Hypnos News: Sleep Diagnostics

Here is more in depth information about the sleep diagnostic tests and equipment we run at the ACCQ Sleep Labs.

diagnostic

Sleep Diagnostic info at ACCQ SLEEP LABS

Sleep diagnostic testing is available at the ACCQ SLEEP LABS seven nights a week. Sleep testing is also performed during the day – Monday through Friday. Testing will generally coincide with your patient's normal sleep hours. Sleep studies are performed to evaluate snoring, breathing, arousals, movements, and certain behaviors during sleep. In addition, studies are performed to assess sleepiness or one's ability to stay awake.

Types of Sleep Studies:

Polysomnography (EEG, EOG, EMG, ECG, Airflow, Respiratory Effort, O2 Sat, and Co2) Polysomnography with Positive Airway Pressure Multiple Sleep Latency Test (MSLT) Maintenance of Wakefulness Test (MWT) – a test performed usually on transportation professionals to assess efficacy of therapy. During any sleep study, the registered sleep technologist stages sleep and then is scored by a scoring technician. When the sleep test is completed, the sleep physician can review "scored" raw data and have a sleep report ready for interpretation. This type of efficiency allows the sleep physician to follow up quickly with the patient and establish a diagnosis and treatment plan. This also means that the referring physician will receive a report in a timely manner.

Sleep Disorder Titration Diagnostic Equipment

ACCQ SLEEP LABS has a full suite of titration equipment including CPAP, BiPAP, and Adaptive Servo Ventilation.

Continuous pressure devices - CPAP (Continuous Positive Airway Pressure)

Obstructive sleep apnea occurs when the upper airway becomes narrow as the muscles relax naturally during sleep. This reduces oxygen in the blood and causes arousal from sleep. The CPAP machine stops this phenomenon by delivering a stream of pressurized air via a hose to a nasal pillow, nose mask or full-face mask, splinting the airway (keeping it open under air pressure) so that unobstructed breathing becomes possible, reducing and/or preventing apneas and hypopneas. It is important to understand, however, that it is the air pressure, and not the movement of the air, that prevents the apneas. When the machine is turned on, but prior to the mask being placed on the head,mask a flow of air comes through the mask. After the mask is placed on the head, it is sealed to the face and the air stops flowing. At this point, it is only the air pressure that accomplishes the desired result. This has the additional benefit of reducing or eliminating the extremely loud snoring that sometimes accompanies sleep apnea.

The CPAP machine blows air at a prescribed pressure (also called the titrated pressure). The necessary pressure is usually determined by a sleep physician after review of a study supervised by a sleep technician during an overnight study (polysomnography) in a sleep laboratory. The titrated pressure is the pressure of air at which most (if not all) apneas and hypopneas have been eliminated and sleep quality improved. It is usually measured in centimeters of water (cm H2O). The pressure required by most patients with sleep apnea ranges between 6 and 14 cm H2O. A typical CPAP machine can deliver pressures between 4 and 20 cm H2O. More specialized units can deliver pressures up to 25 or 30 cm H2O.

CPAP treatment can be highly effective in treatment of obstructive sleep apnea. For some patients, the improvement in the quality of sleep and quality of life due to CPAP treatment will be noticed after a single night's use. Often, the patient's sleep partner also benefits from markedly improved sleep quality, due to the amelioration of the patient's loud snoring.

Given that sleep apnea is a chronic health issue and doesn't go away, ongoing care is needed to maintain CPAP therapy. Based on the study of cognitive behavioral therapy (referenced above), ongoing chronic care management is the best way to help patients continue therapy by educating them on the health risks of sleep apnea and providing motivation and support.

Bi-level pressure devices – BiPAP

BiPAP(Bi-level Positive Airway Pressure) provides two levels of pressure: Inspiratory Positive Airway Pressure (IPAP) and a lower Expiratory Positive Airway Pressure (EPAP) for easier exhalation. (Some people use the term BPAP to parallel the terms APAP and CPAP.)

Modes:

S (Spontaneous) - In spontaneous mode the device triggers IPAP when flow sensors detect spontaneous inspiratory effort and then cycles back to EPAP.

T (Timed) - In timed mode the IPAP/EPAP cycling is purely machine-triggered, at a set rate, typically expressed in breaths per minute (BPM).

S/T (Spontaneous/Timed) - Like spontaneous mode, the device triggers to IPAP on patient inspiratory effort. But in spontaneous/timed mode a "backup" rate is also set to ensure that patients still receives a minimum number of breaths per minute if they fail to breathe spontaneously.

What is BiPAP used for?

A BiPAP unit is very similar to a CPAP unit in terms of look and size. As mentioned above, the main difference between a CPAP and a BiPAP machine is that a BiPAP unit delivers two different pressures – one pressure for inspiration and a second lower pressure for expiration. By providing the patient with these two pressures, it reduces the work of breathing (which results in higher than normal carbon dioxide levels) for patients suffering from conditions such as COPD, neuromuscular disorders, restrictive disorders (ie. Kyphoscoliosis) and obesity hypoventilation, to name a few. It does so by assisting the patient with a high pressure upon inspiration and then dropping the pressure to allow the patient to exhale easier. BiPAP can also be used in situations where a patient is having a difficult time adjusting to high CPAP pressures (> 15 cm H2O).

End-Tidal CO2 Monitoring within the Sleep Lab

The sleep lab presents a unique opportunity to measure CO2 (carbon dioxide) concentrations against the stages of sleep. Respiration is often compromised during sleep, most notably in REM (rapid eye movement) sleep.

End-tidal CO2 monitoring is a noninvasive technique used to directly monitor the concentration of CO2 in respiratory gases at the end of expiration. The result is an indirect representation of arterial CO2 concentration. Monitoring CO2 levels during sleep is particularly important for patients with conditions presenting increased CO2 levels, such as:

  • obesity hypoventilation
  • COPD (chronic obstructive pulmonary disease)
  • restrictive diseases, such as kyphoscoliosis
  • neuromuscular diseases, such as ALS (amyotrophic lateral sclerosis)

CO2 retention occurs when not enough CO2 is removed by the lungs. Elevated arterial CO2 levels can result in reduced respiratory effort, a reduced level of consciousness, and a rapid heart rate (tachycardia). Severely elevated CO2 levels can lead to respiratory arrest.

Elevated CO2 levels during sleep can be better controlled with Bi-level positive airway pressure therapy. Bi-level is a therapy prescribed by the sleep lab that reduces the work-of-breathing, thus reducing arterial CO2 concentration. Bi-level titrations are most successful when completed in conjunction with CO2 monitoring, allowing the patients work-of-breathing to be monitored.

What is Adaptive Servo Ventilation Used for?

An adaptive servo-ventilator is designed specifically to treat central sleep apnea (CSA) in all its forms, including complex and mixed sleep apnea. Unlike conventional sleep-disordered breathing (SDB) therapies such as continuous positive airway pressure (CPAP), adaptive servo-ventilation:

  • treats complex sleep apnea syndrome and central sleep apnea
  • normalizes breathing, completely suppressing CSA and/or Cheyne-Stokes respiration (CSR)
  • improves sleep architecture (the amount of time the patient spends in slow-wave and REM sleep increases).

Peer-reviewed literature shows that adaptive servo-ventilation enhances quality of life for patients with CSA.

handback to top