Introduction to Arterial Blood Gas (ABG) NCLEX® ReviewAt first, it may often be difficult to read ABGs as the subject depends on an understanding of complex physiological processes. The complexity of this topic may often steer nurses and other practitioners into believing that blood gas interpretation may be the job of respiratory therapists or reserved for physicians to understand. Show
Instead, it’s important for all healthcare workers to have a strong understanding of ABGs as this can dramatically impact the outcomes of clients hospitalized with respiratory or metabolic acidosis. This ABG NCLEX® Review aims to provide readers with a thorough understanding of arterial blood gases in order to prepare for both daily practice as a nurse and for the NCLEX® exam. Key Concepts for ABGWhen interpreting ABGs the first step will always be to determine whether the client has normal, acidic, or basic (alkalotic) measurements. The first step will be to observe the pH of the blood via laboratory tests. The next step will be to evaluate the partial pressure of carbon dioxide (PaCO2) and the concentration of bicarbonate (HCO3) in the serum. Refer below for the normal values of these laboratory parameters to aid in your evaluation of blood gases.
When a client presents with a pH that is out of the normal range, you can interpret the value as either acidic or basic. Acidosis is observed when the pH is below the normal range < 7.35 whereas alkalosis or (basic blood gas) is measured as > 7.45. PaCO2 in general is referring to the concentration of carbon dioxide in the blood. Abnormalities in these readings will indicate that the client has a respiratory issue instead of a metabolic one. In short, it may suffice to know that higher concentrations of carbon dioxide will increase the acidity of the blood (therefore lowering the pH). Thus, values > 45 mmHg can be interpreted as respiratory acidosis whereas values < 35 mmHg are considered respiratory alkalosis. Notice that high values, in this case, suggest acidosis, in contrast to pH where high values suggest alkalosis. You may recall from basic chemistry that bicarbonate (HCO3) is a basic chemical compound that raises pH (decreasing acidity). Therefore, elevated bicarbonate readings (> 27 mEq/L) will increase pH, causing alkalosis. In this case, you can interpret these values as metabolic alkalosis as it has nothing to do with the expiration or inhalation of CO2. Clients who have values < 22 mmHg may have metabolic acidosis as the concentration of bicarbonate in the blood is low, therefore lowering the blood pH and causing acidosis. Unfortunately, when reading blood gases, it may be necessary for practitioners to take additional considerations with respect to the bodies tendency to compensate for pH abnormalities. This may complicate matters as it may appear that the pH of the blood is within normal limits (e.g. between 7.35-7.45) but still indicative of potential underlying issues. Compensation mechanisms often make interpretation of ABGs very difficult, so it is important to keep some basic concepts in mind. First, clients that present with primary metabolic acidosis may have a disorder causing decreased bicarbonate. The body will compensate this by increasing the rate of expiration of carbon dioxide via the lungs to drive the pH of the blood up. Clients that present with primary metabolic alkalosis may have increased levels of bicarbonate in the body. The body will compensate for this by reducing the ventilation of carbon dioxide, thus retaining more pCO2 in the blood causing compensation of the pH abnormality. Compensation of primary respiratory alkalosis and acidosis generally involves the kidney’s ability to either retain bicarbonate or increase the excretion of it. Retention of bicarbonate of course will increase the pH of the blood where excretion of it will decrease it. For example: A client may have respiratory acidosis as they were initially failing to expire the appropriate amount of carbon dioxide from the body. As a result, the kidneys will opt to retain more bicarbonate in order to increase the pH of the body and temporarily resolve the blood pH. Upon arriving to the hospital, it may appear that the client has a normal pH despite having high readings of both carbon dioxide and bicarbonate. This would be an example of fully compensated respiratory acidosis. This NCLEX quiz will test your ability to differentiate between respiratory acidosis vs respiratory alkalosis. You will be required to know the causes, signs and symptoms,
and how to interpret blood gas values in this quiz. As a nursing student, it is crucial you know the basics about acid-base imbalances. Below are common test questions you may encounter on your nursing lecture exam or NCLEX licensing exam. Also, don’t forget to take our free
Arterial Blood Gas (ABGs) Quiz. This NCLEX quiz will test your knowledge on the differences between respiratory alkalosis & respiratory acidosis.
(NOTE: When you hit submit, it will refresh this same page. Scroll down to see your results.)
Respiratory Acidosis and Respiratory Alkalosis Quiz NCLEX1. A patient is post-opt from knee surgery. The patient has been receiving Morphine 4 mg IV every 2 hours. You notice the patient is exhibiting a respiratory rate of 8 and is extremely drowsy. Which of the following conditions is the patient at risk for? A. Respiratory acidosis B. Respiratory alkalosis C. Hypokalemia D. Metabolic acidosis 2. A patient attempted to commit suicide by ingesting a bottle of Aspirin. Which of the following conditions is this patient at risk for? A. Hyperkalemia B. Hypercalcemia C. Respiratory alkalosis D. Respiratory acidosis 3. Respiratory alkalosis can affect other electrolyte levels in the body. Which of the following electrolyte levels can also be affected in this condition? A. Calcium and sodium levels B. Potassium and sodium levels C. Calcium and potassium levels D. Potassium and phosphate levels 4. A patient is experiencing respiratory alkalosis. What is the most classic sign and symptom of this condition? A. Bradypnea B. Tachypnea C. Bradycardia D. None of the options are correct 5. A patient has the following blood gases: PaCO2 25, pH 7.50, HCO3 19. Which of the following could NOT be the cause of this condition? A. Anxiety attack B. Chronic obstructive pulmonary disease (COPD) C. Fever D. Aspirin toxicity 6. A patient on mechanical ventilation has the following blood gases: PaCO2 29, pH 7.56, HCO3 23. Which of the following conditions is the patient experiencing? A. Respiratory alkalosis not compensated B. Respiratory alkalosis partially compensated C. Respiratory alkalosis fully compensated D. Respiratory acidosis partially compensated 7. A patient is experiencing respiratory acidosis due to brain trauma. Which of the following lab values correlates with this acid imbalance? A. Potassium level of 6.0 B. Potassium level of 2.5 C. Potassium level of 5.0 D. Potassium level of 3.5 8. Which patient is experiencing partially compensated respiratory acidosis? A. PaCO2 30, pH 7.35, HCO3 26 B. PaCO2 53, pH 7.23, HCO3 28 C. PaCO2 45, pH 7.49, HCO3 21 D. PaCO2 50, pH 7.30, HCO3 23 9. Which of the following is not a cause of respiratory acidosis? A. Pulmonary emboli B. Asthma C. Chronic obstructive pulmonary disease (COPD) D. Hyperventilation 10. A patient with COPD has the following blood gases: PCO2 59, pH 7.26, HCO3 42. Which of the following conditions is presenting? A. Respiratory alkalosis B. Respiratory acidosis C. Metabolic alkalosis D. Metabolic acidosis Answer Key
 Don’t forget to tell your friends about this quiz by sharing it your Facebook, Twitter, and other social media. You can also take more fun nursing quizzes. *Disclaimer: While we do our best to provide students with accurate and in-depth study quizzes, this quiz/test is for educational and entertainment purposes only. Please refer to the latest NCLEX review books for the latest updates in nursing. This quiz is copyright RegisteredNurseRn.com. Please do not copy this quiz directly; however, please feel free to share a link to this page with students, friends, and others. What lab values would you expect to see with metabolic alkalosis?Normal human physiological pH is 7.35 to 7.45. A decrease in pH below this range is acidosis, an increase over this range is alkalosis. Metabolic alkalosis is defined as a disease state where the body's pH is elevated to greater than 7.45 secondary to some metabolic process.
What does metabolic alkalosis indicate?What is metabolic alkalosis? In metabolic alkalosis there is excess of bicarbonate in the body fluids. It can occur in a variety of conditions. It may be due to digestive issues, like repeated vomiting, that disrupt the blood's acid-base balance.
Is hco3 high or low in metabolic alkalosis?Metabolic alkalosis involves a primary increase in serum bicarbonate (HCO3-) concentration, due to a loss of H+ from the body or a gain in HCO3-.
What happens to urine pH in metabolic alkalosis?Urine pH generally is <6.0 in patients with metabolic alkalosis because proximal reabsorption of bicarbonate and net acid excretion are increased to sustain the process.
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A nurse is reviewing the laboratory results of a client who has metabolic alkalosis
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