Literature

Clinical Pearls & Morning Reports


By Carla Rothaus

Published April 10, 2019

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What is the apnea-hypopnea index (AHI)?

Persons with untreated obstructive sleep apnea have three times the risk of motor vehicle accidents as the general population. Many patients with obstructive sleep apnea are unaware that their breathing is affected and may not present to physicians for evaluation. Read the Clinical Practice article here.

Clinical Pearls

Q: What symptoms contribute to concern for obstructive sleep apnea in a patient who complains of sleepiness?

A: Obstructive sleep apnea should be considered in all patients who report sleepiness. Because chronic sleepiness is common in the general population, other findings, including loud or irregular snoring, nocturia, dry mouth on awakening, and morning headaches, support pursuing evaluation for obstructive sleep apnea. It is important to note that not every patient with obstructive sleep apnea perceives sleepiness or has been told of snoring.

Q: What are some of the potential health consequences of obstructive sleep apnea?

A: Obstructive sleep apnea is associated with an increased risk of cardiovascular disease. In addition, obstructive sleep apnea is associated with an increased risk of diabetes and glucose dysregulation, independent of obesity, as well as increased levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides and decreased levels of high-density lipoprotein cholesterol.

Morning Report Questions

Q: What is the most important risk factor for obstructive sleep apnea?

A: Risk factors for the disease are conditions that reduce the size of the resting pharynx or increase airway collapsibility. Obesity is the most important risk factor for obstructive sleep apnea. Increased adipose tissue within the tongue and pharynx compromises upper-airway dimensions and makes the airway more prone to collapse during sleep. Male sex is another important risk factor, although the scientific bases for the differences between sexes are unknown. The prevalence of obstructive sleep apnea is also substantially increased among persons with hypothyroidism or acromegaly. Increased tonsillar and adenoid tissue and certain craniofacial abnormalities (retrognathia and maxillary insufficiency) may also confer a predisposition to obstructive sleep apnea.

Q: What is the apnea-hypopnea index (AHI)?

A: Traditionally, obstructive sleep apnea has been diagnosed with the use of overnight polysomnography in a clinical sleep laboratory to measure the frequency of obstructed breathing events — apneas and hypopneas — during sleep. Obstructive apneas are defined as near-complete (>90%) cessations in airflow for more than 10 seconds in sleep, despite ventilatory effort, and hypopneas are generally defined as reductions in airflow by more than 30% with concurrent reductions in oxyhemoglobin saturation by at least 3% or arousals from sleep. Collectively, the number of apneas and hypopneas per hour of sleep is termed the apnea–hypopnea index (AHI), in which the presence of obstructive sleep apnea is defined as an AHI of 5 or more events per hour. The AHI is used to categorize disease severity; persons with an AHI of 5 to 15, 16 to 30, and more than 30 events per hour are considered to have mild, moderate, and severe obstructive sleep apnea, respectively. Currently, treatment is recommended for all patients with an AHI of 15 or more events per hour, as well as for persons with an AHI of 5 to 14 events per hour with symptoms of sleepiness, impaired cognition, mood disturbance, or insomnia or with coexisting conditions such as hypertension, ischemic heart disease, or a history of stroke.

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