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Since the measurement systems were validated, conventional polysomnography (PSG) has been the "Gold Standard" for diagnosing sleep disorders, especially sleep apnea syndrome. The PSG is without doubt the most effective way to define the presence or absence of disease, but also the least operational by the complex infrastructure, that requires its use. Increased interest in sleep disorders has also resulted in an increase in demand for patients, who declare a cut in the dilated rewaiting times in the sleepunits. The need to provide urgent diagnosis is a claim shared by professionals, who have been forced to develop diagnostic alternatives, that address the weaknesses of the PSG. These alternatives are simplified by multiple teams, that monitor fewer sensors and which aim is to document or refute the diagnosis time and cost cutting.
The diagnostic methodology for the evaluation of sleep breathing disorders can be divided into different levels depending on the number of variables to be monitored. In 1994, the Practice Committee of the American Sleep Disorders Association (ASDA) identified four levels of recording for the assessment of obstructive sleep apnea. Such categorization of registry systems is still in force today, and divides the levels of sleep studies, level I: conventional polysomnography PSG monitored in the sleep laboratory, level II, PSG polysomnography unsupervised home or in hospital, level III, portable systems and respiratory polygraphy not monitored to assess a minimum of four channels, level IV which includes simplified registration systems continue for one or two parameters. According to ASDA practice parameters in the diagnosis of OSAHS are indicated level systems II, III and portable recordings as alternatives to standard PSG only in the following situations: for patients with severe clinical symptoms suggestive of OSA and polysomnography laboratory standard is not available, for patients, who have disabilities of any kind for not being able to be evaluated in the sleep laboratory studies and monitoring and evaluation of response to therapy assignment. Despite these restrictive guidelines, ambulatory systems are now widely used and proven despite the concreteness of the parameters evaluated. The simplified study limitations are mainly related to its inability to determine, if the patient is fully asleep, because they are not the monitored neurophysiological variables.
Conventional Polysomnography (PSG)
It is the main technique in the diagnosis of sleep apnea. It is the most complete test, which records simultaneously physiological, neurophysiological and respiratory variables. It is the method of choice for excellence in the diagnosis of OSAHS and it is performed in a sleep unit under the supervision of staff. It is a record to be done at night, or at the usual time of sleep, the patient is totally safe and it is easily tolerated by patients. For proper monitoring of all variables, twelve channels are required, a minimum of six hours record time including at least 180 minutes of sleep. The interpretation of polysomnographic indicators to determine sleep stages, differentiating sleep from wakefulness and detection of arousals in the electroencephalogram (considered clinically relevant when changes lasting more than 3 seconds).
Changes in EEG sleep stages identified NREM (Phase 1,2,3 and 4) and REM sleep periods of 20 or 30 seconds, that are called periods. It is useful also to place electrodes motion detectors to record the body movements during sleep (mainly the lower limbs). The records of respiratory events identified apneas and hypopneas, that combined with the awakenings and respiratory effort are the respiratory disturbance index RDI. The PSG is the gold standard for diagnosis of OSA, but not without problems. The high economic cost required in number of technical and human resources, change the PSG into a prohibitive system and difficult to get general access. This relative difficulty has been forced to seek new diagnostic alternative, simpler, which can substitute for PSG as a reference system for the diagnosis.
Polygraph Studies Home
The new methods seek to reduce the time spent on records, monitoring only specific variables and to facilitate patient access to perform this in their own homes thus avoiding troublesome journeys. The house searches are acceptable alternatives to PSG and the validity and effectiveness has been proven in numerous studies.
Respiratory polygraphy (RP)
Although conventional polysomnography remains the reference test in the diagnosis of SBD, the excessive infrastructural forces required to develop new simplified methods, that are increasingly present in medical practice. Respiratory polygraphy is the main alternative to PSG as a diagnostic technique it is supported by the regulations of the Spanish Society of Pneumology and Thoracic Surgery (SSPTS) and the American Sleep Disorders Association (ASDA).
First raised in 1974 (Holland, Dement and Raymond) it is the most versatile and complete home study with a multiple use of both units as sleep in their own homes. Cardiac and respiratory variables are monitored, while ignoring the neurophysiological ones. The advantages of RP is its simplicity and low cost and it is accepted by the medical community as a diagnostic method for the TRS. The PR does not register neurophysiological variables and it can not assess the quantity and quality of sleep. Without the total number of hours of sleep it can not be established the AHI (index of respiratory events, apneas and hypopneas, between the hours of sleep total), so the results may not be reliable. The number of apneic events is divided by the recording time in bed, that does not necessarily coincide with the actual hours of sleep of the patient. This limitation gives erroneous results of false positive, because the number of hours in bed is usually less, than the actual hours in which the patient is asleep. The PR does not give us an effective analysis like the PSG, but is very useful in cases of asymptomatic subjects with low probability of OSAHS and to exclude the diagnosis in cases of grave or severe OSAHS, where rates have distorted downwards, are sufficient to establish a clinical diagnosis.
Portable. Home Studies
The scarcity and saturation of sleep laboratories forced to seek alternative methodologies to solve an urgent need for diagnosis as a disease of high prevalence. With over two million patients with possible significant apnea, which may require treatment, professionals and the sleep units actually installed on the system, both public and private health care are insufficient to meet the integrated needs of patients. Portable PSG systems and RP permit its use and registration outside hospitals dodging the main constraint, which is the lack of hospital resources. The introduction of these manageable systems in the context of OSAHS diagnosis leads to savings in health costs and staff and alleviates of the endless waitings, that patients have to experience at the hospital sleep units. Technological advances and the different contrast studies ensure the appropriateness and validity of data obtained through these procedures at home.
Among the devices included in level IV of the American Sleep Disorders Association there are those, that monitor only one or two cardiorespiratory parameters, such as oximetry. It is a portable home system, that quantifies oxyhemoglobin saturation (SaO2) by spectrophotometer and monitors the arterial pulse. The approach varies according to authors, but some would be considered as a significant decrease in arterial oxygen saturation of between 2 and 5%. Applied to the diagnosis of OSAHS the presence of apneas and hypopneas in an indirect manner was identified by the effects, that the respiratory events on the curve of nocturnal SaO2 have. This technique records a single channel and its use is not recommended, if it is in combination with alternative records, because it can provide false-negative results 20, especially in patients with apnea, that may not lead to desaturation. You are also at risk for false positives, as in patients with COPD, cardiac gaps or neuromuscular diseases,which due to nocturnal desaturations unrelated to a blockage of the upper airway.
These terminals record oronasal flow of the patient by detecting the presence of significant respiratory events (apneas and hypopneas). Due to the recent raid on the clinical picture of these devices, their use is still not widespread and medical authorities have already ruled favorably on some of these systems, which are already approved. They represent the most interesting line of research on portable diagnostic procedures and some authors have theorized about their main advantage, "designed as expert systems, that can be handled by non-experts."
Currently on the market there are several home validated devices, among which SleepStrip, MicroMESAM and ApneaLink. The ApneaLink is the most recent validation and presents exciting possibilities. This device uses a pressure transducer connected to a nasal cannula, that detects changes in airflow. It includes software, that automatically generates a report on the apnea-hypopnea index. The main advantage is, that that data validation is performed by the professional in a simple way and the time of registration required does not exceed two hours. These features make the Apnealink is regarded as a tool for clinical diagnosis in the dental field.
The recording system of Embletta
It's a PG device fully supporting the recommendations of the American Academy of Sleep Medicine for sleep monitoring with portable devices. There are two RIP technology channels, and a nasal pressure channel and several thermistors. The Embletta is now a global standard for home sleep studies, with more than half a million worldwide. It has been designed by the American Foundation of sleep medicine for use in their pioneering study of portable monitoring systems in the diagnosis of obstructive sleep apnea. Along with its user-friendly software, the Embletta is ideal for direct measurement of sleep quality and sets the standard for diagnosing sleep breathing disorders. Embletta offers unmatched diagnostic accuracy, is compact, has a lightweight design and is easy to use. It can be adapted to a variety of clinics and online research through its adaptable connections. The variables monitored by Embletta include body position and activity, oxygen saturation, pulse, oral flow and two respiratory effort signals through XactTrace respiratory inductive plethysmograph (RIP) sensors. It is a diagnostic of the first order and can also be used to determine the effectiveness of treatment. The choice of these systems is supported by the American Academy of Sleep Medicine (AASM). In a special article in 2007 it published a guide on recommended use of the home unsupervised devices. "PM (portable monitors) can be used as alternative to polysomnography (PSG) for diagnosis of OSA in patients with high pretest probability of moderate to severe" OSA, The emergence of these simplified systems in the landscape diagnosis is very positively and valued by the medical staff as for patients, who are offered a simple and fast way of getting his diagnosis. The addition of portable systems is reflected positively in decongestion of hospital sleep units, indiscriminate access to a broader segment of the population, substantial reduction in waiting lists and restoration of quality of life of patients by shortening the time from detection to the start of the treatment of choice.