Appeared in DIVER March 2007

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PULSE-CHECKER MD300-D Pulse Oximeter
 Its for making an instant spot check on blood oxygen saturation and pulse-rate. You simply clip it to an index finger and read the display.
I like pulse-rate competitions because I seem to be endowed with a slow-revving heart, though I really dont know whether thats good or not. During a short stay in hospital for a routine procedure, I caused a bit of excitement when I decided to fully relax, and my heart rate set off alarms suggesting that I might be shuffling off my mortal coil.
In fact, I had simply decided to leave my body with the medical experts while I took my mind off somewhere far more pleasant.
Anyway, suffice to say that I can get a pulse-rate in the low 50s sitting down, and sitting down is something Id rather do than running for a bus. Well, I might be running for a bus more often once it becomes free for me to ride on, and that probably explains why my blood oxygen saturation rarely rises above 95%.
My fit young wife has a much faster pulse while at rest (well, I am looking at her, and I make any womans pulse race) but her blood oxygen saturation levels are close to 99%. That must be why I run out of puff when she doesnt.
Vandagraph can supply a little watertight box so that the Pulse Oximeter can be safely taken aboard dive-boats. I took it on my next diving trip and checked myself before and after every dive.
This instrument uses the latest in display technology with a coloured OLED display. The O stands for organic, following the discovery that LEDs could be made from polymers as well as semi-conductors.
In brief, this means that the MD300-D provides a bright coloured display with self-luminous properties, eliminating the need for a backlight. It needs only a tiny battery that will last a long time, and the unit can be small too.
This technology was used during the NASA Licanbur expedition to Bolivia to dive the highest lake in the world and find out what happens to human bodies at high altitudes. The indication was that, above 6000m, the oxygen level in the body can fall to as low as 65% of normal.
Im not sure if the MD300-D Pulse Oximeter has any application specific to diving at sea level, but its a lot of fun if you get healthy-looking readings!
I took it on a dive-boat, and once I had finished rigging my tank and was relaxed again I got a similar reading to that at home. Ray Sheppard, my young guide from Camel Diving, recorded a similar reading to that of my wife.
Then we went diving. Taking a reading immediately afterwards, but once we had sat down up on the sundeck for a relaxing surface interval, we noted that the oxygen content was more or less the same as before diving but that my heart-rate was in the high 70s and occasionally in the low 80s. Rays was in the high 90s and even topped 100 from time to time.
We checked other divers, and found that everyones heart was racing after diving. All were in the range of 70-100 beats per minute, while the oxygen content remained the same at around 98% for most of the younger people.
So what do we deduce from this Perhaps our hearts race to shunt as much blood around our bodies as possible to rid ourselves of excess dissolved nitrogen. No doubt a medical man can tell us more.
In the meantime, I can tell you that the MD300-D Pulse Oximeter costs 106.
  • Vandagraph, www.vandagraph.co.uk


  • Divernet
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    + Good fun for healthy people


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    - You may need medical knowledge to understand the significance of what it tells you