Jonnathan Busko, MD

Dr Busko,

We had an interesting hypothetical question today that I thought would be a good jump off for the blog.

You are presented with a hypothetical 16yo female hyperventilating with carpal spasm. After a thorough assessment you determine that there is no detectable medical stimulus for the rapid breathing and it is most likely due to an anxiety issue (previous diagnosis). A provider on scene suggests you should shut the O2 off on the NRB mask to promote rebreathing of CO2. I was hoping you might weigh in with your thoughts.

Thanks,

DB

Dr. Busko Responds:

Hyperventilation is “excessive ventilation; specifically: excessive rate and depth of respiration leading to abnormal loss of carbon dioxide from the blood; called also overventilation” (1).  Hyperventilation can be done on purpose.  For example, when a skin diver hyperventilates, he lowers the carbon dioxide levels in his blood and decreases the drive to breathe (remember that most of us are triggered to breathe when the carbon dioxide levels in our blood rise).  It can also happen unintentionally and is called “psychogenic hyperventilation,” “hyperventilation syndrome,” “behavioral breathlessness,” or “psychogenic dyspnea.”  The hyperventilation results from the underlying behavioral condition.

When carbon dioxide levels get low the blood is less acidic (more alkalotic).  This makes the salts in the blood and the cells (the electrolytes) move in and out of the cells in ways they usually wouldn’t.  These “electrolyte shifts” cause many of the symptoms the patient has.  In particular, the calcium shift causes the carpopedal (hand and foot) spasms that are very painful.  The patient can also have general weakness and numbness and tingling (low blood phosphorus), leg cramps (low blood potassium), central nervous system symptoms including syncope and seizure (decreased blood flow to the brain), chest pain with EKG changes (from many electrolyte changes), and wheezing (bronchospasm caused by low blood carbon dioxide levels).  Although the risk of death from psychogenic hyperventilation is low, it can have major impacts on the body.

Even more importantly, it is important to figure out whether the patient has hyperventilation (as defined above) versus tachypnea (fast breathing) or hyperpnea (deep breathing), both of which are signs of underlying disease.  The major difference is that in hyperventilation the minute ventilation (how much volume moves in and out of the lungs each minute) is more than the body needs; in tachypnea and hyperpnea, the breathing rate and/or volume is increased because the body’s metabolic demand has increased.  Can you really rule out a pulmonary embolus as the cause to the patient’s rapid or deep respiratory rate?  Pneumonia?  Early congestive heart failure?  Carbon monoxide poisoning?  Sepsis?  Diabetic ketoacidosis?  Spontaneous pneumothorax?  In all these cases, the respiratory rate is increased because the body needs more oxygen.  And a patient with a history of hyperventilation syndrome can develop all of these diseases.

In emergency medicine and EMS, our job is not so much to diagnose what a patient has, but rather to make sure that nothing bad is going on.  If we happen to diagnose something benign (not bad) along the way, great, but most importantly, we need to be sure that we’re not missing something bad.  Since psychogenic hyperventilation is a diagnosis of exclusion (that is, all that’s left after you’ve made sure nothing else is going on), you need to be really sure it’s what you’re dealing with so that you don’t miss anything else important or life threatening.

The theory of having a patient rebreathe carbon dioxide, whether from a brown paper bag or a non-rebreather without additional oxygen flowing in, is that the rebreathed carbon dioxide increases the level of carbon dioxide in the blood and reverses the problems caused by the respiratory alkalosis (low blood acid levels caused by low carbon dioxide).  There has never been a study to show that this treatment for acute hyperventilation syndrome actually works.  What is much more concerning is that there are many deaths from acute MI (2), asthma (3), DKA (4), pulmonary embolus (5), and other organic diseases (2) that resulted from the patient being diagnosed with “acute hyperventilation syndrome “ and not being worked-up or treated for their real underlying disease.  These reports apply to emergency department and EMS patients.  Furthermore, a major contributor to these deaths is hypoxia.  Patients with underlying organic disease have increased metabolic needs.  When carbon dioxide rebreathing is used, they actually get lower oxygen than is in room air (21%) because very little new oxygen is being added to the paper bag or non-rebreather.  The technique, quite literally, suffocates the patient and studies from as long ago as 1989 demonstrated rebreathing to be a dangerous treatment technique (6).  Acute hyperventilation syndrome may be uncomfortable but it is not life threatening.  Misdiagnosising a life-threatening condition by calling it “just hyperventilation” may be.

No matter what the cause, the assessment and treatment of the patient who is breathing rapidly includes:
-Protect yourself (lots of environmental toxins and atmospheric conditions cause rapid ventilation)
-Perform good initial assessment and resuscitation interventions (“resusassesment” as needed
-Try to determine the underlying cause but remember that many of the tools used in the emergency department to rule out bad stuff are not available in the field (and therefore you can never rule out all the bad stuff)
-Prevent hypoxia.  They may not all need high flow O2 but no one needs to be put into a hypoxic environment either (e.g. rebreathing techniques)
-Treat things that you find (asthma, STEMI, etc…)
-Do not use rebreathing techniques
-Coach the patient if there appears to be an underlying psychological component
-Never blow these patients off as having “just hyperventilation”

Be safe, play well with others and remember, we help people.

Additional Resources
Kern B, Rosh AJ.  Hyperventilation Syndrome.  Emedicine.com.  Retrieved February 02, 2009, from emedicine.com website: http://emedicine.medscape.com/article/807277-overview
http://emedicine.medscape.com/article/807277-diagnosis
http://emedicine.medscape.com/article/807277-treatment

References:
(1)    hyperventilation. (n.d.). Merriam-Webster’s Medical Dictionary. Retrieved February 02, 2009, from Dictionary.com website: http://dictionary.reference.com/browse/hyperventilation
(2)    Saisch SGN, Wessely S, Gardner WN.  Patients with acute hyperventilation presenting to an inner-city emergency department.  Chest 110(4);1996:952-57.
(3)    Gardner WN, Bass C, Moxham J. Recurrent hyperventilation tetany due to mild asthma. Respir Med 1992; 86:349-51
(4)    Treasure RAR, Fowler PBS, Millington HT, et al. Misdiagnosis of diabetic ketoacidosis as hyperventilation syndrome. BMJ 1987; 294:630
(5)    Kern B, Rosh AJ.  Hyperventilation Syndrome.  Emedicine.com.  Retrieved February 02, 2009, from emedicine.com website: http://emedicine.medscape.com/article/907277-treatment
(6)    Callahan M. Hypoxic hazards of traditional paper bag rebreathing in hyperventilating patients. Ann Emerg Med 1989; 18:622-28

Tags: Clinical

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