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Long COVID breathlessness: Novel scans uncover hidden lung damage

Some people with long COVID may have hidden damage to their lungs, a small pilot study in the UK suggests.

Scientists used a novel xenon gas scan method to pick up lung abnormalities not identified by routine scans. They focused on 11 people who had not needed hospital care when they were first got COVID but experienced long-lasting breathlessness after their initial infection.

A larger, more detailed study is under way to confirm the results. The work builds on an earlier study that looked at people who had been admitted to hospital with COVID, reports the BBC.

Researchers say the findings shed some light on why breathlessness is so common in long COVID – though the reasons for feeling short of breath are often many and complex.

Long COVID refers to a host of symptoms that continue for many weeks after a coronavirus infection and cannot be explained by another cause.

'The oxygen journey'

The team, from Oxford, Sheffield, Cardiff and Birmingham universities, compared xenon gas scans and other lung-function tests in three groups of people.

This included people with long COVID and breathlessness who had not been admitted to hospital when infected, 12 people who had been admitted to hospital with COVID but did not have long COVID, and 13 healthy people as “controls”.

Using the novel approach, developed by the University of Sheffield, all participants inhaled xenon gas during a magnetic resonance imaging (MRI) scan.

The gas behaves in a very similar way to oxygen but can be traced visually during scans, so scientists were able to “see” how well it moved from the lungs into the blood stream – a crucial step in transporting oxygen around the body.

Researchers found for the majority of people with long COVID, gas transfer was less effective than in healthy controls. People who had been admitted to hospital for COVID had similar abnormalities.

Lead researcher and lung specialist Dr Emily Fraser said it was frustrating having people coming into clinic and not being able to explain to them exactly why it was that they were breathless. Often X-rays and CT scans show no abnormalities.

“This is important research and I really do hope this will shed more light on that.”

But she added: “It is important people know that rehabilitation strategies and breathing retraining can be really helpful. When we see people in clinic who are breathless we can make progress.”

The study’s co-chief investigator, Prof Fergus Gleeson, said: “There are now important questions to answer, such as, how many patients with long COVID will have abnormal scans, the significance of the abnormality we’ve detected, the cause of the abnormality, and its longer-term consequences.

“Once we understand the mechanisms driving these symptoms, we will be better placed to develop more effective treatments.”

The paper is a pre-print and has not yet been through the formal process of peer review.

Study details

The investigation of pulmonary abnormalities using hyperpolarised xenon magnetic resonance imaging in patients with long-COVID

James Grist, Guilhem Collier, Huw Walters, Mitchell Chen, Gabriele Abu Eid, Aviana Laws, Violet Matthews, Kenneth Jacob, Susan Cross, Alexandra Eves, Marianne Durant, Anthony Mcintyre, Roger Thompson, Rolf F. Schulte Betty Raman, Peter A. Robbins, Jim M. Wild, Emily Fraser, Fergus Gleeson.

Published in NIHR January 2022

Abstract

Background
Long-COVID is an umbrella term used to describe ongoing symptoms following COVID-19 infection after four weeks. Symptoms are wide-ranging but breathlessness is one of the most common and can persist for months after the initial infection. Investigations including Computed Tomography (CT), and physiological measurements (lung function tests) are usually unremarkable. The mechanisms driving breathlessness remain unclear, and this may be hindering the development of effective treatments.

Methods
Eleven non-hospitalised Long-COVID (NHLC, 4 male), 12 post-hospitalised COVID-19 (PHC,10 male) patients were recruited from a Post-COVID Assessment clinic, and thirteen healthy controls (6 female) were recruited to undergo Hyperpolarised Xenon Magnetic Resonance Imaging (Hp-XeMRI). NHLC and PHC participants underwent contemporaneous CT, Hp-XeMRI, lung function tests, 1-minute sit-to-stand test and breathlessness questionnaires. Statistical analysis included group and pair-wise comparisons between patients and controls, and correlations between patient clinical and imaging data.

Results
NHLC and PHC patients were 287 ± 79 [range 190-437] and 149 ± 68 [range 68-269] days from infection, respectively. All NHLC patients had normal CT scans, and the PHC had normal or near normal CT scans (0.3/25 ± 0.6 [range 0-2] and 7/25 ± 5 [range 4-8], respectively). There was a significant difference in TLco (%) between NHLC and PHC patients (76 ± 8 % vs 86 ± 8%, respectively, p = 0.04) but no differences in other measurements of lung function. There were significant differences in RBC:TP mean between volunteers (0.45 ± 0.07, range [0.33-0.55]) and PHC (0.31 ± 0.11, [range 0.16-0.37]) and NHLC (0.35 ± 0.09, [range 0.26-0.58]) patients, but not between NHLC and PHC (p = 0.26).

Conclusion
There are RBC:TP abnormalities in NHLC and PHC patients, with NHLC patients also demonstrating lower TLco than PHC patients despite their having normal CT scans. These abnormalities are present many months after the initial infection.

Summary statement
Hyperpolarised Xenon MRI and TLco demonstrate significantly impaired gas transfer in non-hospitalised long-COVID patients when all other investigations are normal.

 

BBC article – Long COVID: hidden lung damage spotted on scans (Open access)

 

See more from MedicalBrief archives:

 

Fauci announces new name for 'COVID long-haulers' and a new study

 

Long COVID is ‘exaggerated’ and ‘overblown’

 

Long COVID-19 may have affected 2m in England – REACT-2

 

Opera singing is helping long-haul COVID patients to recover

 

 

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