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Accuracy of Spirometry (Part 1)

Several years ago when I had my first spirometry I recall really struggling to keep blowing as long as I was being instructed to blow. Last June I had another spirometry so when I blew, I blew at a much more even pace rather than blowing as hard as I could right from the start and just wondered how this might affect the results?
I wasn't aware of the importance of the first second of breath until I started doing some research on the internet, so now am wondering if I had blown as hard as I could right from the start of the test is it likely my FEV1 would have been higher? Here are the results of the PFT. This PFT was taken a 6 weeks before I finally quit smoking.
I am a 60 year old Caucasian male 71.5 inches tall and weighing 166 pounds and smoked a pack a day for 42 years. At that time I was only taking Spiriva and the most recent dose was the previous day about 8 PM.
PREDICTED - PRE DRUG REPORTED - % OF PREDICTED
FVC     4.71 – 4.03 – 86%
FEV1    3.77 – 2.52 – 67%
FEV1/FVC    80 – 63 – 78%
FEV3    4.30 – 3.52 – 82%
PEF   8.92 – 5.19 – 58%
Since quitting smoking I have purchased a hand held electronic meter that measures PEF and FEV1, and have to say that the readings vary dramatically. I appreciate that this meter is nowhere near as accurate as a spirometer but most of my FEV1 readings are in the 1.85-2.25 range and have only had a very few that were in the 2.40-2.50 range, which are all well below the FEV1 shown on the spirometry shown above.

As I have now gone over the character limit please see part 2 of this post.
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242587 tn?1355424110
MEDICAL PROFESSIONAL
You ask, “if I had blown as hard as I could right from the start of the test is it likely my FEV1 would have been higher?”  Three factors come into play.  First, the effort must be forceful but smooth; not a sudden “grunting” of air.  Second- with proper technique there is an upper limit to air flow, beyond which further effort does not heighten flow and may actually distort overall (7-8 second) flow.  Another way to put this is that optimum effort should cause a perceived smoothness of flow rather than a bearing-down jerkiness of flow.  So the answer to your question is, maybe.

You state that, “most of my FEV1 readings are in the 1.85-2.25 range and have only had a very few that were in the 2.40-2.50 range, which are all well below the FEV1 shown on the spirometry shown above.”  That is not quite the case even if you weren’t having a very good day on the day of the Spirometry.  That is because for all practical purposes normal variation in flow rate can vary more than you might expect on a day to day basis, 2.25 -2.50 being very common;  2.10-2.50, less common but still within the range of normality, and thus your home device measurements may be reasonably accurate.

Even if Spirometry reflects the true state of affairs, the key for monitoring is to establish your personal best on your device and interpret the significance of subsequent measurements on that device with your established personal best.

You should also discuss your questions with your lung specialist.

Good luck
Helpful - 1
Avatar universal
Thank you very much.
Helpful - 0

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