The measurement allows one to quickly and easily assess patency of the upper airway and the ability to force air through the vocal cords. If the pressures are elevated, greater than 10 cm of water on inhalation phase and 30cm of water on the exhalation phase, it would indicate an obstruction in the upper part of the trachea (i.e. subglottic stenosis). The pressures can also evaluate respiratory function prior to considering patients for placement of the valve.