Heterogeneity of respiratory disease in children and young adults with sickle cell disease
Alan Lunt, Lucy Mortimer, David Rees, Sue Height, Swee Lay Thein and Anne Greenough
Published in the journal Thorax, November 2017
The purpose of this study was to look at the different types of breathing problems which affect people who have sickle cell disease (SCD). This is important because although it is known that many people with SCD also suffer from lung disease, not every person with SCD is affected in the same way, so it is important to try to categorise the different presentations with the goal of improving future treatment of SCD.
In order to achieve this goal, the study first measured several physical characteristics in each of 114 people with SCD. These included the volume and speed at which they could breathe in and out, the capacity of their lungs, how easy it was for air to travel through their airways, the amount of blood circulating in the lungs, and how well their blood carries oxygen.
The researchers then used a technique called cluster analysis to find three groups of individuals who shared particular characteristics. The first group had more blood in the vessels supplying the lungs, and respiratory disease caused by a combination of narrowed airways and a restricted lung expansion (which makes it harder to breathe). The second group was composed of older patients who had respiratory disease caused by restrictions on how much the lungs can expand, poorer uptake of oxygen in the lungs, and only mild anaemia. The third group were younger patients with lung disease caused by narrowed airways, more evidence of damage to red blood cells., and were most likely to benefit from a reliever asthma inhaler. The people in the third group had been admitted to hospital for their SCD more often.
Further analysis showed that people could be classified into one of the three groups based on results from two simple breathing tests and a blood test, meaning that identifying which group people with SCD fall into could be done relatively easily in future studies or in the clinic.
The results of this study show that respiratory disease experienced by people with SCD can be categorised into three groups, which may help to make future management of this condition easier by delivering more individual treatments.
This summary was produced by Gideon Bernstein, Year 12 student from JFS School, Harrow, as part of our departmental educational outreach programme.
The influence of dilution on the offline measurement of exhaled nitric oxide
Victoria MacBean, Dharmika Pooranampillai, Catherine Howard, Alan Lunt, and Anne Greenough
Published in the journal Physiological Measurement, February 2018
Asthma is a serious and growing health issue. Asthma UK say that 5.4 million people in the UK receive treatment and that, on average, three people die every day from asthma. People with asthma have inflamed airways and this causes them to breathe out higher-than-normal levels of a gas called nitric oxide (NO). By measuring the amount of NO in a person’s exhaled breath (which scientists call fractional exhaled nitric oxide or “FeNO”) asthma can be diagnosed and other health conditions that affect breathing can be ruled out. FeNO testing also allows the severity of asthma to be tracked so that the patient can know if the treatments they are using are helping or not.
The standard FeNO test requires a long, steady blow into a machine. This makes it unsuitable for young children and so an alternative test is often used, which involves them breathing normally into a bag and then analysing the exhaled air separately afterwards.
The authors of this study wanted to see whether the alternative FeNO test used for young children was accurate and, if not, whether it could be made accurate by adjusting the results using a mathematical equation. The authors devised an equation that took into account the amount of air already in the testing equipment and by how much that air ought to dilute a patient’s FeNO result.
Thirty-five adult participants underwent the standard and alternative FeNO tests using different numbers of exhalations. The alternative FeNO test was also conducted as a laboratory experiment using a precisely measured sample of gas instead of air exhaled by an adult participant.
The study showed that if a participant took multiple breaths during the alternative FeNO test then the FeNO measurements were very different from those provided by the standard test. The results provided by the laboratory experiment showed that the mathematical equation could accurately predict by how much the amount of FeNO detected would be reduced if multiple breaths were used. However, the mathematical formula did not provide accurate predictions when an adult participant undertook the alternative FeNO test. The authors suggested that this might be because the samples of exhaled air were becoming contaminated by air from the participants’ noses (where NO levels are much higher).
The authors of the study concluded that a patient’s true FeNO measurements could not be obtained using the alternative FeNO test if the patient took multiple breaths. This meant that the test is not suitable for young children.
This summary was produced by Joseph Henley, Year 12 student from JFS School, Harrow, as part of our departmental educational outreach programme.