In the age of the Fitbit, it is only a matter of time before devices designed for babies appear on the market. There are a whole bunch available now. There is a pacifier that doubles as a thermometer. You can buy a device to prevent heat stroke in your baby. There is even a GPS tracking devices for babies. The particular segment of the infant wearables market that concerns us here are the devices that measure infant blood oxygen levels. The unstated reason for buying such devices is the prevention of death by SIDS, or other sleep-related infant deaths.
Infant Wearables in the Age of Back-to-Sleep
These devices are based on a well-tested technology from the world of medicine called pulse oximetry. The “pulse ox” works by shining a red light onto the skin and simultaneously measuring the wave-length of the light that bounces back. The device then calculates the amount of oxygen in the bloodstream. Such devices have been used in even tiny babies for many years. Now, several companies are marketing these devices for parents worried about SIDS.
Do they work? Do infant wearables really prevent SIDS?
These are obviously two separate questions. We’ll tackle them one at a time.
To address the question of whether home pulse oximeters work, a few studies have been published. The study that best answers the question was published the the UK in 1991.
The British investigators focused on a group of babies that recently had been discharged from hospitals with apparent life-threatening events. Translated into English, the babies had turned blue at home, either because of choking or lung disease related to prematurity. This was a good population to study. The chance that these babies would actually need the alarm was greater than the general population of babies. Most of these babies had some kind of medical problem that made them more vulnerable to dropping their oxygen levels. This means the investigators were not measuring rare events and it would be unlikely that the number of events measured would be too small to give meaningful results.
The investigators also gave monitors to parents who had already lost a baby to SIDS.
The study looked at the number of events that the wearable devices picked up. Importantly, they also looked at false alarms, and measured side-effects of the devices, such as blisters and other skin burns.
A total of 201 babies were monitored for 30 months. Only 19 families withdrew from the study before it ended.
The pulse oximeters recorded 81 events, of which 52 were true episodes of blueness. No episodes were missed. In other words, the sensitivity of the device was 100%. Any time a test shows a 100% sensitivity (no true positives missed), there is going to be a substantial false positive rate. For these parents, that means an alarm going off for no reason. Sometimes the sensor would move out of position or fall off, activating the alarm. Sometimes it was a true false alarm. The device would go off when nothing was wrong. In the UK study, false alarms happened about once every 4 days.
Very few of the babies got skin redness from the red light source and none were burned.
Four babies actually died during the study. One sibling of a SIDS victim died while the infant wearables were in calibration mode. That is to say they were not turned on correctly. The cause of death was ruled SIDS as well. The other three babies died of the severe congenital heart and lung problems that got them included in the study.
There are two important take-aways from this study. Pulse oximeters work well. They will catch every dip in a baby’s blood oxygen level. But the devices cannot prevent death in severely ill babies. As was demonstrated catastrophically in this study, the devices won’t work if they are not turned on.
Infant Wearables and SIDS
The second question we asked was whether these devices can prevent your baby from dying of SIDS. The honest answer is “nobody knows”. In the UK study, the only baby to die of SIDS was not wearing an alarm. One other sibling of a SIDS victim in the study had a substantial dip in her oxygen and was later found to have meningitis. The answer remains open. We simply do not know if infant wearables prevent SIDS.
But wait! Didn’t this study show that the alarm always goes off when the baby’s oxygen dips too low? If so, won’t any baby in danger of SIDS set off the alarm?
It’s a reasonable question. The answer is “yes, you are probably right”. And yet, we simply do not know because the studies have not proven the point to a degree of scientific certainty.
The Question You Didn’t Ask
It’s clear that pulse oximeters for use at home are very sensitive. They catch every event. This also means they “catch” events that are not events. Imagine how unbelievably frightening it must be to be awakened in the middle of the night by such an alarm. You cannot be sure if you are answering a false alarm or if you will be dialing 911. The question we didn’t ask at the outset was “do you think infant wearables make you more relaxed, or more anxious?”
The American Academy of Pediatrics has not taken a position on these devices for healthy infants. The organization’s silence probably reflects the absence of scientific evidence on SIDS prevention. Pediatricians disagree as to whether or not it’s a good idea for parents to buy such a device. My recommendation would be to discuss it with your pediatrician before buying.
And if you have any issues or (non-medical) concerns about your baby’s sleep, I’m a sleep consultant.