Chapter 9 | Ventilation Changes based on ABGs

You have reached the final chapter! As you have worked your way through this book, you have overviewed the differences between spontaneous breathing and mechanical ventilation, and learned that ventilation is not a “one size fits all” approach. To ventilate as safely and effectively as possible, as clinicians we need to choose our mode and ventilation settings based on our patient and what they need. You have learned about

  • Control modes, including initial settings,
  • Spontaneous modes, including initial settings,
  • Non-invasive ventilation, and
  • Arterial blood gas (ABG) interpretations.

Finally, you already understand that, once initial settings are chosen, these settings will be evaluated for effectiveness by testing an ABG of the patient. But what do you do to the ventilation settings when you have an ABG in front of you? How do you know what to change and what to keep the same? In this chapter, we will overview:

  • The goals of making changes to ventilation
  • What values can you fix on an ABG with ventilation
  • Which ventilator settings impact CO2 and O2 levels
  • Identify one or more issue(s) in the ABG
  • Identify all changes that could improve the ABG, and choose which setting would be most appropriate
  • What is the appropriate degree of adjustment in order to correct ABG issues


This chapter builds on everything you have learned in this book to put the entire picture together: from determining that a patient needs ventilation using ABGs, to choosing the correct mode for the patient, to selecting appropriate settings. Then, you will understand that you must redo ABGs to check on how the patient is doing on their treatment, and know how to use this information to adjust the ventilator settings. By working through the case study provided in this chapter, you will move with a patient through the full progression of ventilation from initial assessment to weaning, seeing how all of the pieces of the ventilation puzzle fit together. At chapter end, you should feel confident to work with ventilators and ventilated patients in your professional role.

Learning Objectives

At the end of this chapter, you will be able to:

  1. Articulate the goals of making changes to ventilation.
  2. Identify what values you can fix on an ABG with ventilation.
  3. Relate ventilator settings to CO2 and O2 levels.
  4. Identify one or more issue(s) in the ABG.
  5. Evaluate all changes that could improve the ABG to select the setting that would be most appropriate.
  6. Determine the appropriate degree of adjustment that is required for a patient.

Key Terms

  • blowing off CO2
  • intrathoracic pressure
  • venous return
  • ejection fraction
  • over-vented

Whenever these terms are first introduced in this chapter, they are bolded. However, if you need additional information about a term than what is provided here, you can research it in The Free Dictionary: Medical Dictionary.


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