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A Case of Respiratory Distress



Co Authors:

Brahmadeo Dewprashad
Department of Science
Borough of Manhattan Community College / City University of New York
bdewprashad@bmcc.cuny.edu

Geraldine S. Vaz
Ambulatory Care Department
Jamaica Hospital Medical Center

Sharon A. Vaz
Department of Health
State of Oklahoma
sharonav@health.ok.gov

Abstract:

This clinical case study was developed to engage students by making connections between core concepts in chemistry and physiological processes in the body. The case pertains to medication-induced methemoglobinemia, its etiology, diagnosis, and treatments. Concepts taught by the case include the use of conversion factors, pH, buffering, Le Chatelier's principle, blood chemistry, and respiratory and metabolic acidosis and alkalosis. The case is suitable for use in a General, Organic, and Biological (GOB) Chemistry course or other introductory general chemistry course as well as undergraduate physiology courses. The case also could be adapted for use in undergraduate pharmacology and medicinal chemistry courses.

Objectives:
  • Use conversion factors in determining possibility of pneumonia and dosage of medication.
  • Apply pH, buffering, and Le Chatelier's principle to blood chemistry.
  • Understand the principles underlying respiratory and metabolic acidosis and alkalosis.
  • Understand the etiology, manifestation, diagnosis, and treatment of methemoglobinemia.
Keywords: Acidosis; alkalosis; blood chemistry; buffering; conversion factors; Le Chatelier’s principle; methemoglobinemia; methylene blue; oxygen therapy; pH; pulse oximetry; respiratory distress
Topical Area: N/A
Educational Level: Undergraduate lower division, Undergraduate upper division
Formats: PDF
Type/Method: Directed
Language: English
Subject Headings: Chemistry (General)   Organic Chemistry   Biochemistry   Medicinal Chemistry   Physiology   Pharmacy / Pharmacology  
Date Posted: 1/12/2011
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

Teaching Notes


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Answer Key


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Author's Response to Jan Machart's Comment of 4/19/2011

The PO2 would be below normal initially as less O2 is carried by the hemoglobin (as indicated in the case). The peripheral chemoreceptors detect variation in O2 concentration in arterial blood. Presumably they send a signal to the brainstem that is translated to increased ventilation rate. This can result in the O2 level increasing to normal or near to normal level. However, the SPO2 level does not increase (as there is not sufficient Hb) until after the patient is treated with methylene blue.


Brahmadeo Dewprashad
Department of Science
Borough of Manhattan Community College / City University of New York
New York, NY
BDewprashad@bmcc.cuny.edu
4/25/2011

Hi, I am reading the answer key to the Respiratory Distress case study, and have a question about the answer to 8d--how would the body likely compensate for decreased Hb? By the answer, do you intend to imply that decreased HbO2 (in the presence of normal plasma PO2) triggers chemoreceptor-mediated ventilation?


Jan Machart
Biological Sciences
University of Texas
Austin, TX
janmachart@mail.utexas.edu
4/19/2011
I truly enjoyed this case, and found it highly successful in my course. I want to call one problem to your attention, and that has to do with your answer key. In your answer to #5 of the case ([H3O+] deficit), you can not use the change in pH to directly calculate the change in [H3O+] – the true concentration of H3O+ is about 4x10^-8 at a normal pH, and the deficits calculated should be in the 1x10^-8 range, and not .71. This also throws off your calculation in the next problem.


Colleen Fried
Chemistry
Hiram College
Hiram, OH
friedca@hiram.edu
4/22/2011



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