RecruitingInterventional

The role of the carotid chemoreflex in long-COVID

This study aims to understand why many people with Long COVID experience lasting breathing difficulties, even when their lungs appear healthy. We believe a small organ in the neck, called the carotid body, which monitors blood chemistry and controls breathing, might be too active. Early research suggests this 'chemoreflex' system is more sensitive in Long COVID patients. The study will temporarily calm down these carotid bodies to see if it improves breathing at rest and during exercise. The goal is to determine if targeting this system could lead to new treatments for Long COVID-related breathing problems. We are looking for people with Long COVID and ongoing breathlessness, as well as those who had COVID but recovered quickly without breathlessness, to take part.

At a glance

Status

Recruiting

Sponsor

University of Bristol

Enrolment target

Start

24 Feb 2025

Estimated completion

05 Jan 2027

Long-COVID

What is this study about?

For many people, health problems can continue for months or even years after a COVID-19 infection. This is known as Long COVID. A common and challenging symptom is ongoing breathing difficulties, which can happen even when doctors can't find a problem with the lungs themselves. It's a big issue in the UK, affecting millions and having a significant impact on daily life.

Our research suggests that this breathing problem might be linked to a vital body system called the carotid chemoreflex. This system involves tiny organs in your neck, called carotid bodies, which act like sensors. They check your blood's chemical balance and send signals to your brain to adjust your breathing. When the COVID-19 virus enters these carotid bodies, it might make them overactive, causing the breathlessness some people with Long COVID feel. Our previous work has already shown that these carotid bodies are more sensitive in people with Long COVID.

This study wants to find out if temporarily making these carotid bodies less active can improve how people with Long COVID breathe, both when they're resting and when they're exercising. If we find that it helps, it could mean that the carotid body is a good target for developing new treatments to ease the breathing problems experienced by those with Long COVID. This could make a real difference to people's lives.

Key takeaways

Long COVID can cause lasting breathing problems, even with healthy lungs.
This study investigates if a neck organ, the carotid body, is overactive in Long COVID.
Researchers will temporarily calm the carotid body to see if breathing improves.
The findings could lead to new treatments for Long COVID breathing difficulties.
Participation involves three visits for tests and monitoring in Bristol.
Study is funded by UK's Medical Research Council, running until 2027.

Who may be eligible?

To take part in this study, you need to be aged between 18 and 75 years old and have had a positive COVID-19 test (PCR or antibody) in the past. We are looking for two groups of people: a Long COVID group and a comparison group.

If you have Long COVID, you must have been diagnosed with it and experience breathlessness that affects your daily life. If you are in the comparison group, you must have had COVID-19 but your symptoms lasted less than four weeks, and you don't experience breathlessness.

There are also some reasons why you might not be able to join. These include being pregnant or breastfeeding, having certain health conditions like severe asthma, uncontrolled diabetes, or heart disease, or taking certain medications. You also can't take part if you've had major surgery recently, smoke tobacco, or drink a lot of alcohol.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you between 18 and 75 years old?
Did you have a positive COVID-19 test at some point?
If you have Long COVID, does breathlessness affect your daily life?
If you don't have Long COVID, did your COVID symptoms last less than 4 weeks and you don't have breathlessness?
Do you have a BMI under 30?
Are you able to understand instructions in English?

Answer every question to see your result.

What does participation involve?

If you take part, you will have three visits at the Clinical Research Facility in Bristol. The first visit is a screening visit to make sure you're suitable for the study. This will involve filling out some questionnaires, having an ECG (heart tracing), lung function tests, urine and pregnancy tests (if applicable), height, weight, blood pressure checks, and a blood sample. You will also take home a blood pressure monitor to wear for 24 hours.

Visits 2 and 3 will be identical, but on each of these days, you will receive a different liquid given through a drip (either dopamine or a salt solution – the order is random). During these visits, your breathing will be assessed while you rest, and we'll test how your breathing changes when oxygen levels are lowered for a short time. You will also do an exercise test on a bike. Throughout these visits, we will continuously monitor your breathing, blood pressure, oxygen levels, and heart rate. The study is expected to run from August 2024 to January 2027.

Potential risks and benefits

Taking part offers some potential benefits, as you'll receive a heart tracing, full blood pressure check, and blood tests, which can be useful for a general health review. However, these tests aren't meant to diagnose new medical conditions. Most importantly, your involvement will help us learn more about Long COVID and how the carotid body contributes to breathing problems, potentially leading to new treatments. As for risks, having a drip inserted might cause some discomfort or bruising, with a very small chance of a clot or infection. Breathing tests using a mask are generally safe. We'll use a very low dose of dopamine, a medication that exists naturally in your body, and we don't expect side effects. You will be closely monitored, and any drip can be stopped quickly if needed. Breathing a mixture that briefly lowers oxygen (hypoxic ventilatory response testing) might cause temporary dizziness, but this can be stopped immediately. Finally, the bike exercise test will be supervised by a nurse and researcher, and you can stop at any time if you feel unwell. You are free to withdraw from the study at any time without giving a reason.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

University Hospitals Bristol and Weston - Clinical Research Facility
City only
Bristol, United Kingdom

Common questions

What is the carotid body?

It's a small organ in your neck that acts like a sensor for your blood, telling your brain how to adjust your breathing.

What does 'hyperactive' mean for the carotid body?

It means the carotid body might be too sensitive or working too hard, which could lead to breathing problems.

Will I receive any treatment for my Long COVID as part of this study?

The study aims to understand the cause of breathing problems in Long COVID, not to provide direct treatment. However, the information gained could lead to future treatments.

Who is funding this research?

The study is funded by the Medical Research Council in the UK.

How can I contact the research team?

You can contact Hazel Blythe at hazel.blythe@bristol.ac.uk for more information.

How to find out more

Emma Hart

emma.hart@bristol.ac.uk +44 (0)117 331 1971 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.