As an ILD-patient, you are probably familiar with 'Pulmonary Function Tests'. For example, blowing into a device as hard as you can, so that a technologist can tell from a computer screen how well your lungs perform. But what exactly happens when you blow into that machine? And what are those mysterious graphs that show your results all about? In this article, we take a closer look at pulmonary function testing by looking over the shoulder of a dedicated professional.
To make a good assessment of your lung function, pulmonologists need to have as much information as possible. A lot of this information is provided by the pulmonary function technologist. For this article, BELUNG visited Anita Jansen, a pulmonary function technologist from the Netherlands.
Anita spends much of her time testing patients' lung functions, for example in the context of interstitial lung disease (ILD).
'I started the education for pulmonary function technologist in 1996', Anita says. 'In the third year of my education I was hired by this hospital and I've been working here ever since.' As a pulmonary function technologist, Anita spends much of her time testing patients' lung functions, for example in the context of interstitial lung disease (ILD).
The first two patients of the day, are coming in for a spirometry test', Anita explains. 'This is also known as a flow-volume loop.' The first thing Anita does, after she has greeted the first patient and explained what that nosey reporter is doing in her office, is measuring the patient's weight and length: 'We want to standardize the testing. When we know a patient's age, race, gender, weight and length, we know what the normal lung function of the patient should roughly be. For example, a 50 kilogram, 75 year old woman will have a different lung function than a 90 kilogram, 40 year old man, regardless of any illnesses.'
After the weight and length are measured, Anita asks the patients whether there are any medical conditions she should know about. 'I have to be sure that the patient is fit for the tests', Anita explains. 'If the patient has recently had an operation for example, some tests are too risky to perform.' After Anita has asked whether the patient has taken his medication today (since this can influence the results), the actual tests can be performed.
This is where the spirometer comes into play. The device looks something like a blowpipe attached to a small crane.
First, Anita removes the plastic from a new mouthpiece, and attaches the mouthpiece to the blowpipe. 'With a spirometer, one of the things you can measure is the volume of air inspired and expired by the lungs', Anita explains. 'Because of hygiene, every patient gets his own mouthpiece, which is discarded after the testing.'
Anita asks the patient to breathe normally for some time, after which the patient is stimulated to take the deepest breath she can and then to exhale as hard as possible, for as long as possible, preferably at least six seconds. This is then concluded by a rapid inhalation. While the patient tries to follow Anita's directions as best as she can, the graphs on the computer screen show us how all of this is working out. 'The spirometer contains a sensor', Anita explains. 'The sensor measures the air that is inspired and expired by the lungs and immediately translates it into digital graphs.' On the computer screen, we can see two different graphs. 'These are called spirograms', Anita says. 'The upper graph is a volume-time curve, which shows the volume along the vertical axis and time along the horizontal axis. The other one is a flow-volume loop, which depicts the rate of airflow on the vertical axis and the total volume inspired or expired on the horizontal axis.' (See picture)
Anita explains to the patient that she needs three good graphs, to make sure that the measurements are as reliable as possible. 'I immediately send the test findings to the pulmonologist,’ Anita says. 'After the patient is done here, she goes to the doctor who can make an assessment of the findings and discuss them with the patient.'
When the doctor receives the graphs, he can make an assessment of the lung function of the patient. For example, when a patient has IPF, the 'loop' in the flow-volume loop is narrowed. This happens because the fibrosis causes the lung volumes to diminish (see picture). At the same time, the airflow is greater than in a 'normal' spirogram, because the fibrosis also causes the lungs to stay open for a longer time.
After Anita has done spirometry tests with two patients, she sees a patient who is coming in for a diffusion test. 'With a diffusion test, we measure how well gas is taken up by the blood through the lung buds', Anita explains. As you inhale air, the oxygen passes from the smallest part of your lungs, through a tiny membrane, into the bloodstream. However, this process can be impaired, for example because of thickening of the membrane, as happens in ILD. For this test, we use the same device, only now I open a slide, so that when the patient inhales, she inhales gasses from that cylinder over there.' Indeed, there is a gas cylinder standing against the wall of the office, attached to the device by hoses, like a diving tank attached to a scuba diver. Anita points out that the gas tank contains two different types of gas: carbon monoxide and methane.
'First I ask the patient to blow out all the air that she can', Anita says. 'She then inhales as much of the gas mixture from the cylinder as she is able to, holds the gas in the lungs for about ten seconds, and exhales.' The test works as follows: one type of gas is taken up by the blood (the carbon monoxide), while the other gas is not (the methane). By comparing the amount of both gasses in the air that is exhaled, Anita can determine how well the carbon monoxide has diffused from the lungs into the blood. The next test Anita shows us is a little easier to comprehend: it's the so called 'walking test.'
Together with an upbeat elderly patient, we move to an empty corridor of the hospital. Here, Anita sets up a track with cones and attaches a pulse oximeter to the finger of the patient. 'With this device, we can measure the heartbeat and the oxygen saturation of the blood', Anita explains. 'With the walking test, we get information about the distance a patient walks and the desaturation of the blood. We then translate that information to the ability of the patient to perform daily activities. We also use the test to monitor the medical interventions by the doctor.'
The doctor might for example have prescribed an anti-fibrotic drug for the treatment of IPF. This drug can slow the disease progression in lung function in patients with IPF. When the doctor has prescribed the drug, he of course will want to know if the lung function of a patient with IPF has actually stabilized. The walking test can be used to investigate this. For the test, the patient has to walk around for six minutes on a flat surface. 'Before and after the test, we ask the patient how he experiences his shortness of breath. It gives us information about how the lungs react to exercise.'
After the patient from the walking test is back in the waiting room to take a well-earned rest, Anita shows us the apparatus for another kind of test. 'This is called the body box', Anita says, while she points at something that looks like a telephone cell with a chair in it.
'With a body box you can measure whether a patient has a restrictive lung function.' For testing in the body box, the patient is placed inside the sealed chamber. The idea behind the device is that as the lungs expand, the pressure in the lungs decreases. This in turns increases the pressure within the box, since it is a closed system. With this mechanism, the technician can measure the so called functional residual capacity (FRC) of the lungs.
After this last insightful explanation, the consultation of patients has come to an end. 'I really like my job', Anita says, while we enjoy a cup of coffee and discuss life as a pulmonary function technologist. 'I had the desire to work with people and with technology. Pulmonary Function Testing turned out to be an excellent combination of those things.' Although Anita comes across as a confident and calm professional, she has to admit it hasn't always gone that smoothly. 'When I first started in this line of work, I was a little startled at how out of breath people can get. I found it hard to get people to exhale for longer during spirometry, when I saw that they were obviously struggling.'
And I get to work with people and with technology. So what's not to like about it'
But as Anita got more experienced, she grew into the job. 'I find it easier now, partly because the age difference between myself and the patients becomes smaller. When you're twenty-two, patients might wonder if that young whipper-snapper really knows what she's asking of them. Anita thinks she has a very engaging job. 'One of the nicest things about my work is that every patient is different. Everyone needs their own approach. As such, I have both variety and routine activities. And I get to work with people and with technology. So what's not to like about it', Anita brightly concludes.