Multiple factors limit exercise capacity in cystic fibrosis

Feasibility of the A-STEP for the assessment of exercise capacity in people with cystic fibrosis

OBJECTIVES

To evaluate feasibility of the Alfred Step Test Exercise Protocol (A-STEP) for the assessment of exercise capacity in adults and children with cystic fibrosis (CF); in adults to test whether demographics and/or lung function correlated with exercise capacity.

METHODS

Adults and children with stable CF from two centres completed the A-STEP (a recently developed incremental maximal-effort step test). Feasibility was evaluated by: usefulness for exercise capacity assessment (measures of exercise capacity were: level reached, exercise-induced desaturation, and achievement of at least one maximal effort criteria); safety; operational factors; time to complete; floor and/or ceiling effects. We used multiple linear regression to test whether demographics and/or lung function correlated with exercise capacity.

RESULTS

A total of 49 participants: 38 adults (18 male), percent predicted (pp) forced expiration in one second (FEV₁ ) 29-109, aged 22-48 years and 11 children (6 male), ppFEV₁ 68-107, aged 10-15 years were included. Levels reached (mean (SD) [range]) were 10.2 (2.4) [6-15] (adults), 10.1 (2.5) [7-14] (children); desaturation (change between baseline and peak-exercise SpO₂ ): was 8.4 (3.8 [0-15]% (adults), 2.0 (2.0) [0-7]% (children). A total of 8 (21%) adults and no children desaturated <90% SpO₂ . At least one criterion for maximal effort was reached by 33 (84%) adults and 10 (91%) children. There were no adverse events. The A-STEP was straightforward to use and carried out by one operator. A total of 26 (68.4%) adults and 7 (63.6%) children completed the test within the recommended 8-12 min. All participants completed a minimum of 6 levels, and completed the test before the final 16th level. In adults, ppFEV₁ and ppFVC correlated with the level reached (r = 0.55; p = <0.001 and r = 0.66, p = <0.0001) and desaturation (r = 0.55, p = <0.001 and r = 0.45, p = <0.005).

CONCLUSION

In adults and children with stable CF, the A-STEP was feasible, safe, and operationally easy to use for the assessment of exercise capacity, without floor or ceiling effects. In adults, lung function correlated with exercise capacity.

Development of the A-STEP: A new incremental maximal exercise capacity step test in cystic fibrosis

BACKGROUND

Exercise testing is important in people with cystic fibrosis (pwCF). The aim was to develop an incremental maximal step test to assess exercise capacity across the range of pwCF, without floor or ceiling effects, within restrictions of space, and infection prevention.

METHODS

The step test was developed in adults with stable CF. Subjects assisted in selecting: step height, start rate, increments, stage and test duration parameters. Equipment to externally pace and time the test and measure exercise parameters were selected. Reasons for stopping, criteria for achieving a maximal test, and key outcome measures were determined. Documentation to record and standardize the test and instructions to set up the metronome and timer App were developed. Infection control practices were considered.

RESULTS

Eight subjects were recruited to develop the Alfred Step Test Exercise Protocol (A-STEP) on a 20 cm portable step. The A-STEP package included a pretest information sheet, clinical assessment and instructions, recording worksheet, and the metronome/timer instructions. The test started at 18 steps/min. Each level increased by two steps/min to a maximum of 48 steps (Level 16). Results were presented as mean (SD) [range] for: age 30.63 (5.89) [21-39] years; FEV₁ 58.13 (18.33) [32-89]%; levels: 10.31 (3.29) [6-15.5]. The A-STEP required space of 2 m² and complied with current infection control guidelines.

CONCLUSIONS

The A-STEP is a new incremental maximal step test to assess exercise capacity in pwCF, without floor or ceiling effects. It addresses the issues of space restrictions and the need for strict infection prevention in the clinical setting.

Exercise Physiology Across the Lifespan in Cystic Fibrosis

Cystic fibrosis (CF), a severe life-limiting disease, is associated with multi-organ pathologies that contribute to a reduced exercise capacity. At present, the impact of, and interaction between, disease progression and other age-related physiological changes in CF on exercise capacity from child- to adult-hood is poorly understood. Indeed, the influences of disease progression and aging are inherently linked, leading to increasingly complex interactions. Thus, when interpreting age-related differences in exercise tolerance and devising exercise-based therapies for those with CF, it is critical to consider age-specific factors. Specifically, changes in lung function, chronic airway colonization by increasingly pathogenic and drug-resistant bacteria, the frequency and severity of pulmonary exacerbations, endocrine comorbidities, nutrition-related factors, and CFTR (cystic fibrosis transmembrane conductance regulator protein) modulator therapy, duration, and age of onset are important to consider. Accounting for how these factors ultimately influence the ability to exercise is central to understanding exercise impairments in individuals with CF, especially as the expected lifespan with CF continues to increase with advancements in therapies. Further studies are required that account for these factors and the changing landscape of CF in order to better understand how the evolution of CF disease impacts exercise (in)tolerance across the lifespan and thereby identify appropriate intervention targets and strategies.

Expert's Choice: 2018's Most Exciting Research in the Field of Pediatric Exercise Science

This commentary highlights 23 noteworthy publications from 2018, selected by leading scientists in pediatric exercise science. These publications have been deemed as significant or exciting in the field as they (a) reveal a new mechanism, (b) highlight a new measurement tool, (c) discuss a new concept or interpretation/application of an existing concept, or (d) describe a new therapeutic approach or clinical tool in youth. In some cases, findings in adults are highlighted, as they may have important implications in youth. The selected publications span the field of pediatric exercise science, specifically focusing on: aerobic exercise and training; neuromuscular physiology, exercise, and training; endocrinology and exercise; resistance training; physical activity and bone strength; growth, maturation, and exercise; physical activity and cognition; childhood obesity, physical activity, and exercise; pulmonary physiology or diseases, exercise, and training; immunology and exercise; cardiovascular physiology and disease; and physical activity, inactivity, and health.

Physiological markers of exercise capacity and lung disease severity in cystic fibrosis

BACKGROUND AND OBJECTIVE

Peak aerobic capacity (VO₂ peak) is an important outcome measure in cystic fibrosis (CF), but measurement is not widely available and can be influenced by patient motivation, pain and fatigue. Alternative markers of disease severity would be helpful. Neural respiratory drive, measured using parasternal intercostal muscle electromyography (EMGpara), reflects the load to capacity balance of the respiratory system and provides a composite measure of pulmonary function impairment in CF. The aim of the study was to investigate the relationship between exercise capacity, EMGpara and established measures of pulmonary function in clinically stable adult CF patients.

METHODS

Twenty CF patients (12 males, median (range) age: 22.3 (17.0-43.1) years) performed the 10-m incremental shuttle walk test (ISWT) maximally with contemporaneous measures of aerobic metabolism. EMGpara was recorded from second intercostal space at rest and normalized using peak electromyogram activity obtained during maximum respiratory manoeuvres and expressed as EMGpara%max (EMGpara expressed as a percentage of maximum).

RESULTS

VO₂ peak was strongly correlated with ISWT distance (r = 0.864, P < 0.0001). Lung gas transfer (T_L CO) % predicted was best correlated with VO₂ peak (r = 0.842, P < 0.0001) and ISWT distance (r = 0.788, P < 0.0001). EMGpara%max also correlated with VO₂ peak (-0.757, P < 0.0001), while the relationships between exercise outcome measures and forced expiratory volume in 1 s (FEV₁ ) % predicted and forced vital capacity (FVC) % predicted were less strong. A T_L CO% predicted of <70.5% was the strongest predictor of VO₂ peak <32 mL/min/kg (area under the curve (AUC): 0.96, 100% sensitivity, 83.3% specificity). ISWT distance and EMGpara%max also performed well, with other pulmonary function variables demonstrating poorer predictive ability.

CONCLUSION

T_L CO% predicted and EMGpara%max relate strongly to exercise performance markers in CF and may provide alternative predictors of lung disease progression.

Physiotherapy management of cystic fibrosis

For many years physiotherapy for cystic fibrosis (CF) was synonymous with a daily routine of postural drainage and percussion. Improved longevity and a desire for independence, together with a clearer understanding of the pathophysiology of the disease, has led to the development of many airway clearance techniques. The contribution of ‘chest’ physiotherapy remained unchallenged until recent times when lack of robust evidence and the presentation of asymptomic infants and adults led some physiotherapists to question this traditional approach. As survival increases into the fourth and fifth decade unique complications have evolved and physiotherapy management is challenged with nonrespiratory aspects of treatment. This review will consider the evidence for, and current practice of airway clearance, the value of exercise and the emerging problems of musculoskeletal complications and incontinence.

Cardiorespiratory and sensory responses to exercise in adults with mild cystic fibrosis

The purpose of this study was to evaluate cardiorespiratory fitness and reasons for exercise curtailment in a contemporary adult cystic fibrosis (CF) cohort with mild lung disease. Adults with mild CF (n = 19, forced expiratory volume in 1 s = 95 ± 17% predicted) were age-, sex-, ethnicity-, and body mass index-matched to healthy controls (n = 19) and underwent a detailed cardiopulmonary cycle exercise test. While CF subjects had a reduced peak oxygen uptake compared with controls, the values were normal when expressed as %predicted in 14/19 (74%) of subjects. Both groups demonstrated a normal cardiovascular limitation to exercise and stopped exercise primarily because of leg fatigue. Despite not being exercise-limited by respiratory factors, there was some evidence of ventilatory abnormalities as patients with mild CF had increased end-inspiratory lung volumes and reached an inflection/plateau in tidal volume relative to minute ventilation at lower exercise intensities compared with controls. Subjects with CF were not more likely to demonstrate expiratory flow limitation compared with controls and did not have evidence of dynamic hyperinflation during exercise. Despite increased end-inspiratory lung volumes and an earlier tidal volume inflection/plateau, CF subjects did not experience higher levels of dyspnea. In an exploratory analysis, a significant inverse correlation was observed between sweat chloride and peak work rate. Adult CF subjects with relatively well preserved spirometry have normal exercise performance relative to reference values and are primarily limited by nonrespiratory factors. However, ventilatory abnormalities were detected even in this mild CF cohort and should be evaluated in future therapeutic trials focused on disease-modifying therapies in mild CF.

Physiological correlates of pulmonary function in children with cystic fibrosis

RATIONALE

Although peak aerobic capacity (VO(2peak)) has been linked to outcome in patients with cystic fibrosis (CF), measuring is time consuming, and requires expensive equipment and expertise that is not readily available in all centers. Other fitness parameters such as peak anaerobic power, measures of power and strength may be simpler to deliver in the clinic. The relationship between these measures and established outcomes such as forced expiratory volume in one second (FEV(1)) and peak aerobic power (VO(2peak)) in CF remains unclear. Therefore we evaluated (a) aerobic fitness, (b) anaerobic fitness, and (c) upper and lower body muscle strength to determine their relationship to FEV(1) and VO(2peak) in children with CF.

METHODS

Eighty-two patients (7-18 years) with CF (40 female) from the CF clinic at The Hospital for Sick Children in Toronto performed a maximal incremental cycling test to exhaustion. Anaerobic power (W) for 10 and 30 sec cycling trials as well as vertical jump (VJ) and hand grip strength (HG) were compared to FEV(1) and VO(2peak).

RESULTS

Absolute VO(2peak) (R(2)  = 0.16, P < 0.001), anaerobic power (R(2)  = 0.21, P < 0.001), and hand grip strength (R(2)  = 0.10, P = 0.003) were significantly correlated to lung function whereas measures of explosive lower body strength (VJ) were not. Anaerobic power (R(2)  = 0.16, P = 0.001) and hand grip strength (R(2)  = 0.08, P = 0.01) were related to VO(2peak). Vertical jump was correlated with VO(2peak) (R(2)  = 0.29, P < 0.001) but not FEV(1).

CONCLUSIONS

Simple fitness tests such as hand grip strength and anaerobic cycle tests may be useful indicators of lung health and fitness.

Determinants of exercise capacity in cystic fibrosis patients with mild-to-moderate lung disease

Background

Adult patients with cystic fibrosis (CF) frequently have reduced exercise tolerance, which is multifactorial but mainly due to bronchial obstruction. The aim of this retrospective analysis was to determine the mechanisms responsible for exercise intolerance in patients with mild-to-moderate or severe disease.

Methods

Cardiopulmonary exercise testing with blood gas analysis at peak exercise was performed in 102 patients aged 28 ± 11 years: 48 patients had severe lung disease (FEV₁ < 50%, group 1) and 54 had mild-to-moderate lung disease (FEV₁ ≥ 50%, group 2). VO₂ peak was measured and correlated with clinical, biological, and functional parameters.

Results

VO₂ peak for all patients was 25 ± 9 mL/kg/min (65 ± 21% of the predicted value) and was < 84% of predicted in 82% of patients (100% of group 1, 65% of group 2). VO₂ peak was correlated with body mass index, C-reactive protein, FEV₁, FVC, RV, DLCO, V_E/VCO₂ peak, V_D/V_T, PaO₂, PaCO₂, P(A-a)O₂, and breathing reserve. In multivariate analysis, FEV₁ and overall hyperventilation during exercise were independent determinants of exercise capacity (R² = 0.67). FEV₁ was the major significant predictor of VO₂ peak impairment in group 1, accounting for 31% of VO₂ peak alteration, whereas excessive overall hyperventilation (reduced or absent breathing reserve and V_E/VCO₂) accounted for 41% of VO₂ alteration in group 2.

Conclusion

Exercise limitation in adult patients with CF is largely dependent on FEV₁ in patients with severe lung disease and on the magnitude of the ventilatory response to exercise in patients with mild-to-moderate lung disease.

Gas exchange in disease: asthma, chronic obstructive pulmonary disease, cystic fibrosis, and interstitial lung disease

Ventilation-perfusion (VA/Q) inequality is the underlying abnormality determining hypoxemia and hypercapnia in lung diseases. Hypoxemia in asthma is characterized by the presence of low VA/Q units, which persist despite improvement in airway function after an attack. This hypoxemia is generally attenuated by compensatory redistribution of blood flow mediated by hypoxic vasoconstriction and changes in cardiac output, however, mediator release and bronchodilator therapy may cause deterioration. Patients with chronic obstructive pulmonary disease have more complex patterns of VA/Q inequality, which appear more fixed, and changes in blood flow and ventilation have less benefit in improving gas exchange efficiency. The inability of ventilation to match increasing cardiac output limits exercise capacity as the disease progresses. Deteriorating hypoxemia during exacerbations reflects the falling mixed venous oxygen tension from increased respiratory muscle activity, which is not compensated by any redistribution of VA/Q ratios. Shunt is not a feature of any of these diseases. Patients with cystic fibrosis (CF) have no substantial shunt when managed according to modern treatment regimens. Interstitial lung diseases demonstrate impaired oxygen diffusion across the alveolar-capillary barrier, particularly during exercise, although VA/Q inequality still accounts for most of the gas exchange abnormality. Hypoxemia may limit exercise capacity in these diseases and in CF. Persistent hypercapnic respiratory failure is a feature of advancing chronic obstructive pulmonary disease and CF, closely associated with sleep disordered breathing, which is not a prominent feature of the other diseases. Better understanding of the mechanisms of hypercapnic respiratory failure, and of the detailed mechanisms controlling the distribution of ventilation and blood flow in the lung, are high priorities for future research.

Active video games as an exercise tool for children with cystic fibrosis

BACKGROUND

Active video games are used in many hospitals as exercise tools for children with cystic fibrosis. However, the exercise intensity associated with playing these games has not been examined in this population.

METHODS

Children with cystic fibrosis [n=30, aged 12.3 (2.6) years, 17 boys, BMI 17.7 (2.8) kg/m(2)] were recruited from outpatient clinics in Dublin hospitals. Age and gender matched control children were recruited from local schools. Oxygen consumption, metabolic equivalents (METs) calculated from resting V˙O2, and heart rate were measured while playing Nintendo Wii™ (Nintendo Co. Ltd., Tokyo, Japan) Sports Boxing and Nintendo Wii Fit Free Jogging using a portable indirect calorimeter (Oxycon Mobile).

RESULTS

Playing Wii Boxing resulted in light intensity activity (2.46METs) while playing Wii Fit Free Jogging resulted in moderate intensity physical activity (4.44METs). No significant difference was seen between groups in the energy cost of playing active video games.

CONCLUSION

Active video games are a useful source of light to moderate intensity physical activity in children with cystic fibrosis.

Ventilatory pattern and energy expenditure are altered in cystic fibrosis mice

BACKGROUND

Altered ventilatory pattern and increased energy expenditure are facets of the complex cystic fibrosis (CF) phenotype. It is not known whether these are inherent attributes of CF, secondary consequences of lung infection or other disease complications.

METHODS

Studies were performed in congenic C57BL/6J, F508del (Cftr((tm1kth))) and CF gut-corrected (F508del) mice. Ventilatory patterns were measured using whole-body plethysmography. Indirect calorimetry was used to determine oxygen consumption, carbon dioxide production and resting energy expenditure.

RESULTS

CF mice (F508del and F508del gut-corrected) have a significantly faster respiratory rate and increased ventilatory pattern variability as compared to non-CF mice. F508del but not CF gut-corrected mice had significantly increased energy expenditure per gram body weight.

CONCLUSIONS

CF mice exhibit a faster, more variable ventilatory pattern. These changes were present in the absence of detectable infection or illness due to gastrointestinal obstruction. Increased resting energy expenditure does not completely account for these differences.

Exercise intensity self-regulation using the OMNI scale in children with cystic fibrosis

Prescribing exercise at intensities that improve fitness is difficult in children with cystic fibrosis (CF) due to ventilatory limitations and fluctuating health status. Our aim was to determine if children with CF could regulate the intensity of cycle ergometer and treadmill exercise using target ratings of perceived exertion (RPE) derived from the Children's OMNI Scale. We examined prescription congruence (similar oxygen consumption [VO₂] and heart rate [HR] for target RPE) and intensity discrimination (different VO₂ and HR for different RPEs), from cycle to cycle and cycle to treadmill. Subjects were 24 children (12 male, 12 female), aged 10-17 years with varying disease severity. Each child participated in one orientation, one estimation trial (graded maximal exercise test), and two production trials (cycle and treadmill, alternating between RPE 4 and 7). At RPE 4, congruence was evident for both VO₂ and HR on the treadmill. On the cycle at RPE 4, VO₂ was significantly higher only in the first production trial, although HRs tended to be higher in the production trials than the estimation trial. Prescription congruence was also supported at RPE 7, with no significant differences in VO₂ or HR between estimation and production trials on cycle or treadmill. Results fully supported intensity discrimination, with significant differences between VO₂ and HR at RPE 4 and 7 (P < 0.0001). Children with CF appear capable of using the OMNI Scale to regulate cycle and treadmill exercise intensity. Training using this methodology has the potential to promote fitness in children with CF of varying severity.

Cardiopulmonary assessment in primary ciliary dyskinesia

BACKGROUND

Primary ciliary dyskinesia (PCD) is a rare, usually autosomal recessive disorder of ciliary dysfunction associated with lung involvement, which has a great impact on health. There is limited information concerning the aerobic fitness of children and adolescents with PCD. The aim of this study was to assess cardiopulmonary functional capacity and its relationship with pulmonary function and physical activity (PA) levels in patients with PCD.

DESIGN

Ten patients with PCD (age 13·2 ± 2·8 years) underwent spirometry and cardiopulmonary exercise testing. PA was investigated through a questionnaire. Eight age- and body mass index-matched healthy children were enrolled as controls. Main variables were forced expiratory volume at 1 s, peak oxygen uptake (VO(2peak) ) and time spent in PA.

RESULTS

Forty per cent of patients with PCD had impaired lung function as expressed by FEV(1) < 85% predicted. Only patients with impaired lung function exhibited reduced VO(2peak) (18·1 ± 7·9 mL/kg/min). Time spent in total daily PA was slightly lower in patients than controls, with no difference between patients with normal or reduced lung function. In multiple regression models, male gender (β = 0·518, P = 0·018), age (β = 0·752, P = 0·035) and time spent in vigorous PA (β = 0·353, P = 0·049) were independent predictors of aerobic fitness.

CONCLUSIONS

Assessment of resting pulmonary function and cardiopulmonary functional capacity could contribute to the evaluation of pulmonary impairment in PCD. Given the benefit of physical exercise on airway clearance and on general health and quality of life, patients with PCD should be encouraged to adopt an active lifestyle.

Effects of an exercise program in children with cystic fibrosis: are there differences between females and males?

OBJECTIVE

To investigate the adaptive responses of an in-patient exercise program in children with cystic fibrosis (CF) and evaluate the effects of sex.

STUDY DESIGN

In total, 158 female and 186 male subjects with CF (age, 12 to 43 years) were studied during a 6-week rehabilitation course. A maximal incremental cycling test was used to determine exercise capacity and responses after 6 weeks of exercise training. Measures included lung function, peak oxygen uptake, peak workload, and peak heart rate.

RESULTS

Lung function values were lower in males (P < .05). Females had a lower aerobic capacity (P < .05) at the beginning and at the end of the exercise training program. Similar training effects (P > .05) were seen between sexes in peak oxygen uptake (mL/min, mL/kg/min) and peak heart rate (beats/min) but not in peak workload (Watts, W/kg).

CONCLUSIONS

The exercise program improved the fitness level similarly in females and males with CF. Basic physiological sex differences were still seen at the beginning and end of the training, despite the better lung function in females. Moreover, the finding suggested that fitness level and not lung function determined the response to training in CF, with those who were less fit at baseline having the largest response to training.

Impaired lung diffusing capacity for nitric oxide and alveolar-capillary membrane conductance results in oxygen desaturation during exercise in patients with cystic fibrosis

BACKGROUND

Exercise has been shown to be beneficial for patients with cystic fibrosis (CF), but for some CF patients there is a risk of desaturation, although the predicting factors are not conclusive or reliable. We sought to determine the relationship between the diffusion capacity of the lungs for nitric oxide and carbon monoxide (DLNO and DLCO) and the components of DLCO: alveolar-capillary membrane conductance (D(M)), and pulmonary capillary blood volume (V(C)) on peripheral oxygen saturation (SaO(2)) at rest and during exercise in CF.

METHODS

17 mild/moderate CF patients and 17 healthy subjects were recruited (age=26±7 vs. 23±8 years, ht=169±8 vs. 166±8 cm, wt=65±9 vs. 59±8 kg, BMI=23±3 vs. 22±3 kg/m(2), VO(2PEAK)=101±36 vs. 55±25%pred., FEV(1)=92±22 vs. 68±25%pred., for healthy and CF, respectively, mean±SD, VO(2PEAK) and FEV(1) p<0.001). Subjects performed incremental cycle ergometry to exhaustion with continuous monitoring of SaO(2) and measures of DLNO, DLCO, D(M) and V(C) at each stage.

RESULTS

CF patients had a lower SaO(2) at rest and peak exercise (rest=98±1 vs. 96±1%, peak=97±2 vs. 93±5%, for healthy and CF, respectively, p<0.01). At rest, DLNO, DLCO, D(M) were significantly lower in the CF group (p<0.01). The difference between groups was augmented with exercise (DLNO=117±4 vs. 73±3ml/min/mmHg; DLCO=34±8 vs. 23±8ml/min/mmHg; D(M)=50±1 vs. 34±1, p<0.001, for healthy and CF respectively). Peak SaO(2) was related to resting DLNO in CF patients (r=0.65, p=0.003).

CONCLUSIONS

These results suggest a limitation in exercise-mediated increases in membrane conductance in CF which may contribute to a drop in SaO(2) and that resting DLNO can account for a large portion of the variability in SaO(2).

High-intensity interval training in an adolescent with cystic fibrosis: a physiological perspective

Nutritional, musculoskeletal, and/or ventilatory status can lead to a decreased exercise capacity in children with cystic fibrosis (CF). Exercise training is already part of the usual care; however, the "optimal" intensity and volume of exercise training to improve exercise capacity is still unknown. Six weeks of high-intensity interval training (HIT) for a patient with CF with a ventilatory limitation was evaluated by a cardiopulmonary exercise test (CPET). Peak oxygen uptake and peak workload increased 19% and 16%, respectively, and there was a rise in peak ventilation from 50 L/min to 75 L/min, with an increase in both breathing depth and respiratory rate. A relative short period of HIT resulted in a significant increase in exercise capacity. In patients with CF, HIT might be an effective and efficient training regimen, especially in CF patients with a ventilatory limitation. Further research is necessary to investigate whether HIT is a better alternative than traditional aerobic training programs especially in ventilatory limited patients with CF.

Motor performance is better than normal in preschool children with cystic fibrosis

The aim of the present study was to assess the motor performance in preschool children with a reliable and valid test battery developed to identify motor dysfunction and normal motor development in children aged from 4 to 6 years. Several aspects of motor performance were examined in 29 preschool children with cystic fibrosis (CF) age range 4-6 years (mean 5.2 +/- 0.8 years), FEV(1) 97.2 +/- 15.3pred and compared to with 22 healthy children of the same age 5.5 +/- 0.8 years. All children performed the "Motoriktest fuer 4-6jaehrige Kinder" (MOT) assessing seven different aspects of motor performance. Compared to healthy children, test score "Motor Quotient" (MQ) as the mean of all test items was significantly higher (P < 0.05) in children with CF (108.1 +/- 16 vs. 93.5 +/- 17.9). In both groups, the MQ can be classified as normal. Children with CF scored higher in MOT subtests "Agility and Coordination" (P < 0.05) and "Balance" (P < 0.01) than healthy children but not in the other subtests. We speculate that chest physiotherapy in preschool children with CF may have an effect on motor performance in general and in some aspects of motor performance.

Exercise testing in children with lung diseases

Exercise is an important aspect of health and development in children. By placing the pulmonary system under stress, exercise testing may reveal subtle dynamic abnormalities that are not apparent on conventional static pulmonary function tests. Furthermore, exercise testing assesses the functional impact of respiratory disease on children. Exercise testing has been used in children with a variety of respiratory diseases such as exercise induced bronchoconstriction, asthma, cystic fibrosis and bronchopulmonary dysplasia to assess the severity of disease as well as response to various interventions. Furthermore, there is good evidence that exercise testing is a useful tool to help determine prognosis in patients with cystic fibrosis. In addition to the clinical utility, exercise testing is also becoming an increasingly important outcome measure in research studies.

Early oxygen uptake recovery following exercise testing in children with chronic chest diseases

The value of exercise testing as an objective measure of disease severity in patients with chronic chest diseases (CCD) is becoming increasingly recognized. The aim of this study was to investigate changes in oxygen uptake (VO2) during early recovery following maximal cardiopulmonary exercise testing (CPXT) in relation to functional capacity and markers of disease severity. Twenty-seven children with CCD (age 12.7 +/- 3.1 years; 17 female) [19 children with Cystic fibrosis (CF) (age 13.4 +/- 3.1 years; 10 female) and 8 with other stable non-CF chest diseases (NON-CF) (age 11.1 +/- 2.2 years; 7 female)] and 27 healthy controls (age 13.2 +/- 3.3 years; 17 female) underwent CPXT on a cycle ergometer. On-line respiratory gas analysis measured VO2 before and during CPXT to peak VO2) (VO2(peak)), and during the first 10 min of recovery. Early VO2 recovery was quantified by the time (sec) to reach 50% of the VO2 (peak) value. Early VO2 recovery was correlated against spirometry [forced expiratory volume in 1 sec (FEV(1)) and forced expiratory flow between 25% and 75% of the forced vital capacity (FEF(25-75))] and aerobic fitness (VO2)(peak)) as a measure of functional capacity. Disease severity was graded in the CF patients by the Shwachman score (SS). Compared to controls, children with CCD demonstrated a significantly reduced VO2(peak) (P = 0.011), FEV(1) (P < 0.001), FEF(25-75) (P < 0.001), and a significantly prolonged early (VO2) recovery (P = 0.024). In the CF patients the SS was significantly correlated with early VO2 recovery (r = -0.63, P = 0.004), FEV(1) (r = 0.72, P = 0.001), and FEF(25-75) (r = 0.57, P = 0.011). In the children with CCD, FEV(1), FEF(25-75), and BMI were not significantly correlated with VO2(peak) or early VO2 recovery. Lung function does not necessarily reflect aerobic fitness and the ability to recover from exercise in these patients. A significant relationship was found between VO2(peak) and early VO2 recovery (r = -0.39, P = 0.044) in the children with CCD, showing that a greater aerobic fitness corresponded with a faster recovery.

Mucoviscidose : du bon usage des explorations fonctionnelles respiratoires

INTRODUCTION

Neonatal screening for cystic fibrosis (CF) leads to early dedicated specialist care for all patients.

BACKGROUND

Pulmonary function tests (PFT) are mandatory for routine monitoring of CF patients. The aim of this article is to review the current guidelines for PFTs in CF, particularly the type of test, the age and the clinical status of the patient.

VIEWPOINT

The regular use of spirometry is generally accepted. Many other tests are used but their clinical value in the routine follow-up of CF patients remains to be established.

CONCLUSION

Further efforts should be made to evaluate the value of PFTs in CF, particularly in very young children.

Thin-Section CT in Patients with Cystic Fibrosis: Correlation with Peak Exercise Capacity and Body Mass Index

PURPOSE

To evaluate whether thin-section chest computed tomographic (CT) findings correlate with exercise capacity, body mass index (BMI), dyspnea, and leg discomfort in patients with cystic fibrosis (CF).

MATERIALS AND METHODS

Institutional ethics committee approval was obtained, and patients provided written informed consent. Twenty-two patients (13 male and nine female patients; mean age, 22 years +/- 5.9; age range, 17-41 years) with stable CF underwent thin-section CT and exercise testing on a cycle ergometer. Three radiologists blinded to the clinical severity of disease and the spirometric findings of all patients independently and randomly scored all scans with a modified Bhalla scoring system. The primary measurement of the outcome of exercise testing was percentage of predicted peak O2 uptake. Univariate (Spearman rank correlation) and multivariate analyses were used to compare thin-section CT, clinical (age, sex, spirometric data, and BMI), and exercise measurements.

RESULTS

The correlation between total thin-section CT score and percentage of predicted peak O2 uptake was stronger than the correlation between the percentage of predicted peak O2 uptake and any clinical measurement (R = -0.60, P < .01). The thin-section CT structural abnormalities that had the strongest correlation with percentage of predicted peak O2 uptake were severity of bronchiectasis and presence of sacculations or abscesses (R = -0.70 and -0.71, respectively; P < .01). Multivariate analysis showed total thin-section CT score to be the only significant predictor of exercise capacity, accounting for 42% of the variance in percentage of predicted peak O2 uptake.

CONCLUSION

In patients with CF, the correlation between thin-section CT score and exercise limitation is stronger than that between spirometry results or BMI and exercise limitation.

Respiratory factors do not limit maximal symptom-limited exercise in patients with mild cystic fibrosis lung disease

To evaluate whether respiratory factors limit exercise capacity in patients with mild cystic fibrosis (CF) lung disease (mean FEV(1) = 76 +/- 7.7% predicted) we stressed the respiratory system of seven patients using added dead space (V(D)). Primary outcomes were exercise duration (Ex(dur)) and maximal oxygen uptake (VO(2max)). Dyspnoea/leg-discomfort were assessed at end-exercise. Ex(dur) was identical between control and V(D) studies (520 +/- 152 versus 511 +/ -166 s, p = NS) as was VO(2max)(1.6 +/- 0.5 versus 1.6 +/- 0.6 L/min, p = NS). Significant resting, sub-maximal and maximal workload increases in minute ventilation (V(E)) were detected (70.8 +/- 13.7 versus 79.5 +/- 16.9 L/min, p < 0.05). Analysis of breathing pattern revealed increases in V(E) were attributable to increases in tidal volume (2.0 +/- 0.5 versus 2.2 +/- 0.6 L, p < 0.05) with no change in respiratory frequency. There was no difference in dyspnoea/leg discomfort between tests. The increase in V(E) in response to V(D), with no change in [Exdur/VO(2max) suggests maximal symptom-limited exercise limitation is not primarily limited by respiratory factors in mild CF lung disease. Focused investigation and treatment of non-respiratory factors contributing to exercise limitation may improve exercise rehabilitation in this patient group.

Effect of low altitude at the Dead Sea on exercise capacity and cardiopulmonary response to exercise in cystic fibrosis patients with moderate to severe lung disease

Oxygen supplementation may improve exercise tolerance and the physiological response to exercise in cystic fibrosis (CF) patients. Elevated barometric pressure at low altitude is a simple means of increasing the quantity of inspired oxygen. Our objectives were to examine the effect of natural oxygen enrichment (at the Dead Sea, 396 m below sea level) on exercise capacity, and the physiological responses to maximal and submaximal exercise in CF patients. Patients were tested twice: at sea level (barometric pressure, 754 +/- 6 mmHg, mean +/- SD), and at the Dead Sea (barometric pressure, 791 +/- 3 mmHg), in a randomized crossover design. We studied 14 CF patients (6 females, 8 males), aged 15-45 years, with moderate to severe lung disease (mean forced expired volume in 1 sec = 50.0 +/- 11.2% predicted). Tests at each site included resting spirometry, anthropometry, a graded submaximal exercise test, a maximal exercise test on a treadmill, and a 6-min walk test. Tests were performed in identical order at both sites. Tests at the Dead Sea were performed 72 hr after arrival. No differences between sites were observed in lung function at rest. Peak oxygen consumption was significantly improved at the Dead Sea compared with sea level (1.68 +/- 0.73 vs. 1.57 +/- 0.74 l/min, respectively, P = 0.05), along with an improvement in the ventilatory equivalent for oxygen (41.2 +/- 6.3 vs. 46.1 +/- 7.1, respectively, P < 0.05). During submaximal exercise, blood oxygen saturation improved at the Dead Sea compared with sea level at all exercise intensities (P < 0.05). In conclusion, these results suggest that even a brief stay at the Dead Sea area may have physiological benefits for CF patients with moderate to severe lung disease.

Relationship between FEV1 and peak oxygen uptake in children with cystic fibrosis

Cross-sectional data do not truly convey the manner in which declining lung function affects peak oxygen uptake (peak VO2) within a given patient with cystic fibrosis. We hypothesized that there would be a concomitant decline in peak VO2 with FEV1 over time. Twenty-eight children aged 8-17 years with cystic fibrosis performed annual ergometer tests over a 5-year period to determine peak VO2 and within-patient predictors of change in peak VO2. Analysis was done using a mixed-effects model. During the study period, the annual decline in FEV1 averaged 2.7% of the predicted value per year. Peak VO2 fell during the observation period in 70% of patients, with an average annualized decline of 1.9 ml x min(-1) x kg(-1). This rate of decline was greater in older children in contrast to younger children, some of whom had an improvement in peak VO2 over the first few years, consistent with growth and maturation. There was no difference in this rate of decline between sexes, but girls started with a slightly lower peak VO2 (37.9 vs. 45.1 ml x min(-1) x kg(-1)). In patients with FEV1 <80% predicted, declining FEV1 was highly correlated with falling peak VO2, whereas it remained stable over 4-5 years in patients whose FEV1 was >80% predicted and remained in that range. We conclude that peak VO2 remains stable or rises slightly over time in younger patients, while it shows a downward trend in older children with CF, particularly once FEV1 falls below 80% predicted. Peak VO2 is correlated with FEV1 during childhood in patients with cystic fibrosis, and both FEV1 and age influence peak VO2.

Role of arterial hypoxemia and pulmonary mechanics in exercise limitation in adults with cystic fibrosis

We tested the hypothesis that maximal exercise performance in adults with cystic fibrosis is limited by arterial hypoxemia. In study 1, patients completed two maximal exercise tests, a control and a test with 400 ml of added dead space. Maximal O2 consumption was significantly lower in the added dead space study vs. control (1.04 ± 0.15 vs. 1.20 ± 0.11 l/min; P < 0.05), with no difference in peak ventilation. There was significant O2 desaturation during exercise that was equal in both control and added dead space studies. The decrease in maximal O2 consumption with added dead space suggests that maximal exercise in cystic fibrosis is limited by respiratory factors. We subsequently examined whether pulmonary mechanics or arterial hypoxemia limits maximal exercise performance. In study 2, patients completed two maximal exercise tests, a control and a test with 400 ml of added dead space while also breathing 38% O2. Added dead space was used to overcome the suppressive effects of hyperoxia on minute ventilation. Maximal O2 consumption was significantly higher with added dead space and 38% O2 vs. control (1.62 ± 0.16 vs. 1.43 ± 0.14 l/min; P < 0.05). Peak ventilation and O2 saturation were significantly greater in the added dead space and 38% O2 test vs. control. The increase in maximal O2 consumption and peak ventilation with added dead space and 38% O2 suggests that maximal exercise in cystic fibrosis is limited by arterial hypoxemia.

Peak oxygen uptake and mortality in children with cystic fibrosis

BACKGROUND

Single measurements of peak oxygen uptake (VO2) have been shown to predict mortality in patients with cystic fibrosis (CF) although no longitudinal study of serial measurements has been reported in children. A study was undertaken to determine whether the initial, final, or the rate of fall of forced expiratory volume in 1 second (FEV1) or peak VO2 was a better predictor of mortality.

METHODS

Twenty eight children aged 8-17 years with CF performed annual pulmonary function and maximal exercise tests over a 5 year period to determine FEV1 and peak VO2, magnitude of their change over time, and survival over the subsequent 7-8 years. Analysis was done using Kaplan-Meier curves and Cox proportional hazard model.

RESULTS

Peak VO2 fell during the observation period in 70% of the patients, with a mean annual decline of 2.1 ml/min/kg. Initial peak VO2 was not predictive of mortality but rate of decline and final peak VO2 of the series were significant predictors. Patients with peak VO2 less than 32 ml/min/kg exhibited a dramatic increase in mortality, in contrast to those whose peak VO2 exceeded 45 ml/min/kg, none of whom died. The first, last, and rate of decline in FEV1 over time were all significant predictors of mortality.

CONCLUSIONS

Higher peak VO2 is a marker for longer survival in CF patients.

Individualised unsupervised exercise training in adults with cystic fibrosis: a 1 year randomised controlled trial

BACKGROUND

Short term studies of exercise training have shown benefits in cystic fibrosis. Transferring exercise programmes to the community and sustaining them long term is a challenge for the patient. The effectiveness of an individualised unsupervised home based exercise programme was examined in adults with cystic fibrosis over a 1 year period.

METHODS

Subjects were randomised to undertake three sessions per week of upper and lower body exercise based on individualised preferences (n = 30) or to a control group (n = 18). They were evaluated at baseline and at 12 months. The primary outcome measure was improved fitness as assessed by change in blood lactate concentration at the end of an identical constant work rate for both arm and leg ergometric testing. Secondary outcome measurements were heart rate and pulmonary function.

RESULTS

For leg exercise, significant differences were seen at 12 months between the active and control groups in the mean (SE) change in blood lactate levels (-0.38 (0.23) mmol/l v 0.45 (0.25) mmol/l, p<0.05) and heart rate (-4.8 (2.5) bpm v 3.4 (2.5) bpm, p<0.05), confirming a training effect. For arm ergometry there was no change in lactate levels at 12 months but there was a significant difference in forced vital capacity (46 (72) ml v -167 (68) ml, p<0.05).

CONCLUSIONS

A training effect, as measured by a reduction in lactate levels and heart rate, can be achieved with unsupervised individualised home exercise in adults with cystic fibrosis. A benefit to pulmonary function was observed and together these findings suggest that exercise programmes should be encouraged as an important component of care in cystic fibrosis.

Exercise testing in pediatrics

This article discusses exercise physiology and its application in the pediatric population. This article discusses exercise physiology and its application in the pediatric population. The authors briefly review the normal physiologic response to exercise. They then discuss populations in which exercise testing is most useful, the indications and contraindications for graded exercise, and the usual parameters that are measured during testing. Finally, the authors review some of the recent data on exercise performance in specific pediatric populations.

Gender differences in habitual activity in children with cystic fibrosis

AIMS

(1) To compare habitual activity levels in prepubescent and pubescent boys and girls with different degrees of CF lung disease severity and healthy controls. (2) To assess the relation between habitual activity levels and measures of fitness, lung function, nutrition, pancreatic status, and quality of life.

METHODS AND RESULTS

A total of 148 children (75 girls and 73 boys) with CF and matched controls were studied. Regardless of disease severity, there were no differences in habitual activity between prepubescent boys and girls with CF. Pubescent boys with CF were significantly more active than girls with the same degree of disease severity. There were no significant differences in habitual activity between prepubescent children with CF and controls. Pubescent children with mild CF were significantly more active than controls, but those with moderate to severe disease were less active than controls. The best correlates with habitual activity levels were anaerobic power, aerobic capacity, and quality of life. In children with moderate to severe disease, nutrition status correlated significantly with activity levels. The impact of pancreatic status on activity levels and other measures of fitness was most apparent in pubescent girls.

CONCLUSION

Gender differences in habitual activity were evident only after the onset of puberty. The impact of pancreatic insufficiency on measures of fitness and habitual activity was greatest in pubescent females. The reason for this gender difference may be an interplay of genetic, hormonal, and societal factors and is the focus of a longitudinal study.

Growth hormone and exercise tolerance in patients with cystic fibrosis

Cystic fibrosis (CF) is a life-limiting inherited disorder characterised by pulmonary disease, pancreatic dysfunction and symptoms of malnutrition that are all interrelated with low exercise capacity and poor survival rate. Therapy with growth hormone (GH) may improve the reduced dimensional and functional capacity associated with poor nutritional status and catabolism and therefore improve exercise tolerance, quality of life and survival rate in patients with CF. The literature about GH treatment and its effect on exercise tolerance are rather limited, not always consistent and methodological concerns restrict further analysis. GH treatment may have beneficial effects on both growth and exercise tolerance without serious complications in prepubertal children with CF. The observed dimensional changes of the muscular, cardiovascular and pulmonary system seem to improve aerobic exercise capacity and respiratory and peripheral muscle strength. The physiological background of the observed changes is not yet fully understood, therefore, larger-scale studies with an optimised design are required.

Longitudinal Determinants of Peak Aerobic Performance in Children With Cystic Fibrosis

BACKGROUND

Several cross-sectional studies in patients with cystic fibrosis (CF) have shown that nutritional status and lung function are important determinants of peak aerobic capacity (peak oxygen uptake [O(2)peak]). In order to account for individual changes, the aim of this study was to determine the longitudinal relationship of changes in nutritional status, lung function, and O(2)peak in children with CF.

DESIGN AND METHODS

Fat-free mass (FFM), lung function, and O(2)peak were assessed in 65 children with CF at baseline (mean +/- SD age, 10.5 +/- 2.9 years; mean FEV(1), 92.6 +/- 20.5%) and again 2 years later. FFM was calculated using skinfold thickness, and O(2)peak was measured using an incremental treadmill test for children < 12 years old or an incremental cycle ergometry test for children > or =12 years old. Lung function was measured before the exercise test.

RESULTS

Over the 2-year study period, an increase was found for absolute values of FFM (6.1 kg, p < 0.001), FEV(1) (229 mL, p < 0.001), and O(2)peak (240 mL, p < 0.001), while a decrease was found for predicted values of FEV(1) (- 8.9%, p < 0.001) and O(2)peak (- 4.4%, p < 0.05). DeltaO(2)peak over the 2-year period best correlated with DeltaFEV(1) (r = 0.619, p < 0.001) and to a lesser degree with DeltaFFM (r = 0.506, p < 0.001). Multiple regression analysis demonstrated that DeltaFEV(1) and DeltaFFM explained 47% of the variation of the DeltaO(2)peak over the 2-year period.

CONCLUSIONS

Our results show that longitudinal changes in O(2)peak are associated with changes in lung function and to a lesser extent with changes in nutritional status in children with CF. Special consideration should be given to exercise training and nutritional intervention, which might improve long-term clinical outcome in children with CF.

Utility of the Breathing Reserve Index at the Anaerobic Threshold in Determining Ventilatory-Limited Exercise in Adult Cystic Fibrosis Patients

OBJECTIVES

Cardiopulmonary exercise testing in cystic fibrosis (CF) patients is useful to assess functional status and prognosis. Using the current interpretation guidelines, the utility of this testing will be limited in those patients who cannot exercise to a near-maximal level. This study investigates the utility of the breathing reserve index at the anaerobic threshold (BRIAT), which is defined as minute ventilation at the anaerobic threshold (AT)/maximum voluntary ventilation (MVV), to distinguish ventilatory-limited (VL) CF patients from nonventilatory-limited (NVL) CF patients.

DESIGN

Exercise studies on 53 adult CF patients at baseline clinical status performed from 1993 to 1999 were reviewed, of which 40 met the inclusion criteria. The studies were performed via ramp protocol to the symptom-limited maximum on a cycle ergometer with breath-by-breath expired gas analysis. AT was determined noninvasively via the V-Slope method. The patients were classified as VL if they had abnormal spirometry findings, reduced exercise capacity, and a breathing reserve index at maximum exercise (BRImax) of > or = 0.7. NVL patients had a normal BRImax and met the criteria for a maximal study.

RESULTS

VL patients (21 patients) had significantly lower FVC, FEV(1), MVV, and body mass index than NVL patients (19 patients). The BRIAT for the VL group was significantly higher than that for the NVL group (p < 0.001). Logistic regression analysis revealed that BRIAT discriminated VL patients from NVL patients better than a variety of nonexercise variables tested. The BRIAT correlated extremely well with BRImax (r = 0.89; p < 0.01), FVC (r = -0.67; p < 0.001), FEV(1) (r = -0.76; p < 0.001), and FEV(1)/FVC ratio (r = -0.683; p < 0.001). A BRIAT value of 0.29 distinguished VL CF patients from NVL CF patients with 95.2% sensitivity and 84.2% specificity.

CONCLUSIONS

The BRIAT assessed noninvasively correlates well with commonly used measurements of pulmonary function and accurately distinguishes CF patients with and without a ventilatory limitation to exercise. The BRIAT may have utility in the interpretation of exercise studies in CF patients who are unable to exercise to a maximal level.

Use of the gas exchange threshold to noninvasively determine the lactate threshold in patients with cystic fibrosis

OBJECTIVE

The anaerobic threshold (AT) is a submaximal index related to endurance exercise performance, which is usually determined by the measurement of blood lactate concentration during an incremental exercise test (lactate threshold [LT]). The LT, and thus the AT, can also be detected noninvasively in normal subjects by means of the gas exchange threshold (GET). This study was undertaken to validate the use of GET in patients with cystic fibrosis (CF) with a wide range of disease severity, and to assess the reproducibility of this index.

METHODS

In patients with CF (FEV(1) range, 23 to 118% of predicted) and control subjects, gas exchange was measured breath by breath during the incremental exercise tests to allow determination of the GET. Arterialized-venous blood was sampled for determination of the LT. The GET and LT were determined in a blinded manner.

RESULTS

The mean differences (GET - LT) for control subjects (n = 18) and patients with CF (n = 23) were - 40 mL/min and + 10 mL/min, respectively, neither being significantly different from zero. The limits of agreement were +/- 550 mL/min and +/- 410 mL/min, respectively. The mean test-retest differences in GET for control subjects (n = 14) and patients with CF (n = 12) were - 50 mL/min and 0 mL/min, respectively, neither being significantly different from zero; the respective limits of reproducibility were +/- 450 mL/min and +/- 350 mL/min.

CONCLUSIONS

This study demonstrates that in patients with CF, the GET can be used to obtain an unbiased estimate of the LT, and that the GET is reproducible.

A randomized controlled trial of a 3-year home exercise program in cystic fibrosis

OBJECTIVES

To evaluate the effects of a 3-year home exercise program on pulmonary function and exercise tolerance in mildly to moderately impaired patients with cystic fibrosis (CF) and to assess whether regular aerobic exercise is a realistic treatment option.

STUDY DESIGN

Seventy-two patients with CF (7-19 years) were randomly assigned to an exercise group (a minimum of 20 minutes of aerobic exercise, at a heart rate of approximately 150 beats/min, 3 times weekly) or a control group (usual physical activity participation). Pulmonary function, exercise tolerance, clinical status, hospitalizations, and compliance with therapy were monitored during scheduled visits to the hospital's CF clinic.

RESULTS

Sixty-five patients were included in the analyses. The control group demonstrated a greater annual decline in percent of predicted forced vital capacity compared with the exercise group (mean slope +/- SD, -2.42 +/- 4.15 vs -0.25 +/- 2.81; P =.02), with a similar trend for forced expiratory volume in 1 second (-3.47 +/- 4.93 vs -1.46 +/- 3. 55; P =.07). Patients remained compliant with the exercise program over the study period. An improved sense of well-being was reported with exercise.

CONCLUSIONS

Pulmonary function declined more slowly in the exercise group than in the control group, suggesting a benefit for patients with CF participating in regular aerobic exercise. Consistent compliance with the home exercise program and a self-reported positive attitude toward exercise provide further evidence of the feasibility and value of including an aerobic exercise program in the conventional treatment regimen of patients with CF.

Reproducibility of maximal exercise ergometer testing in patients with cystic fibrosis

OBJECTIVES

Exercise testing in patients with cystic fibrosis (CF) has become an important tool in assessing disease severity and predicting overall outcome. The reproducibility of maximal exercise testing was examined in adult subjects with stable CF.

METHODS

Nine subjects with CF underwent a total of three maximal exercise tests carried out under identical circumstances over a 28-day period. Oxygen uptake (VO2), minute ventilation (VE), respiratory frequency (f), heart rate (HR), and arterial oxygen saturation (SaO2) were measured at rest, at end exercise, and at 40% and 70% of maximum workload.

RESULTS

There were no significant differences in these measurements among the three tests. Reproducibility of exercise performance was assessed using the coefficient of variation. The mean within-subject coefficient of variation for test variables at end exercise are as follows: VO2, 6.9%; VE, 6.2%; f, 5.8%; IIR, 3.0%; and SaO2, 1.1%. The mean within-subject coefficient of variation for test variables at 40% and 70% of maximal work rates are as follows: VO2, 5.2% and 4.6%; SaO2, 0.3% and 0.9%; HR, 4.0% and 3%; VE, 5.7% and 6.5%; and f, 5.8% and 7.2%, respectively.

CONCLUSIONS

Variables measured during clinical cycle ergometer exercise testing in adult patients with stable CF are reproducible. No learning effect was found on repeated testing.

Validity of a modified shuttle test in adult cystic fibrosis

BACKGROUND

The purpose of this study was to provide some evidence of the validity of a modified shuttle test (MST) by comparing performance on the MST with peak oxygen consumption (VO2peak) measured during a treadmill test in a group of adult patients with cystic fibrosis.

METHOD

Twenty patients with stable cystic fibrosis performed a ramped maximal treadmill test (STEEP protocol) and the MST using a randomised balanced design.

RESULTS

The relationship between the distance achieved on the MST and VO2peak was strong (r = 0.95, p<0.01) with 90% of the variance in VO2peak explained by the variance in MST distance. The relationship was represented by the regression equation (with 95% confidence intervals) VO2peak = 6.83 (2.85 to 10.80) + 0.028 (0.019 to 0.024) x MST distance.

CONCLUSION

This study provides evidence of the construct validity of the MST as an objective measure of exercise capacity in adults with cystic fibrosis.

Collagen degrading activity associated with Mycobacterium species

BACKGROUND

The mechanism of Mycobacterium tuberculosis penetration into tissues is poorly understood but it is reasonable to assume that there is a contribution from proteases capable of disrupting the extracellular matrix of the pulmonary epithelium and the blood vessels. A study was undertaken to identify and characterise collagen degrading activity of M tuberculosis.

METHODS

Culture filtrate protein extract (CFPE) was obtained from reference mycobacterial strains and mycobacteria isolated from patients with tuberculosis. The collagen degrading activity of CFPE was determined according to the method of Johnson-Wint using 3H-type I collagen. The enzyme was identified by the Birkedal-Hansen and Taylor method and its molecular mass determined by SDS-PAGE and Sephacryl S-300 gel filtration chromatography using an electroelution purified enzyme.

RESULTS

CFPE from Mycobacterium tuberculosis strain H37Rv showed collagenolytic activity that was four times higher than that of the avirulent strain H37Ra. The 75 kDa enzyme responsible was divalent cation dependent. Other mycobacterial species and those isolated from patients with tuberculosis also had collagen degrading activity.

CONCLUSIONS

Mycobacterium species possess a metalloprotease with collagen degrading activity. The highest enzymatic activity was found in the virulent reference strain H37Rv.

Exercise limitations and training for patients with cystic fibrosis

Exercise has much to offer to cystic fibrosis patients. Overcoming the limits of decreased pulmonary function by increasing fitness has a considerable potential to improve patients' quality of life; decreased breathlessness allows greater mobility and participation with peers in social and sporting activities, improves confidence and self-esteem and creates a greater pleasure in life for the individual patient. There are also immediate therapeutic gains and potentially long-term gains with improved survival. Above all, cystic fibrosis patients enjoy and prefer exercise as a therapeutic option to most other forms of therapy.

Determinants of aerobic and anaerobic exercise performance in cystic fibrosis

We examined aerobic and anaerobic exercise performance in 17 subjects with cystic fibrosis (CF) (age 25+/-10 [SD] yr; 47% females; FEV1 62+/-21% pred) and 17 age- and sex-matched control subjects (age 25+/-8 [SD] yr; 41% females; FEV1 112+/-15% pred) in relation to pulmonary function and nutritional status. Aerobic capacity was determined as maximal oxygen consumption (VO2max) (ml/kg/min) and anaerobic threshold (AT; ml VO2/kg/min) from a graded exercise stress test on an electronically braked bicycle ergometer. Anaerobic performance was assessed from the average work of two bouts of pedaling to exhaustion at a load corresponding to 130% Vo2max from graded exercise. Both aerobic and anaerobic performances were decreased in subjects with CF (p < 0.001). The duration of anaerobic exercise in subjects with CF was similar to control subjects. In control subjects, pulmonary function did not correlate to aerobic or anaerobic exercise. In subjects with CF significant relationships between FEV1, vital capacity, and FEF25-75% to AT were found, suggesting the pulmonary limitation to aerobic capacity. In both patients with CF and control subjects, lean body mass and arm muscle area significantly correlated with anaerobic performance but not with VO2max or AT. We conclude that nutritional status, rather than pulmonary function, is the major determinant of anaerobic exercise capacity in CF. The preserved duration of anaerobic exercise at equivalent workloads (corresponding to 130% of VO2max from graded exercise) suggests that readily available energy stores in muscle may be similar in CF and normal individuals.

The anaerobic threshold in cystic fibrosis: comparison of V-slope method, lactate turn points, and Conconi test

Physical exercise can improve sputum clearance in patients with cystic fibrosis (CF). To set up individual training protocols it is desirable to know the anaerobic threshold (AT). Established methods such as blood lactate measurements and ergometry can only be performed in specialized centers. Conconi showed that the heart rate threshold (HRT), i.e., the deflection point from the linear relationship between work load and heart rate, correlated significantly with the AT in healthy adults. To assess the reliability of the HRT in CF, we performed ergometry in 32 CF patients (mean age, 21.0 +/- 5.5 years; mean Shwachman score, 77.8 +/- 12.0) according to the Conconi protocol. The HRT was compared with the aerobic threshold (AeT) as determined by the V-slope method and with two turn points in the lactate performance curve (LTP1, LTP2). An HRT could be obtained in only 17 of the 32 patients (53%). In these 17 patients there was a significant correlation between HRT and the other thresholds, but the absolute values for the AT differed considerably: The mean HRT was 132% higher than the AeT according to Beaver, 107% higher than LTP1, and 19% higher than LTP2. Exercise protocols that rely solely on the HRT in CF will lead to excessive exertion during exercise training programs in these patients. According to these results the HRT of Conconi is not a suitable method to determine appropriate exercise levels in CF training programs and might even be harmful in CF patients. These results also indicate the need to test the reliability of a diagnostic procedure that has been developed only for healthy people.

Exercise testing and prognosis in adult cystic fibrosis

BACKGROUND

The assessment of prognosis is an important issue in cystic fibrosis. The prognostic value of exercise testing in comparison with other predictors of mortality was examined.

METHODS

Ninety two adult patients with cystic fibrosis performed progressive maximal exercise tests and outcome was assessed at five years. The results of exercise testing were examined along with spirometric values, age, sex, body mass index (BMI), and sputum culture.

RESULTS

Twenty two subjects died during the five year follow up period and 67 survived. Five subjects received a lung transplant and were excluded from the analysis. There were significant differences between those who survived and those who died: mean (SE) forced expiratory volume in one second (FEV1) 68.9 (2.7) versus 39.7 (3.5)% predicted, BMI 19.0 (0.3) versus 17.1 (0.4) kg/m2, peak oxygen uptake (VO2 peak) 66.6 (2.2) versus (53.7) (3.7)% predicted, peak work rate (Wpeak) 89.4 (3.8) versus 71.2 (5.5)% predicted, peak minute ventilation (VEpeak) 51.3 (2.0) versus 43.3 (3.1) 1/min, and ventilatory equivalent for oxygen (VE/VO2) 32.4 (0.6) versus 38.7 (1.7). Age, sex, oxygen saturation and Burkholderia cepacia colonisation were not found to be significant predictors of mortality. When significant independent factors were entered into a multivariate logistic regression model only FEV1 was found to be a significant correlate of mortality. A cutoff for FEV1 of 55% predicted gave the best combination of specificity and sensitivity with 54% of those below this value dying within five years and 96% of those above it surviving.

CONCLUSIONS

The results of maximal exercise testing are correlated with survival but they are not better than the FEV1 as prognostic indicators.

Long-term change in exercise capacity, body mass, and pulmonary function in adults with cystic fibrosis

STUDY OBJECTIVES

Cross-sectional studies in patients with cystic fibrosis (CF) have shown that exercise capacity is correlated with pulmonary function and body mass. We have examined whether the same relationships are seen longitudinally in adults with CF.

DESIGN

Subjects who first performed progressive maximal cycle ergometry between 1986 and 1989 were retested using an identical protocol a mean of 6.3 years later.

PARTICIPANTS AND SETTING

Adults with CF attending a regional center.

MEASUREMENTS AND RESULTS

The principal exercise measures were peak oxygen uptake (VO2peak), ventilation (VEpeak), oxygen saturation, and heart rate. Spirometry, weight, and height were also recorded at each time point. At baseline, subjects had a mean age of 19.8 years, body mass index (BMI) of 19.0, FEV1 of 69% predicted, VO2peak of 1.56 L/min, and VEpeak of 48.9 L/min. At repeated testing after a mean interval of 6.3 years, the FEV1 had fallen significantly to 54% predicted (p < 0.001) and the BMI had risen significantly to a mean of 20.9 (p < 0.001). There were no significant differences in VO2peak or VEpeak, although VEpeak was a significantly higher proportion (72% vs 61%) of predicted maximal voluntary ventilation.

CONCLUSIONS

Adults with mild to moderate pulmonary dysfunction were able to increase body mass and maintain VO2peak despite a declining FEV1. VO2peak was not reduced by the decrease in FEV1 because VEpeak was unaffected. Improved nutrition may have contributed to maintaining fitness.

Relationship between dyspnoea, pulmonary function and exercise capacity in patients with cystic fibrosis

The median age of survival in patients with cystic fibrosis (CF) has improved considerably. Despite this improvement, deterioration of pulmonary function and decrease in exercise capacity are still the main problems for many patients. Although dyspnoea is a common complaint in CF patients, relatively little regard has been paid to this symptom. This study examined the relationship between dyspnoea, bicycle exercise capacity and pulmonary function in patients with CF. In 14 patients in a stable clinical condition, pulmonary function [forced expiratory volume in 1 s (FEV1), inspiratory vital capacity (IVC)], bicycle exercise capacity [maximum exercise capacity (Wmax)], subjective degree of dyspnoea during daily living [Medical Research Council (MRC) dyspnoea scale], and during exercise (Borg scale) were assessed. The mean (SD) age of the patients was 25 (6.8) years, FEV1 was 41 (19)% predicted, IVC was 63 (17)% predicted and FEV1/IVC ratio was 47 (10)%; median (range) Wmax was 55 (0-79)% predicted. Bicycle exercise test performance appeared to be mainly determined by pulmonary function and MRC dyspnoea grade; multiple regression equation containing FEV1 and dyspnoea accounted for 76% of the variance in Wmax (% predicted) (Wmax = -7.9 dysp + 1.1 FEV1, +24). Exercise dyspnoea, assessed by the Borg scale, showed a significant linear correlation with minute ventilation. (VE), maximal voluntary ventilation (MVV) (%) (r = 0.76; P < 0.001). Medical Research Council dyspnoea score correlated relatively poorly with FEV1 (% predicted) (r = -0.17; n.s.) and IVC (% predicted) (r = -0.48; n.s.). Borg score at maximal exercise did not correlate with MRC dyspnoea score (r = -0.07). Borg50% score correlated significantly with MRC dyspnoea score (r = 0.61; P < 0.05). These results show that dyspnoea has an influence on exercise capacity. Dyspnoea score showed a large inter-individual variation, not strongly related to pulmonary function. It is concluded that dyspnoea deserves more attention in CF patients and needs to be assessed in rehabilitation programmes and other intervention studies in these patients.

Role of exercise in the evaluation and management of pulmonary disease in children and youth

Asthma is the most common chronic pulmonary disorder affecting children in the U.S. Cystic fibrosis is the most common life-shortening inherited disease affecting white populations. With both disorders, children may have impaired exercise tolerance and abnormal cardiopulmonary responses to exercise. Exercise testing can aid in the diagnosis of exercise-induced asthma, and in determining prognosis in cystic fibrosis. Children with asthma and cystic fibrosis have been shown to benefit from exercise training, mainly through improved aerobic fitness and cardiopulmonary efficiency. In summary, exercise plays a valuable role in the evaluation and management of children with asthma and cystic fibrosis.

Factors limiting anaerobic performance in adolescent males with cystic fibrosis

Forty-one adolescent males (11.1-18.3 yr) with cystic fibrosis (CF) and 37 healthy adolescent males (11.1-17.9 yr) performed a Wingate Anaerobic Test (WAnT). The group with CF was subdivided by sexual maturity, nutritional status, and degree of airway obstruction. The subjects with CF had lower absolute power outputs than the healthy controls [mean power in Watts (mean +/- SD): 350.2 +/- 135.9 vs 424.5 +/- 120.4, P < 0.001; peak power: 525.2 +/- 178.4 vs 665.9 +/- 191.3, P < 0.001). When absolute power was corrected for lean body mass, the subjects with CF had lower power outputs than the healthy controls (mean power in W.kg-1: 8.9 +/- 1.7 vs 9.6 +/- 0.9, P < 0.05; peak power: 13.4 +/- 2.1 vs 15.0 +/- 1.6, P < 0.05). The subgroup with CF with a higher body mass index (BMI > 17.5 kg.m-2) had higher peak and mean power output than subjects with CF with a lower BMI in both absolute power and when power was expressed per lean body mass. When sexual maturation was considered, subjects with CF with salivary testosterone greater than 4.0 ng.dl-1 had a higher mean and peak power in both absolute terms and relative to lean body mass than subjects with CF with salivary testosterone less than 4.0 ng.dl-1. Multiple regression analysis indicated that the nutritional factor accounted for 70%-80% of the variability in power output in the subjects with CF, while testosterone accounted for 10% of the variability. Pulmonary function was not a significant independent correlate of anaerobic power. Our results suggest that nutritional status, and to a lesser extent maturational factors, may play a more important role than pulmonary function in determining anaerobic fitness in male adolescents with CF.

An expanded scoring system including an index of nutritional status for patients with cystic fibrosis

Evaluation of success or failure of therapy for patients with cystic fibrosis (CF) commonly relies on the results of a single pulmonary function test (PFT). Most PFT measurements reflect different functional aspects of the lung. Although no single parameter can summarize all aspects of lung function, a combination of several may provide an advantage by reflecting the overall abnormality of lung function in one number. Cropp et al. (1982, Am Rev Respir Dis 126:211-216) developed a multiparameter pulmonary function score (PFS) using the results of six separate parameters obtained from a PFT. In CF, there is also the potential for declining nutritional status (NS), leading to malnutrition and skeletal muscle wasting. Our aim was to expand the PFS by including weighted information on NS, and to determine whether the expanded score (nutritional-pulmonary function score, NPFS) was more sensitive in detecting change in outcome variables than the PFS. Individual PFT parameters, percent ideal body weight (%IBW), and an index of anaerobic performance (AP) were measured in 21 patients on admission to the hospital and again at discharge. In the group as a whole, in-hospital therapy resulted in improvement (P < 0.01) in individual PFT parameters, %IBW, PFS, and NPFS, and no change in AP. While the PFS more effectively reflected improvement in lung function than did any single PFT parameter, the NPFS resulted in an even more sensitive index of change. Based on these results, we believe that the NPFS, which includes both lung and nutritional status, provides an effective and sensitive index of disease severity that can be used as a unifying measure to: 1) detect disease progression; 2) guide rehabilitation and training; 3) stratify patients for clinical trials; or 4) evaluate the effects of a therapeutic intervention.