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.
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.
I 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.
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.
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.