Useful Medical Gadgets – Measure and Monitor Yourself

At Quantitative Medicine, we love measurement. Want to be a QM do-it-yourselfer? Here is a selection of gadgetry, some useful, and some otherwise that I have tried out. Please let us know of any gadget we omitted and we will duly evaluate them and post a sequel.

Heart Rate Monitor.HR Mon

This one is important for exercise. Specifically, it is important to know maximum heart rate, resting heart rate, and how much the heart rate goes down 1 minute after peak exercise. The ‘leader’ in heart rate monitors is Polar. The monitors are a bit pricey and not awfully user friendly.

The polar system involves a chest-strap, which some find uncomfortable. The chest strap transmits heart rate information to a watch, which displays it. You can have the simple display model for around $50, one that can download general data to a PC for around $70. You can get one that will record every heartbeat for around $250. The PC software is Windows only.

Ideally, every heartbeat of an exercise session should be recorded. This can reveal any heart abnormalities that occur under stress. However, the only Polar model that can do this, besides being pricey, is a bit cranky, and has a tendency to eat batteries. A better solution would be welcome. So far Polar is the only one that provides an exportable data stream that we can pool and analyze for statistical purposes across our patient population. Using this data we can also match heart rate response to varieties of exercise, patients fitness levels and as a predictor of future heart disease.

There are other watches that measure heart rate without the strap. These are significantly cheaper. You have to touch the watch and wait 5 seconds or so. This isn’t really adequate and can be inconvenient and inaccurate.

There are now Bluetooth chest straps that connect directly to smart phones. How well this works is unknown. Perhaps this is the way to go. Any readers that know about this please chime in.

Glucose Level.

GlucoseI decided to track my glucose levels for a 24 hour period and bought a blood glucose meter intended for diabetic use. The procedure is to insert a test strip into the meter, and then obtain a drop of blood by ‘lancing’ your palm or finger. When the test strip touches the drop, it soaks up the blood and returns a result a few seconds later.

When the gadget arrived, I did three ‘lancings’, thus analyzing three separate drops of blood. Glucose levels ranged from 95 to 115. Hmmm. Next, I got a quite large drop of blood and wet three different test strips form the same drop, and got reading from 103 to 127.  The test strip package insert seemed to indicate that the accuracy was within ±4 mg/dl. We would prefer 2, but the reality appears to be ±15.

I then called the manufacturer. The customer service people seemed to think this was a bit excessive and promised to send a new one. It arrived, and seemed to have about the same ±15 mg/dl performance. This degree of accuracy may be fine for a diabetic use, but it is rather useless for determine glucose to the accuracy I wanted. So into the trash went the glucose meters, (much to the relief of my palms and fingers).


This gadget actually measures your electrocardiogram, a real one. Wonderful but a little pricey. Are you familiar with white-coat-syndrome, wherein your blood pressure or cortisol will shoot up in the presence of medical personel.

There is also anti-white-coat-syndrome, wherein your symptom disappears as soon as you get to the doctor’s office. You describe the now vanished affliction, but all you get is this: ‘He who self diagnoses himself has a quack for a doctor’ look.

Ever had your heart skip a beat, or a couple? It common and almost always harmless, but scary, and of course, it would be nice if the doctor would take it seriously.

This gadget, also by Omron, could solve the problem. It works by holding it in you right hand, and pressing it to your chest under your left breast, (or where one would be if you were a woman, but are not). If duly records a 30 second EKG, and even displays it. The data can be transferred to a PC (C- for the software), printed and sent to the doctor. So far, the doctor I showed it to, pronounced it to be a genuine, bona fide, useful EKG. The printout looks like this. Street price, around $250.ECG

Cuff blood pressure.

This device consists of a doctor’s office like cuff that goes around the upper arm, and a machine that inflates it and make the measurements. It measure systolic and diastolic blood pressure as well as pulse rate. The official name for this device is sphygmomanometer. The leader appears to be Omron. I bought one. The cuff has to be positioned just so, but the machine will twarn you if you don’t have it right. It seems to be quite accurate and consistent. You see these same machines in doctor’s offices. Street price $65. Remember the ‘gold standard’ for diagnosing and certainly for managing high blood pressure is a 24 hour ambulatory monitor (around $1500) and next is a series of home monitor readings. The worst method of diagnosing and monitoring high blood pressure is medical-office based pressures. They are flat wrong.

Wrist blood pressure.

These are inexpensive, convenient, fast, and quite inaccurate. I bought one of the more reputable manufacturers models, and got systolic numbered ranging from 97 to 125 in one sitting.  My actual resting systolic pressure in 115, so maybe this device is useful for determining the ballpark. Street price: $24-$75


If you are doing a very low carb diet, you might be interested in knowing if you are in ‘ketosis’. There is nothing wrong or dangerous about ketosis. If the liver cannot make enough glucose for the brain, it will make ketones as a back-up supply. This is ketosis. The brain functions perfectly well on ketones. It may, in fact, functions better. Very low card diets are sometimes recommended for people with Alzheimer’s. I have never tried these out. Cost is around 10¢ per strip. Keep in mind that some people’s liver is so adept at gluconeogenesis – making new glucose molecules out of anything handy to the liver –  that they never go into true ketosis absent full-blown long-term fasting.

BAC level.

Not exactly a medical test, but worth a mention. I decided to see if I could learn to guess my blood alcohol. I bought 4 $100 premium blood alcohol BAC meters. The range in the California for ‘legal’ driving is 0.08%. Anyone with that much alcohol in their blood is definitely tipsy and shouldn’t be driving. Many European countries have a limit of 0.05%, and some have a max of 0. Of my four premium meters, two gave identical readings, one read 0.02 higher and one 0.04 higher. Come on, 0.04 is halfway to jail.  No way to tell which was right. I then bought a $300 meter. This one measures to an additional decimal place and is, at least according to the sales pitch, widely used by police forces. So I trust it. In any case, I have managed to calibrate myself. I can guess my blood alcohol content to within 0.005%, and would bet on it. Dr. Mike can guess his to 0.0000%. He doesn’t drink. I am now working on associating blood alcohol level with success at repeating ‘sphygmomanometer’. Will keep you posted.

Dr. Mike update: Dr. Davis can’t say ‘sphygmomanometer’ sober so the test was cancelled.

  15 comments for “Useful Medical Gadgets – Measure and Monitor Yourself

  1. Helene
    April 12, 2015 at 1:24 pm

    Lovely and so appropriate for Sunday reading! And the last bit is particularly funny. Thankyou for making me laugh.
    Starting my ‘intensive driving course’ soon I am now planning to confront my advance driving instructor (during final lessons on the motorway) by asking him: – “And what are you going to tell me about … sphygmomanometer”? As soon as I’ll finish saying this word (which I would have to memorise first!) I will quickly watch his face… as he may ask me back: – “What on earth is that”!?

    My test results of course would be slightly better – 0.00000%.

    As for other gadgets, do I really need to use Ear Plugs for long flights? Or it’s not necessary? Are they all good quality and reusable?

    I still have old Mercury Thermometer at home. Hardly used. Is it okay to continue to use it, if needed? Or there are others and the best? What temperature is considered to be normal? 36.6? My daddy told me when I was little…

    • April 13, 2015 at 4:06 pm


      It is fine to use it. For the record, absent disease, almost all of my patients have a temperature lower than the reported normal of 98.6F/37C. There is a lot of diurnal variance that clouds this picture too. Dr. Mike

      • Helene
        April 14, 2015 at 12:23 pm


  2. Jim
    April 13, 2015 at 7:06 am

    Can you tell me, is the Polar RS800 the only wrist unit capable of downloading R-to-R intervals? I currently use an RS400 and understand from the Polar literature that the tests the RS400 unit can perform (such as Own Optimizer) utilize R-to-R evaluation to come up with their version of an index. If the watch truly uses R-to-R, is there a way to get that info from the RS400?

    BTW – even tough retail, these units are pricey, if you are patient and persistent, ebay sometimes has units you can get more reasonably. I was able to get (through separate purchases) the RS400, chest strap, foot pod and IR adapter for a total of ~$125 – retail at the time was closer to $300.

    • April 13, 2015 at 3:56 pm

      I apologize for the brevity, too busy just now, but the 800 is the only one I have reliably been able to get R-to-R from as a useful data stream.
      Dr. Mike

      • Jim
        April 16, 2015 at 1:46 pm


        Can you tell me, in your experience, do the chest straps loose ability to conduct the electrical impulse from the heart? Mine seems to be getting finicky, sometimes loosing communication. I don’t use any conductive gels – just water to wet the strap. Can be annoying when I’m right at the peak of a great sprint, and then the signal drops.

        • April 16, 2015 at 2:46 pm

          Short version: even with the conducting gels they have to be replaced when the data gets flaky. And to some extent this doesn’t make sense as the contact points are not always even where the band is wearing out. Yes, you need to change the chest straps. Polar; can’t live with it, can’t live without it. Dr. Mike

      • Jim
        May 19, 2015 at 10:04 am

        So – managed to get my hands on an RS800. I am starting to look at my R-R data and have been looking into (web surfing) metrics derived from the data. I also see that Polar software (Protrainer 5) can show a summary that seems to calculate many of the metrics I have stumbled upon like RMSSD, pNN50, and so on. Do you have any suggestions on metrics to monitor – I’m pretty good with computers, so I can work with raw data files from the watch as well. Thanks,


        • May 19, 2015 at 3:51 pm

          Hi Jim,

          I was going to do an entire blog site just about heart rate based training; I don’t have time. However, know that the details of the workout and your metabolic response to training and life is in that data. Let me illustrate, take 20/10 rowing intervals as an example: by looking at the heart rate crescendo you can see if you are truly maxing out your sequence. If you are dogging it even a little you will see a nice little stair step of crescendo from the fist through the nth. If you see the crest after the 3-5th interval you are probably either, and this is where more data comes in, either holding back or fried. (Humans are such that, believe it or not, you cannot always tell just by what you think you have done.) You unpack this by cutting the number of intervals down and switching to some kind of linear scale like watts to assess output and fix the number of strokes in the 20 second work period. You can then begin to see the actual work product against the heart rate response and peak. Other markers like recovery and recovery plateau’s also provide information on whether you were tired when you started or dehydrated for example. Jim, this whole area is very dense. For now this will have to do as a point of encouragement to start experimenting. Get clearance from you doc before intense interval training. Dr. Mike

    • QMWebJockey
      April 13, 2015 at 7:05 pm

      Jim – Please let us know if you find an alternative – even a smartphone based one.
      Charles Davis

  3. Helene
    April 14, 2015 at 2:08 pm

    I would like to consider now buying Heart Rate Monitor.
    Which of the following two is the most suitable?
    Advice would be much appreciated.

    1. Polar H7 Bluetooth 4.0 Heart Rate Sensor. Set for
    iPhone 4S/S – ?

    2. Samsung Heart Rate Monitor Band E1-HH10 – ?
    (“Monitor and adjust the intensity of your exercise.
    Whether walking, running, or cycling, your
    smartphone will monitor your heart-rate and
    provide you with information in real time for a more
    efficient and safe work-out”).

    • April 15, 2015 at 11:34 am

      Hi Helene,
      I haven’t worked with the Samsung band but have used Polar in various iterations thousands of times. I am always amazed as are my patients how frustrating the Polar software can be and how unhelpful their documentation tends to be. However, when it comes to accurate usable heart rate data the Polar stuff usually comes through. I am always on the lookout for better but that is the state of my current experience. I have used several other brands and wound up going back to Polar. All of that said I have no experience with Samsung. If you purchase the Samsung I would love to hear your experience. Thank you for your role in the dialog. Dr. Mike PS I will probably wind up with an Apple watch just to see what I can get out of that.

      • Helene
        April 16, 2015 at 12:19 am

        Thankyou, Doctor. I am very grateful to you for reminder of the new Apple iWatch (not on sale here until 24 April).

        Of course, I don’t want now either Samsung, or Polar Bands! Far better when something comfortably fits on your wrist and, as I already understood, the wrist is a convenient area for collecting data. Would be very sophisticated heart rate sensor (if it can even send my heart beat!). I also like weekly summary on Calorie burn – provided the battery charged overnight, as it only lasts for about 18 hours (would be interesting what the feedback will be on this).

        All other features are also extremely useful. Rain in 10 minutes? I just can look for weather forecast!

  4. Jim Wholey
    April 21, 2015 at 2:50 pm

    Another instrument – very compact and easy to use, is the pulse oximeter to measure % saturation of O2. I use it on hiking trips to altitude both at rest and when powering uphill. It’s also valuable for flying in light unpressurized aircraft.

    • April 22, 2015 at 8:35 am

      Hi Jim,
      As you know I have a genetic problem with evolving emphysema and check my ox sat occasionally; especially when sprinting hills. Thus I am curious: how low have you noted your ox sat to be and under what conditions do you most desaturate? Dr. Mike

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