A pulmonary function test visualization that plots airflow rate (L/s) against lung volume (L) during forced expiration and inspiration, forming a characteristic loop shape. The expiratory limb rises sharply to Peak Expiratory Flow (PEF) then declines, while the inspiratory limb forms a more symmetric curve below the x-axis. This plot is essential for diagnosing obstructive and restrictive lung diseases by comparing measured loops against predicted normal values.
