Posted by Bird Watcher on March 27, 2007 at 12:04:20:

In Reply to: Do APAPs use Algorhythms? (techie ? posted by Captin Cannuck on March 27, 2007 at 00:38:28:

All this from what I know from electronics training: The term algorithm (also spelled algorhythm) is defined as a mathematical rule or procedure for solving a problem. The math problem in this case is a distorted breathing pattern of a person who has disordered sleep breathing. It solves much like a thermostat in your house solves the condition of it being too hot or too cold in the house. With a thermostat, there is a set temperature to achieve. If the actual temp goes below the set temp, the thermostat commands heat until the set temp is achieved. Once achieved, the heat turns off and the process repeats if the heat is not held. With an APAP, the setting to achieve is a smooth wave form and a normal volume of air. Snoring, apneas, and hypopneas are distored waves. Pressures settings don't necessarily come into play...the machine is only trying to achieve a wave form which it defines as normal and will use pressure to achieve that. The APAP starts at it's lower limit and will stay there if it detects a normal pattern. The machine doesn't care, necessarily, which pressure this is. But if the pattern goes distorted, it pumps more air to bring it back to normal, up to the programmed limit. It will then start to back off as long as the pattern remains normal, all the way to the lower limit.

The APAP manufacurer defines how fast it goes up in response to an abnormal condition, how long it stays at a pressure after becoming normal again, and how fast it drops, if all remains normal. This is different from Respironics to ResMed. In response to a sudden apnea, it pumps a lot immediately, kind of like a door opening in a house and the furnace not waiting until the temp drops at all to start pumping heat again. This programming is called the algorithm of the machine. Inside the APAP, the main processor is comparing voltages, capactances, and resistances to standards it already holds. Twenty years ago, this technology was not available. Ten years ago, it was perhaps available but too expensive to package to the consumer, but now, building something like this is really not considered to be that complicated. The price of programmable logic devices has gone way down. Programmable logic devices are off the shelf chips that can be used for a variety of applications, such as adjusting the air/gas mixtures in your car's fuel injection system.

Follow Ups:

• Re: Do APAPs use Algorhythms? (techie ? Captin Cannuck 01:54 4/05/07 (1)
  • Re: Do APAPs use Algorhythms? (techie ? Bird Watcher 19:27 4/06/07 (0)

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