What is this study about?
This study is looking at the role of the carotid bodies in people with long-COVID. The carotid bodies have been found to be overactive in people with long-COVID.
Why is this study important?
Some people with long-COVID experience symptoms of breathlessness at rest and have poor exercise tolerance. These symptoms can be severely debilitating. This study aims to determine if switching off the carotid bodies can improve breathing efficiency during exercise and reduce hyperventilation at rest in people with long-COVID.
Who can take part?
- Men and women
- Aged 18-75 years old
- Without major illness
- With previous COVID-19 infection with symptoms lasting <4 weeks OR a diagnosis of long-COVID and breathlessness that impacts daily life
What does taking part involve?
A 30-minute telephone screening call to check your eligibility. Three visits to the Clinical Research Facility (CRF), Bristol. The duration of the first visit will be up to 2.5 hours. The second and third visits will be up to 2 hours and 15 minutes. In the first visit, we will complete screening tests to make sure you can safely take part. This involves:
- Medical history questionnaire
- Breathlessness questionnaire
- ECG recording of your heart
- Blood pressure measurements
- Urine dipstick and pregnancy tests
- Blood tests
- Spirometry (lung function tests)
- Lung diffusion testing
- 24-hour blood pressure monitoring
In the second and third visits, we will give you an infusion of dopamine or saline, and measure your breathing, heart rate and blood pressure at rest, during hypoxia, and during exercise.
What is involved in carotid body testing at rest?
We will assess how your body controls your breathing, heart rate and blood pressure by breathing normally through a tight-fitting face mask. We will give you a low dose of dopamine or saline into a cannula in your arm to test if switching off the carotid bodies can help reduce hyperventilation at rest. This will be completed in visits 2 and 3.
What is a chemoreflex test?
We will measure the ability of your receptors in the carotid artery to adapt to changes in oxygen levels. First, you will breathe room air, then we will add pure pharmaceutical grade nitrogen gas to the air for 10-45 seconds to achieve short-lived falls in your oxygen levels. We will assess how your body increases your breathing rate to compensate. This is known as the hypoxic ventilatory response.
What is involved in carotid body testing during exercise?
Similar to at rest, you will wear a tight-fitting face mask whilst receiving an infusion of dopamine or saline. You will complete a ramped exercise tolerance test in visits 2 and 3 which involves cycling for up to 12 minutes. We will record your heart rate, blood pressure, oxygen saturations and breathing throughout the exercise. We will also measure the gases you breathe in and out during the exercise test.
What are the benefits of taking part?
You will get a full blood pressure, blood test and ECG screen. We will reimburse you for your travel to the CRF.
How do I take part?
If you are interested in taking part in the study, or have any questions, please contact Hazel Blythe on hazel.blythe@bristol.ac.uk or call 07483 973262
To read the full participant information sheet, please follow this link: Participant information sheet V3 27012025 IRAS 348370_CLEAN.pdf