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When the Flu Is Not the Flu


Elaine B. Bohórquez
Department of Physiology
North Carolina State University


This case study explores the progression of COVID-19 from initial flu-like symptoms to acute respiratory distress syndrome (ARDS) due to infection with the SARS-CoV-2 virus. It details the story of a 32-year-old emergency department nurse who begins to show signs of a respiratory illness. The case follows the development of his respiratory distress based on arterial blood gas values and chest radiograph results. A series of directed questions guide students through exploring respiratory physiology and acid-base balance, focusing on the unique consequences of ARDS in COVID-19 patients. The questions fall into three categories: (1) acid-base disturbance due to respiratory insufficiency, (2) decreased diffusion capacity due to diffuse alveolar damage and fluid accumulation as the cause of respiratory insufficiency, and (3) mechanical ventilation as a treatment to improve gas exchange by increasing the fraction of inspired oxygen and positive end-expiratory pressure, both of which improve gas exchange and therefore oxygen delivery to the bloodstream. The case was designed for upper-level undergraduate or graduate-level physiology/biology students but would also be relevant for students in nursing/medicine/physician assistant programs, pathophysiology courses, and respiratory therapy programs.


  • Describe the relationship between carbon dioxide in the blood and blood pH.
  • From blood values, analyze and determine acid-base disturbances and distinguish between compensated and uncompensated acid-base disturbances.
  • Explain the factors that affect diffusive transport of a gas between alveolar gas and pulmonary capillary blood.
  • Discuss how partial pressure of inspired gas relates to the concentration of dissolved gas in the blood.
  • Explore the challenges that arise in a clinical setting when deciding on treatment methods for fragile tissues.


Respiratory physiology; acid; base; gas exchange; COVID-19; SARS-CoV-2; coronavirus; acute respiratory distress syndrome; ARDS;

Topical Areas


Educational Level

Undergraduate upper division, Graduate, Professional (degree program), Clinical education



Type / Methods




Subject Headings

Biology (General)  |   Physiology  |   Medicine (General)  |   Chemistry (General)  |   Nursing  |   Science (General)  |   Physics  |  

Date Posted


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