Exercise Testing and the Physiological Responses to Exercise in Young Patients With Chronic Chest Diseases

The use of exercise is a valuable tool in the healthcare management of young patients with chronic chest diseases (CCD). Indeed, exercise testing yields important prognostic data which are a strong predictor of survival. Such information can indicate to the clinician to increase drug therapy treatment, and functional capacity of the patient can be monitored over time with repeated testing. Exercise training has been shown to improve both aerobic and anaerobic fitness and quality of life in patients with lung disease. The use of exercise testing and training in the healthcare of patients with lung disease in the UK, however, has not been investigated. In order for recommendations for exercise testing and training based on scientific evidence to be implemented, they should relate to current standards and resources. Therefore, the first study of the present thesis sought to characterise the use of both exercise testing and training in UK Cystic fibrosis (CF) clinics through a nationwide audit. Data from the audit showed that exercise testing and training are underused despite recognition of the importance of each in the healthcare of the patient by clinicians and other healthcare providers. Indeed, resources for exercise testing in UK CF clinics are limited. A patient over the age of 8 y will only have a 41.1 % chance of receiving an exercise test of any type over a 12 month period, and the exercise test will be quite crude. Exercise training is frequently discussed with the patient; however, there is a strong likelihood (72.9 %) that the advice given will only be general encouragement. The prognostic value of exercise testing is becoming increasingly recognised. Indeed, peak oxygen uptake (VO2peak) derived through maximal cardiopulmonary exercise testing (CPET) has been reported to be equal or superior to that of resting spirometric lung function tests in the prognostic evaluation of patients with CCD. Furthermore, a high correlation between VO2peak and long term survival in both adults and children with CF has been reported. Other physiological data from CPET, such as oxygen uptake (VO2) recovery following CPET, has not been investigated in young patients with CCD and may provide an additional physiological marker of patient health. The aim of study two, therefore, was to investigate recovery following CPET in young patients with CCD, and determine if any significant relationships exist between VO2 recovery and measures of disease severity in these patients. Data from study two showed that young patients with CCD compared to healthy controls had significantly reduced aerobic fitness (t52 = - 2.64, P = 0.011), and the fast component of the VO2 recovery following CPET, analysed by a mono-exponential model, is significantly prolonged (t52 = 2.63, P = 0.011). Furthermore, the fast component of the VO2 recovery is significantly related to disease severity, as assessed by the Shwachman score (SS), in the CF subgroup (r = - 0.75, P < 0.001), and as assessed by forced expiratory volume in 1 s (FEV1), in the young patients with CCD (r = - 0.49, P = 0.009). Thus, indicating that greater disease severity is associated with a longer VO2 recovery following CPET. A significant relationship between VO2peak and VO2 recovery was shown in the young patients with CCD (r = - 0.45, P = 0.018). Although the relationship is significant, however, it is still quite weak, and, therefore, indicates that the VO2 recovery is not closely related to the VO2peak in these patients. Quality of life and likelihood of survival are greater in patients with CCD with higher levels of aerobic fitness, and regular exercise has been shown to improve both lung function and exercise capacity in these patients. Indeed, exercise training programmes tailored to the individual patient are recommended in the standards of patient healthcare in the UK. Whilst the chronic effects of regular exercise have been investigated, the acute physiological responses to exercise training have not been studied in young patients with CCD. In study three young patients with CCD and healthy controls performed intermittent exercise (IE) designed to replicate the typical activity and exercise patterns of young people. Following IE, in the healthy controls the VO2 required to sustain moderate steady-state exercise fell significantly from 3 min to 1 h and 1 h to 24 h, however, in the young patients with CCD VO2 during moderate steady-state exercise increased significantly from 3 min to 1 h and then decreased significantly from 1 h to 24 h (main effect for time: F1.5,79.2 = 22.82, P < 0.001). A significant time × group interaction between young patients with CCD and controls in VO2 during moderate steady-state exercise 3 min, 1 h and 24 h following IE (interaction: F1.5,79.4 = 30.01, P < 0.001) may suggest that metabolic stress is still evident over this time period, which may be indicative of fatigue. Data from the present thesis shows that exercise is underused in UK CF clinics, with the availability of equipment and personnel both being limiting factors. Furthermore, a lack of standardisation in the provision of exercise between clinics is evident. In studies two and three, data shows different physiological responses following CPET and IE, respectively, between children with CCD and controls. The present thesis has advanced our understanding of the provision of exercise in the healthcare of CF in the UK, and furthered knowledge in how young patients with CCD respond physiologically to exercise.School of Sport and Health Sciences, University of ExeterRoyal Devon and Exeter NHS Healthcare Trus