Ddasdas

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE

A Case of Respiratory Distress
by
Brahmadeo Dewprashad, Department of Science, Borough of Manhattan Community College, The City University of New York
Geraldine S. Vaz, Ambulatory Care Department, Jamaica Hospital, Queens, New York
Sharon A. Vaz, Department of Health, Oklahoma
A 68-year-old, non-smoking female presented to the EmergencyRoom for evaluation
of dyspnea (shortness of breath) of 1-hour duration. On examination, her vital signs
were: temperature of 98.8°F; pulse of 90 beats/minute; respiratory rate of 20 breaths/
minute; and weight of 140 lbs. In addition, lung sounds were clear (without wheezes
or dullness). She indicated that she had been feeling unwell for over three days and
that several of her family membershad been coughing. She also indicated that she had
self medicated on Bactrim™, a sulfonamide antibiotic that her much younger sister
had been prescribed.
Initial arterial blood gas analysis indicated a pH of 7.50; PO2 of 96 mm Hg; PCO2
of 25 mm Hg; bicarbonate level of 24mmol/L; and oxygen saturation (SpO2) of
88%. The patient’s labored breathing subsequently worsened. The patient’s pulseoximetry (SpO2) reading worsened to 86% and did not increase after the patient was
given oxygen by nasal cannula. A pulse oximetry reading measures oxygen levels in
oxygenated blood; a healthy person normally has a value of 98–100%.
Blood drawn from the patient’s left arm (from a vein) was chocolate colored. In a healthy individual, such blood is dark
red. A second blood sample was drawn fromthe radial artery. Blood gas analysis revealed a methemoglobin level of 23%,
a level that is way above the normal (of about 1%). This is consistent with the original findings and the lack of response
to oxygen therapy.
Oxygen therapy was continued and methylene blue (1 mg/kg) was co-administered. Pulse oximetry readings indicated
that SpO2 improved to approximately 89%. Approximately 5 minutesafter the first dose, another 1 mg/k dose of
methylene blue was given and the SpO2 improved to 92%. The patient was moved to the ward and, after two uneventful
days, was discharged. She was provided with an inhaler containing a bronchodilator and instructed in its use. She was
asked to use it in case of onset of renewed shortness of breath. She was cautioned to stop taking additional Bactrim™and any prescription medication not specifically prescribed for her. She was also asked to follow up with her private
physician.

Pre-Case Questions
To be done individually as an assignment prior to undertaking the case study in class.
1. Explain Le-Chatelier’s principle.
References:
http://en.wikipedia.org/wiki/Le_Chatelier’s_Principlehttp://www.chemguide.co.uk/physical/equilibria/lechatelier.html
2. Explain what is meant by pH.
References:
http://www.youtube.com/watch?v=pvB6XEGSY7A
http://www.gpb.org/gpbclassroom/chemistry/1102

“A Case of Respiratory Distress” by Dewprashad, Vaz and Vaz

Page 1

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
3. Explain the difference between an acidic, a basic, and a neutral solution. Why can water be acidic, neutral, or basic?Reference:
http://en.wikipedia.org/wiki/Self-ionization_of_water
4. What is the pH range of blood in a healthy individual?
Reference:
http://es.youtube.com/watch?v=IBJtQtzN7O8
5. Explain a “buffer solution” and the principles underlying its action.
Reference:
http://en.wikipedia.org/wiki/Buffer_solution
6. Explain the principles underlying the buffering system of the blood.
References:http://academic.brooklyn.cuny.edu/biology/bio4fv/page/bicarbo.htm
http://scifun.chem.wisc.edu/CHEMWEEK/BioBuff/BioBuffers.html
http://www.youtube.com/watch?v=WXOBJEXxNEo&feature=related
7. Explain the difference between respiratory acidosis, metabolic acidosis, respiratory alkalosis, and metabolic alkalosis.
Reference:
http://scifun.chem.wisc.edu/CHEMWEEK/BioBuff/BioBuffers.html
8. Blood...