**5.3. Anatomical factors**

pressure to the airway lumen. The increased negative airway pressure, decreased muscle activity, and airway lumen diameter lead to upper airway obstruction and apnea. During apnea the blood oxygen desaturation decreases, carbon dioxide saturation increases, and pH decreases. This change leads to the stimulation of central nervous system chemoreceptors, and awakening occurs to end up in apneic process. When the patient awakens, the tension of the muscles increases, which ends up in the obstruction of the upper airway. Blood oxygen saturation increases, carbon dioxide saturation decreases, pH increases, and the patient falls asleep again.

The etiology of OSAS is multifaceted. The factors that lead to OSA can change in adults and

General factors: Age, gender, obesity, alcohol consumption, sedative medicine consumption. Anatomical factors: Lesions and anatomical variations, nasal obstruction, neck circumference,

Mechanical factors: Supine position, upper airway resistance, upper airway compliance, intraluminal pressure, extraluminal pressure, thoracic caudal traction, mucosal adhesive

Neuromuscular factors: Upper airway dilator muscles, upper airway reflexes, dilator muscle,

Central factors: Hypocapnic apneic threshold, periodical breathing, arousal, and cytokines.

**1.** Age: OSA can be seen in all ages but mostly seen in middle ages. The tissue elasticity, ventilation on central, and pulmonary and cardiovascular functions decrease with age,

**2.** Gender: Men are affected more than women because of testosterone hormone inhibits respiration and men have more pharyngeal and supraglottic airway resistance than women. **3.** Obesity: There is a close correlation between obesity and apnea. Obese patients have more fat deposits around soft palate. The fat infiltration from lateral to upper airway decreases

**4.** Alcohol and sedative medicine consumption: Investigations indicate that the activity of genioglossus and tensor veli palatini muscles decreases when the patient is asleep in a supine position. Alcohol and sedative medicine consumption can exaggerate this condi-

This sleeping, apnea, awakening cycle continues during total sleep time [3, 5, 6, 8].

**5. Etiology of obstructive sleep apnea**

head and neck position, airway shape, and dimension.

pediatric and adolescent patients.

**5.1. Adult OSAS etiology**

178 Current Approaches in Orthodontics

affects, vascular factors.

and diaphragm relations.

and those factors lead to OSAS.

the airway area and leads to apnea.

tion; the airway area decreases leading to apnea.

**5.2. General factors**

