Exercise as it relates to Disease/Pulmonary Function and Response to Exercise in Cystic Fibrosis

What study is being critiqued?

This (https://adc.bmj.com/content/archdischild/46/246/144.full.pdf) study investigated the effects of exercise on pulmonary function in patients who have been diagnosed with cystic fibrosis.

What background research led to this study?

• Cystic fibrosis is now recognised as the most common cause of chronic pulmonary disease in children.
• it is accepted that the earlier diagnosis and treatment of the disease occurs, the greater the improvement and results of the patient.
• Studies by (Doershuk et al., 1965;Beier et al., 1966; Mearns, 1968; Featherby et al.,1969) which look into lung mechanics reveal that airways of these patients are obstructed, and this effect increases as the patients condition deteriorates with time.
• Studies have been undertaken before on children, however they have been somewhat disturbing and it may be argued that the procedures used may not be clinically justifiable.
• New techniques have since been unearthed which allow children with cystic fibrosis to have their pulmonary function analysed during exercise, the indirect fick method (Godfrey and Davies, 1970) does not involve cardiac or systematic catheterisation, allowing the method to be acceptable by children.

Where is this research from?

This study was conducted at the Institute of Diseases of the Chest, and the Queen Elizabeth Hospital for Children in London. It is a part of the Archives of Disease in Childhood. The authors, S. Godfrey and Margaret Mearns have both produced additional studies relating to pulmonary diseases, with S. Godfrey also releasing studies relating to asthma based populations. The Institute of Diseases of the Chest has an impeccable record for research, and the Queen Elizabeth Hospital for Children had a good record of research before it's closing down in 2014. Both institutes show credibility and validity, thus showing this study to be valid and credible.

What kind of Research was this?

The study was a cross-sectional study. The patients were split into three groups, depending on which health outcome they were determined to be in at the time. All participants completed the same exercise testing.

What did the research involve?

• 41 patients (24 males, 17 females) who had been diagnosed with cystic fibrosis spent a full day as outpatients at a department where the testing was conducted.
• The patients participated in a series of spirometry tests pre and post exercise, as well as other physiological recordings including height, weight, lung volume, residual volume and the transfer factor for carbon dioxide.
• Patients were assigned to two exercises, the first being a progressive exercise on the cycle ergometer, where pulse and ventilation were recorded. The second exercise was a steady state exercise also conducted on the cycle ergometer, this involved cycling at a steady state at one-third and two-thirds of maximum intensity. For this test gas was analysed (Co2 and O2) along with an electrocardiograph and the patients arterialised ear lobe blood.
• After the exercise study, maximal ventilation rate was measured via a 15-second sprint method.

Group 1	Group 2	Group 3
Patients with good health who showed some symptoms of bronchitis or who had a small cough	Patients with good health, but had heavy respiratory symptoms and had chest x-rays showing a localised change	Patients with persistent pulmonary infection with or without abnormal findings in the lungs on clinical examination, chest x-rays showed generalised changed
Started with a progressive exercise test of a cycle ergometer, followed by a steady state test at one-third of maximal exercise, followed by another test at two thirds.	Started with a progressive exercise test of a cycle ergometer, followed by a steady state test at one-third of maximal exercise, followed by another test at two thirds.	Started with a progressive exercise test of a cycle ergometer, followed by a steady state test at one-third of maximal exercise, followed by another test at two thirds.

Limitations to methodology include biases in design, populations and data analysis. This cannot be avoided in the real world and is inevitable, meaning that the results are only relevant to certain aspects that the study is trying to find. The study is now almost 50 years old, so methodology may be outdated with science methodology changing over time. It is also slightly unclear as to what variables are going to be assessed and measured pre and post exercise testing.

What were the overall results?

• Overall, the differences between groups 1, 2 and 3 were significantly different. correlating with their different physiological abilities and problems.
• Maximal work and transfer factor of CO deteriorated when looking at results from group 1,2,3
• Maximal voluntary ventilation (MVV) results showed groups 1 and 2 had no significant difference before and after exercise, however grade 3 showed large deterioration of restricted airways.
• Physiological dead space was considerably enlarged in almost all children at a rate of 200% compared to normal.
• MVV correlated directly with maximal work as intensity increased over time, whilst also correlating with Force Expired Volume in 1 second.
• Almost all parameters showed little significant change between groups 1 and 2, however group 3 saw large changes in their results from pre and post exercise.

What conclusions were taken from this research?

• The ability of patients with different levels of cystic fibrosis symptoms to exercise is commonly found to be extremely low due to their pulmonary functions deteriorating, however, this study aims to find if exercise can be beneficial to a patient, or if the exercise is further declining their condition.
• Research indicates that patients who have somewhat good general health, although still being diagnosed with cystic fibrosis (possible in early stages), have improvements in variables including ventilation rate and forced expired volume in one second. Research also indicates that these variables decrease within patients who have extremely obstructed airways.
• Due to the large amounts of variables seeing significant drops in results from groups one and two compared to group 3, it might be possible that grouping may have not been even from grades one through to grade 3.
• The study believes based on its findings that adequate physiological assessment can be achieved in children with cystic fibrosis, being able to measure multiple variables during exercise which in turn, allowed the conductors to find the connection between exercise and pulmonary function in these patients.
• No clear physiological differences were documented after the testing was conducted, meaning that the exercise did not have an effect on the children in the long term. However, the study does give indication to the levels of exercise which could help these patients if they were to continue with the exercise process.
• Other more recent studies using exercise programs to try and increase exercise tolerance and overall pulmonary fitness suggest that exercise can have an effect on respiratory muscle strength, however, no additional adverse effects have been found.
• Overall, exercise has yet to show a full improvement in pulmonary function in patients with cystic fibrosis, however, there is data to suggest that a long enough exercise program may have benefits.

Practical advice for the future

• Participating in exercise routines and functional activities is beneficial to the body when tailored to the individuals needs.
• In the case of patients with cystic fibrosis, whilst studies suggest that the effect of exercise may not increase pulmonary functions significantly, exercise has been shown to have an adverse effect on other areas such as bone density, sleep improvement, mental health and more.
• Programs written by exercise professionals which are long term and ongoing may help these patients improve their overall quality of life.
• Depending on level of symptoms, lower intensity an resistance may be necessary to keep the patient engaged, but also make sure the exercise is being detrimental to their health.

References

1. Godfrey S, Mearns M. Pulmonary function and response to exercise in cystic fibrosis. Archives of Disease in Childhood. 1971 Apr 1;46(246):144-51.