Less than a few months from now the new AASM Recommendations for standardization in methodology will take effect. The recommendations apply to all sleep facilities that are either accredited or applying for accreditation. Sleep facilities will be expected to use the same types of equipment and rules for scoring various events and staging sleep studies. These recommendations will standardize procedures so that patients can expect to receive the same quality of polysomnography at all accredited facilities. The recommendations also will make it easier for a technologist to transfer skills from one laboratory to another.
Polysomnography systems purchased after July 1, 2008 must satisfy new filtering and sampling standards. Given that new techniques are constantly being refined and introduced, aspects of the Technical and Digital Specifications are expected to undergo additional fine-tuning on an ongoing basis. Papers outlining the evidence behind the rules in the AASM manual were published in the March 2007 issue of the Journal of Clinical Sleep Medicine (Vol. 3, No. 2).
The Visual Rules have changed the names of some electrode placements and added more electrode sites. The inclusion of frontal electrodes was based on evidence that K complexes and slow waves are expressed maximally in the frontal region, spindles are central and alpha rhythm is more over the occipital region. The Movement Rules have established that periodic limb movements will be measured by changes in muscle tone through the use of an EMG and not through the use of piezo crystal-based vibration sensors. The goal is accuracy by measuring muscle tone directly.
The Respiratory Rules encompass the guidelines that are likely to result in the most changes for the testing facility:
- Respiratory effort must be measured by Respiratory Inductance Plethysmography (RIP) technology belts. The aim is to increase accuracy through the use of more accurate sensors. RIP technology uses a wire through the belt that extends the entire circumference of the chest and abdomen providing a superior and quantifiable signal. Piezo belts had a sensor that was from half an inch to three inches long, covering little of the patientâ€™s body. These belts measured the amount of â€œpullâ€ on them and produced an analogous signal. Improperly fit piezo belts could lose signal when the patient changed to a side position and also in situations in which the patient possesses a smaller chest circumference. Additionally, piezo belts could shift and produce false paradoxing signals, also called a sudden polarity shift in the belt signal.
- Airflow will now be measured by two devices concurrently. This is designed to ensure greater accuracy by using an oral-nasal thermal device and a nasal pressure cannula. The oral-nasal thermal device is used in detecting apneas and the pressure cannula is used for detecting hypopneas. Acombination of these two sensors is important, not only for the detection of hypopneas with nasal breathing, but also because the thermal sensor is more reliable than the nasal pressure cannula when oral breathing predominates.
- Alveolar hypoventilation in children is to be measured by transcutaneous or end-tidal CO2 (EtCO2) monitors. Yet, to monitor for hypopneic events one still needs a pressure transducer and a thermal device for apneas, making for three different devices to monitor three different parameters. There are cannulas made for monitoring both pressure and EtCO2 parameters. Most of these have been adapted from measuring CO2 and administering O2; some were designed specifically for EtCO2 and pressure monitoring.
The technical and digital recommendations may, in some cases, require updates from your data acquisition system manufacturer. You will need to be aware of how, and when, your manufacturer will have these changes ready for you. The Movement Rules will require new electrodes for those who have been using piezo-based movement sensors and resetting of the montages to reflect this change. The Respiratory Rules may be the most costly to introduce as:
- Most facilities have been using piezo effort bands and now must buy all new and different RIP belt technology.
- Thermal flow devices and pressure cannulas will need to be used.
- Pediatric studies now require pressure and EtCO2 monitoring.
Sleep facilities that have been keeping up with technological advances should only have to introduce a few changes. The rule changes can be implemented by adjusting how your facility performs these individual processes which can be done through a gradual phase-in procedure.
Getting ready for the new rules and technical specifications will take time, money, and planning.
July 2008 is not far away. Are you ready for it?
Rick Swanson, RPSGT, CRTT
Pro-Tech, a Respironics Company, Mukilteo, WA