Flow–Volume Loop
A graphical representation of airflow (y-axis) plotted against lung volume (x-axis) during a maximal forced expiratory and inspiratory maneuver, used to characterise obstructive, restrictive, or variable airflow patterns.
Full Definition
The flow–volume loop is generated during spirometry and provides visual and quantitative information about airway mechanics that complements raw spirometric values. In children, the characteristic concave expiratory limb is associated with obstructive disorders such as asthma, while a truncated expiratory or inspiratory limb may indicate fixed or variable upper airway obstruction. Pediatric laboratories require age- and height-appropriate reference equations to interpret loop morphology. Editors must hyphenate 'flow–volume' consistently (en dash preferred per major style guides) and should not substitute 'flow/volume' or 'flow-volume' with a hyphen unless house style specifies otherwise.
Usage
Usage note: Use an en dash (–) between 'flow' and 'volume' per ATS/ERS convention. Do not use a hyphen or forward slash.
In Context
- "The flow–volume loop showed a characteristic scalloped expiratory limb, consistent with variable intrathoracic obstruction." — Pulmonary function test report
- "House style requires an en dash in 'flow–volume loop'; the copyeditor corrected the hyphen throughout the manuscript." — Copyediting note