The ROME method can be used to interpret arterial blood gases (ABGs). This review is made for nursing students and can be used during lecture exams to help you determine respiratory/metabolic acidosis/alkalosis along with uncompensation vs. compensation.
The ROME method is a simple and quick way to solve ABG problems found on an exam. In the previous review, we discussed the Tic-Tac-Toe ABG method for solving arterial blood gases, which is another great method.
In this review you will learn:
- Normal vs. abnormal blood pH, CO2, HCO3 levels
- Basics about the buffering system in acid-base imbalances
- ROME method
- Solving for respiratory/metabolic alkalosis/acidosis
- Solving for uncompensation vs compensation
Lecture on the ROME Method
ROME Method ABGs Review
What’s the purpose of interpreting arterial blood gases? It helps us identify a potential acid-base imbalance in the body. The following acid-base imbalances can occur in the body:
The body has a buffering system in place that helps keep the blood’s pH within a normal level, which is 7.35-7.45. A value lower than 7.35 is considered an acidic blood pH, and a value higher than 7.45 is considered an alkalotic blood pH.
When the blood’s pH becomes abnormal, the body has two systems (the respiratory and metabolic system) that will attempt to correct the abnormal state of acidosis or alkalosis. When you’re solving ABG problems you are solving to see if these systems are compensating for the abnormal blood pH.
On exams you will be given the pH, CO2, and HCO3 level. The CO2 level (carbon dioxide) always represents the RESPIRATORY system. While HCO3 level (bicarbonate) always represents the METABOLIC system. Remember these concepts…they’re very important for when solving ABG problems.
Nurse Sarah’s Notes and Merch
Just released is “ABG Interpretation Notes, Mnemonics, and Workbook by Nurse Sarah“. These notes contain 64 pages of Nurse Sarah’s illustrated, fun notes with mnemonics, and worksheets that include over 90 ABG practice problems and 60 test review questions covering ABG concepts.
You can get an eBook version here or a physical copy of the book here.
When solving ABG problems always ask these 3 Questions:
- Is it a respiratory or metabolic problem?
- Is this alkalosis or acidosis?
- Is this uncompensated, partially compensated, or fully compensated?
ROME stands for
Respiratory
Opposite
Metabolic
Equal
*Tip: When applying the method for ABG interpretation, remember to keep the R and O together and the M and E.
What does Respiratory Opposite mean? The CO2 (remember carbon dioxide represents the respiratory system) and pH will be OPPOSITE of each other…one will be elevated while the other will be decreased…this means it’s a respiratory disorder.
- CO2 ⬆, pH ⬇: Respiratory acidosis
- CO2 ⬇, pH ⬆: Respiratory alkalosis
What does Metabolic Equal mean? The HCO3 (remember bicarb represents the metabolic system) and pH will be EQUAL…either both will be elevated or decreased….this means it’s a metabolic disorder.
- HCO3 ⬇, pH ⬇: Metabolic acidosis
- HCO3 ⬆, pH ⬆: Metabolic alkalosis
Before solving ABG problems, you must commit to memory the following lab values:
Blood pH:
- Normal: 7.35-7.45
- Acidosis: <7.35
- Alkalosis: >7.45
CO2 (carbon dioxide):
- Normal: 35-45 mmHg
- Acidosis: >45 mmHg
- Alkalosis: <35 mmHg
HCO3 (bicarbonate):
- Normal: 22-26 mEq/L
- Acidosis: <22 mEq/L
- Alkalosis: >26 mEq/L
Now, let’s apply the ROME method and solve practice ABG problems:
Problem 1:
pH 7.28, CO2 50, HCO3 24
Setup ROME:
- R: ⬆ (CO2 is 50 and acidotic)
- O: ✔
- M: NORMAL
- E:
pH: ⬇(pH is 7.28 and is acidotic)
Answer: CO2 ⬆, pH ⬇= Respiratory acidosis, uncompensated: this is a respiratory problem and the pH is abnormal (acidotic)…the metabolic system (HCO3) is normal and is not at this time trying to compensate…if it was the bicarb would be abnormal (alkalotic) in an attempt to increase the pH to normal range.
Problem 2:
pH 7.30, CO2 40, HCO3 18
Setup ROME:
- R: NORMAL
- O:
- M: ⬇ (HCO3 is 18 and acidotic)
- E: ✔
pH: ⬇(pH is 7.30 and is acidotic)
- Answer: HCO3 ⬇, pH ⬇: Metabolic acidosis, uncompensated: this is a metabolic problem and the pH is abnormal (acidotic)…the respiratory system (CO2) is normal and is not at this time trying to compensate…if it was the carbon dioxide would be abnormal (alkalotic) in an attempt to increase the pH to normal range.
Problem 3:
pH 7.42, CO2 26, HCO3 18
Setup ROME:
- R: ⬇ (CO2 is 26 and alkalotic)
- O: ✔
- M: ⬇ (HCO3 is 18 and acidotic)
- E:
pH: ⬆ (pH is 7.42 and is NORMAL but alkalotic*)
*You need to ask yourself what side of “normal” is the pH on? 7.40 is the absolute normal for pH…any value greater than 7.40 is considered on the alkalotic side, while any value less than 7.40 is considered on the acidotic side.
- Answer: CO2 ⬇, pH ⬆: Respiratory alkalosis, fully compensated: this is a respiratory problem and the pH is normal (on the alkalotic side of normal)…the metabolic system (HCO3) is ABNORMAL and on the acidotic side, so it is compensating. Since the blood pH level is back to normal, there is full compensation. However, if the blood pH was abnormal it would be partial compensation.
Problem 4:
pH 7.51, CO2 47, HCO3 32
Setup ROME:
- R: ⬆ (CO2 is 47 and acidotic)
- O:
- M: ⬆ (HCO3 is 32 and alkalotic)
- E: ✔
pH: ⬆ (pH is 7.51 and is alkalotic)
- Answer: HCO3 ⬆, pH ⬆: Metabolic alkalosis, partially compensated: this is a metabolic problem and the pH is abnormal (alkalotic)…the respiratory system (CO2) is ABNORMAL and on the acidotic side, so it is trying to compensate. However, it is only partially compensating at this time because the blood pH level is still abnormal. If the blood pH level was normal, there would be full compensation.
Problem 5:
pH 7.37, CO2 32, HCO3 17
Setup ROME:
- R: ⬇ (CO2 is 32 and alkalotic)
- O:
- M: ⬇ (HCO3 is 17 and acidotic)
- E: ✔
pH: ⬇ (pH is 7.37 and is NORMAL but acidotic*)
* You need to ask yourself what side of “normal” is the pH on? 7.40 is the absolute normal for pH…any value greater than 7.40 is considered on the alkalotic side, while any value less than 7.40 is considered on the acidotic side.
- Answer: HCO3 ⬇, pH ⬇: Metabolic acidosis, fully compensated: this is a metabolic problem and the pH is normal (on the acidotic side of normal)…the respiratory system (CO2) is ABNORMAL and on the alkalotic side, so it is compensating. Since the blood pH level is back to normal, there is full compensation. However, if the blood pH was abnormal it would be partial compensation.
Test your knowledge on the ROME method with this ABG quiz.