing difficulties can be frightening, for both the survivor and their loved ones, and there can be a reluctance to address them. Sometimes this fear stems from inaccurate information about the problem and the solutions or from earlier polio-related experiences.