Sleep Apnea (Continued) RISK FACTORS & Diagnosis

Risk factors

Sleep apnea affects people of all ages including children. Risk factors include being male, overweight, obese, or over the age of 40; or having a large neck size (greater than 16–17 inches), enlarged tonsils, enlarged tongue, small jaw bone, gastroesophageal reflux, allergies, sinus problems, family history of sleep apnea, or deviated septum causing nasal obstruction.  Alcohol, sedatives and tranquilizers also promote sleep apnea by relaxing the throat. People who smoke have sleep apnea at three times the rate of people who have never smoked.   All the factors above may contribute to obstructive sleep apnea. Central sleep apnea is more influenced by being male, being older than 65 years, having heart disorders such as atrial fibrillation, and stroke or brain tumor. Brain tumors may hinder the brain’s ability to regulate normal breathing.

Diagnosis

The diagnosis of sleep apnea is based on the conjoint evaluation of clinical symptoms (e.g. excessive daytime sleepiness and fatigue) and of the results of a formal sleep study (polysomnography, or reduced channels home based test). The latter aims at establishing an “objective” diagnosis indicator linked to the quantity of apneic events per hour of sleep (Apnea Hypopnea Index(AHI), or Respiratory Disturbance Index (RDI)), associated to a formal threshold, above which a patient is considered as suffering from sleep apnea, and the severity of their sleep apnea can then be quantified. Mild OSA (Obstructive Sleep Apneas) ranges from 5 to 14.9 events per hour of sleep, moderate OSA falls in the range of 15–29.9 events per hour of sleep, and severe OSA would be a patient having over 30 events per hour of sleep.

Nevertheless, due to the number and variability in the actual symptoms and nature of apneic events (e.g., hypopnea vs apnea, central vs obstructive), the variability of patients’ physiologies, and the intrinsic imperfections of the experimental setups and methods, this field is opened to debate. Within this context, the definition of an apneic event depends on several factors (e.g. patient’s age) and account for this variability through a multi-criteria decision rule described in several, sometimes conflicting, guidelines.  One example of a commonly adopted definition of an apnea (for an adult) includes a minimum 10 second interval between breaths, with either a neurological arousal (a 3-second or greater shift in EEG frequency, measured at C3, C4, O1, or O2) or a blood oxygen desaturation of 3–4% or greater, or both arousal and desaturation.

Oximetry

Oximetry, which may be performed overnight in a patient’s home, is an easier alternative to formal sleep study (polysomnography). In one study, normal overnight oximetry was very sensitive and so if normal, sleep apnea was unlikely.  In addition, home oximetry may be equally effective in guiding prescription for automatically self-adjusting continuous positive airway pressure.

Screen Shot Of a Plysomnograph showing an Obstructive apneaPolysomnogram

 

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