OBSTRUCTIVE SLEEP APNOEA (OSAS)
Sleep-disordered breathing (SDB) represents a spectrum of clinical disorders ranging from simple snoring to upper-airway resistance syndrome (UARS), and
OSAS. In UARS, there is increased respiratory effort required to maintain airflow during habitual snoring in the absence of OSAS. OSAS, on the other hand, is
characterized by partial or complete cessation of airflow during sleep and oxygen desaturation with the continuation of respiratory effort.
Respiratory events are recorded as either apneas or hypopneas. Apnea is defined as cessation of airflow for >10 seconds associated with at least a 70% reduction in thoraco-abdominal movement or airflow and with at least 4% oxygen desaturation, and hypopnea was defined as cessation of airflow >10 seconds associated with at least a 30% reduction in thoraco-abdominal movement or airflow and with at least 4% oxygen desaturation.
Obstructive sleep apnea (OSA) is associated with serious health consequences such as increased risk of motor vehicle accidents, stroke, neurocognitive dysfunction, insulin resistance, and a number of cardiovascular conditions— hypertension, coronary artery disease, and atrial fibrillation.It is also associated with significant decrement in quality of life measures.
Awareness of the variety of presenting complaints of patients with sleep apnea assists in timely diagnosis and treatment. The typical patient with OSA complains of excessive daytime sleepiness, snoring, and witnessed apneas. However, up to 75% of patients with OSA present with fatigue, tiredness, or lack of energy as their primary complaint rather than sleepiness.Many patients with OSA do not have a history of witnessed apneas. Younger, leaner patients and women tend to experience sleep disruptions or arousals instead of apneas during sleep.Patients may also present with cognitive complaints such as memory defects or mood disorders.
Risk factors for the diagnosis of OSA include Male gender, age >40 years, history of hypertension, smoking, alcohol use, and a family history of sleep apnea. Physical examination findings including a BMI >30, neck circumference >17 inches in men and 14.5 inches in women, tonsillar hypertrophy, and maxillomandibular anomalies, such as maxillary retrusion and retrognathia, are associated with an increased risk of OSA.
A sleep history should be should taken and includes an assessment of the degree of sleepiness that the patient is experiencing using the Epworth Sleepiness Scale (ESS). A sleep history also includes the number of hours of sleep, napping, quality of sleep, difficulty with sleep onset or sleep maintenance insomnia, and the presence of snoring or respiratory distress during sleep. The occurrence of behaviors such as sleep talking, walking, bruxism, leg movements, or dream-enacting behavior should be documented. A sleep diary may useful to identify patients with inadequate sleep time and those with significant insomnia or circadian rhythm disorders. Physical examination in the sleep patient includes height and weight with BMI, neck circumference, assessment of facial morphology, and evaluation of the nasal airway, oropharynx and hypopharynx and larynx. Flexible endoscopy in the seated and supine position can offer insight into the site of collapse of the airway.
Cine MRI provides a high resolution examination of the dynamic airway without added risk of ionizing radiation exposure. Images of the airway can be simultaneously gathered in different projections without overlap of structures as is seen with fluoroscopic studies. It is particularly helpful in evaluating children with multiple sites of obstruction.
Polysomnography (PSG) and home sleep studies
Although male gender, age, snoring, excessive daytime sleepiness, BMI, and other clinical features are associated with apnea-hypopnea index (AHI), these associations are far from predictive of OSA. Currently, polysomnography (PSG) is the gold standard for the diagnosis of apnea. Although it represents the best diagnostic tool, PSG has many limitations including inconvenience, high cost, long waiting times, limited availability, and an artificial setting. Home sleep studies have been developed to provide a simplified, cost-effective analysis of sleep-disordered breathing obtained in a more natural environment. While some home equipments have attempted to duplicate most of the parameters obtained by PSG, this remains impractical and expensive. Others have tried to make the diagnosis of OSAS based on home pulse oximetry alone. Patients who are not appropriate candidates for home sleep testing include those with moderate-to-severe pulmonary disease, congestive heart failure, or neuromuscular disease.
The AHI is the most commonly reported result in the PSG, but there are many other parameters measured within this study, which have significance in the patient with sleep disordered breathing (SDB). The presence of sustained
hypoxemia, arrhythmia, periodic breathing, or AHI>30 is strongly associated with adverse outcomes. Severely disrupted sleep, indicated by a high arousal index, frequent awakenings, or poor sleep efficiency is often seen in patients with SDB. These patients can be very symptomatic despite a low AHI or respiratory disturbance index (RDI). The sleep architecture may also be abnormal with a lack of stage N3 (slow-wave sleep) and rapid eye movement (REM) sleep. REM sleep is associated with an increase in respiratory obstructive events, thus a lack of REM may lead to an underestimation of the severity of the OSA.
Treatment and follow-up of OSAS
Treatment of OSA is indicated to reduce morbidity, mortality and to improve quality of life. In sleepy patients with OSAS, treatment of OSA has been shown to reduce motor vehicle accidents and workplace accidents.
Continuous positive airway pressure (CPAP) therapy is used as the gold standard of therapy, but it is not without significant issues. It has been estimated that as many as 50% of OSA patients for whom CPAP is initially recommended
are not using this therapy 1 year later. Positive airway pressure (PAP) therapy is the initial treatment in most patients. PAP compliance can present a barrier to adequate treatment, but with adequate provider support, compliance can be improved. Heated humidification, frequent follow-up with the prescribing
sleep center staff, and proper mask fit have been shown to increase PAP Compliance.The first month of therapy is pivotal in patient acceptance of PAP. Treatment of nasal obstruction also has a beneficial effect on PAP compliance.
Behavioral interventions including the avoidance of alcohol and muscle-relaxing sedatives should be advised in patients with OSA. In patients with positional OSA, avoidance of the supine position, although difficult to achieve, can be beneficial. Weight loss can result in significant reduction of the AHI and improvement in symptoms of OSA. A 10% loss in body weight can result in a 25% decrease in
AHI.Oral appliances are successfully used in treatment of OSA.
Surgery may be first-line treatment in patients with marked anatomic obstruction such as tonsillomegaly or patients who have rejected PAP as a treatment option.
Since the introduction of uvulopalatopharyngoplasty (UPPP) by Fujita et al5 in 1979, the surgical treatment of OSAS has evolved dramatically. Modern surgical
management of OSAS using multiple techniques, including uvulopalatoplasty (LAUP), UPPP, genioglossus advancement, hyoid suspension, tongue base reduction, and maxillomandibular advancement, has achieved a significant improvement in the surgical results. The traditional assessment of surgical success
has been based on the improvement of objective polysomnographic results.