Teaching acid/base physiology in the laboratory (original) (raw)
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Integrating Acid-Base and Metabolic Lab Panels Across Systems in an M1 Classroom Activity
MedEdPORTAL, 2018
Introduction: It is important to deliver acid-base balance concepts in the context of multiple physiological systems and metabolic processes that influence acid-base homeostasis. This activity combines the interactions of the respiratory, gastrointestinal, and renal systems in conjunction with basic metabolism to generate an integrated activity for first-year medical students. Methods: We developed four concise case scenarios around various presentations of acid-base disturbance along with five sets of arterial blood gases (ABGs) and five different metabolic lab panels. M1 students were given class time to match the three different types of data in order to address how the underlying biochemistry and physiology of a scenario translated into ABG and metabolic laboratory values. Results: Although not statistically significant, the students' performance on acid-base questions was marginally higher than on standardized National Board of Medical Examiners questions on other topics covered in the same exam, and the improvement over national average scores on the same questions increased. Student evaluation of the activity was positive, with general appreciation of its application and integration of concepts. Discussion: The incorporation of this activity into the M1 year was positively received and enhanced integration of content related to acidbase balance. The activity is flexible and can be adapted to most any curricular structure, with the potential to include additional content depending on the level of the learner.
Physiology of Acid Base Balance
Journal of Evidence Based Medicine and Healthcare, 2014
Acid-base, electrolyte, and metabolic disturbances are common in the intensive care unit. Almost all critically ill patients often suffer from compound acid-base and electrolyte disorders. Successful evaluation and management of such patients requires recognition of common patterns (e.g., metabolic acidosis) and the ability to dissect one disorder from another. The intensivists needs to identify and correct these condition with the easiest available tools as they are the associated with multiorgan failure. Understanding the elements of normal physiology in these areas is very important so as to diagnose the pathological condition and take adequate measures as early as possible. Arterial blood gas analysis is one such tool for early detection of acid base disorder. Physiology of acid base is complex and here is the attempt to simplify it in our day to day application for the benefit of critically ill patients.
HAPS EDucator, 2018
Students find it hard to understand acid-base homeostasis and the mechanisms involved in compensating for acid-base imbalances, including the role of the lungs and kidneys in this process. We have developed a laboratory activity based on collaborative problem-based learning and human patient simulators (HPSs) to teach this topic. Students (n=50) were divided into small groups and presented with five cases of acid-base imbalances simulated in HPSs. After recording various parameters including arterial blood gases, they collaborated in identifying the specific acid-base imbalance. An anonymous survey following the laboratory activity revealed that this laboratory improved their understanding of acid-base regulation (92%), improved quantitative understanding of acid-base physiology (90%), and improved understanding of acid-base imbalances (94%).
Evaluation of a computer-based approach to teaching acid/base physiology
Advances in physiology education, 2002
Because acid/base physiology is a difficult subject for most medical and veterinary students, the first author designed a software program, Acid/Base Primer, that would help students with this topic. The Acid/Base Primer was designed and evaluated within a conceptual framework of basic educational principles. Seventy-five first-year veterinary students (of 81; 93% response rate) participated in this study. Students took both a pre- and posttest of content understanding. After completing the Acid/Base Primer in pairs, each student filled out a survey evaluating the features of the program and describing his/her use and experience of it. Four pairs of students participated in interviews that elaborated on the surveys. Scores improved from 53 +/- 2% on the pretest to 74 +/- 1% on an immediate posttest. On surveys and in interviews, students reported that the program helped them construct their own understanding of acid/base physiology and prompted discussions in pairs of students when ...
Teaching renal physiology in the 21st century: focus on acid–base physiology
Clinical Kidney Journal, 2015
A thorough understanding of renal physiology, and in particular acid-base physiology, is essential for an understanding of nephrology. Difficulties in both teaching and learning this material are major impediments to attracting medical trainees into nephrology. Approaches to teaching renal physiology include collaborative learning, computer-based learning and laboratorybased learning. Computer-based learning applications are becoming increasingly popular and can be useful, but are most successful when they incorporate interactive components. Students also note that the presence of a live instructor remains desirable. Some concepts of renal and in particular acid-base physiology can be taught using structured self-experimentation, a practice with a long tradition that possibly should be revitalized.
An Easy Approach to Understanding Acid-Base Balance in a Blood Buffer System
The American Biology Teacher
Understanding acid-base disorders using weak-acid concepts learned in general chemistry class is challenging for pre-nursing and pre-professional biology students enrolled in anatomy/physiology and biochemistry classes. We utilized a graphic seesaw model of carbonic acid-bicarbonate equilibrium using the Henderson-Hasselbalch (H-H) equation of a weak acid. We then used real-world clinical case studies for students to identify acid-base disorders and the appropriate compensatory responses of the lungs and kidneys. Students developed a working knowledge of how the bicarbonate blood buffer system maintains a physiological pH of 7.4 using a “seesaw” with metabolic [HCO3−] on one side, and respiratory PCO2 on the other at a ratio of 20:1 in the H-H equation. When the dysfunction of either the kidneys or lungs causes the seesaw to tip, homeostasis pH is disrupted, causing an acid-base disorder classified as metabolic or respiratory acidosis or alkalosis. The functioning organ can “level t...
The ABC's of Acid-Base Balance
The journal of pediatric pharmacology and therapeutics : JPPT : the official journal of PPAG, 2004
A step-wise systematic approach can be used to determine the etiology and proper management of acid-base disorders. The objectives of this article are to: (1) discuss the physiologic processes involved in acid-base disturbances, (2) identify primary and secondary acid-base disturbances based upon arterial blood gas and laboratory measurements, (3) utilize the anion gap for diagnostic purposes, and (4) outline a stepwise approach for interpretation and treatment of acid-base disorders. Case studies are used to illustrate the application of the discussed systematic approach.
ENCYCLOPEDIA OF RESPIRATORY MEDICINE. Acid-base balance (feb 2005) Acid-Base Balance
The acid-base balance or neutrality regulation maintains a pH around 7.4 in the extracellular fluid by excreting carbon dioxide in the lungs and non-carbonic acid or base in the kidneys. The result is a normal acid-base status in blood and extracellular fluid, i.e. a normal pH, a normal carbon dioxide tension (pCO 2), and a normal concentration of titratable hydrogen ion (ctH +). A pH, log pCO 2 chart illustrates the acid-base status of the arterial blood. The chart shows normal values as well as values to be expected in typical acid-base disturbances, i.e. acute and chronic respiratory acidosis and alkalosis, and acute and chronic non-respiratory (metabolic) acidosis and alkalosis. The chart allows estimation of the concentration of titratable H + of the extended extracellular fluid (including erythrocytes), ctH + Ecf. This quantity is also called standard base deficit but the term base does not directly indicate that the quantity refers to the excess or deficit of hydrogen ions. ctH + Ecf is the preferred indicator of a non-respiratory acid-base disturbance being independent of acute changes in pCO 2 in vivo. While pH and pCO 2 are directly measured, ctH + Ecf is calculated from pH and pCO 2 using the Henderson-Hasselbalch equation and the Van Slyke equation. Description The acid-base balance or neutrality regulation maintains a pH around 7.4 in the extracellular fluid by excreting carbon dioxide in the lungs and non-carbonic acid or base in the kidneys. The result is a normal acid-base status in blood and extracellular fluid, i.e. a normal pH, a normal carbon dioxide tension (pCO 2), and a normal concentration of titratable hydrogen ion (ctH +). A graphical illustration is an aid in the description of the acid-base status of the blood (Fig. 1). pH and the Hydrogen Ion Concentration (cH +) pH and cH + of the plasma are both indicated on the abscissa of the chart (Fig. 1). cH + is calculated as 10 9-pH nmol/L. pH and pOH are closely related: pH + pOH = pK w = 13.622 at 37 °C, where K w is the ionization constant of water. If H + is considered a key component of an aqueous solution, then OH¯ is a derived component. Accounting for H + and H 2 O, indirectly accounts for OH¯ as well. It is the authors conviction that the relevant component is the hydrogen ion, not hydrogen ion binding groups (base) nor hydroxyl ions. Carbon Dioxide Tension of the Blood (pCO 2) pCO 2 , i.e. the partial pressure of carbon dioxide in a gas phase in equilibrium with the blood, is shown on the ordinate on a logarithmic scale. When pCO 2 increases, the concentration of dissolved carbon dioxide and carbonic acid increases, and hence the hydrogen ion concentration increases: CO 2 + H 2 O → H 2 CO 3 → H + + HCO 3 ⎯ .. Concentration of Titratable Hydrogen Ion (ctH +) ctH + is indicated on the scale in the upper left corner of the chart. The amount of hydrogen ion added or removed in relation to a reference pH of 7.40 may be determined by titration to pH = 7.40 at pCO 2 = 5.33 kPa (= 40 mmHg) at 37 °C using strong acid or base, depending upon the initial pH. Titratable hydrogen ion or hydrogen ion excess, is also called base deficit, or with opposite sign base excess. Unfortunately, the term base is ambiguous (has been associated with cations) and does not directly indicate that the relevant chemical component is the hydrogen ion. If a nick name is needed it may be hydrogen ion excess; acronym: HX. Note: by definition ctH + of blood refers to the actual hemoglobin oxygen saturation, not the fully oxygenated blood. Acid and base are defined by the equilibrium: Acid z H + + Base z-1 , where Acid z and Base z-1 is a conjugate acid-base pair. The charge number z may be positive, zero, or negative. A strong acid, e.g. HCl, dissociates completely: HCl → H + + Cl⎯. A strong base, e.g. OH⎯, associates completely with hydrogen ion: OH⎯ + H + → H 2 O. A weak acid (buffer acid) is in