Signs and Symptoms of Obstructive Sleep Apnea and Upper Airway Resistance Syndrome

2.1.1

Snoring

Snoring is a fluttering sound created by the vibrations of pharyngeal tissues during sleep, which is a ubiquitous complaint of bed partners worldwide and leads to many patient requests for treatment recommendations. Most authors support a continuum of snoring from simple snoring through upper airway resistance syndrome (UARS) and to various degrees of OSA. Patients who snore but have an AHI <5 tend to be classified as primary or habitual snorers, but may fall in the category of UARS patients. Although the prevalence of snoring varies between studies because of its highly subjective nature, its prevalence has been reported as 5% to 78% in males and 2% to 59% in females. The gender difference is perhaps not surprising given that being male is one of the risk factors for snoring. This is highlighted in one of the few meta-analyses in the epidemiology of snoring. In addition to gender, sleep positions affect snoring such that supine positions are associated with more snoring and apneas than lateral sleeping positions.

2.1.2

Witnessed Apneas and Nocturnal Choking/Gasping

Witnessed apneas and nocturnal choking are related to apneic events and are the second most common nocturnal symptom reported in OSA. Up to 75% of OSA patients' bed partners report witnessed apneas. Patients themselves are rarely aware of the apneas. Nocturnal choking or gasping, sometimes described by patients as a sensation of suffocation, has been observed in 18% to 31% of patients with OSA. These episodes typically occur with arousals, are associated with feelings of panic and anxiety, and generally subside within a few seconds. During apneas or hypopneas, greater negative intrathoracic pressures are generated as patients increase their inspiration efforts to overcome the upper airway obstruction. This increases venous return to the heart and thus elevates pulmonary capillary wedge pressure, which produces the sensation of dyspnea. Nocturnal choking or gasping is the more reliable indicator of OSA compared with snoring. However, choking or gasping from OSA must be differentiated from other causes of nocturnal breathlessness such as gastroesophageal reflux (GER) paroxysmal nocturnal dyspnea in patients with left ventricular failure, nocturnal asthma, or Cheyne–Stokes respiration ( Table 2.2 ).

2.1.3

Sleep Bruxism

Sleep bruxism is defined as a stereotyped movement disorder occurring during sleep and is characterized by teeth grinding and clenching, which is also a common finding in OSA patients. There is a positive correlation between the frequency of OSA and sleep bruxism events in OSA patients.

However, sleep bruxism is not directly dependent on apneic episodes but rather seems to be related to sleep disruption and arousal, which is influenced by sympathetic/parasympathetic fluctuations during sleep. It was observed that there is a rise in autonomic sympathetic cardiac activity before bruxism with increasing brain activity, heart rate, suprahyoid muscle tone, amplitude of respiration, and masseter and temporalis muscle activity. The bruxism episodes are followed by activation of the parasympathetic system with bradycardia, hypersalivation, and increased patency of the upper airways. It is also known that due to arousals and hypoxia, the sympathetic nervous system is activated. It is possible that sleep bruxism is part of the arousal process in which respiratory disturbances, leading to sleep fragmentation and arousals, trigger the muscles of the masticatory organ to restore normal breathing. Continuous positive airway pressure (CPAP) alone could eliminate sleep bruxism episodes in OSA patients whose episodes parallel arousal responses. Because the presence of sleep bruxism could represent a contraindication for the use of oral appliances in the treatment of OSA, CPAP treatment may be preferred.

2.1.4

Gastroesophageal Reflux

The prevalence of GER has been reported in 58% to 62% of patients with OSA. However, GER and OSA share several risk factors, which are both confounded by obesity. Apneas may increase respiratory effort, thereby increasing transdiaphragmatic pressure and decreasing intrathoracic pressure, eventually facilitating the retrograde movement of the gastric contents into the esophagus. However, some studies have failed to show a significant relationship between GER and OSA. Although the relationship between the two is not clear, treatment of OSA has been shown to improve GER, and CPAP has been demonstrated to reduce the total 24-hour esophageal acid contact time.