A 2-day CPET is a
cardiopulmonary exercise test
A cardiac stress test (also referred to as a cardiac diagnostic test, cardiopulmonary exercise test, or abbreviated CPX test) is a cardiological test that measures the heart's ability to respond to external stress in a controlled clinical enviro ...
given on two successive days to measure the effect of
post-exertional malaise (PEM) on a patient's ability to exercise.
PEM is a
cardinal symptom of
myalgic encephalomyelitis/chronic fatigue syndrome and is common in
long COVID as well.
Background
Several differences have been found between people with and without ME/CFS, including people with other diseases or who are sedentary. On the first test, people with ME/CFS exhibit lower performance and
heart rate, and on the second test, performance is even lower, while for controls, it is the same or slightly better. The largest decrease is in anaerobic threshold, which signifies a shift from
aerobic to
anaerobic metabolism at a lower level of exertion, and is not influenced by effort.
Peak power output, heart rate, and VO
2max also decrease, and in ME/CFS, but effort and familiarity with the test may affect VO
2max and power.
Additionally, healthy people generally recover from a CPET within 24 hours while people with ME/CFS do not.
A 2-day CPET can objectively measure PEM and its effect on physical functioning.
(Objective indicators of maximal effort during both tests control for effort.)
However, its utility has not been completely confirmed, as many studies of it have been small.
While it should not be required for a diagnosis, a 2-day CPET can show that symptoms are not due to
deconditioning and provide evidence for obtaining
disability benefits
Disability benefits are funds provided from public or private sources to a person who is ill or who has a disability.
United Kingdom
In the United Kingdom disability benefits are covered by Department for Work and Pensions. There are numerous ben ...
.
Because PEM is also a symptom of long COVID, the 2-day CPET may be useful in evaluating exercise intolerance there as well.
The cause of decreased performance is not understood. Proposals include impaired oxygen transport, impaired aerobic metabolism, and mitochondrial dysfunction.
The test provokes symptoms by design, and recovery may be prolonged. In some cases, it may worsen the illness long-term.
References
{{Chronic fatigue syndrome
Medical tests
Myalgic encephalomyelitis/chronic fatigue syndrome
Long COVID
Exercise physiology