Sunday, 7 February 2016

Hyperventilation

The term "hyperventilation" is one I am not particularly fond of. I think there are three separate causes of hyperventilation:

  1. Pathological - eg PE, pneumonia, pain 
  2. Iatrogenic - "overbagging"
  3. Panic / anxiety/ hysteria
The third is the cause of hyperventilation we are now going to focus on. It seems to me to be an exaggeration of a normal physiological response - a form of control system dysfunction. The respiratory distress is driven by the brain. 

The DSM-IV criteria for a panic attack is quite specific. They define it as a period of intense fear or discomfort developing abruptly, and peaking within ten minutes + 4 of:
a. Chest pain/ discomfort, b. Chills or hot flushes, c. Derealisation or depersonalisation, d. Fear of loosing control, e. Feeling dizzy, f. Feeling of choking, g. Nausea, h. Palpitations, i. Paraesthesias. j. SOB, k. Impending doom, l, Sweating, m. Trembling

Carpopedal Spasm
  • Rapid breathing results in excess excretion of carbon dioxide in the lungs 
  • This reduces the concentration of CO2 in the blood
  • The blood pH becomes alkali
  • This causes increased binding of calcium ions to proteins in the blood
  • The reduced level of calcium causes "carpopedal spasm"
  • This could also lead to tetany 
Investigation
The lactate can be high - is not helpful 
ABG would show a normal PO2 and a marked respiratory alkalosis. The Ca may be low. 

Treatment
Control the breathing. This is really difficult to do, and very frustrating! Telling them to control their breathing or calm down is likely to make matters worse, not better. 
  • Give them a cold drink
  • Ask them to read a sentence out loud 
  • Paper bags are NOT recommended - lots of patients ended up getting a paper bag for asthma
  • Long term - CBT may be needed
References

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