I've had Pulmonary Function Tests but I don't know what they mean

Full pulmonary function tests ( PFT's) are carried out by specialist centres sometimes within large general hospitals but more often or not in cardio-thoracic centres like The Royal Brompton or Papworth hospitals.

The tests consist of blowing into machines that are connected to computer systems. The main tests measure how quickly you can blow air out of your lungs, how much air is being trapped in your lungs and how well the exchange of gasses is taking place within the lungs. Before the tests are carried out patients will be measured and their height, age and sex entered into the computer. Tables exist that allow the computer to compare the test results to a stored set of "'predicted values" that are based on age, sex, height and "ethnicity".

FEV1

This stands for Forced Expiratory Volume in 1 second. This measures how much air you can blow out in one second and the units are in litres/second. FEV1 is useful because although it is a pretty blunt instrument, it does give a generally good idea of how "obstructed" a patients airways are. The results are often also presented alongside the "percentage of predicted value".

FVC

Forced Vital Capacity. During this test the patient takes a deep breath and blow, and blows, and blows... This tests measures just how large your lungs are. Most COPD patients will have hyper-inflated lungs that trap air. The ratio of FEV1 and FVC is another useful guide to enable changes to be noted.

DLCO

This is Diffusion Testing and measures the ability of the lungs to allow Oxygen in and Carbon Dioxide out. Personally I hate this test as it always seems to take so long and requires lots of long blows! Typically a very small amount of carbon monoxide is inhaled through the machine and, after holding your breath, is exhaled via the machine into a "bag". The machine then is able to calculate the amount of the gas exhaled giving a measure of the lungs ability to exchange gas.

The Box

You are placed in a plastic box which is sealed against atmospheric changes. You are told to breathe through a mouthpiece and after a warning a shutter drops. Several tests are carried out by this unit amongst them the ability of the lung to "recoil" and also more accurate measurements of lung volume and lung capacity.

Spirometry

This is a more simple test that is often carried out in GP's surgeries or by nurses. You blow into a mouthpiece and it records FEV1 and FVC. We have worked hard to get GP's to do this at least once a year for all patients, like blood pressure checks. I'm pleased to say that it is starting to happen now. It has been shown that someone who is prone to COPD will be showing signs of obstructed airways in their late twenties. What a strong incentive to quit smoking it would be to be shown the graphs in your GP's surgery.