This patient’s lungs were so bad, gas exchange had to take place outside of his body. 

Learning to read ABGs, and understanding what to do with that information is a very important skill for any nurse.   

I am excited to walk you through it, but first head to nursing.com/labvalues for a FREE copy of our brand-new Lab Values Pack.  

Meet Nurse Abby

Hi, my name is Abby!

I loved working in the cardiovascular ICU - it was truly one of my favorite nursing jobs. 

Today I want to share with you the story of one of my MORE complicated patients.  For several months I took care of a complex COVID patient - we will call her Esther.  Because of Esther’s COVID infection, her lungs were in such bad shape that she had to endure a highly specialized type of lung support called ECMO. 

My Patient On ECMO

Esther came to my hospital from a rural area out of state.  When she came to us, ALL the functions of her lungs were being handled by machines.  

1. A ventilator was actually moving air through her airway.  
2. And an ECMO Machine was pulling blood from her body for “gas exchange” that normally takes place in the lungs. This is when carbon dioxide and oxygen are exchanged in the alveoli.  After the blood flows through the ecmo machine and becomes oxygenated, it’s returned to the patient’s body.  

Nursing Care for an ECMO Patient 

So what did this mean for ME as a nurse?  

I am going to really focus on the special things I needed to be aware of for the ECMO machine.  Even though there were a lot of other things going on with this patient.  

So for a patient on ECMO, there are some key areas to focus: 

• Monitoring ABGs
  • For a patient on ECMO we needed to take ABGs at least every 4 hours 
  • We need to watch these closely, spot any abnormalities, and use them to make adjustments. . .

• Adjusting the Sweep
  • This is WHY we really need those ABG values. 
  • The ECMO machine is connected to oxygen.  The term sweep refers to the oxygen coming from the wall that connects to the oxygenator in the ECMO machine. 
  • We make adjustments to the sweep based on those ABG values. 
• Monitoring EVERYTHING connected to my patient
  • The ECMO cannula is pretty large and must stay exactly in place where the surgeon placed and sutured it, since it’s located in a large vessel and hemorrhage can happen fast.
  • That makes turning, or transporting very tricky and requires a close eye on all tubes, and lines attached to the patient.

Monitoring Patient ABGs

Ok, so now you know what I am looking for.  Now let me tell you what happened to Esther.  

One day I had an aide, and another RN with me giving my patient a bed bath. We had turned her to one side to wash her backside and finish replacing the sheets. We got her back onto her back and repositioned her carefully. 

Suddenly, we noticed that Esther was getting agitated.  We used a tiny bolus of propofol but that didn’t help to calm her down.  

I checked her vitals on the monitor:  Her SpO2 was dropping rapidly, BUT the vent settings hadn’t changed, and nothing was wrong with the position of her endotracheal tube.  

AND then I see something unusual.  

Out of the corner of my eye, I notice something!   In the tube going from the ECMO machine BACK to my patient . . .  the blood is starting to change color.  

The beautiful bright red it should be was missing, the blood was turning deep, dark - almost purple red.  The color of deoxygenated blood.  

That’s NOT good.  Deoxygenated blood should NOT be going back into my patient.  

After some panic from all of us, the RN helping me had the brilliant idea to check the sweep. Indeed, at some point through turning, repositioning, and changing the bed sheets, the sweep had come unplugged.  The ECMO machine was no longer getting Oxygen from the wall so the ECMO machine was no longer able to exchange oxygen for carbon dioxide.  

Can you guess what this patient’s ABG values would have looked like after an event like this? Do you think they would have been acidotic, or alkalotic?

I mentioned that ABGs are taken at least every 4 hours on a shift, but in the CVICU, and especially when a patient is on ECMO, they’re often taken more frequently. 

ABGs are taken to analyze the effectiveness of the sweep, and to gauge if the lungs are healing.  

So let’s talk about ABGs for a minute!  What are we looking for and why?  

Where I worked, the ABGs are processed by respiratory therapy, and results appear on the EHR. 

From there one must pay attention to the critical pieces of the report.  

• pH, which should be between 7.35-7.45
• PCO2, which is partial pressure of carbon dioxide and should be between 35-45 mmHg, and accounts for acidity
• Bicarbonate or HCO3, whose normal values should be between 22 – 26 mEq/L, which is the base, or alkaline piece of ABGs, and regulated by the kidneys.  
• PaO2, which should be between 80-100 mmHg, is the partial pressure of oxygen

How well do you know your ABGs? Can you guess what my patient’s ABGs would have looked like?   I put a link below for a quick practice quiz you can take on ABGs to see what your current level of understanding is. 

Go ahead, i’ll wait . . . just click here.  

How did you do? 

Now back to the story…

Well, Esther had become acidotic.  Did you guess it right? 

Since the sweep was unplugged, and their lungs were so bad, gas exchange wasn’t happening and the patient was growing acidotic. 

No gas exchange means O2 isn’t being added to the blood, CO2 isn’t being removed.  

CO2 is building up in the blood. . . uh oh.  So why acidosis?  

Well →  CO2 is an acid in water.  In the blood it will react with water and create hydrogen ions.  pH is literally a measure of the concentration of hydrogen ions.  However just a reminder, it is an inverse relationship, the more ions the lower the pH!  

So our PaCO2 (our acid) has increased, we would expect to see our pH decreasing - becoming more acidic.  Because the cause is respiratory related, this is respiratory acidosis.  

The body, being all about homeostasis, tries to compensate for acidosis by having the kidneys retain current and produce more of a substance called Bicarb, bicarbonate, or HCO3. 

Bicarb is a base.  It will bind with the free hydrogen ions, and raise the blood pH 

HOWEVER, it takes far too long in a scenario like this for it to actually be effective.

So how does the story end? What did I need to do with ABGs throughout the rest of the shift?

Well, we quickly got the sweep attached back to the O2 on the wall, and watched as the blood turned bright red again as it cycled through the oxygenator. 

With gas exchange once again taking place, the patient started to calm down. Remember, restlessness is a hallmark sign of respiratory acidosis. 

With such a significant hypoxic event, I almost had to start over with sweep titration.

I took the first ABG after plugging the sweep back in, to determine a baseline. I wondered if it needed to be adjusted from the number of liters that had been flowing before it was disconnected. I recall that I actually had to turn the sweep up, because the CO2 was high, and the pH was low. The patient initially needed additional O2 flowing through the oxygenator to get the excess CO2 removed from the blood.  Other values like the PaO2 hadn’t budged much despite the event, and I recall the value staying near 80%. 

Another thing that I needed to really watch out for with Esther, was low oxygen levels at the cellular level.  When this occurs anaerobic metabolism may start taking place in the body, because if cells aren’t getting enough oxygen, they go through an alternate metabolic pathway and lactic acid is the byproduct.

It’s something that’s also watched closely, and even trended so pressors, and IV fluid resuscitation can be balanced to optimize organ perfusion and blood pressure. 

Subsequent ABGs allowed me to titrate the sweep back down to where it was when I started the shift, and thankfully her lactate didn’t budge from the normal level it had been despite lack of oxygenated blood flowing back to her body through the ECMO machine during the hypoxic event. 

Bicarbonate or HCO3, is indicative of kidney function. Sometimes patients will even need supplementation and bicarb will be administered by push dose via IV to help regulate acidosis. The ABGs help the nurse, and the provider determine when that’s necessary, and how many ampules are needed to replace bicarb to restore normal levels in the blood. Thankfully, we didn’t need to intervene with administering bicarb to my patient, and titrating the sweep was enough to correct the acidosis.

Although you may never treat a patient on ECMO, I hope you learned the importance and implementation of ABGs in the care of patients, and how learning and understanding interpretation will help you in your role as the nurse!

If you need some more resources and help you can find more at nursing.com/labvalues. 

I hope this has helped you understand ABGs a bit better. We are rooting for you . . . Go out and be your best self today… happy nursing

Gas Exchange Pathophysiology

• Alveolar-Capillary Membrane Dysfunction:
  • Impaired gas exchange often begins with dysfunction of the alveolar-capillary membrane, the site where oxygen and carbon dioxide exchange occurs in the lungs. Conditions such as pneumonia, acute respiratory distress syndrome (ARDS), or pulmonary edema can compromise the permeability of this membrane.
• Ventilation-Perfusion Mismatch:
  • Conditions leading to impaired ventilation or perfusion in the lungs can disrupt the optimal matching of airflow and blood flow. Examples include airway obstructions (e.g., asthma, chronic bronchitis) or pulmonary embolism, causing areas of the lung to be poorly ventilated or poorly perfused.
• Decreased Surface Area for Gas Exchange:
  • Reduction in the available surface area for gas exchange, often due to conditions like emphysema or interstitial lung diseases, limits the exchange of oxygen and carbon dioxide. This results in decreased efficiency of respiratory function.
• Altered Oxygen-Carrying Capacity:
  • Conditions affecting the oxygen-carrying capacity of blood, such as anemia or carbon monoxide poisoning, can lead to inadequate oxygen delivery to tissues despite normal lung function.
• Impaired Respiratory Muscle Function:
  • Dysfunction of the respiratory muscles, as seen in conditions like myasthenia gravis or severe neuromuscular disorders, can compromise the ability to effectively move air in and out of the lungs, affecting gas exchange.
    

I stressed about passing my class and ultimately passing the NCLEX. 

I found success when I started using NURSING.com because it helped me find the must-know information with clear and concise videos, and then I would check my knowledge with the lesson quizzes.  

The underlying causes of respiratory acidosis or metabolic alkalosis became abundantly clear.  

I used the SIMCLEX to not only evaluate if I was ready for the NCLEX, but it would also give me personalized suggestions on what I should study to fill in my knowledge gaps. 

I could focus on those topics further with custom quizzes as well as using the additional study tools that are adapted to my personal learning style.

If you are still looking for those moments where everything clicks and you start to think like a nurse. . .  what worked for me was NURSING.com - and for more resources specifically on the many many lab values, you can go to nursing.com/labvalues.  

Now, to help build your ABG knowledge and start piecing together the beginnings of a gas exchange care plan.  

Gas Exchange Care Plan

Impaired gas Exchange is a common condition you will deal with working as an RN.  Let me share part of my care plan with you, that I would use to help a patient with impaired gas exchange

Let’s start with the desired outcomes for the patient

Desired Outcomes for Nursing Care:

• Improved Oxygenation
• Stabilized Respiratory Rate and Effort
• Enhanced Lung Function
• Patient Education on Self-Management
  

Nursing Interventions and Rationales for Impaired Gas Exchange

Evaluation for Impaired Gas Exchange Nursing Care:

The entire Gas Exchange Care Plan, along with 230+ other care plans, are available on NURSING.com.  

Looking for more?  Visit NURSING.com/labvalues now to download a Nursing cheat sheet for free.

I hope this has helped you understand heart failure a bit better so you know what to look out for. 

We’re rooting for you . . . Go out and be your best self today. . .

Happy Nursing!