(image courtesy )
You can use your smartphone in many ways to track your health; to keep an eye on what you eat, how far you run, how often you work out, etc. And now, you can also use your phone camera to track your heart rate!
I don’t know much about medicine, but according to the app, it works “similar way [sic] as a medical pulse oximeter but without a dedicated light source.” Now, to paraphrase Dr. McCoy, Dammit I’m a geek, not a doctor…so I consulted my good buddy Wikipedia:
A blood-oxygen monitor displays the percentage of arterial hemoglobin in the oxyhemoglobin configuration. Acceptable normal ranges are from 95 to 100 percent, although values down to 90% are common. For a patient breathing room air, at not far above sea level, an estimate of arterial pO2 can be made from the blood-oxygen monitor SpO2 reading.
A pulse oximeter is a particularly convenient noninvasive measurement instrument. Typically it has a pair of small light-emitting diodes (LEDs) facing a photodiode through a translucent part of the patient’s body, usually a fingertip or an earlobe. One LED is red, with wavelength of 660 nm, and the other is infrared, 905, 910, or 940 nm. Absorption at these wavelengths differs significantly between oxyhemoglobin and its deoxygenated form; therefore, the oxy/deoxyhemoglobin ratio can be calculated from the ratio of the absorption of the red and infrared light. The absorbance of oxyhemoglobin and deoxyhemoglobin is the same (isosbestic point) for the wavelengths of 590 and 805 nm; earlier oximeters used these wavelengths for correction for hemoglobin concentration.
The monitored signal bounces in time with the heart beat because the arterial blood vessels expand and contract with each heartbeat. By examining only the varying part of the absorption spectrum (essentially, subtracting minimum absorption from peak absorption), a monitor can ignore other tissues or nail polish, (though black nail polish tends to distort readings) and discern only the absorption caused by arterial blood. Thus, detecting a pulse is essential to the operation of a pulse oximeter and it will not function if there is non.
Well, that cleared everything up, now didn’t it?
In all seriousness, Instant Heart Rate uses the same idea, but with the camera (and LED flash if available) on your phone. Just put your index finger gently on the camera lens, wait about ten seconds, and the app comes back with a pulse rate. I tried this several times, and each time my pulse came back in the 50-54 range. My coworker also tried it, and his came back in the same general range.
We then did the wonderfully unscientific “take your pulse for 10 seconds and then multiply by 6” method as a comparison. The first time I counted 8 (which is a pulse rate of 48) and the second time I came up with 9 (or a rate of 54). Since both could be rounded to the “low 50’s”, it’s safe to say that app seemed reasonably accurate.
Where is something like this helpful? I wouldn’t advocate using it as a replacement for a serious heart monitoring system; this is just for fun and general edification. On the other hand, if you’re like me and too cheap to buy a heart monitor for exercise, but also have trouble doing math after several miles of brain jarring running, this is better than nothing. As a baseline “how hard was I running” it works moderately well, though again if you’re concerned about getting very specific this isn’t the right tool.
Still, it’s a free app that’s easier than trying to track your pulse off your sweaty neck or wrist. And it’s a fun way to force your coworkers to check their cardiac health. I am curious, for any medical professionals out there, how accurate is something like this? Does it mean anything, or is it all just a gimmick? Educate us all below!
Instant Heart Rate for Android can be found in the Marketplace for free.
What I liked:
Fun to see what movement does to your heart rate; easy to use.
What I didn’t like:
Awkward to hold and measure; need a very light touch to get a quick read.