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Assessing Lung Function and
Cardiac Output with Capnography



Tom Ahrens, PhD, RN, FAAN

Founder, Viven Health, Inc.


Capnography has the unique ability to aid clinicians in assessing both ventilation and blood flow.  It can, along with oximetry and arterial blood gases, provide both a basic and advanced assessment of pulmonary function.  In this program, a review of the physiology that allows PetCO2 and SpO2 to monitor ventilation, perfusion and lung function is presented.  The emphasis in this program is using capnography to assess lung function, prevent errors (such as oversedation) and monitor cardiac output.  The use of these two technologies can be argued to be the most important techniques in assessing lung function, particularly in the COVID environment.


Learning Outcomes:  

  1. Discuss how capnography can reflect a patient at risk for oversedation

  2. Discuss how the reason why capnography is a rapid assessment of inadequate ventilation and perfusion

  3. Discuss how to combine PaCO2 and Pet CO2 values in a pulmonary assessment

  4. Describe how capnography and SpO2 can be used in COVID patients


Faculty Bio

Tom Ahrens, PhD, RN, FAAN is a Research Scientist at Barnes Jewish Hospital in St. Louis, MO. Dr. Ahrens has more than 25 years of experience as a critical care nurse, and is the author of five books, more than 100 papers, and more than 40 scientific publications. His book Essentials of Oxygenation received the Book of the Year Award from the American Journal of Nursing. He is also a grant reviewer for the National Institutes of Health and formerly served on the board of directors for AACN. He is a recognized authority in sepsis and has given numerous lectures around the country on the subject. Dr. Ahrens is a Fellow of the AAN which named him one of its first Edge Runners in 2006; the award recognizes innovations resulting in better care for patients, families, and the community.

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