Respiratory Acid-Base Imbalances

Have you ever felt confused or even intimidated by Acid-Base Imbalances?  If so, you’re not alone…the topic of Fluids and Electrolyte is one of the most asked about here at Your Nursing Tutor.  Which is good, because Fluids and Electrolytes are also one of the most important topics that you need to be successful as a nursing student. It goes way beyond just memorizing lab values to decide if they’re normal or abnormal, you need to really understand what’s happening in the body in order to become a successful nurse.  And being able to understand Acid-Base Imbalances are a big part of that.  Let’s jump into how we can better understand Respiratory Acid-Base Imbalances.

Respiratory Acidosis and Respiratory Alkalosis

It should be no big surprise that the lungs are the primary regulator for respiratory imbalances.  I use an easy, over-simplified way to help me remember how the lungs can effect the acid-base balance in the body.  Pretty much everyone can remember that CO2 (carbon dioxide) is the primary gas that we exhale.  So the first thing you have to remember is that Hydrogen ions (H+) always go the same direction as CO2!  That means that if CO2 increases, then H+ increases too.  The second thing you have to remember is that H+ is acidic.  So that means that as CO2 increases, H+ will increase, which means that there will be more acid in the body…which means that pH will decrease to become more acidic.  Which leads me to the third thing you have to remember:  the direction of pH can be tricky, and it’s easy to make a mistake!  So make sure that you are familiar with how the pH scale works before you tackle Acid-Base Imbalances.

(By the way, here’s a less simplified explanation of what I wrote above for those of you that want more info:  When there’s too much CO2 in the body, the body tries to get rid of it by combining with H2O to become Carbonic Acid (H2CO3).  Some of the Carbonic Acid separates to become Bicarbonate (HCO3-, which is a base) and H+.  The Bicarb and H+ neutralize each other, but there’s still extra Carbonic Acid which makes the body’s pH turn acidic.  As long as you understand the simplified explanation in the last paragraph, though, you’ll be fine for nursing school.  This is just in case you wanted to get a little deeper with your understanding!)

So that’s what happens when CO2 in the body increases.  But just as you’d expect, the opposite happens if CO2 decreases.  Which is nice, cause it’s easier to remember that something is the “opposite” than to try and memorize a whole new set of information!  So if CO2 decreases, then H+ also decreases because it “follows” CO2.  The decrease in H+ causes the pH increase to become more basic.

(Here’s the extra explanation for this part:  You remember that other technical explanation I gave a couple paragraphs back?  Well now we simply see the reverse of that reaction.  The H+ and the bicarbonate recombine to become Carbonic Acid again, and then the Carbonic Acid breaks up into CO2 and H2O again.  Now the H+ are tied up in the H2O, which gets exhaled along with the CO2.  Pretty nifty!)

That’s the physiology underneath Respiratory Imbalances.  Now let’s look at how it plays out in a patient.

Causes of Respiratory Acidosis and Respiratory Alkalosis

There’s two primary mechanisms you’ll see with respiratory imbalances:  breathing too fast (hyperventilation) and breathing too slow (hypoventilation).  Whenever you analyze a question about respiratory imbalances, remember to think about what’s happening to the CO2.

If someone is hyperventilating, then they are “blowing off” CO2, which means they are getting rid of it.  So it is decreasing in the body.  That means H+ is decreasing, too, which causes pH to increase and become more basic.  You can help a patient reverse this by helping them to retain more CO2.  That’s why the classic “breath into a paper bag” trick is so frequently used to help with hyperventilation.  It’s a way to help the patient “rebreath” some CO2 to get it back into their body and start decreasing their pH again.

If someone is hypoventilating, then they are retaining CO2, which means that CO2 levels in the body will be steadily increasing.  Of course that means H+ is increasing, too, which causes pH to decrease and become more acidic.

Once you understand of the physiology of Respiratory Imbalances, it’s easier to start thinking like a nurse.  Suddenly it makes a lot more sense why COPD and pneumonia patients are at increased risk of developing Respiratory Acidosis.  These types of illnesses make it difficult for patients to get rid of CO2, so it builds up in their body (along with H+!).

Taking the time to understand how and why symptoms or illnesses develop and interact will always be easier then trying to memorize a different list of symptoms for each disease (have you SEEN the long list of COPD symptoms??).  It cuts down on your total study time and builds up your confidence in your nursing knowledge.

I hope this article helped you in your quest to think like a nurse!  Got a question or comment about Respiratory Acid-Base Imbalances?  Leave a comment below and let me know!

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5 Comments

  1. Anna

    I’m a LPN in school finishing my RN, and I never understood this. After reading this article I do and it makes sense. Thanks!

  2. Eniko

    I almost finishing first semester of nursing , having a final and the last test , but I need to know the fluid and electrolytes imbalances . I would appreciate any help to memorize and understand the whole concept . Thank you Eniko

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