8-step Guide To Abg Analysis: Tic-tac-toe Method
An arterial blood gas (ABG) is a blood test that measures the acidity (pH) and the levels of oxygen and carbon dioxide in the blood . Blood for an ABG test is taken from an artery whereas most other blood tests are done on a sample of blood taken from a vein. This test is done to monitor several conditions that can cause serious health complications especially to critically ill individuals. Every day, a lot of nursing and medical students assigned in acute areas encounter ABG results, which they may not necessarily be able to interpret with its knotty aspect. They struggle over the interpretation of its measurements, but they are not especially complicated nor difficult if you understand the basic physiology and have a step by step process to analyze and interpret them. There may be various tips and strategies to guide you, from mnemonics, to charts, to lectures, to practice, but this article will tell you how to interpret ABGs in the easiest possible way. And once you have finished reading this, youll be doing actual ABG analysis in the NCLEX with fun and excitement! Here are the steps: Know the normal and abnormal ABG values when you review the lab reports. Theyre fairly easy to remember: for pH, the normal value is 7.35 to 7.45; 35-45 for paCO2; and 22-26 for HCO3. Remember also this diagram and note that paCO2 is intentionallyinverted for the purpose of this method. 2. Determine if pH is under acidosis or alkalosis Next thing to do is to determine the acidity or alkalinity of the blood through the value of pH. The pH level of a healthy human should be between 7.35 to 7.45. The human body is constantly striving to keep pH in balance. 3. Determine if acid-base is respiratory or metabolic Next thing you need to determine is whether the acid base is Respiratory or Meta Continue reading >>
Abg Interpretation
Arterial blood gas (ABG) interpretation is something many medical students find difficult to grasp (we’ve been there). We’ve created this guide, which aims to provide a structured approach to ABG interpretation whilst also increasing your understanding of each results relevance. The real value of an ABG comes from its ability to provide a near immediate reflection of the physiology of your patient, allowing you to recognise and treat pathology more rapidly. To see how to perform an arterial blood gas check out our guide here. If you want to put your ABG interpretation skills to the test, check out our ABG quiz here. Normal ranges pH: 7.35 – 7.45 PaCO2: 4.7-6.0 kPa PaO2: 11-13 kPa HCO3-: 22-26 mEg/L Base excess: -2 to +2 mmol/L Patient’s clinical condition Before getting stuck into the details of the analysis, it’s important to look at the patient’s current clinical status, as this provides essential context to the ABG result. Below are a few examples to demonstrate how important context is when interpreting an ABG. A normal PaO2 in a patient on high flow oxygen – this is abnormal as you would expect the patient to have a PaO2 well above the normal range with this level of oxygen therapy A normal PaCO2 in a hypoxic asthmatic patient – a sign they are tiring and need ITU intervention A very low PaO2 in a patient who looks completely well, is not short of breath and has normal O2 saturations – likely a venous sample Oxygenation (PaO2) Your first question when looking at the ABG should be “Is this patient hypoxic?” (because this will kill them long before anything else does). PaO2 should be >10 kPa on air in a healthy patient If the patient is receiving oxygen therapy their PaO2 should be approximately 10kPa less than the % inspired concentration / FiO Continue reading >>
Compensated Respiratory Acidosis
Definition In a compensated respiratory acidosis, although the PCO2 is high, the pH is within normal range. The kidneys compensate for a respiratory acidosis by tubular cells reabsorbing more HCO3 from the tubular fluid, collecting duct cells secreting more H+ and generating more HCO3, and ammoniagenesis leading to increased formation of the NH3 buffer. Compensated respiratory acidosis is typically the result of a chronic condition, the slow nature of onset giving the kidneys time to compensate. Common causes of respiratory acidosis include hypoventilation due to: Respiratory depression (sedatives, narcotics, CVA, etc.) Respiratory muscle paralysis (spinal cord injury, Guillan-Barre, residual paralytics). Chest wall disorders (flail chest, pneumothorax) Lung parenchyma disorders (ARDS, pneumonia, COPD, CHF, aspiration) Abdominal distension (laporoscopic surgery, ascites, obesity, etc.). Subspecialty Keyword history Similar Keyword: Respiratory acidosis: Compensation Sources Miller’s Anesthesia, 7th ed. Ch. 49. PubMed Continue reading >>
Uncompensated, Partially Compensated, Or Combined Abg Problems
Arterial Blood Gas (ABG) analysis requires in-depth expertise. If the results are not understood right, or are wrongly interpreted, it can result in wrong diagnosis and end up in an inappropriate management of the patient. ABG analysis is carried out when the patient is dealing with the following conditions: • Breathing problems • Lung diseases (asthma, cystic fibrosis, COPD) • Heart failure • Kidney failure ABG reports help in answering the following questions: 1. Is there acidosis or alkalosis? 2. If acidosis is present, whether it is in an uncompensated state, partially compensated state, or in fully compensated state? 3. Whether acidosis is respiratory or metabolic? ABG reports provide the following descriptions: PaCO2 (partial pressure of dissolved CO2 in the blood) and PaO2 (partial pressure of dissolved O2 in the blood) describe the efficiency of exchange of gas in the alveolar level into the blood. Any change in these levels causes changes in the pH. HCO3 (bicarbonate in the blood) maintains the pH of the blood within normal range by compensatory mechanisms, which is either by retaining or increasing HCO3 excretion by the kidney. When PaCO2 increases, HCO3 decreases to compensate the pH. The following table summarizes the changes: ABG can be interpreted using the following analysis points: Finding acidosis or alkalosis: • If pH is more it is acidosis, if pH is less it is alkalosis. Finding compensated, partially compensated, or uncompensated ABG problems: • When PaCO2 is high, but pH is normal instead of being acidic, and if HCO3 levels are also increased, then it means that the compensatory mechanism has retained more HCO3 to maintain the pH. • When PaCO2 and HCO3 values are high but pH is acidic, then it indicates partial compensation. It means t Continue reading >>
Respiratory Acidosis
Respiratory acidosis is a medical emergency in which decreased ventilation (hypoventilation) increases the concentration of carbon dioxide in the blood and decreases the blood's pH (a condition generally called acidosis). Carbon dioxide is produced continuously as the body's cells respire, and this CO2 will accumulate rapidly if the lungs do not adequately expel it through alveolar ventilation. Alveolar hypoventilation thus leads to an increased PaCO2 (a condition called hypercapnia). The increase in PaCO2 in turn decreases the HCO3−/PaCO2 ratio and decreases pH. Terminology[edit] Acidosis refers to disorders that lower cell/tissue pH to < 7.35. Acidemia refers to an arterial pH < 7.36.[1] Types of respiratory acidosis[edit] Respiratory acidosis can be acute or chronic. In acute respiratory acidosis, the PaCO2 is elevated above the upper limit of the reference range (over 6.3 kPa or 45 mm Hg) with an accompanying acidemia (pH <7.36). In chronic respiratory acidosis, the PaCO2 is elevated above the upper limit of the reference range, with a normal blood pH (7.35 to 7.45) or near-normal pH secondary to renal compensation and an elevated serum bicarbonate (HCO3− >30 mm Hg). Causes[edit] Acute[edit] Acute respiratory acidosis occurs when an abrupt failure of ventilation occurs. This failure in ventilation may be caused by depression of the central respiratory center by cerebral disease or drugs, inability to ventilate adequately due to neuromuscular disease (e.g., myasthenia gravis, amyotrophic lateral sclerosis, Guillain–Barré syndrome, muscular dystrophy), or airway obstruction related to asthma or chronic obstructive pulmonary disease (COPD) exacerbation. Chronic[edit] Chronic respiratory acidosis may be secondary to many disorders, including COPD. Hypoventilation Continue reading >>
Respiratory Acidosis
Practice Essentials Respiratory acidosis is an acid-base balance disturbance due to alveolar hypoventilation. Production of carbon dioxide occurs rapidly and failure of ventilation promptly increases the partial pressure of arterial carbon dioxide (PaCO2). [1] The normal reference range for PaCO2 is 35-45 mm Hg. Alveolar hypoventilation leads to an increased PaCO2 (ie, hypercapnia). The increase in PaCO2, in turn, decreases the bicarbonate (HCO3–)/PaCO2 ratio, thereby decreasing the pH. Hypercapnia and respiratory acidosis ensue when impairment in ventilation occurs and the removal of carbon dioxide by the respiratory system is less than the production of carbon dioxide in the tissues. Lung diseases that cause abnormalities in alveolar gas exchange do not typically result in alveolar hypoventilation. Often these diseases stimulate ventilation and hypocapnia due to reflex receptors and hypoxia. Hypercapnia typically occurs late in the disease process with severe pulmonary disease or when respiratory muscles fatigue. (See also Pediatric Respiratory Acidosis, Metabolic Acidosis, and Pediatric Metabolic Acidosis.) Acute vs chronic respiratory acidosis Respiratory acidosis can be acute or chronic. In acute respiratory acidosis, the PaCO2 is elevated above the upper limit of the reference range (ie, >45 mm Hg) with an accompanying acidemia (ie, pH < 7.35). In chronic respiratory acidosis, the PaCO2 is elevated above the upper limit of the reference range, with a normal or near-normal pH secondary to renal compensation and an elevated serum bicarbonate levels (ie, >30 mEq/L). Acute respiratory acidosis is present when an abrupt failure of ventilation occurs. This failure in ventilation may result from depression of the central respiratory center by one or another of the foll Continue reading >>
Abg Interpreter
pH CO2 HCO3 Result appears in here. Normal Arterial Blood Gas Values pH 7.35-7.45 PaCO2 35-45 mm Hg PaO2 80-95 mm Hg HCO3 22-26 mEq/L O2 Saturation 95-99% BE +/- 1 Four-Step Guide to ABG Analysis Is the pH normal, acidotic or alkalotic? Are the pCO2 or HCO3 abnormal? Which one appears to influence the pH? If both the pCO2 and HCO3 are abnormal, the one which deviates most from the norm is most likely causing an abnormal pH. Check the pO2. Is the patient hypoxic? I used Swearingen's handbook (1990) to base the results of this calculator. The book makes the distinction between acute and chronic disorders based on symptoms from identical ABGs. This calculator only differentiates between acute (pH abnormal) and compensated (pH normal). Compensation can be seen when both the PCO2 and HCO3 rise or fall together to maintain a normal pH. Part compensation occurs when the PCO2 and HCO3 rise or fall together but the pH remains abnormal. This indicates a compensatory mechanism attempted to restore a normal pH. I have not put exact limits into the calculator. For example, it will perceive respiratory acidosis as any pH < 7.35 and any CO2 > 45 (i.e. a pH of 1 and CO2 of 1000). These results do not naturally occur. pH PaCO2 HCO3 Respiratory Acidosis Acute < 7.35 > 45 Normal Partly Compensated < 7.35 > 45 > 26 Compensated Normal > 45 > 26 Respiratory Alkalosis Acute > 7.45 < 35 Normal Partly Compensated > 7.45 < 35 < 22 Compensated Normal < 35 < 22 Metabolic Acidosis Acute < 7.35 Normal < 22 Partly Compensated < 7.35 < 35 < 22 Compensated Normal < 35 < 22 Metabolic Alkalosis Acute > 7.45 Normal > 26 Partly Compensated > 7.45 > 45 > 26 Compensated Normal > 45 > 26 Mixed Disorders It's possible to have more than one disorder influencing blood gas values. For example ABG's with an alkale Continue reading >>
Respiratory Acidosis
Respiratory acidosis is an abnormal clinical process that causes the arterial Pco2 to increase to greater than 40 mm Hg. Increased CO2 concentration in the blood may be secondary to increased CO2 production or decreased ventilation. Larry R. Engelking, in Textbook of Veterinary Physiological Chemistry (Third Edition) , 2015 Respiratory acidosis can arise from a break in any one of these links. For example, it can be caused from depression of the respiratory center through drugs or metabolic disease, or from limitations in chest wall expansion due to neuromuscular disorders or trauma (Table 90-1). It can also arise from pulmonary disease, card iog en ic pu lmon a ryedema, a spira tion of a foreign body or vomitus, pneumothorax and pleural space disease, or through mechanical hypoventilation. Unless there is a superimposed or secondary metabolic acidosis, the plasma anion gap will usually be normal in respiratory acidosis. Kamel S. Kamel MD, FRCPC, Mitchell L. Halperin MD, FRCPC, in Fluid, Electrolyte and Acid-Base Physiology (Fifth Edition) , 2017 Respiratory acidosis is characterized by an increased arterial blood PCO2 and H+ ion concentration. The major cause of respiratory acidosis is alveolar hypoventilation. The expected physiologic response is an increased . The increase in concentration of bicarbonate ions (HCO3) in plasma ( ) is tiny in patients with acute respiratory acidosis, but is much larger in patients with chronic respiratory acidosis. Respiratory alkalosis is caused by hyperventilation and is characterized by a low arterial blood PCO2 and H+ ion concentration. The expected physiologic response is a decrease in . As in respiratory acidosis, this response is modest in patients with acute respiratory alkalosis and much larger in patients with chronic respir Continue reading >>
Res 140
Res 140 ex 3 Question Answer Correction of metabolic alkalosis may involve which of the following? D) I, II, and III I. Restoring normal fluid volume II. Administering acidifying agents III. Restoring normal K+ and Cl– levels In order to eliminate the influence of PCO2 changes on plasma HCO3- concentrations, what additional measures of the metabolic component of acid-base balance can be used? D) Standard bicarbonate Which organ system actually excretes H+ from the body? A) Kidneys An ABG result shows the pH to be 7.56 and the HCO3- to be 23 mEq/L. Which of the following is the most likely disorder? D) Respiratory alkalosis What compensates for a metabolic alkalosis? B) Hypoventilation Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.43, PCO2 = 39 mm Hg, HCO3- = 25.1 mEq/L A) Acid-base status within normal limits. What explains the lack of an increased anion gap seen in metabolic acidosis caused by HCO3- loss? A) For each HCO3- ion lost, a Cl- ion is reabsorbed by the kidney. Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.08, PCO2 = 39 mm Hg, HCO3- = 11.8 mEq/L A) Acute metabolic acidosis What affect does hyperventilation have on the closed buffer systems? B) Causes them to release more H+. A patient has a confirmed metabolic acidosis with a normal PCO2. What inference can you draw from these findings? A) A ventilatory disorder must coexist. What drives the bicarbonate buffer systems enormous ability to buffer acids? D) Ventilation continually removing CO2 from system. Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.38, PCO2 = 21 mm Hg, HCO3- = 11.7 mEq/L B) Fully compensated metabolic acidosis With partially compensated respiratory alkalosis, which o Continue reading >>
Perfecting Your Acid-base Balancing Act
When it comes to acids and bases, the difference between life and death is balance. The body’s acid-base balance depends on some delicately balanced chemical reactions. The hydrogen ion (H+) affects pH, and pH regulation influences the speed of cellular reactions, cell function, cell permeability, and the very integrity of cell structure. When an imbalance develops, you can detect it quickly by knowing how to assess your patient and interpret arterial blood gas (ABG) values. And you can restore the balance by targeting your interventions to the specific acid-base disorder you find. Basics of acid-base balance Before assessing a patient’s acid-base balance, you need to understand how the H+ affects acids, bases, and pH. An acid is a substance that can donate H+ to a base. Examples include hydrochloric acid, nitric acid, ammonium ion, lactic acid, acetic acid, and carbonic acid (H2CO3). A base is a substance that can accept or bind H+. Examples include ammonia, lactate, acetate, and bicarbonate (HCO3-). pH reflects the overall H+ concentration in body fluids. The higher the number of H+ in the blood, the lower the pH; and the lower the number of H+, the higher the pH. A solution containing more base than acid has fewer H+ and a higher pH. A solution containing more acid than base has more H+ and a lower pH. The pH of water (H2O), 7.4, is considered neutral. The pH of blood is slightly alkaline and has a normal range of 7.35 to 7.45. For normal enzyme and cell function and normal metabolism, the blood’s pH must remain in this narrow range. If the blood is acidic, the force of cardiac contractions diminishes. If the blood is alkaline, neuromuscular function becomes impaired. A blood pH below 6.8 or above 7.8 is usually fatal. pH also reflects the balance between the p Continue reading >>
Easy Way To Interpret Abg Values
ABG values can be very intimidating! Its hard to remember all the different normal values, what they mean, and which direction theyre supposed to be going. With so much information, its super easy to get mixed up and make a stupid mistake on an exam, even when you really DO know how to interpret ABGs. In this article, Im focusing more on the How to, rather than understanding whats going on with the A&P, which Ive already done in previous articles. If you want to understand whythese steps work (which you should do anyway to become a great nurse!),take some time to review my articles on Respiratory Imbalances and Metabolic Imbalances . Heres my 7-step method to interpreting ABGs. We have three puzzle pieces to put together: B)uncompensated, partially compensated, or compensated 1) Across the top of your page, write down the normal values for the three most important ABG lab results: pH (7.35-7.45), PaCO2 (35-45), and HCO3 (22-26). 2) Underneath pH, draw arrows to remind you which direction is acidic (down), and which direction is basic (down). 3) UnderneathPaCO2, and HCO3, draw arrows to remind you what abnormally high and low values would do to the bodys pH. When youre done, your page should look something like this: So far, we havent even looked at the question yet, were just trying to prevent any stupid mistakes!! 4) Now you can finally look at the patients ABG values. Check the pH and decide if the value is normal, high, or low. 4a) If the pH is normal, check PaCO2, and HCO3. If they are both normal, then you patient is fine and you can stop here. But if one or both of these values is abnormal, then continue to step 5. 5) Identify if the patient has alkalosis or acidosis. 5a) If the pH is abnormal, then compare it to the arrows you wrote at the top of your paper and Continue reading >>
Abg’s—it’s All In The Family
By Cyndi Cramer, BA, RN, OCN, PCRN RealNurseEd.com 3.0 Contact Hour Self Learning Module Objectives: Identify the components of the ABG and their normal ranges Interpret ABG values and determine the acid base abnormality given Identify the major causes of acid base abnormalities Describe symptoms associated with acid base abnormalities Describe interventions to correct acid base abnormalities Identify the acceptable O2 level per ABG and Pulse Oximetry Identify four causes of low PaO2 The Respiratory System (Acid); CO2 is a volatile acid If you increase your respiratory rate (hyperventilation) you "blow off" CO2 (acid) therefore decreasing your CO2 acid—giving you ALKLAOSIS If you decrease your respiratory rate (hypoventilation) you retain CO2 (acid) therefore increasing your CO2 (acid)—giving you ACIDOSIS The Renal System (Base); the kidneys rid the body of the nonvolatile acids H+ (hydrogen ions) and maintain a constant bicarb (HCO3). Bicarbonate is the body’s base You have Acidosis when you have excess H+ and decreased HCO3- causing a decrease in pH. The Kidneys try to adjust for this by excreting H+ and retaining HCO3- base. The Respiratory System will try to compensate by increasing ventilation to blow off CO2 (acid) and therefore decrease the Acidosis. You have Alkalosis when H+ decreases and you have excess (or increased) HCO3- base. The kidneys excrete HCO3- (base) and retain H+ to compensate. The respiratory system tries to compensate with hypoventilation to retain CO2 (acid) To decrease the alkalosis Compensation The respiratory system can effect a change in 15-30 minutes The renal system takes several hours to days to have an effect. RESPIRATORY ACIDOSIS: pH < 7.35 (Normal: 7.35 - 7.45) CO2 > 45 (Normal: 35 – 45) 1. Causes: Hypoventilation a. Depressio Continue reading >>
4.5 Respiratory Acidosis - Compensation
Acid-Base Physiology 4.5.1 The compensatory response is a rise in the bicarbonate level This rise has an immediate component (due to a resetting of the physicochemical equilibrium point) which raises the bicarbonate slightly. Next is a slower component where a further rise in plasma bicarbonate due to enhanced renal retention of bicarbonate. The additional effect on plasma bicarbonate of the renal retention is what converts an "acute" respiratory acidsosis into a "chronic" respiratory acidosis. As can be seen by inspection of the Henderson-Hasselbalch equation (below), an increased [HCO3-] will counteract the effect (on the pH) of an increased pCO2 because it returns the value of the [HCO3]/0.03 pCO2 ratio towards normal. pH = pKa + log([HCO3]/0.03 pCO2) 4.5.2 Buffering in Acute Respiratory Acidosis The compensatory response to an acute respiratory acidosis is limited to buffering. By the law of mass action, the increased arterial pCO2 causes a shift to the right in the following reaction: CO2 + H2O <-> H2CO3 <-> H+ + HCO3- In the blood, this reaction occurs rapidly inside red blood cells because of the presence of carbonic anhydrase. The hydrogen ion produced is buffered by intracellular proteins and by phosphates. Consequently, in the red cell, the buffering is mostly by haemoglobin. This buffering by removal of hydrogen ion, pulls the reaction to the right resulting in an increased bicarbonate production. The bicarbonate exchanges for chloride ion across the erythrocyte membrane and the plasma bicarbonate level rises. In an acute acidosis, there is insufficient time for the kidneys to respond to the increased arterial pCO2 so this is the only cause of the increased plasma bicarbonate in this early phase. The increase in bicarbonate only partially returns the extracel Continue reading >>
Partially Compensated Vs. Fully Compensated Abgs Practice
This is an NCLEX practice question on partially compensated vs fully compensated ABGs. This question provides a scenario about arterial blood gas results. As the nurse, you must determine if this is a respiratory or metabolic problem, alkalosis or acidosis along with if it is uncompensated, partially or fully compensated based on the results. This question is one of the many questions we will be practicing in our new series called “Weekly NCLEX Question”. So, every week be sure to tune into our YouTube Channel for the NCLEX Question of the Week. More NCLEX Weekly Practice Questions. To solve ABGs problems, I like to use the Tic Tac Toe method. If you are not familiar with this method, please watch my video on how to solve arterial blood gas problems with this method. The Tic Tac Toe method makes solving ABG problems so EASY. However, if the ABG values are partially or fully compensated you must take it a step further by analyzing the values further with this method, which is the purpose of this review. My goal is to show you how to use the Tic Tac Toe method for partially and fully compensated interpretation. So let’s begin: NCLEX Practice Questions on Partially vs. Fully Compensated ABGs Problem 1 A patient has the following arterial blood gas results: blood pH 7.43, PaCO2 28 mmHg, and HCO3 18 mEq/L. This is known as: A. Partially compensated respiratory alkalosis B. Fully compensated metabolic acidosis C. Partially compensated respiratory acidosis D. Fully compensated respiratory alkalosis The first thing you want to do is to pull from your memory bank the normal values for arterial blood gases. Here they are: <-Acid Base-> pH: 7.35-7.45 (less than 7.35 ACID & greater than 7.45 ALKALOTIC) PaCO2: 45-35 (greater than 45 ACID & less than 35 ALKALOTIC)** HCO3: 22-26 Continue reading >>
Why Measure Blood Gases? A Three-part Introduction For The Novice. Part 2.
Why measure blood gases? A three-part introduction for the novice. Part 2. Why measure blood gases? A three-part introduction for the novice. Part 2. Arterial blood gases (ABG), a clinical test that involves measurement of the pH of arterial blood and the amount of oxygen and carbon dioxide dissolved in arterial blood, is routinely used in the diagnosis and monitoring of predominantly critically/acutely ill patients being cared for in hospital emergency rooms and intensive care units. The test allows assessment of two related physiological functions: pulmonary gas exchange and acid-base homeostasis. This is the second of three articles intended to explain the clinical value of ABG to those with little or no experience of the test. The first article focused on the physiological aspects that underpin an understanding of patient ABG results. The concepts of pH, acid, base and buffer were explained, and the parameters generated during ABG were defined and related to pulmonary gas exchange and acid-base homeostasis. In this second article attention turns to the clinical significance of abnormal ABG results, specifically abnormality in three ABG parameters (pH, pCO2(a) and bicarbonate) that determine patient acid-base status. A major focus of the article will be an explanation of the four classes of acid-base disturbance: respiratory acidosis, metabolic acidosis, respiratory alkalosis and metabolic alkalosis. The causes and physiological consequence of each of these disturbances will be discussed. Reference (normal) range for the blood gas parameters under discussion here: pH 7.35-7.45 pCO2(a) 4.7-6.0 kPa (35-45 mmHg) Bicarbonate 22-28 mmol/L DISTURBANCE OF ACID-BASE HOMEOSTASIS - GENERAL CONSIDERATION Disturbance of acid-base homeostasis is characterized by abnormality in o Continue reading >>
