9.4: Which ventilation setting affects which ABG value? — Read

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At this point in your learning, the terms ventilation (the exchange of pCO₂) and oxygenation (pO₂) are probably very familiar to you. Remember, pCO₂ and pO₂ are values in an ABG reading. Let’s relate these concepts to settings on the ventilator, and learn which specific setting affects ventilation or oxygenation.

We have repeatedly discussed how ventilation refers specifically to the exchange of air in and out of the lungs. In terms of blood gas effects, ventilation directly refers to the removal of CO₂. So, what ventilator settings would affect this? What settings directly impact the amount of air going in and out of the lungs? If you guessed the tidal volume, you are correct! The size of breath will directly impact the amount of air going in and CO₂ coming out of the lungs.

There is another setting that will impact the amount of CO₂ clearance. What do the chemoreceptors in the brain trigger if the CO₂ levels start to rise? If you answered the respiratory rate $A simple black silhouette of a smartphone with a blank screen.$ , then you are remembering correctly! The $A simple black line drawing of a megaphone facing right.$ also has direct impact on the amount of CO₂ leaving the lungs over time. If you breathe faster, you are getting rid of CO₂ more often and this will help drive CO₂ levels down.

Increased CO₂ clearance is commonly referred to as blowing off CO₂.

Key Takeaway

To affect ventilation, the $A simple black line drawing of a megaphone facing right.$ and the tidal volume are the two settings with direct impact on the amount of air into the lungs and CO₂ out of the lungs. Remember $A simple black silhouette of a cat with a long tail and pointed ears.$ .

What about oxygenation? Which ventilator settings directly impact the patient’s oxygenation status? This concept should not be new to you. We have talked extensively about FiO₂ and PEEP as working together to deliver oxygen into the body. The FiO₂ can be increased to deliver higher amounts of oxygen to the lungs, while PEEP can push the oxygen across the alveolar-capillary membrane.

Please note that this is a slight simplification of these concepts. There is some crossover between the ventilator settings that affect oxygenation and ventilation. But for beginner learners, it is better to keep oxygenation and ventilation and the settings that affect them separate in your minds without crossover. With practice you will be able to see the big picture and even make predictions on what order to use ventilation settings.

Take a look at the following table, which summarizes the mechanical ventilation settings that affect oxygen versus ventilation (keep in mind that $A simple black silhouette of a cat sitting upright with its tail curved.$ can also be affected by other settings on a ventilator):

Table 9.4.1: Settings that Affect Oxygenation and Ventilation
Settings that affect Oxygenation	Settings that affect Ventilation
$Two stylized arrows forming a circular shape, indicating a refresh or reload action.$	$A simple black line drawing of a megaphone facing right.$
$A silhouette of a person playing a saxophone, shown in profile view.$	$A simple black silhouette of a cat sitting upright with its tail curved.$

A green helicopter flying in a clear blue sky, with its rotor blades in motion. — If you ever get the chance to work in flight medicine or medevacs, you may be the sole or lead care provider for a ventilated patient and need to know how to make appropriate decisions. Photo by ArtisticOperations, Pixabay Licence.

“Which ventilation setting affects which ABG value?” from Basic Principles of Mechanical Ventilation by Melody Bishop, © Sault College is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

This page titled 9.4: Which ventilation setting affects which ABG value? was last modified on Fri, 16 Oct 2026 18:21:45 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Yvonne Drasovean via source content that was edited to the style and standards of the LibreTexts platform.

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Key Takeaway