1.02 Hyperventilation
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agk's Library of Common Simple Emergencies

Presentation
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The patient is anxious and complains of 
shortness of breath and an inability to fill 
the lungs adequately. A patient may also have 
palpitations, chest or abdominal pain, and 
tingling or numbness around the mouth and 
fingers, or possibly even flexor spasm of the 
hands and feet. His respiratory volume is 
increased, which may be apparent by an 
increased respiratory rate, or only be an 
increased tidal volume or frequent sighing. The 
remainder of the physical examination is 
normal. The patient's history may reveal an 
obvious precipitating emotional cause (such as 
having been caught stealing or being in the 
midst of a family quarrel).

What to do:
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- Perform a brief physical examination, 
   checking especially that the patient's 
   mental status is good, there is no unusual 
   breath odor, there are good, equal excursion 
   and breath sounds in both sides of the 
   chest, and there is no swelling, pain or 
   inflammation of the legs.
- Measure pulse oximetry, which should be 98- 
   100%.
- Explain to the patient the cycle in which 
   rapid, deep breathing can cause physical 
   symptoms upsetting enough to cause further 
   rapid, deep breathing. Repeat a cadence 
   ("in...out...in...") to help him voluntarily 
   slow his breathing, or have him voluntarily 
   hold his breath for a while.
 - If he cannot reduce his ventilatory rate and 
   volume, provide a paper bag or length of 
   tubing through which to breathe, keeping the 
   pulse oximetry monitor on to avoid hypoxia. 
   This will allow him to continue moving a 
   large quantity of air, but provide air rich 
   in carbon dioxide, allowing the blood Pco2 
   to rise towards normal. Carbogen gas (5% 
   CO2) may also be used, if available. 
   Administration of 50-100mg of hydroxyzine 
   (Vistaril) im often helps to calm the 
   patient.
- If you cannot reverse these symptoms and 
   reduce respiratory effect in this manner in 
   15-20 minutes, you should double check the 
   diagnosis by obtaining arterial blood gases, 
   looking for a metabolic acidosis or hypoxia 
   indicative of underlying disease.
- Reexamine the patient after hyperventilation 
   is controlled.
- Make sure the patient understands the 
   hyperventilation syndrome and knows some 
   strategies for breaking the cycle next time. 
   It may be valuable to have him reproduce the 
   symptoms voluntarily. Arrange for followup 
   as needed.

What not to do:
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- Do not miss the true medical emergencies 
   which also present as hyperventilation, 
   including: pneumothorax, pneumonia, 
   pulmonary embolus, diabetic ketoacidosis, 
   salicylate overdose, sepsis, uremia, 
   myocardial infarction and CVA.
- Do not use a paper bag on a patient with a 
   low oxygen saturation on pulse oximetry 
   (<96%)

Discussion
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The acute metabolic alkalosis of hyper- 
ventilation causes transient imbalances of 
calcium, potassium, and perhaps other ions, 
with the net effect of increasing the irrita- 
bility and spontaneous depolarization of 
excitable muscles and nerves. First-time 
victims of the hyperventilation syndrome are 
the most apt to visit the ED. This is an 
excellent time to educate them about its 
pathophysiology and the prevention of 
recurrence. Repeat visitors may be overly 
excitable or may have emotional problems and 
need counseling.

References:
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- Demeter SL, Cordasco EM: Hyperventilation 
   syndrome and asthma. *Am J Med* 1986;81: 
   989-994.
- Callaham M: Hypoxic hazards of traditional 
   paper bag rebreathing in hyperventilating 
   patients. *Ann Emerg Med* 1989;18:622-628.

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