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Lung function tests

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ok..i went to c cons on 20th decembere nd she sed she wasnt goin 2 change my meds despite numerous admission but they were goin to do more tests..she mentioned lung function tests..i sed id done spirometry b4 but she sed there were more complex tests was wondering if anybody has had these and could give me some more information

thanx

Emma

4 Replies

Hi there,

Years ago I had a series of more complete lung function tests done, which involved sitting in a small bubble-car like thing. I don't remember what all the tests were but I think some of them measured my complete breathing volume cycle and pressures in the lungs ... or something. It was all totally non-invasive so nothing to worry about. This probably doesn't help much, because I can't remember much about it (it was about 11 years ago), so maybe someone who's had the tests more recently will be able to give you more info.

Becky.

There ok its like the spirometry where you blow into aa tube but a more complex machine, some breathing in so out some deep and some normal breathing and some with a clip on your nose, but all should be non invasive so nothing to worry about but gives the doc a much wider picture of your airways. They can also give you a neb and repeat to see if theres an improvement and how much. You will not doubt have more spirometry and breathing tests as a one off isnt much help they need to see if any improvement or deterioration.

hope this puts you at ease.

love andrea xxx

Hello Me,

I’ve had quite a few PFT’s, (Pulmonary Function Tests) - the sort of tests I think your doctor wants you to have.

They are quite useful, especially when trialing new drug combination/therapies and monitoring, over time, to see if these drugs have a positive and measurable effect upon improvement in lung function

Most importantly, you need to talk through all results ( lots of numbers and abbreviations) with your doc, and make sure you BOTH understand what, - if any – ‘trends’ that may have been highlighted. Plus any sort of ‘Greek’ words (and Latin) that you might not understand. (It was all ‘Greek’ to me when I had my first PFT. LOL!)

The accuracy of these tests are dependent on a few factors - the effort of the person taking the test is a biggie (that's why they make you do it three times- to make sure it is reproducible), the equipment (is it checked regularly and has calibrations done i.e. comparing known volumes to the result from the machine), and the operator (do they use the equipment properly?, do they coach you well?).

Some of the tests -like spirometry - will also require you to use your short acting reliever inhaler.

The tests don’t hurt and are non invasive, - i.e. hmm… don’t hurt!

I’ve copied and edited some info for you to read.

Good luck.

Mia

xxx

""PFTs"", or pulmonary function testing, is simply the evaluation of lung function. PFTs are used to determine:

• the presence of lung disease or abnormality of lung function

• the extent of abnormalities

• the extent of impairment caused by abnormal lung function

• the progression of the disease

• the nature of the physiologic disturbance

• a course of therapy and treatment, as indicated

PFT definitions

Normal: for comparative purposes, observed values that fall at 80% or greater than the predicted values.

Predicted Values: these are average numbers based upon one's age, height, sex, and at some institutions, race.

PFTs:

A. Pulmonary mechanics

1. FVC - Forced Vital Capacity is the maximum volume of gas that can be forcefully and rapidly expired after a maximal inspiration. This maneuver may also be called a ""Flow-Volume Loop"", which is the same maneuver that is graphically displayed comparing volume and flow rate.

2. FEV1 - Forced Expiratory Volume after 1 second is the volume of gas expired after one second from the beginning of the FVC manoevre

3. FEV1/FVC - The ratio of FEV1 to FVC expressed in a percentage. significance: usually decreased in obstructive airways and is independent of the relative values of FVC and FEV1.

4. FEF 25-75% - Forced Expiratory Flow from 25 to 75%, is the average rate of flow during the middle half of an FVC maneuver based upon a segment of the FVC that included the flow from medium-sized and small airways. Also known as ""mid flow rates"".

5. FEFMAX or PEFR - Forced Expiratory Flow at Maximum effort or Peak Expiratory Flow Rate, is the maximum flow rate attained during the FVC maneuver. significance: Generally, FEFMAX is a good index of the patient's effort and relative strength in forceful exhalation. Also, may have relative meaning in evaluation of the effectiveness of a patient's cough.

6. Raw - Airway resistance is the ""resistance"" created by the airways and the friction against the walls of the airways caused by the flow of air through these passageways. This test is performed in the so-called ""body box"" or Plethysmograph, where one performs ""panting"" maneuvers.

B. Lung volumes

""Air-trapping"" - a term used to describe the state where one actually maintains a large amount of air in one's chest, even at the end of both normal and maximal exhalation.

1. SVC - Slow Vital Capacity is the volume of gas measured on a slow, complete expiration after or before a maximal inspiration, without forced or rapid effort. significance: often the SVC is significantly larger than FVC, which indicates to some degree the existence of air-trapping.

2. FRC or TGV - Functional Residual Capacity, or Thoracic Gas Volume, is the volume of gas remaining in the lungs after exhalation of a normal breath. This test is performed in several different ways. Perhaps the most accurate is by the ""body box""; other less accurate ways (especially in light of poorly communicating airways) include the Nitrogen Washout method, Helium Dilution, and Single-Breath Nitrogen Washout. significance: relative to the predicted values, larger values of FRC or TGV indicate the degree of air-trapping.

3. RV - Residual Volume is the volume of gas remaining in the lungs after complete exhalation. Value is obtained by any of the above methods mentioned for FRC. significance: Like FRC, RV is compared to the predicted values to determine the degree of air-trapping.

4. TLC - Total Lung Capacity is the volume contained in the lungs at the end of a maximal inspiration. This value is obtained from determination of SVC and FRC, in methods previously mentioned.

5. Diffusing capacity

DLCO - Diffusing Capacity measures the transfer of a diffusion-limited gas (Carbon Monoxide, CO 0.3%) across the alveolocapillary membrane. CO combines with hemoglobin approximately 210 times more readily than oxygen does. In the presence of normal amounts of hemoglobin and normal ventilatory function, the primary limiting factor of diffusion of CO is the status of the alveolocapillary membrane.

C. Other measurements

1. ABG - Arterial Blood Gasses are samples drawn from an artery (usually the radial near one's wrist), which enables us to measure the following values:PH - the measurement of your arterial blood's acid-base balance. This ""balance"" is controlled by several factors, but primarily metabolism and ventilation. If there is an imbalance with one or the other or both, there will be a definite effect on the PH. The approximate ""normal"" range of PH is 7.335 to 7.45, with 7.4 being the mean. Values less than 7.4 are considered to be more ""acidic"", while those greater than 7.4 are more basic or ""alkaline"". 2.PaCO2 - Partial Pressure of Carbon Dioxide in arterial blood. This value is an indicator of how effectively your lungs are able to rid themselves of a by-product of metabolism, CO2. The ""normal"" range for PaCO2 is 35 to 45 mm Hg. Elevated values greater than 40-45 mainly indicate that the lungs are not able to rid themselves of the CO2 (""CO2 retainer"").

2. 3.PaO2 - Partial Pressure of Oxygen in arterial blood. This is a measure of the actual amount of oxygen there is in your arterial blood. The ""normal"" for PaO2 is generally greater than 75-80 mm Hg, relative to your age. For the most part, it should be greater than 55-60 mm Hg,

3. PULSE OXIMETRY or SaO2 - This is a non-invasive measure of one's oxygen saturation; that is, the amount of oxygen saturated in one's hemoglobin in terms of a percentage. This is not as accurate as the values obtained from an ABG and should only be used as a gauge of one's oxygenation. Normal ranges are between 95-100%.

Author: Len Moriyama, RPFT, RRT, RCP Respiratory Technician for Alpha1 Registry California Pacific Medical Center, San Francisco

wow great info thanx every1

Emma

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