At my clinic, my FEV1 is measured in litres rather than percentage. I've asked how to convert it, as I find it so much easier to figure it out in percent but they say its too difficult. I'm confused because almost every other clinic seems to do it in percent. Does anyone know how to convert litres to percent? PLEASE HELP!! I'd just like to compare how my progress is going now, compared to when it used to be measured as a %. Last time I had it done percentage wise it was 53, so I'd love to see if I've gotten better, worse or remained the same. Thanks!!
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FEV1
- Thread starter Milla21
- Start date
To work out the percentage you need to know what your predicted LF is in litres. then you divide what you can blow, by your predicted and X100.
(having just written that i am now having doubts....too early in the morning for maths....so feel free to correct me anyone!!) <img src="i/expressions/face-icon-small-wink.gif" border="0">
(having just written that i am now having doubts....too early in the morning for maths....so feel free to correct me anyone!!) <img src="i/expressions/face-icon-small-wink.gif" border="0">
Here's some equations to figure out your expected values. My doctor uses both the Morris source and the Knudson source. The FEV1 is obtained by dividing the actual number by the expected number and then multiply by 100. The site that I pulled these calculations from is at the bottom.
Tammy 43wcf
Morris Source
Morris JF, Koski A, and Johnson LC. Spirometric Standards for Healthy
Non-Smoking Adults. Am. Rev. of Respir. Dis. 1971; 103:57-67.
Equations
FVC = 0.1481*Height(inches) - 0.0250*Age(years) - 4.2410 [Men]
FVC = 0.1151*Height(inches) - 0.0240*Age(years) - 2.8520 [Women]
FEV1 = 0.0919*Height(inches) - 0.0320*Age(years) - 1.2600 [Men]
FEV1 = 0.0889*Height(inches) - 0.0250*Age(years) - 1.9310 [Women]
FEV1% = Predicted FEV1 / Predicted FVC
Knudson Source
Knudson, RJ, et. al. The Maximal Expiratory Flow-Volume Curve Normal Standards, Variability,
and Effects of Age. Am. Rev. Respir. Dis. 113:589-590, 1976.
Equations
FVC = 0.1270*Height(inches) + 0.0780*Age(years) - 5.508 [Young Men, Age To 24]
FVC = 0.1651*Height(inches) - 0.0290*Age(years) - 5.459 [Men, Age Greater Than 24]
FVC = 0.0838*Height(inches) + 0.0920*Age(years) - 3.469 [Young Women, Age To 19]
FVC = 0.0940*Height(inches) - 0.0220*Age(years) - 1.774 [Young Women, Age Greater Than 19]
FEV1 = 0.1168*Height(inches) + 0.0450*Age(years) - 4.808 [Young Men, Age To 24]
FEV1 = 0.1321*Height(inches) - 0.0270*Age(years) - 4.203 [Men, Age Greater Than 24]
FEV1 = 0.0686*Height(inches) + 0.0850*Age(years) - 2.703 [Young Women, Age To 19]
FEV1 = 0.0686*Height(inches) - 0.0210*Age(years) - 0.794 [Young Women, Age Greater Than 19]
FEV1% = Predicted FEV1 / Predicted FVC
http://www.hopkinsmedicine.org/pftlab/predeqns.html
Tammy 43wcf
Morris Source
Morris JF, Koski A, and Johnson LC. Spirometric Standards for Healthy
Non-Smoking Adults. Am. Rev. of Respir. Dis. 1971; 103:57-67.
Equations
FVC = 0.1481*Height(inches) - 0.0250*Age(years) - 4.2410 [Men]
FVC = 0.1151*Height(inches) - 0.0240*Age(years) - 2.8520 [Women]
FEV1 = 0.0919*Height(inches) - 0.0320*Age(years) - 1.2600 [Men]
FEV1 = 0.0889*Height(inches) - 0.0250*Age(years) - 1.9310 [Women]
FEV1% = Predicted FEV1 / Predicted FVC
Knudson Source
Knudson, RJ, et. al. The Maximal Expiratory Flow-Volume Curve Normal Standards, Variability,
and Effects of Age. Am. Rev. Respir. Dis. 113:589-590, 1976.
Equations
FVC = 0.1270*Height(inches) + 0.0780*Age(years) - 5.508 [Young Men, Age To 24]
FVC = 0.1651*Height(inches) - 0.0290*Age(years) - 5.459 [Men, Age Greater Than 24]
FVC = 0.0838*Height(inches) + 0.0920*Age(years) - 3.469 [Young Women, Age To 19]
FVC = 0.0940*Height(inches) - 0.0220*Age(years) - 1.774 [Young Women, Age Greater Than 19]
FEV1 = 0.1168*Height(inches) + 0.0450*Age(years) - 4.808 [Young Men, Age To 24]
FEV1 = 0.1321*Height(inches) - 0.0270*Age(years) - 4.203 [Men, Age Greater Than 24]
FEV1 = 0.0686*Height(inches) + 0.0850*Age(years) - 2.703 [Young Women, Age To 19]
FEV1 = 0.0686*Height(inches) - 0.0210*Age(years) - 0.794 [Young Women, Age Greater Than 19]
FEV1% = Predicted FEV1 / Predicted FVC
http://www.hopkinsmedicine.org/pftlab/predeqns.html