Using FeNO testing in sport, a conversation with Professor John Dickinson

In this edition of FeNO Stories, we talk to John Dickinson, Professor of Sport and Exercise Sciences and Head of the Exercise Respiratory Clinic at the University of Kent, with a specialism in assessing exercise respiratory symptoms in athletes. He describes how FeNO testing supports athletes training and competing at the highest level and shares his experience of using FeNO to help uncover asthma-related conditions in unsuspecting players, with some remarkable case-studies.

When and how did you come across FeNO testing?

Professor Dickinson has been using FeNO testing for more than 20 years. He first discovered the use of FeNO when he was helping Team GB prepare for the 2004 Olympic Games. “We were trying to work out ways to get a better idea of the underpinning reasons why athletes might be developing asthma-related conditions, like exercise-induced bronchoconstriction (EIB). We started to look for ways to measure airway inflammation and came across exhaled nitric oxide (FeNO). It was a good fit because it was a simple test to run and we got the results relatively quickly.” Professor Dickinson explains that FeNO provides snapshots that show the healthcare team how well the athletes are responding to treatment, such as inhaled corticosteroids (ICS).

Does FeNO testing fit in well with your respiratory checks for athletes?

Measuring FeNO is really quite straightforward, Professor Dickinson says. “We tend to do it at the start of any respiratory assessment. It takes us about 30 seconds to take a measurement and then you wait about a minute for the finding to come through. If you pop it at the very start of an assessment, before spirometry, you get a good idea of the athlete’s exhaled NO, which helps to build a picture of the airway inflammation within that athlete.”

Have you seen the benefits of using FeNO testing with athletes?

Professor Dickinson says FeNO testing for airway inflammation is built into his team’s screening protocol and they have seen real benefits from it. “If we pick up athletes with high FeNO who then give us a positive bronchoprovocation test, that helps to build up a diagnostic picture for the medic.” Professor Dickinson says the team also uses FeNO in follow-up assessments. “We use FeNO, maybe on a monthly basis, to track how much impact any therapy has been having on the athlete. It allows us to get a good feel for how the treatment is working without having to perform a full bronchoprovocation challenge. It’s a good monitoring tool.”

Professor Dickinson says the team has published research looking at the use of FeNO in elite football players. The results demonstrate that screening with FeNO revealed approximately 30% of the group had high FeNO but that their levels dropped with appropriate treatment, giving the medics confidence that they had reduced the players’ airway inflammation and improved their health.

Do you notice a difference in FeNO levels between sports?

“We certainly see a difference in FeNO levels between athletes,” Professor Dickinson says, explaining that this could be attributable to the varying phenotypes of asthma and EIB. Summer and winter asthma are also viewed separately. There may be a difference between an athlete who is triggered by allergy, for example, compared to one whose symptoms are driven by dry air.

“We don’t have complete evidence to demonstrate that there are just these two phenotypes – there might be more – but when we screen athletes for EIB, generally we see that half of those who give us a positive test have high FeNO and the other half have low. That would suggest that half of athletes with EIB have a Type 2 airway inflammatory pathophysiology. It doesn’t mean there is a 50-50 split but that is what we’re seeing in the athletes we’re testing.”

Do you think asthma is sometimes overlooked in elite sports?

This is an interesting question, Professor Dickinson says. Respiratory concerns are the most frequently reported symptoms by athletes and asthma is the most common chronic disease among them. The problem is asthma might not be at the forefront of medical assessment, which can focus on musculoskeletal issues and heart health, meaning a more thorough respiratory assessment could be beneficial.

“We know that athletes are more likely to experience asthma-related conditions than the general population, especially in sports with a high ventilatory requirement. The British population has an asthma prevalence of around 10%. When we look at the British Olympic team, there is a prevalence of asthma of around 20%. When we break it down by sport, we see that those with a high ventilatory requirement and which take place in an outdoor environment, potentially training in cold, dry air, or in polluted environments, have a much higher prevalence. In elite football, there is a 25-30% prevalence. Cycling is around 40%. Rowing and rugby are around 25-30%. Our research suggests that prevalence of EIB among elite swimmers who train in indoor pools can go all the way up to 70%.”

Do athletes realise their breathlessness could be asthma?

“We recommend screening athletes for asthma-related conditions because a lot may have the symptoms but not recognise them as anything other than ‘I get a bit tight-chested after training and why wouldn’t I, because I’ve just trained really hard?’

“A rugby player we tested a while ago was playing half a game in a position that required a lot of running and then moving into a position where they didn’t have to run as much. That’s how they managed their breathing. But when we screened this individual using FeNO and bronchoprovocation challenges, their FeNO was high, at around 60 ppb.

“During the eucapnic voluntary hyperpnea (EVH) challenge, the amount of air they could breathe out in one second dropped 40% – a positive test is a drop of 10% or more so this was a severe drop. The player said: ‘It feels like I’ve just done a training session!’ We gave them some salbutamol and their lung function popped straight back to where it was to start with.”

Professor Dickinson says the player was then started on a combination therapy of ICS and a long-acting beta 2 agonist. Monitoring demonstrated that when they used their preventer inhaler, the player’s response to the EVH challenge was a drop of under 10% so the healthcare team knew their EIB was well controlled.

“Their FeNO dropped to below 25 ppb so that suggested their airway inflammation was also under control,” Professor Dickinson explains. More importantly for the player, he adds, this control meant they could play more in the position that required high ventilation and sustain that for the entire game. “They went from being a talented professional player to reaching the top of the international game.” He points out that it would be a shame for those athletes not being thoroughly tested to be held back from the very top because they were suffering from symptoms they did not recognise as a problem when they could benefit from similar support.

Have you ever seen an asymptomatic athlete where a FeNO test revealed surprise airway inflammation?

Professor Dickinson says his team tests many groups of athletes who do not report any respiratory symptoms but in whom assessments reveal high FeNO. “This is not always because of asthma-related conditions. There have been instances where FeNO has been almost 200 ppb but the athletes have given a negative bronchoprovocation challenge. When we delve deeper, we have found these athletes have some form of allergy but they didn’t realise, so that is supporting them in a different way.”

The team has frequently worked with athletes who have not reported any symptoms but have high FeNO and produce a positive EVH challenge. Further investigation and asking athletes whether they experience a feeling of tight-chestedness in training sees some say they do but that they believed it to be a normal response to the exertion. Appearing asymptomatic is not the same as having no symptoms, it’s a question of exploring further.

Certain food and drink may impact FeNO. Should athletes with asthma or EIB follow a specific diet?

Awareness is key and potential influences should be factored in but not dominate food choices. Professor Dickinson says: “We know that foods that are high in nitrate, such as beetroot, can elevate FeNO but high-nitrate foods can actually be good for endurance performance. As long as we’re aware of what the athlete is eating, we don’t restrict them, but we need to know if an athlete has had a high-nitrate diet because that might elevate their FeNO.”

Interestingly, Professor Dickinson points out that certain diets can help to reduce the severity of EIB. Fish oil and prebiotics can reduce airway inflammation, he says, which will of course reduce FeNO. As a secondary supportive measure, Professor Dickinson adds, once an athlete is using appropriate inhaler therapy, they could potentially include a high fish oil diet or take prebiotic drinks.

When you test athletes for asthma or EIB, is there an order in which you perform tests?

Professor Dickinson says a systematic respiratory assessment with his team always starts with a FeNO test. “We want to avoid breathing off any exhaled NO, which can happen with tests like spirometry. The order that we go through in assessments is usually FeNO first, then we add a sniff test to look at peak nasal flow, followed by spirometry. If they have normal lung function at rest, we then do some form of provocation challenge. This is usually an indirect airway challenge, which means we try to trigger any inflammatory process inside their lungs that brings in a bronchoconstriction. Those challenges could be exercise, EVH – which mimics the breathing in exercise but allows the team to control the gas the player breathes so it’s cold and dry – or we do a mannitol challenge, where you inhale increasing doses of mannitol to trigger an asthmatic response similar to an allergic reaction.

“We then measure spirometry again. If we used an exercise or EVH challenge, we measure spirometry after three, five, seven, 10 and maybe 15 minutes, depending on what we’re seeing. We are looking for the amount of air the athlete breathes out in one second as fast as they can and whether that changes. That value is the FEV1. If the FEV1 remains within 10% of the personal baseline, that would be a negative challenge and suggest the athlete is not exhibiting a form of asthma or EIB. If the drop in FEV1 is greater than 10%, that would suggest the athlete has some form of asthma-related condition. After that, the report is sent to the appropriate medic or to the player’s GP for final diagnosis.”

It’s inspiring to hear how FeNO can help athletes realise their true potential and reach the top flight of international sport. For information on including FeNO testing in your asthma diagnosis and management routine, head now to niox.com.