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Memory monitor unit

What is a memory monitor unit?

Also called an MMU, this testing device records breathing effort and heart rate whenever they fall outside of set ranges. This is done to check your baby’s breathing maturity. An MMU recording can be done in the hospital or at home. Oxygen level in the blood can be measured at the same time or separately. Other key details are written in an event log.

How is the recording done?

Two electrodes are placed on your baby’s chest to record breathing and heart rate. The electrodes may be self-sticking, or they may be held in place by a soft belt. If oxygen level is measured, another sensor is taped to a finger, toe, hand, or foot.

If the breathing, heart rate, or oxygen level (if being measured), fall outside of certain ranges, an alarm will sound and the MMU will begin recording.

To record in the hospital, a respiratory therapist or nurse will set up the MMU and your baby will be monitored through the night. Those caring for your baby will write details in the event log, including the start and stop times of all feedings, your baby’s skin color when an alarm sounds, and so on.

To record at home, the respiratory therapist from the equipment company will bring the MMU to the hospital or your home and teach you how to set it up. The respiratory therapist will teach you how to respond to the alarms, and will return to pick up the unit when the recordings are done.

What else should I do?

Feed and care for your baby as usual except no bathing during the recording. Let your baby sleep as much as possible; this gives the most accurate results. If the alarm sounds, check your baby and the monitor as you have been taught.

The therapist or nurse will tell you what details to watch for and write down in the event log. Be sure to list start and stop times of all feedings. If an alarm sounds, note what the baby was doing:

  • feeding
  • sleeping (in which position)
  • changes in skin color
  • choking

When will I get the test results?

The recording information will be sent to the diagnostic lab. The information will be analyzed and the results sent to your baby’s doctor within about 2 days. The doctor will explain the results to you.


This is not specific to your baby, but provides general information. If you have any questions about the reasons for the test or the results, call the doctor. If you have equipment problems at home during the study, please call the monitor company: 


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This page is not specific to your child, but provides general information on the topic above. If you have any questions, please call your clinic. For more reading material about this and other health topics, please call or visit Children's Minnesota Family Resource Center library, or visit

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