Tests of Upper Airway Function

The upper airway is surrounded by skeletal muscles that exhibit respiratory-related activity (Figures 1 and 2) (1-4). The mechanical effects of respiratory-related upper airway muscle activation are very different from those of the respiratory pump muscles. Laryngeal muscles regulate the size of the valvelike glottic aperture. Loss of innervation to the intrinsic laryngeal muscles can cause stridor leading to respiratory arrest. Pharyngeal muscles stiffen and dilate this potentially collapsible segment of the upper airway. Changes in upper airway muscle activity can alter upper airway caliber and thereby influence the mechanical effects of respiratory pump muscle activation. Motor output to upper airway muscles is state dependent. The suppression of upper airway muscle activity during sleep is felt to play an important role in the pharyngeal airway closure during sleep in patients with obstructive sleep apnea. Electromyography, measurements of upper airway resistance, and upper airway imaging can be used to directly or indirectly evaluate upper airway muscles. Specific tests are of use in the clinical evaluation of specific disorders such as ex-trathoracic airway obstruction and stridor. Evaluation of the upper airway in the awake patient with obstructive sleep apnea (OSA) can identify the presence of anatomic abnormalities; however, upper airway evaluation during wakefulness is of limited value in determining airway function during sleep.

Sleep Apnea

Sleep Apnea

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