Stress tests can provide important information for diagnosing Long COVID, choosing suitable therapies and monitoring patient progress. There are simple tests that can be carried out in any family practice (we have written about this here). Additional information can be provided by cardiopulmonary exercise testing, which needs to be performed by a specialist.
For example, in a study from Germany that was published in 2022, spiroergonometry provided important insights on lung function, especially in younger patients with pneumological symptoms. While only 25% of the 41 patients studied showed abnormal body plethysmography and only 17.1% showed a relevant change on chest CT, 87.8% of the participants in the study showed impaired recruitment reserve during spiroergometry.
But what needs to be taken into account here? What additional value is offered by cardiopulmonary exercise testing, when is it a sensible option and what are the potential risks? Julia Jermann and Silvio Catuogno from Balgrist University Hospital explain.
What are the benefits of cardiopulmonary exercise testing compared to more straightforward stress tests?
Julia Jermann: Not only does cardiopulmonary exercise testing make a performance impairment measurable and comparable, but it also provides a more accurate picture of where the problem is. We can see which of the cogs in the overall system (heart, lungs, muscles) is most likely to cause problems, and above all we can work out why this is the case. Simpler stress tests don’t provide enough information about this, but it’s important if we want to adapt the therapy and training in a targeted way.
According to a study, what’s known as the “peripheral system” is responsible for intolerance to exercise in patients with Long COVID. What does this mean?
Jermann: This means that there is no damage to the heart or the lungs, but the problems instead come from the periphery – the skeletal musculature or the blood vessels, for example. There seems to be something wrong with the supply of energy to the muscles in this area. Oxygen isn’t able to get to where it’s needed.
The literature on the subject, however, does indicate that the functioning of the heart and lungs is impaired after being infected with Covid. This is why it’s important to rule out any impairments in these areas, with heart muscle inflammation (myocarditis) being particularly worthy of mention here.
So what do you see when you examine your patients?
Jermann: Up to now, we’ve luckily been able to rule out heart or lung damage in most patients affected by Long COVID. In some cases, however, further tests were needed due to the presence of abnormalities in the blood pressure or cardiac rhythm. This is the only way to be sure that the complaints are not caused by damage to the heart and/or lungs. Failing to spot this could be dangerous, and the therapy would also be very different.
Porträts Jermann und Catuogno
Assuming that other causes can be ruled out, what are the specific benefits of exclusion diagnostics for patients?
Jermann: It can possibly be a bit frustrating at first to find nothing that can be directly treated, but in most cases it’s usually a relief for patients too. I believe there are two benefits: Firstly, the reassuring knowledge that there is no damage or dysfunction in the vital organs of the heart and lungs and that training or physical activity wouldn’t pose a risk of any such damage or dysfunction. Secondly, the values obtained from the cardiopulmonary exercise testing help to create a gentle development program with clearly defined therapy methods and limits that is tailored to the individual patient. With Fatigue in particular, it’s important to find the right intensity.
What do you mean by the right intensity?
Jermann: We often provide support for athletes who are very familiar with their bodies and their regeneration pace after an illness or accident. But it’s different with Long COVID: performance drops quickly and to a disproportionately low level. Progress is much slower, sometimes barely perceptible, and past experience no longer means anything. In this case, we can work out a program with slow increases in stress that is based on the values measured – individually tailored Pacing.
If a patient isn’t a professional athlete, it’ll be even more difficult to work out how much stress to apply, as the person’s awareness of their own body and their understanding of exertion and fatigue will be less developed. Clear recommendations for rehabilitation training are almost more important in this case. With patients with clear clinical complaints, this should be carried out under professional guidance, as is the case at our center, where support is provided by a sports physiotherapist as part of an interdisciplinary team. And of course, this makes it possible to measure a patient’s progress later on. The literature increasingly shows that symptoms are usually reversible in the long run.
Some people affected by Long COVID suffer from post-exertional malaise (PEM). Their condition can become significantly worse after exercise. Should cardiopulmonary exercise testing be avoided in certain circumstances?
Silvio Catuogno: We have carried out over 50 cardiopulmonary exercise tests on patients following a Covid infection. To date, none of them have experienced a deterioration of their condition in this way. One thing, however, is clear: Cardiopulmonary exercise testing is not indicated for all patients after a Covid infection, and this is not always the correct time for it to be carried out. Anyone who has experienced PEM in their daily lives, meaning that they become disproportionately exhausted for a long time after even the smallest exertions, should not be pushed toward their physical limit by any means.
For cases like this, there are test protocols that do not take a patient to their absolute maximum capacity. Alternatively, you could choose a testing method such as the walking test or the sit-to-stand test, which involve much less stress and are more comparable with day-to-day activities.
How do you find out who should not be pushed to their limit?
Catuogno: The decision on which test is necessary is made during a prior consultation. The overriding principle is to apply the tests that are suitable for the current situation. Cardiopulmonary exercise testing should be seen as going hand-in-hand with the patient’s medical history as recorded by the physician as well as with other accompanying tests such as an electrocardiogram (ECG), lung function test, laboratory testing or other examinations.
There are benefits to a clear diagnosis: Since affected people are no longer able to control their training load through an awareness of their body and earlier training experience, we need objective criteria for controlling the training load. Cardiopulmonary exercise testing provides important insights in this area, and is of great benefit when it comes to rehabilitation.
’We see anyone affected by persistent complaints and limitations.’
Who comes to you for cardiopulmonary exercise testing?
Catuogno: In principle, anyone affected by persistent complaints and limitations. This could be people who have been to us before and so for whom we have comparative figures, but it could also be people who have been referred to us by their family doctor or a specialist, or even those who have registered with us independently.
Do you see particular types of patients? People with different reactions to stress?
Catuogno: Covid can progress in a variety of different ways and can affect an many different organs. Research into the various types of Long COVID is currently running at full speed. We’re now seeing the preliminary trends (have a look at link 2), but there are not yet any clearly defined distinctions and criteria. At the moment, we’re learning something new every day.