flow-volume loop interpretation quiz 2147

asthma

emphysema

restriction

variable intrathoracic obstruction

variable extrathoracic obstruction

fixed obstruction

fixed obstruction factors

variable extrathoracic obstruction causes

stridor, vocal cord paralysis, tumor, thyroid enlargement, tracheal malacia (above neck)

variable intrathoracic obstruction causes

swelling, tracheal malacia, bronchial stenosis, scarring, prolonged intubation, radiation therapy (below neck)

x-axis of flow-volume loop

volume (liters)

y-axis of flow-volume loop

flow (liters/sec)

flow-volume loop measured by

spirometry

line in flow-volume loop

flow

RV in flow-volume loop

volume left in lung after forced expiration

TLC in flow-volume loop

volume left in lung after maximal force inhalation

what happens in obstructive lung disease

expiratory curve coves in, RV increases, TLC increases, shift left because of obstruction, inspiration normal (slightly reduced), PEFR decreased

what happens in restrictive lung disease

decreased PEFR, decreased RV, decreased TLC, decreased inspiratory flow, loop shifts right. No cove because no obstruction.

what happens in fixed obstruction

decreased PEFR, increased RV, flattens both inspiratory and expiratory curve (decrease)

normal flow-volume loop

flow-volume loop improves after bronchodilator

asthma, reverse obstruction

flow-volume loop does not improve after bronchodilator

COPD, fixed obstruction