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Flashcards in volume flow loop Deck (15):

flow volume loop

flow volume loop consist of forced expiatory maneuver followed expiratory maneuver followed by forced inspiratory maneuver
volume is on x-axis
flow is on y-axis


volume calibration

one cm equal 1 liter
one volt equals 1 liter


flow calibration

two cm equals 2 l/sec
one volt equals 2 l/sec


FEF max

peak of expiratory curve


FIF max

peak of inspiratory curve


FEF and FIF fir 25, 50, 75%

at the flow rate measured at 25,50,75 points on expiatory and inspiratory curve



the volume measure from the beginning to end of the expiatory curve


Tidal volume

the volume measured from the repeated tracing at one end of FVC curve


restrictive changee

the volumes are decreased which result a skinny loop


obstructive changes

peak flow maybe decreased or same
the expiratory portion of the curve flattens toward the volume axis this is called scooped appearance


fixed large airway obstruction

flow is limited during both expiration and inspiration
this causes the flow volume curve to flatten both the exp. and insp. portion of flow loop
causes: tracheal stenosis


Variable intrathoracic obstruction

dynamic compression of the airway during expiration and dilation of the airway
the increase intrathoracic pressure during expiration causes airway to collapse and during inspiration the negative intrapleural pressure cause airway to expand
and flow volume curve is flat during expr. and normal during inspr.
causes: tracheomalacia
tumors in the lower trachea


variable extrathoracic obstruction

dynamic compr. of the airway during inspr.
neg. intrapleural pressure tend to collapse the airway during insp.
the positive intrapleural press. during force exhalation dilate the airway
the flow volume curve is normal in expiration phase and flattened in inspiratory
causes: croup
vocal cord paralysis
acute epiglottis
adenotonsillar hypertrophy


post-bronchodialator change

air flow limitation diminishes and improving the scooped appearance of an obstructive tracing
PEF increase


poor effort identification

poor reproducibility
flow rates are lower at high lung volumes
flat expiratory portion of the curve