The New York State Nurses Association is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center’s Commission on Accreditation.

This course has been awarded 1 contact hour.

You are caring for a 67-year-old female with breathing difficulties. The treatments you have given her have not helped to improve her breathing status. You return to the physician to update her on your patient. The physician orders an arterial blood gas. You head to the phone and call the Respiratory Therapist. Once you have relayed the order for an arterial blood gas to the Respiratory Therapist, you hang up the phone and return to care for your other patients. You take no part in gathering the “blood gas,” allowing the respiratory therapist to draw, send and interpret the test results with the physician. If you are lucky, you may be able to overhear a discussion on the ABG results. In the back of your mind you would like to take a more active role in this scenario, if only you were more comfortable with ABGs.

If you can relate to the above patient scenario you’re not alone. Arterial blood gases can be challenging to all nurses despite their level of expertise. The purpose of this course is to provide nurses with information regarding blood gases and their basic interpretation.

An arterial blood gas provides two types of information: acid-base balance and oxygenation.  Acid-base balance is measured using a pH scale.  The pH is a measurement of the concentration of hydrogen ions (H⁺) in a solution.  In this case, our solution is the arterial blood.  Oxygenation is measured both by the partial pressure of oxygen in the arterial blood (PaO₂) and by the arterial oxygen saturation (SaO₂).  The arterial oxygenation saturation tells us the percentage of heme sites on the hemoglobin molecules that are saturated with oxygen.  Arterial oxygen saturation can also be measured non-invasively with a pulse oximeter probe and is then represented by the abbreviation SpO₂ instead of SaO₂.  In order for the body to function normally, the pH must be continually maintained within a narrow range.  This management is accomplished by the lungs and the kidneys.

Before we jump into numbers and attempt to interpret an ABG, let’s take some time to understand the fundamentals. We will begin by explaining how we measure gases in the blood and review how we move oxygen and carbon dioxide into and out of our bodies. Following on from this we will review pH balance and the concept of compensation, before continuing on to explain how to take an arterial blood gas. Lastly we will learn to interpret arterial blood gases and work through some examples before completing a mini-quiz to test our newly gained knowledge. Intentionally, this course is designed to review pertinent information without “bogging down” the reader with technical equations and explanations. Further reading beyond this course is encouraged to build on the basic skills taught.

Content Outline

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Course Objectives

At the completion of this learning activity the learner will:

• Describe components of the respiratory process.
• Describe pH and the concept of compensation.
• Describe the role of the respiratory process in maintaining normal pH.
• Describe the role of metabolic processes in maintaining normal pH.
• Identify lab values that indicate compensated/uncompensated respiratory acidosis and alkalosis and metabolic acidosis and alkalosis.