Update on the role of exercise in cystic fibrosis

Current and Emerging Therapies to Combat Cystic Fibrosis Lung Infections

The ultimate aim of any antimicrobial treatment is a better infection outcome for the patient. Here, we review the current state of treatment for bacterial infections in cystic fibrosis (CF) lung while also investigating potential new treatments being developed to see how they may change the dynamics of antimicrobial therapy. Treatment with antibiotics coupled with regular physical therapy has been shown to reduce exacerbations and may eradicate some strains. Therapies such as hypertonic saline and inhaled PulmozymeTM (DNase-I) improve mucus clearance, while modifier drugs, singly and more successfully in combination, re-open certain mutant forms of the cystic fibrosis transmembrane conductance regulator (CFTR) to enable ion passage. No current method, however, completely eradicates infection, mainly due to bacterial survival within biofilm aggregates. Lung transplants increase lifespan, but reinfection is a continuing problem. CFTR modifiers normalise ion transport for the affected mutations, but there is conflicting evidence on bacterial clearance. Emerging treatments combine antibiotics with novel compounds including quorum-sensing inhibitors, antioxidants, and enzymes, or with bacteriophages, aiming to disrupt the biofilm matrix and improve antibiotic access. Other treatments involve bacteriophages that target, infect and kill bacteria. These novel therapeutic approaches are showing good promise in vitro, and a few have made the leap to in vivo testing.

Sildenafil improves exercise capacity in patients with cystic fibrosis: a proof-of-concept clinical trial

Background:

Exercise intolerance is a common phenotype observed in patients with cystic fibrosis (CF). Treatment with sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, has previously been shown to improve exercise capacity (VO₂ peak) in other patient populations. Thus, the present study sought to determine the acute and subacute effects of sildenafil on exercise capacity in patients with CF.

Methods:

The present investigation utilized a randomized, double-blind, placebo-controlled, crossover study with an acute dose of either sildenafil (50 mg) or placebo (n = 13, age 25 ± 10), followed by a 4 week open-label extension with sildenafil (20 mg, TID; n = 15, age 23 ± 11). A comprehensive evaluation of pulmonary function and a maximal exercise test were each performed at every visit.

Results:

A significant increase in VO₂ peak was observed after the acute sildenafil dose with no changes following placebo (77 ± 13 versus 72 ± 13% predicted; p = 0.033). In addition, after 4 weeks of treatment, patients showed a significant increase in exercise capacity (72 ± 12 versus 75 ± 12% predicted; p = 0.028) and exercise duration (409 ± 98 versus 427 ± 101 s; p = 0.014). A robust correlation (r = 0.656; p = 0.008) between baseline FEV₁ (% predicted) and the change in exercise capacity following 4 weeks of treatment was identified.

Conclusions:

This proof-of-concept clinical trial demonstrates that sildenafil treatment can improve exercise capacity in patients with CF and that pulmonary function may play an important role in the effectiveness of treatment. Future investigations of sildenafil treatment in patients with CF are certainly warranted.

Analysis of oxygen uptake efficiency parameters in young people with cystic fibrosis

PURPOSE

This study characterised oxygen uptake efficiency (OUE) in children with mild-to-moderate cystic fibrosis (CF). Specifically, it investigated (1) the utility of OUE parameters as potential submaximal surrogates of peak oxygen uptake ([Formula: see text]), and (2) the relationship between OUE and disease severity.

METHODS

Cardiopulmonary exercise test (CPET) data were collated from 72 children [36 CF, 36 age- and sex-matched controls (CON)], with OUE assessed as its highest 90-s average (plateau; OUEP), the gas exchange threshold (OUE_GET) and respiratory compensation point (OUE_RCP). Pearson's correlation coefficients, independent t tests and factorial ANOVAs assessed differences between groups and the use of OUE measures as surrogates for [Formula: see text].

RESULTS

A significant (p < 0.05) reduction in allometrically scaled [Formula: see text] and all OUE parameters was found in CF. Significant (p < 0.05) correlations between measurements of OUE and allometrically scaled [Formula: see text], were observed in CF (r = 0.49-0.52) and CON (r = 0.46-0.52). Furthermore, measures of OUE were significantly (p < 0.05) correlated with pulmonary function (FEV_1%predicted) in CF (r = 0.38-0.46), but not CON (r = -0.20-0.14). OUEP was able to differentiate between different aerobic fitness tertiles in CON but not CF.

CONCLUSIONS

OUE parameters were reduced in CF, but were not a suitable surrogate for [Formula: see text]. Clinical teams should, where possible, continue to utilise maximal CPET parameters to measure aerobic fitness in children and adolescents with CF. Future research should assess the prognostic utility of OUEP as it does appear sensitive to disease status and severity.

A single bout of maximal exercise improves lung function in patients with cystic fibrosis

BACKGROUND

Responses to a single bout of exercise may provide critical information for maximizing improvements in pulmonary function following exercise training in cystic fibrosis (CF). We sought to determine if acute maximal exercise improves pulmonary function in patients with CF.

METHODS

Thirty-three patients with CF completed a comprehensive assessment of pulmonary function to determine forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), and lung clearance index (LCI) prior to and immediately following maximal aerobic exercise on a cycle ergometer.

RESULTS

Following exercise, FVC (∆0.08±0.14L) and FEV₁ (∆0.06±0.15L) increased, while LCI decreased (∆-0.71±0.93) (all p<0.05). Changes in FEV₁ (%predicted) were associated with peak work (r=0.40, p=0.02) and peak pulmonary ventilation (r=0.45, p=0.01).

CONCLUSIONS

A single bout of maximal exercise acutely improves pulmonary function in patients with CF and improvements may be related to peak work and peak pulmonary ventilation.

Perspective on cystic fibrosis and physical activity: Is there a difference compared to healthy individuals?

OBJECTIVES

The aim of this study was to compare habitual physical activity between cystic fibrosis (CF) patients and healthy controls and to investigate possible predictors for reduced physical activity in CF patients.

METHODS

Sixty-six patients with CF (3-44 years) and 65 healthy controls (3-55 years) were asked to wear an accelerometer (Actigraph GT1M) for 9 days (at least 10 hr/day). Physical activity was classified in five categories from very low to very strenuous.

RESULTS

In general, there was no difference in physical activity between CF patients and healthy controls. However, young school-aged 6-13 years old children with CF spent less time with strenuous and very strenuous activity than healthy controls (adjusted difference in activity -0.43 (-0.69, -0.17)). Patients with very low lung function were significantly less active, but other CF-associated conditions did not affect physical activity.

CONCLUSIONS

While we found similar levels of physical activity measured by accelerometry in patients with CF compared to healthy controls in general, young school-aged children showed less engagement in strenuous activities than their healthy counterparts. As the reduced physical activity in young school children was not likely to be explained by the disease state, strenuous physical activity may be enhanced by advocating exercise and sport. Pediatr Pulmonol. 2016;51:1020-1030. © 2016 Wiley Periodicals, Inc.

Oxygen uptake kinetics and exercise capacity in children with cystic fibrosis

Exercise capacity, an objective measure of exercise intolerance, is known to predict quality of life and mortality in cystic fibrosis (CF). The mechanisms for exercise intolerance in patients with cystic fibrosis (CF), however, have yet to be fully elucidated. Accordingly, this study sought to investigate oxygen uptake kinetics and the impact of fat-free mass (FFM) on exercise capacity in young patients with CF. 16 young patients with CF (age 13 ± 4 years; 10 female) and 15 matched controls (age 14 ± 3 years; nine female) participated. Pulmonary function and a maximal exercise test on a cycle ergometer using the Godfrey protocol were performed. Exercise capacity (VO2 peak), VO2 response time (VO2 RT), and functional VO2 gain (ΔVO2 /ΔWR) were all determined. Lung function was the only demographic parameter significantly lower (P < 0.05) in CF compared to controls. Exercise capacity was lower in CF (P < 0.014) only when VO2 peak was normalized for FFM (43.5 ± 7.7 vs. 50.6 ± 7.4 ml/kg-FFM/min) or expressed as % predicted (70.1 ± 14.3 vs. 85.4 ± 16.0%). The VO2 RT was slower (36.1 ± 15.1 vs. 25.0 ± 12.4 sec; P = 0.03) and the ΔVO2 /ΔWR slope was lower (8.4 ± 3 ml/min/watt vs. 10.1 ± 1.4 ml/min/watt; P = 0.02) in patients compared to controls, respectively. In conclusion, a delayed VO2 response time coupled with the lower functional VO2 gain (ΔVO2 /ΔWR) suggest that young patients with CF have impairment in oxygen transport and oxygen utilization by the muscles. These data in addition to differences in VO2 peak normalized for FFM provide some insight that muscle mass and muscle metabolism contribute to exercise intolerance in CF.

Eucapnic Voluntary Hyperventilation to Detect Exercise-Induced Bronchoconstriction in Cystic Fibrosis

BACKGROUND

Exercise-induced bronchoconstriction (EIB) has not been well studied in cystic fibrosis (CF), and eucapnic voluntary hyperventilation (EVH) testing has not been used as an objective assessment of EIB in CF to date.

METHODS

A prospective cohort pilot study was completed where standard EVH testing was completed by 10 CF patients with forced expiratory volume in 1 s (FEV1) ≥70% of predicted. All patients also completed a cardiopulmonary exercise test (CPET) with pre- and post-CPET spirometry as a comparative method of detecting EIB.

RESULTS

No adverse events occurred with EVH testing. A total of 20% (2/10) patients were diagnosed with EIB by means of EVH. Both patients had clinical symptoms consistent with EIB. No patient had a CPET-based exercise challenge consistent with EIB.

CONCLUSIONS

EVH testing was safe and effective in the objective assessment for EIB in patients with CF who had well-preserved lung function. It may be a more sensitive method of detecting EIB then exercise challenge.

Feasibility of using pedometers to measure daily step counts in cystic fibrosis and an assessment of its responsiveness to changes in health state

BACKGROUND

Evaluation of physical activity is integral to the assessment of daily physical function and a potential objective outcome measure for clinical trials. We evaluated the feasibility of using pedometers to measure physical activity in adolescents and adults with cystic fibrosis (CF) and assessed the responsiveness of its measurement to changes in health state.

METHODS

Participants were recruited through two CF clinics in Seattle, WA. Subjects were instructed to use their pedometer for at least one ill and two well periods (each lasting 7 days). Step rate was calculated as steps per hour of use. Daily symptoms were also recorded using the CF Respiratory Symptom Diary (CFRSD). Generalized estimating equation linear regression was used to compare mean step rate between health states and by self-reported symptom category.

RESULTS

We enrolled 30 CF patients with a mean (±SD) age of 22 (±7) years and a mean forced expiratory volume in 1s (FEV(1)) of 57% (±25%) predicted. The mean period step rate increased from 397 (95% CI 324-497) steps/hour when ill to 534 (95% CI 413-654) steps/hour when well (p=0.015). Pedometer-recorded step rate also correlated with self-reported physical activity items on the CFRSD.

CONCLUSION

Step rate measured with a pedometer correlates significantly with changes in health status and self-reported activity, and could be used as an outcome measure in CF.

Physical activity recommendations for children with specific chronic health conditions: Juvenile idiopathic arthritis, hemophilia, asthma and cystic fibrosis

As a group, children with a chronic disease or disability are less active than their healthy peers. There are many reasons for suboptimal physical activity, including biological, psychological and social factors. Furthermore, the lack of specific guidelines for 'safe' physical activity participation poses a barrier to increasing activity. Physical activity provides significant general health benefits and may improve disease outcomes. Each child with a chronic illness should be evaluated by an experienced physician for activity counselling and for identifing any contraindications to participation. The present statement reviews the benefits and risks of participation in sport and exercise for children with juvenile arthritis, hemophilia, asthma and cystic fibrosis. Guidelines for participation are included.

Exercise and quality of life in patients with cystic fibrosis: A 12-week intervention study

It was hypothesised that increased exercise capacity is related to improved quality of life (QoL) in patients with cystic fibrosis (CF). A 12-week individually tailored unsupervised aerobic exercise programme was offered to 42 patients with CF. At the start and at the end of the exercise programme, data on QoL, current exercise habits and preferences, anthropometric data, exercise test, and lung function test were collected. Adherence was observed by a heart rate (HR) monitor. A total of 24 patients accepted to be enrolled in the exercise programme and 14 completed the programme. Another 14 patients declined to be enrolled in the exercise programme but completed the Cystic Fibrosis Questionnaire for Adolescents and Adults (CFQ-R 14+). Four patients did not want to participate at all. The 14 patients completing the exercise programme had a significantly increased VO_2max, but they showed no significant change in total QoL score. However, the scores in the domain of treatment burden and emotional functioning increased significantly. There was no significant difference in QoL and lung function between patients participating in the exercise programme (n = 24) and non-participants (n = 14). A 12-week individually tailored unsupervised aerobic exercise programme where HR monitors were used significantly affected VO_2max. Improvement in QoL could not be demonstrated in this study.

Effects of a short-term rehabilitation program on airway inflammation in children with cystic fibrosis

BACKGROUND

Respiratory therapy in cystic fibrosis (CF) consists of airway clearance, infection control, and reduction of airway inflammation. It is well recognized that physical activity as well as daily chest physiotherapy, enhance airway clearance. We investigated the effects of pulmonary rehabilitation, including physical activity and chest physiotherapy, on airway inflammation in children with CF.

METHODS

Eighteen children with stable CF (six females), aged 8.2-16.2 years, participating in a 3-week multidisciplinary inpatient rehabilitation program were recruited. Assessment at the beginning and the end of the program included clinical score, pulmonary function test, exhaled breath condensate (EBC) and sputum analysis. Sputum supernatant and EBC were analyzed for interleukin (IL)-1b, 6, 8, 10, 12, tumor necrosis factor-alpha (TNF-alpha) and LTB4.

RESULTS

Median (IQR) symptom scores decreased from 19 [23] to 16 [21], P = 0.005. Vital capacity and FVC increased significantly (P < 0.05). However no difference was found for the total sputum cells and sputum as well as EBC cytokines between the two visits. Significant correlations were found for sputum IL-1 (+), IL-6 (-), and IL-8 (+) to total sputum cell count and neutrophils and for IL-8 to TNF-alpha.

CONCLUSIONS

We have shown that a short-term inpatient rehabilitation for children with stable CF with intensive physical activity mainly improve subjective clinical symptoms and measures of lung function such as VC and FVC but does not influence airflow obstruction and airway inflammation as assessed by sputum and EBC analysis.

Physical activity recommendations for children with specific chronic health conditions: juvenile idiopathic arthritis, hemophilia, asthma, and cystic fibrosis

As a group, children with a chronic disease or disability are less active than their healthy peers. There are many reasons for suboptimal physical activity, including biological, psychological, and social factors. Furthermore, the lack of specific guidelines for 'safe' physical activity participation poses a barrier to increasing activity. Physical activity provides significant general health benefits and may improve disease outcomes. Each child with a chronic illness should be evaluated by an experienced physician for activity counselling and for identifying any contraindications to participation. The present statement reviews the benefits and risks of participation in sport and exercise for children with juvenile arthritis, hemophilia, asthma, and cystic fibrosis. Guidelines for participation are included.

Exercise and physical activity in children with cystic fibrosis

Regular exercise and habitual physical activity are important for patients with cystic fibrosis (CF). Research has demonstrated the benefits of aerobic, anaerobic, and strength exercise training programs for health and quality of life, however, the CF patient is faced with unique barriers and challenges to participation. Recently, increased levels of habitual physical activity have been shown to slow the decline in lung function in patients with CF, and regular participation in a variety of activities may result in greater adherence in the long term. Research is now available to justify the incorporation of exercise into the routine care of patients with CF. This paper provides the background and rationale for the implementation of exercise and habitual physical activity recommendations by the health care team. Education of health care providers regarding the importance of exercise and habitual physical activity for patients with CF is needed in order for exercise and physical activity to be incorporated as key components of clinical practice and into the lives of patients with CF.

Substrate utilization during and after exercise in mild cystic fibrosis

PURPOSE

To determine substrate utilization and energy expenditure during maximal and submaximal exercise and recovery in adolescents with cystic fibrosis (CF) and healthy age-matched controls (C).

METHODS

Ten clinically stable CF patients (four girls, six boys; age = 10-22 yr) were matched by body mass index, age, gender, and Tanner stage to healthy controls. Subjects completed VO(2peak) testing and submaximal exercise (20 min) on a cycle ergometer at a relative intensity of 50% VO2(peak) and at an absolute power output (PO). Metabolic parameters were assessed during exercise and recovery (20 min).

RESULTS

Similar respiratory quotient (RQ) values occurred in both groups during maximal exercise and recovery, despite differences in the maximal PO [CF = 114 (60-180) W and C = 171 (105-280) W, P = 0.006], the total work completed [CF = 27 (9.0-54.3) kJ and C = 55 (25.3-126.5) kJ, P = 0.008], or the VO(2peak) value attained [CF = 30.6 (8.5-45.2) mL kg(-1) min(-1) and C = 40.6 (29-64.5) mL kg(-1) min(-1), P = 0.027]. Submaximal exercise at the same absolute PO resulted in similar RQ values during exercise and recovery despite higher heart rates and average VO2 [CF = 18.8 (9.3-28.7) mL kg(-1) min(-1) and C = 15.2 (6.5-20.1) mL kg(-1)min(-1), P = 0.031] values in CF adolescents, and submaximal exercise at the same relative intensity also resulted in similar RQ values despite significantly greater average PO in the C group [CF = 38.7 (12.3-80) W and C = 67.8 (25.5-140) W, P = 0.039]. Excess postexercise oxygen consumption (EPOC) was greater in CF [2.79 (1.14-5.24) L O2] than C [1.46 (0.56-2.80) L O2] after submaximal exercise at a fixed PO (P = 0.036) but not after the relative exercise bout.

CONCLUSIONS

Habitual physical activity participation does not warrant adjustment of macronutrient intake ratios in adolescents with mild to moderate CF, but total caloric intake may need to be increased based on the level of EPOC and upon the intensity and the duration of the habitual activity.

Health-related fitness and trainability in children with cystic fibrosis

The objective of this study was to examine the effects of a supervised exercise training program performed during an in patient rehabilitation course on various attributes of health-related fitness, e.g., flexibility, balance and coordination. 286 patients with CF, age range 6-18 years (11.8 +/- 3.4 years), mean forced expiratory volume in 1 sec (FEV1 82.7 +/- 22.3% predicted) were included. Patients performed the modified Munich fitness test (mMFT) to assess flexibility, balance, strength and coordination. To assess aerobic capacity a 6-min walk-test (6MWT) was performed. In addition, some of the patients performed an incremental exercise test on a bicycle ergometer using the Godfrey protocol before and after the exercise training program. The supervised training program consisted of 4-6 weeks of different sports activities 5 times per week. After training, pulmonary function showed a significant (P < 0.05) increase. All test items of the mMFT improved significantly (P < 0.05). Compared to healthy children test scores achieved from children with CF in the mMFT were lower but within a normal range. Our children with CF had a lower walk distance in 6MWT (P < 0.05) compared to healthy. Our findings clearly demonstrated benefits of a systematic exercise training program on components of physical fitness in patients with CF, with improvements of test-tasks to predicted normal in some cases. The results from our study suggested that an exercise training program in CF should be focused on several aspects of physical fitness including all components of physical fitness, e.g. aerobic endurance, flexibility, balance and motor skills.

Dangerous exercise: lessons learned from dysregulated inflammatory responses to physical activity

Exercise elicits an immunological “danger” type of stress and inflammatory response that, on occasion, becomes dysregulated and detrimental to health. Examples include anaphylaxis, exercise-induced asthma, overuse syndromes, and exacerbation of intercurrent illnesses. In dangerous exercise, the normal balance between pro- and anti-inflammatory responses is upset. A possible pathophysiological mechanism is characterized by the concept of exercise modulation of previously activated leukocytes. In this model, circulating leukocytes are rendered more responsive than normal to the immune stimulus of exercise. For example, in the case of exercise anaphylaxis, food-sensitized immune cells may be relatively innocuous until they are redistributed during exercise from gut-associated circulatory depots, like the spleen, into the central circulation. In the case of asthma, the prior activation of leukocytes may be the result of genetic or environmental factors. In the case of overuse syndromes, the normally short-lived neutrophil may, because of acidosis and hypoxia, inhibit apoptosis and play a role in prolongation of inflammation rather than healing. Dangerous exercise demonstrates that the stress/inflammatory response caused by physical activity is robust and sufficiently powerful, perhaps, to alter subsequent responses. These longer term effects may occur through as yet unexplored mechanisms of immune “tolerance” and/or by a training-associated reduction in the innate immune response to brief exercise. A better understanding of sometimes failed homeostatic physiological systems can lead to new insights with significant implication for clinical translation.

Chest physical therapy, breathing techniques and exercise in children with CF

Chest physiotherapy in the form of airway clearance techniques and exercise has played an important role in the treatment of cystic fibrosis. Until the 1990s the primary airway clearance technique used was postural drainage combined with percussion and vibration (PD&P). It was introduced into the treatment of CF with little evidence to support its efficacy and once established, it has been difficult ethically to perform a study comparing PD&P to no treatment. A common question, yet unanswered is when should it be commenced, especially for the newly diagnosed asymptomatic CF patient? Recently, the technique of PD&P has been modified to include only non-dependant head-down positioning due to the detrimental effects of placing a person in a Trendelenburg position. In the 1990s other airway clearance techniques gained popularity, in that they could be performed independently, in a sitting position and avoided many of the detrimental effects of PD&P. These techniques include the Active cycle of breathing technique, formally called the Forced expiration technique and Autogenic drainage. Both these breathing techniques aim at using expiratory airflow to mobilize secretions up the airways and incorporate breathing strategies to assist in the homogeneity of ventilation. Studies suggest that both these techniques are as effective if not more effective than as PD&P and offer many advantages over PD&P. It has been suggested that exercise can be used as an airway clearance technique; however the literature does not support this. Rather, when exercise is used in addition to an airway clearance technique there is enhanced secretion removal and an overall benefit to the patient. Further research needs to be directed at assessing the effects of an airway clearance technique on the individual patient using appropriate outcome measures.

Exercise testing and chronic lung diseases in children

Exercise activity is an important part of daily life for both healthy children and children with respiratory diseases. Overall fitness level and responses to exercise can be assessed through cardiopulmonary exercise tests (using a treadmill or a cycloergometer). In asthmatic children exercise tests are useful to diagnose exercise-induced bronchoconstriction, which may affect up to 80% of asthmatic subjects. In cystic fibrosis patient, as the disease progresses, lung function deteriorates and exercise tolerance likewise diminishes. This reduced tolerance may not be predicted on the base of a standard spirometry while an exercise test can offer useful information. Eventually, exercise testing is useful in children with bronchopulmonary dysplasia to determine any presence and extent of gas exchange and ventilation dysfunction during exercise. Exercise challenges are a valuable tool to assess exercise tolerance that may be not adequately reflected by resting lung function tests.