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Wednesday, July 13, 2011

Neurological disorders

Any disease that effects any part of the respiratory pump can lead to respiratory failure. In some cases the process is quick (trauma) and in some cases the process can take years. In either case, neuromuscular disorders can have a significant effect on the life of a person, and may result in the eventual need for mechanical ventilation and possibly death.

Before reading on, it might be beneficial for you to read about the respiratory pump.
The following are the neurological diseases and what part of the pump they effect*:

1. Central Nervous System:
  • Central Sleep Apnea: This is defined as cessation of breathing while sleeping. It usually only affects adults with cerebral vascular injury, and is caused by an inadequate respiratory drive. This is often directly caused by any disease process that effects the respiratory center or the neural passageways.
  • Ondine's Curse:
  • Primary alveolar hypoventilation:
  • Sedative hypotonic overdose: Slow breathing due to relaxed neural system in response to drugs or alcohol. May also result in no breathing
2. Neural pathways:
  • Spinal cord injury: Nerve damage due to trauma affects respiratory pump. Nerves below the injury are paralyzed
  • Multiple Sclerosis:
  • Amyotrophic lateral sclerosis (ALS): Loss of motor neurons in the anterior horn of the spinal cord. Respiratory failure will eventually develop.
  • Polio: Virus destoys motor neurons in the anterior horn of spinal cord and this may effect nerves that control the respiratory pump. This may result in apnea.
  • Guillain-Barre Syndrome: Progressive ascending (ground to brain) paralysis. This is caused by a virus, and results in inflammation of the spinal roots and peripheral nerves and this causes destruction of the myelin sheaths and this causes associated nerves to malfunction. This damage is reversible after a few weeks.
3. Neuromuscular junction:
  • Myasthenia gravis: Destruction of acetylcholine receptors on the muscle
  • Botulism poisoning: Failure of nerve to release acetylcholine
  • Organophosphate poisoning: This is an insecticide that breaks down acetylcholine at this junction (chemical warfare)
4. Muscular function:
  • Muscular dystrophy: Muscle wasting disease caused by defective genes for muscle proteins. It's genetic. Slow breakdown of muscle fibers results in gradual breakdown of muscles. They usually die of respiratory failure, or pneumonia.
  • Myotonic dystrophy: A type of muscular dystrophy that results in gradual muscle wasting. Characterized by prolonged muscle contractionsa and inability to relax muscles.
  • Multi system atrophy: Slow loss or shrinkage of neural cells that effect motor functions of infoluntary functions of the body, such as heart rate, bladder, blood pressure, temperature, body movement and slowed breathing. These patients slowly lose muscular function.
Respiratory complications generally don't appear until later in the disease process, yet as muscle weakness progersses respirations will eventually become impaired.

Respiratory muscle weakness will result in the following complications of neuromuscular disease:
  1. Loss of adequate lung volumes
  2. Decreased ability to cough
  3. Retained secretions
  4. Mucus plugging
  5. Increased risk for atelectasis
  6. Increased risk for pneumonia
  7. Inadequate respirations
  8. Rapid, shallow breathing
To monitor lung muscle strengh, it's important to monitor:
  1. Negative inspiratory pressure (NIF): Shows if lung muslces are getting weaker or stronger. Want to maintain greater than 20 cm H2O
  2. FVC

  1. Wilkins, Robert L, Respiratory Disease, 1993
  2. See links above

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