Chapter 8 | Introduction to ABGs and Interpretation

Arterial blood gases (ABGs) are the cornerstone of assessing the respiratory status of a patient that may require mechanical ventilation or is already being mechanically ventilated. It is important that all health care providers that use mechanical ventilators have an understanding of ABGs and how to interpret them, in order to identify the issues that the patient is experiencing and know how to fix them. This chapter will introduce ABGs, how to approach an interpretation of ABGs, and the issues that are occurring based on the blood gas.

This chapter covers:

  • The theory behind ABGs
  • Normal ABG values
  • How to interpret ABGs, with examples
  • How to comment on oxygenation status


ABGs are a key piece in ventilation, as they are used to identify issues that require ventilation-based treatments, and they are used to check on how well a patient is responding to ventilation. Interpreting ABGs is essential to identifying the issues that a patient is experiencing.

Learning Objectives

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

  1. Relate ABGs to the acid-base relationship in the body.
  2. Identify normal ABG values.
  3. Interpret ABGs.
  4. Comment on oxygenation status.

Key Terms

  • Arterial Blood Gases (ABGs)
  • Homeostasis
  • Acidic pH
  • Alkaline/Basic pH
  • Neutralization/Buffering
  • HCO3 or bicarbonate
  • Respiratory failure/ventilatory failure
  • Hypercarbia
  • Hypocarbia
  • Alkalosis
  • Acidosis
  • pCO2
  • Hypoxemia

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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