Virus destroys the anterior horn motor neurons in the spinal cord
Physiology
Pulmonary HTN due to neuromuscular disease
Hypoventilation leads to hypoxia/ acidosis (with resultant pulmonary vasoconstriction)
Ventilatory response to hypercapnia is decreased (related to the reduction in VC and MVV) while ventilatory response to hypoxia is relatively preserved
Diagnosis
ABG: hypoxemia/ hypercapnia
PFT’s: restriction
Decreased VC (typically 40-70% predicted/ due to muscle weakness, decreased lung compliance, and decreased chest wall compliance): characteristically lower VC for a given level of respiratory muscle strength compared to other neuromuscular diseases (probably due to more aggressive current treatment of pulmonary complications of polio)
Decreased TLC
Increased RV (due to inability to overcome recoil of chest wall outward at volumes below FRC)
Decreased MVV
Decreased MIP/MEP
Decreased lung compliance (due to chronically low lung volumes: microatelectasis/ reduced surface tension/ alteration in elastic fibers in lung interstitium)
Muscle Weakness/Paralysis (of limbs, truncal, and respiratory muscles) are most severe in early febrile stage of disease
Significant respiratory muscle weakness occurs in 15% of cases (from 1953 epidemic): distribution and severity is variable (usually, inspiratory > expiratory muscle weakness)
Partial recovery (due to recovery of anterior horn cells or improved function of unaffected muscles) during convalescence
Kyphoscoliosis
Aspiration Pneumonia
Sleep-Disordered Breathing
Pulmonary Hypertension/Cor Pulmonale: due to chronic hypoventilation
Post-Polio Syndrome
Denervation of previously reinnervated muscles
Generally involves same muscle groups that were previously affected
Occurs 20-30 years after recovery from primary disease
Treatment
Prevention: polio vaccine
Mechanical ventilation: may be required
Ventilatory endurance time (time that patient is able to breathe without ventilator) is linearly related to VC
Corrects polycythemia but does not improve work of breathing, lung compliance, or MVV
Glossopharyngeal breathing: see Amyotrophic Lateral Sclerosis [[Amyotrophic Lateral Sclerosis]])
