Final answer:
In fixed upper airway obstruction, such as laryngeal edema, the flow-volume loop shows a characteristic pattern of decreased inspiratory and expiratory flow rates. The loop becomes asymmetrical, indicating a narrowed upper airway and restricted airflow.
Step-by-step explanation:
In fixed upper airway obstruction, such as laryngeal edema, the flow-volume loop shows a characteristic pattern. The flow-volume loop graphically represents how air flows in and out of the lungs during breathing. In the case of fixed upper airway obstruction, the loop shows a decrease in both the inspiratory and expiratory flow rates.
Normally, the inspiratory and expiratory flows are symmetrical on the flow-volume loop. However, in fixed upper airway obstruction, the loop becomes asymmetrical with decreased inspiratory and expiratory flows, especially during the midportion of the forced vital capacity (FVC).
This pattern is indicative of a narrowed upper airway, which restricts the airflow. The reduced flow rates during inspiration and expiration are consistent with the obstruction caused by laryngeal edema or any other condition affecting the upper airway.