Are you ready to learn how to perform a Modified Allen Test? Or maybe you’re wondering what is the purpose of the Allen’s Test? If so, you’re in the right place because that is what this article is all about.
So if you’re ready, let’s go ahead and dive right in.
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What is the Modified Allen Test?
The Allen Test for assessment of blood flow was originally developed by Edgar V. Allen in 1929 as a non-invasive method of assessing the patency of a patient’s arteries. Since then, it has been adopted as the Modified Allen Test, and is used to check for collateral circulation of the radial and ulnar arteries in the wrist.
The difference between the Modified Allen Test and the original Allen Test is that Modified Allen Test efficiently evaluates the adequacy of blood circulation on one hand at a time.
The Modified Allen Test measures the competency and quality of the artery and should be performed prior to performing an arterial puncture.
How to Perform a Modified Allen Test (Step by Step):
Step #1: Have the Patient Make a Fist
Step #2: Locate the Radial and Ulnar Arteries
Make sure to locate both the radial and ulnar pulses.
Step #3: Grab the Patient’s Hand
Do whichever is more comfortable to both you and the patient.
Step #4: Locate the Pulse
Step #5: Apply Pressure to Both Arteries
Be sure to tell the patient to relax his or her hand while doing this.
Step #6: Have the Patient Open Their Hand
Blanching means that you have completely occluded the radial and ulnar arteries with your fingers. At this time, the hand should have a white-ish appearance in color.
Step #7: Slowly Release the Pressure on the Ulnar Artery
You can release pressure on the ulnar artery while keeping the radial artery occluded. The patient’s hand should flush within 5 to 15 seconds, meaning that it should turn pink. If it does, this indicates that the ulnar artery is patent and has good blood flow.
This is considered a positive Modified Allen Test and you can proceed to stick and collect the ABG sample at this site.
However, if flushing is not observed within 5 to 15 seconds, this result suggests that collateral circulation is not present and this is considered as a negative Modified Allen Test.
In this case, it is recommended not to puncture the radial artery at this site. You should either try the Modified Allen Test on the other hand or move on to the brachial artery.
So there you have it. That pretty much wraps up everything you need to know about performing a Modified Allen Test.
Be sure to perform the Modified Allen Test before each and every ABG stick that you perform on a patient. It’s important to do so because the test helps to check for collateral circulation in the radial and ulnar arteries.
Unfortunately, many healthcare providers skip this critical step but I want to encourage you not to. Always strive to be diligent and professional as a Respiratory Therapist and performing this required step is one way to do just that.
Also, be sure to read our full article on ABG Interpretation. Thank you so much for reading all the way to the end and as always, breathe easy my friend.
The following are the sources that were used while doing research for this article:
- —. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020. [Link]
- Faarc, Heuer Al PhD Mba Rrt Rpft. Wilkins’ Clinical Assessment in Respiratory Care. 8th ed., Mosby, 2017. [Link]
- “Modified Allen Test – WHO Guidelines on Drawing Blood – NCBI Bookshelf.” NCBI, 30 July 2020, www.ncbi.nlm.nih.gov/books/NBK138652.
- “Performing a Modified Allen Test : Nursing2020.” LWW, Mar. 2005, journals.lww.com/nursing/Citation/2005/10000/Performing_a_modified_Allen_test.20.aspx.
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