Health Tests

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Harvard Medical School

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What Happens During the Test?

You wear a hospital gown and sit on a bed or table leaning forward against some pillows. The doctor listens to your lungs with a stethoscope and may tap on your back to find out how much fluid has collected.

An antiseptic solution is used to disinfect an area of skin on one side of your back. A small needle is used to numb a patch of skin between two of your lower ribs. The numbing medicine usually stings for a second.

A needle on an empty syringe is then inserted into the skin and pushed forward between the ribs. The needle is advanced until it enters the fluid collection inside your chest wall. You might feel some minor pressure as the needle is inserted.

The syringe draws out a fluid sample. If your doctor wants to remove a larger amount of fluid, a thin, soft plastic tube is used instead. The tube leads to a large jar. While the doctor is attaching the tubing, he or she might ask you to hum out loud. This humming is for your safety: It prevents you from taking a deep breath, which could expand your lung, causing it to touch the needle.

It sometimes takes 15 minutes or longer to remove the necessary amount of fluid. Most patients feel no discomfort during this time, although a few patients feel some chest pain at the end of the procedure as their lung expands and touches the chest wall. After the fluid is removed, a bandage is placed on your back.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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