ABSTRACT
Obstructive sleep apnea (OSA) is characterized by repetitive partial or complete collapse of the upper airway during sleep. Apnea and hypopnea during sleep increase the risk of cardiovascular disease, hypertension, arrhythmias, and myocardial infarction, as well as cerebrovascular disease; OSA is considered a public health problem that requires attention because it can lead to motor vehicle and public transportation accidents.
OSA is more prevalent in men than in women, and its prevalence increases in both genders with aging, independent of body weight. Computed tomography scan studies radiographically evaluated the upper airway in prepubertal and postpubertal boys and girls. The studies found equivalent lengths in prepubertal girls and boys, but the mean airway length was greater in postpubertal boys than in girls.
In both genders, OSA prevalence increases with age. Several reports found that the pharyngeal closing pressure in healthy subjects increased with age, independent of sex or BMI. The airway cross-sectional area or volume is actually larger in men than in women.
Another dynamic change of the pharynx is the liquid surface tension that has been linked with OSA. Some investigators found minimal difference in surface tension and in pharyngeal collapsibility. The clinical implications of these findings remain unclear.
Evidence suggests that patients with OSA may have diminished neuromuscular responses to maintain upper airway potency.
HISTORY
Surgical History
Surgical history especially in relation to tonsillectomy with/without adenoidectomy, septoplasty, or another surgery from segment of the upper airway, is required.2
Sleep Hygiene
The sleep environment, temperature, light and sound exposure, and the bed can help address a patient's sleep complaints. Activities prior to bedtime must also be discussed.
Ingestions (food, caffeine, alcohol, sedatives medications, and tobacco) close to bedtime can have varied effects on sleep, reducing neuromuscular control of the upper airway during sleep.
Stimulating activities prior to bedtime, such as exercise, television watching, reading, working, and music listening (rock and roll, heavy metal, and rap), can all affect sleep quality.
Bedtime rituals (i.e., clothing worn to sleep, etc.) can also affect sleep quality.
The schedule abnormalities in wake and sleep times are more common sleep disorders (i.e. insomnia and circadian rhythm disorders) and may suggest the presence of other disorders of sleep, such as sleep deprivation—chronic or acute.
It is important to know the features (e.g. diary, 2–3 times a week) and the length of the nap.
The occupation of the patient, driving performances, and possible night-working habits are important questions related to sleep quality.
Excessive Daytime Sleepiness
Excessive daytime sleepiness (EDS) is very common; it is a challenging symptom because of a significant overlap with features of fatigue. Sleepiness is the tendency to fall asleep; it may occur more often during inactive conditions, such as watching television or sitting as a passenger in a car.
Several instruments have been developed to identify and measure symptoms of EDS. The Epworth sleepiness scale is the most useful instrument. It is a list of eight questions that measure the propensity to sleep in familiar situations. The cuff point is >10 for the EDS.
Snoring
Snoring is a sound produced by the vibrating structures of the upper airway. During the anamnesis, knowing if snoring occurs or not, in body position lying on the side versus on the back, duration, intensity, and associated features, is a major problem that is very important for the patient himself/herself, for his/her bed partner, or for other people.
Witnessed Apneas
The prevalence of witnessed apneas in the general adult population ranges from 3.8% to 6%. Sleep clinic-based studies have all demonstrated a strong relationship between sleep apnea and witnessed apneas.3
Sleep Paralysis
Sleep paralysis is a transient, generalized inability to move or to speak during the transition between sleep and wakefulness.
Movements during Sleep
The most important entities are restless leg syndrome (RLS), periodic limb movement disorder (PLMD), and parasomnias.
RLS is characterized by an irresistible urge to move the legs and is usually accompanied by uncomfortable and unpleasant sensations in the legs.
Periodic limb movements during sleep are manifested by kicking or jerking leg movements at night, but can also affect the arms.
Impact on Daytime Functioning
Irritability, mood swings, hyperactivity, automatic behaviors, work performance, behavior of concern (inattentiveness), and absences from work or school are the most prevalent cognitive manifestations in patients with obstructive sleep apnea (OSA).
CLINICAL PREDICTORS
The goal of screening is to detect a risk factor or disease at an early stage.
The clinical prediction models would arise in an effort to diagnose OSA. An ideal clinical evaluation method would be predictive of the site or the sites of upper airway obstruction.
Clinical evaluation is subjective and fiberoptic endoscopy for physical examination is usually performed with subjects awake or falling asleep, which are not true sleep conditions. For these reasons, it is difficult to identify largely accepted predictive value patients who may benefit from surgery.
OSA is characterized by loud snoring, witnessed apneas, disturbed nocturnal sleep, daytime sleepiness, and impaired cognition, and is associated with obesity and a large neck size.
A number of predictive models, based on the different combinations of witnessed apneas, snoring, BMI, age, sex, and hypertension, were developed and validated in patients in sleep.
Pharyngeal and craniofacial morphology play an important role in the etiology of sleep apnea.
One measure used in the assessment is the Mallampati score; two other pharyngeal measurements that were independently associated with sleep apnea are tonsillar enlargement and lateral narrowing of the pharyngeal wall. Other potentially useful pharyngeal measures include tongue size, uvula size, and palatal height.
Retrognathia, micrognathia are characteristics that are associated with a restricted posterior pharynx also belong to craniofacial abnormalities, most frequently associated with OSA.4
However, the occurrence of OSA is far more prevalent than can be handled by the available sleep laboratories.
Therefore, an assessment tool is necessary to stratify patients according to their clinical symptoms, physical examination, and their risk factors in order to identify patients at high-risk or low-risk to determine the need for polysomnography (PSG) or portable monitoring (PM).
LABORATORY DIAGNOSIS OF SLEEP APNEA
According to the American Academy of Sleep Medicine (AASM), the PSG is gold standard for diagnosis. Type 1 is considered to be performed in a sleep with an expert technical assistance in PSG. Standard PSG involves recordings of sleep-related electroencephalography (EEG), electromyography (EMG) of the chin and leg muscles, electrooculography (EOG), and electrocardiography (ECG), and measuring oxygen saturation, respiratory effort and airflow (nasal pressure and oronasal thermistor), and transcutaneous CO2, snoring sensor, and body position.
The AASM published “The practice parameters for the indications for polysomnography and related procedures: An update for 2005” and made the following recommendations:
- PSG is routinely indicated for the diagnosis of sleep-related breathing disorders (SRBDs).
- Full-night PSG is recommended for the diagnosis of SRBDs.
- For patients in the high-pretest-probability stratification group, an attended cardiorespiratory (type 3) sleep study may be an acceptable alternative to full-night PSG, provided that repeat testing with full-night PSG is permitted for symptomatic patients who have a negative cardiorespiratory sleep study.
- A preoperative clinical evaluation that includes PSG or an attended cardiorespiratory (type 3) sleep study is routinely indicated to evaluate for the presence of OSA in patients before they undergo upper airway surgery for snoring or OSA.
Electroencephalography and Sleep Stage
The wake and sleep are classified into the following stages:
Wakefulness
W is defined by the presence of alpha-rhythm on the electroencephalography (EEG), train sinusoidal 8–13 Hz activity recorder over the occipital region with eye closure.
NREM
N1 is defined by the presence of low-amplitude, mixed-frequency, predominantly 4–7 Hz activity. Over the central region (EEG), it may show vertex sharp waves.5
N2 is defined by the presence of K complexes without associated arousals or one or more trains of sleep spindles.
A K complex is a well-defined biphasic wave (negative and positive component) with a total duration greater than or equal to 0.5 seconds over the frontal regions.
A sleep spindle is a train of waves with frequency 11–16 Hz, but usually 12–14 Hz, with a duration greater than or equal to 0.5 seconds over the central region.
N3 consists of slow wave activity, defined as waves of frequency 0.5–2 Hz, and amplitude greater than 75 mV recorded over the frontal regions.
REM
R includes low amplitude, mixed frequency in the EEG, and rapid eye movements (REMs) defined as conjugate, irregular, sharply peaked eye movements with an initial deflection.
Respiratory Rules
- Apneas: There is a drop in the peak signal excursion by ≥90% of pre-event baseline using an oronasal thermal sensor (recommended).The duration of the ≥90% drop in sensor signal is ≥10 seconds.
- Apnea obstructive: Occurs when apnea criteria are met and is associated with a continuous or increased inspiratory effort throughout the entire period of absent airflow.
- Apnea central: Occurs when apnea criteria are met and is associated with absent inspiratory effort throughout the entire period of absent airflow.
- Apnea mixed: Occurs when apnea criteria are met and is associated with absent effort in the initial portion of the event, followed by resumption of inspiratory effort in the second portion of the event.
- Hypopneas: There is a peak signal excursion's drop by 30% of pre-event baseline using nasal pressure (recommended).The duration of the ≥30% drop in signal excursion is ≥10 seconds and there is ≥3% oxygen desaturation from pre-event baseline or the event is associated with an arousal.Hypopneas obstructive: Occurs when any of the following criteria are met:
- Snoring during the event.
- Increased inspiratory flattening of the nasal pressure or PAP device flow signal compared to baseline breathing.
- Associated thoracoabdominal paradox occurs during the event but not during pre-event breathing.
The hypopneas central is when none of the hypopneas obstructive criteria are met (Figs 1.1 to 1.4).6
Fig. 1.1: PSG the C4-O4 channel shows alpha rhythm, which defined the epoch as stage W (Wakefulness)
Fig. 1.2: PSG the EEG channel shows low amplitude, mixed-frequency, and EOG left and right rapid eye movements defined as conjugate, irregular which defined the epoch as stage R (REM)
Fig. 1.3: PSG the EEG channels shows low amplitude, mixed-frequency, arousals, and respiratory sensor shows apneas central
Fig. 1.4: PSG the EEG and EOG channels shows stage REM, and respiratory sensor shows hypopneas obstructive
Portable Monitoring
A number of portable monitoring techniques have been developed in an attempt to simplify the ambulatory diagnosis of sleep apnea.
The PMs are divided into three categories:
- Type 2 includes a minimum of seven channels, including EEG, EOG, chin EMG, ECG or heart rate, airflow, respiratory effort, and oxygen saturation.
- Type 3 includes a minimum of four channels, including ventilation or airflow (at least two channels of respiratory movement, or respiratory movement and airflow), heart rate or ECG, and oxygen saturation.
- Type 4 measures a single parameter or two parameters.
The AASM made recommendations for the use of PMs:
- They may be used in patients with a high pretest probability moderate-to-severe OSA and they are not appropriate in patients with concomitant diseases.
- They are not appropriate for the diagnostic evaluation of OSA in patients suspected with central sleep apnea, PLMD, insomnia, parasomnias, circadian rhythm disorders, or narcolepsy, and for general screening of asymptomatic populations.
- They may be indicated to monitor the response to non-CPAP treatments for OSA, including oral appliances, upper airway surgery, and weight loss.
- PM devices must allow for the display of raw data for manual scoring or editing of automated scoring by a trained and qualified sleep technician/technologist.
Fig. 1.5: Portable monitor (PM) two channels of respiratory movement and airflow, heart rate, oxygen saturation and position
Fig. 1.6: PM the oxygen saturation channel shows desaturation curve, airflow chanel snoring, and respiratory movement curve
Fig. 1.7: PM the oxygen saturation chanel shows desaturation curve, heart rate, airflow and respiratory movement curves, and supine position
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