Solving Your Sleep Diagnostic Computer Quandry

It wasn't that long ago when working in a sleep diagnostics laboratory required a technologist to be intimately familiar with the mechanics and hardware of a polysomnograph. Constant attention to detail coupled with good eyes and ears were necessary to properly operate the machine and diagnose potential problems with both the machine and patient. It is an acquired skill that is not mastered overnight.

As technology races ahead at breakneck speed, technologists and managers in the sleep diagnostic field now find themselves in an entirely different world. In the past, some of the most daunting problems involved making a perfect pen adjustment, or a recurring ink clog when no replacement pen was available.


Be aware that your choice in sleep systems will directly affect the types and sizes of required cables and conduit necessary for each room.
Some of these problems could even cause the most patient person to utter words not suitable for print. Although most labs have long bid good riddance to these older machines, both technicians and managers now seem to pine for the annoyance of a clogged pen as they do battle with page fault errors and corrupt Internet Protocol (IP) addresses. Long gone are the days of paper reams and mechanical filters; no longer do technicians have to actually stand up in order to change a sensitivity setting and in the dawn of this digital era, the towering devices that were once the epitome of modern technology, have suddenly gone the way of the dinosaur.

A continual demand for more power from the software makers requires that the hardware manufacturers build machines not only capable of doing more, but also able to handle simultaneous processing tasks and larger software programs. Many sleep diagnostic systems are designed and built to take full advantage of the processing power and various storage and retrieval options available in today's PC.

If you are wondering what makes a computer into a sleep system from the kind of PC people use to surf the Internet or process data at work, the answer is simple-not much. Most computers and software are born as integral parts of each other. A home PC, a business workstation or a full-blown sleep diagnostics acquisition and evaluation network are all similar. It is the software and dedicated peripherals that make one computer a satellite tracker and another a sleep system.

Getting the right parts and having everything organized into a useful network of components is the key to a successful system. Many vendors offer turnkey setups with all the trimmings, but a budget-constrained lab may have to opt for something with a more personal touch. Recycled or scratch-built systems are gaining popularity as operating systems incorporate plug-n-play systems, and computers become more modular and easier to snap together. The hard part is locating a suitable machine that can be easily upgraded and fits the budget. For example, a 166 Megahertz (MHz) computer is not a good candidate for upgrade as it simply isn't capable of handling the task due to upgrade limitations.

So what does it take to make a good sleep system? First and foremost, it takes a good plan. Know the system required and how things will be done. Take into account future plans and changes. Study and research the devices and options available then decide what your lab needs. Many new computers are running at speeds in excess of 2 Gigahertz (GHz), but purchasing or upgrading to a machine that uses an 800-1200 MHz (800MHz-1.2 GHz) processor will easily satisfy the current software demands with room to spare.

The next subject to address is memory. Often confused with hard drive space, the available random access memory (RAM) in a computer is extremely important. RAM is the elbow room your data has and directly affects the speed and efficiency of processing. Without enough RAM, your lightning-fast processor will spend its time hurrying along only to end up waiting on other data to move out of the way.


Many sleep diagnostic systems are designed and built to take full advantage of the processing power and various storage and retrieval options available in today's PC.
Errors also are more apt to be generated due to increased swapping of data in and out of a small space. While most computers come equipped with 128 Mb (megabytes) of RAM, specifying 256Mb for a sleep system is a better choice, with 512 Mb satisfying almost any need.

Once the data has enough room to romp, it also must have a place to subsist when not being used. This is where disk drives come into play. Several types exist for many different uses, such as the compact disk, read and write or CD-burner, (CD-RW) the compact disk, read-only memory CD-ROM, the 3.5 inch floppy disk drive (FDD) and the hard disk drive (HDD). Other types such as optical drives, tape drives and ZIP drives are available but they have long lost ground to the CD-RW, and the CD-RW is losing ground to the new kid on the block, the digital versatile disk (DVD) and the DVD-Recorder. To be practical, a system should at least include a CD-ROM, FDD and HDD. Despite the many types and styles, all drives serve the singular purpose of storing programs, data or patient records for the long haul.

Aside from any built-in data, the sleep software, applications and patient data are stored on the hard drive. If the processor is the heart of a system, the hard drive is its soul. It is where all the information and instructions reside. When called upon, the data is copied to RAM where it is processed, and just like RAM, the hard drive needs to be both large and fast enough to complete the necessary tasks efficiently. Criteria for a hard drive must account for the size of the operating system or OS, (for example, Windows, Linux,) the diagnostic software, database software and any other necessary applications. Once the needed space is calculated, simply purchase or order a drive that fits your needs. Quality new systems usually have a 7200-RPM, 40 Gb drive; plenty of room for both sleep and operating systems, plus space for a backlog of patient records waiting scoring and archival. However, it can be considered more beneficial and safer to set up systems with two hard drives in the same computer. One drive can be a small 6Gb drive that contains the OS and diagnostic software while a second 40-60 Gb drive is reserved solely for patient data and backups. With a dual-drive format, OS or diagnostic system crashes lessen the chance of compromised patient data waiting to be transferred to yet another drive for long-term storage.

Archival of data can be achieved in a few different ways but the sleep community appears to lean towards the CD-RW. These drives are cheap and effective for storing PSG data on a CD for a single patient or an entire week. Available in many speeds and styles, the CD-RW can pull double duty as both a CD-ROM and a burner if necessary. Lately, drive ratings have gone beyond 36 by 12 by 40, meaning a 36-speed writer, 12-speed re-writer and 40-speed CD-ROM capabilities, but these drives are expensive. A good choice that will keep costs minimal and speeds acceptable is a 24 by 10 by 32. That roughly translates to 15 minutes burn time for a $90 drive versus five minutes burn time for a $180 drive. Compact discs are cheap enough in bulk that studies can be held on a large hard drive, archived once per week and burned individually for inclusion in each patient's chart. Once hardware decisions are made, the computer is then ordered and assembled, the software is installed and the final concerns of making it all work together with other computers and devices are addressed.

Networking is a word that elicits many different responses from people. Either loved or hated, it has become a necessary addition to the modern lab. Efficiency is the driving force behind the local area network or LAN, and PSG collection computers must be equipped with a network interface card (NIC) in order to communicate with each other in a peer-to-peer format. Using a device called a hub, repeater or LAN adapter, the connected computers are aware of each other, making it possible to share devices and manipulate or transfer data from one system to another. This translates to efficiency and money saved if the budget is tight. Networked computers can share a single printer for PSG reports and even share a CD burner for archival. A four-bed lab doesn't need four CD burners when two will suffice as a primary drive with backup redundancy. Another idea would be to maintain a single 80-100 Gb HDD in one of the computers where PSGs and patient information are copied daily from all computers, giving a double-redundancy that significantly reduces the chance of lost data. Maintaining a large disk in that fashion also offers the added benefit of having a few months of PSGs readily available for viewing without having to search for an archival disk. Networking also gives the physician the option of having a single, dedicated review computer in a separate room that either has access to each data collecting system or it is the computer where the large redundant drive resides.

Finally, the peripherals or accessories are added. Peripherals include everything from the keyboard and mouse to the monitor and the vendor's amplifier or DC devices. While keyboards and mice speak for themselves, it is the monitor that sometimes falls short. There is a lot of information to display when running a PSG and the more space there is, the better the viewing quality, and to some extent, the better the completed study. It is sometimes easier to see small EEG changes or pick out upper airway resistance on a larger screen. Some people may prefer 21-inch varieties while a 19-inch will do a good job, and now you are only one step away from having a complete sleep system.

Digital sleep systems and equipment can vary from single, self-contained units to amplifier-only setups. Whichever your preference, they are usually connected and configured by the vendor during a setup and training period. Some sleep systems may offer a built-in pulse oximeter or other device while others require separate units. Pulse oximeters, PAP units and End-Tidal CO2 monitors are referred to as direct current (DC) devices because they use small DC voltages to pass information to the computer. Usually the voltage changes are sent to a vendor's DC expansion box where they are converted to data useable by the PSG software and displayed on the screen. The DC expansion boxes will connect to the computer via the common serial and parallel ports, but others may require the addition of a small computer system interface port, which can be arranged through the vendor or done on your own. Also be aware that your choice in sleep systems will directly affect the types and sizes of required cables and conduit necessary for each room. From this point, the cables are run and the DC devices connected. Simply configure the software, plug in the amplifiers and a sleep system is at last born.

It is obvious that sleep systems have made a quantum leap from what was to what is, but replacing the old and familiar with the new and ever-changing can sometimes wreak havoc with decision-making progression, especially when trying to settle on a particular sleep system or certain computer options. There is so much to choose from and so many ways to build a system that it can become quite overwhelming. Take time to carefully plan each need and every want while keeping the prospect of cost or future upgrades in mind. Research sleep software vendors and the hardware they offer as compared to acquiring or building your own computer, and arm yourself with the most feared weapon, knowledge. So when it comes time to part with your cash, if you have made the commitment to getting the facts and aren't afraid to get your hands dirty, you will not only save money but you also may get a deal.

This article originally appeared in the May 2002 issue of HME Business.

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