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Assessing Flow-Volume Loops. Spirometry tests were originally recorded by a pen trace on kymograph paper as a volume-time (VT) curve. Because the changes in the contour of a volume-time curve that occur with various lung disorders are very subtle it is a less than ideal tool for interpreting results. Flow-volume loop (FVL) contours however, are ...
Our lab software will allow us to display and print flow volume loops in only one of four sizes: 2 L x 4 L/S. 4 L x 8 L/S. 6 L x 12 L/S. 8 L x 16 L/S. There is an option that lets the software automatically select the scale but we decided to mandate the 8×16 format for all flow-volume loops. One reason we did this is that most of the pulmonary ...
Demographics Quiz. 1. If a subject’s height is mistakenly entered as being less than their actual height their predicted (reference) FEV1 will be underestimated. True. False. 2. If a subject’s developmental gender is entered as male when it should have been female, then the percent predicted FVC that is reported will be overestimated. True.
The notion that EFLt could be detected through flow-volume loops was proposed in the 1960’s but subsequent research has shown this approach to be unreliable for a variety of moderately esoteric reasons which include the differences in static lung recoil and airway resistance that occur following a deep inhalation, differences in time ...
Date: FVC(L): %Pred FVC: FEV1(L): %Pred FEV1: FEV1/FVC: %Pred TLC: %Pred DLCO:
One point is that for this kind of analysis to work is that the flow-volume loop must be a truly maximal effort but how this is determined is usually not detailed. The selection criteria in the ATS/ERS standards states that the selected spirometry effort should have the best combined FVC + FEV1.
Brings back all sorts of memories: switching to the red pen on the kymo for the post-bd effort, etc. Peak flow was a guess, being the fef200-1200, and back at the first Snowbird meeting of the ITS the 200ml was the basis of the talk about extrapolated volumes. Long ago, in a galaxy far, far away. cheers, Mike. By: Mike Mulligan
J - Well yes, but given adequate respiratory muscle strength every flow-volume loop contour is mostly a function of an individual's dynamic and occasionally unique airway geometry that occurs during exhalation.
I had to point out that the inspiratory flows on the loop in question came from the pre-FVC inspiration that started at FRC, not RV, and that we don’t emphasize maximal inspiratory flow at that point in the test, just maximal inspiratory volume and for these reasons the flow-volume loop was not a reliable indicator of inspiratory obstruction.
The reduced TLC showed a mild restrictive defect. At the same time the relatively normal DLCO indicates that the restriction is probably not due to interstitial lung disease and more likely either a chest wall or a neuromuscular disorder, both of which can prevent the thorax from expanding completely but where the lung tissue remains normal.