Exercise testing and prognosis in adult cystic fibrosis

Mechanisms of ventilatory limitation to maximum exercise in children and adolescents with chronic airway diseases

INTRODUCTION

Exercise intolerance is common in chronic airway diseases (CAD), but its mechanisms are still poorly understood. The aim of this study was to evaluate exercise capacity and its association with lung function, ventilatory limitation, and ventilatory efficiency in children and adolescents with cystic fibrosis (CF) and asthma when compared to healthy controls.

METHODS

Cross-sectional study including patients with mild-to-moderate asthma, CF and healthy children and adolescents. Anthropometric data, lung function (spirometry) and exercise capacity (cardiopulmonary exercise testing) were evaluated. Primary outcomes were peak oxygen consumption (VO2 peak), forced expiratory volume in 1 s (FEV1 ), breathing reserve (BR), ventilatory equivalent for oxygen consumption (VE /VO2 ) and for carbon dioxide production (VE /VCO2 ), both at the ventilatory threshold (VT1 ) and peak exercise.

RESULTS

Mean age of 147 patients included was 11.8 ± 3.0 years. There were differences between asthmatics and CF children when compared to their healthy peers for anthropometric and lung function measurements. Asthmatics showed lower VO2 peak when compared to both healthy and CF subjects, although no differences were found between healthy and CF patients. A lower BR was found when CF patients were compared to both healthy and asthmatic. Both CF and asthmatic patients presented higher values for VE /VO2 and VE /VCO2 at VT1 when compared to healthy individuals. For both VE /VO2 and VE /VCO2 at peak exercise CF patients presented higher values when compared to their healthy peers.

CONCLUSION

Patients with CF achieved good exercise capacity despite low ventilatory efficiency, low BR, and reduced lung function. However, asthmatics reported reduced cardiorespiratory capacity and normal ventilatory efficiency at peak exercise. These results demonstrate differences in the mechanisms of ventilatory limitation to maximum exercise testing in children and adolescents with CAD.

Resolvin D1 improves airway inflammation and exercise capacity in cystic fibrosis lung disease

Mucus plugging and non-resolving inflammation are inherent features of cystic fibrosis (CF) that may lead to progressive lung disease and exercise intolerance, which are the main causes of morbidity and mortality for people with CF. Therefore, understanding the influence of mucus on basic mechanisms underlying the inflammatory response and identifying strategies to resolve mucus-driven airway inflammation and consequent morbidity in CF are of wide interest. Here, we investigated the effects of the proresolving lipid mediator resolvin (Rv) D1 on mucus-related inflammation as a proof-of-concept to alleviate the burden of lung disease and restore exercise intolerance in CF. We tested the effects of RvD1 on inflammatory responses of human organotypic airways and leukocytes to CF mucus and of humanized mice expressing the epithelial Na + channel (βENaC-Tg) having CF-like mucus obstruction, lung disease, and physical exercise intolerance. RvD1 reduced pathogenic phenotypes of CF-airway supernatant (ASN)-stimulated human neutrophils, including loss of L-selectin shedding and CD16. RNASeq analysis identified select transcripts and pathways regulated by RvD1 in ASN-stimulated CF bronchial epithelial cells that are involved in sugar metabolism, NF-κB activation and inflammation, and response to stress. In in vivo inflammation using βENaC TG mice, RvD1 reduced total leukocytes, PMN, and interstitial Siglec-MΦ when given at 6-8 weeks of age, and in older mice at 10-12 weeks of age, along with the decrease of pro-inflammatory chemokines and increase of anti-inflammatory IL-10. Furthermore, RvD1 treatment promoted the resolution of pulmonary exacerbation caused by Pseudomonas aeruginosa infection and significantly enhanced physical activity and energy expenditure associated with mucus obstruction, which was impaired in βENaC-Tg mice compared with wild-type. These results demonstrate that RvD1 can rectify features of CF and offer proof-of-concept for its therapeutic application in this and other muco-obstructive lung diseases.

Dynamic Hyperinflation While Exercising-A Potential Predictor of Pulmonary Deterioration in Cystic Fibrosis

BACKGROUND

Lung function deterioration in cystic fibrosis (CF) is typically measured by a decline in the forced expiratory volume in one second (FEV1%), which is thought to be a late marker of lung disease. Dynamic hyperinflation (DH) is seen in obstructive lung diseases while exercising. Our aim was to assess whether DH could predict pulmonary deterioration in CF; a secondary measure was the peak VO2.

METHODS

A retrospective study was conducted of people with CF who performed cardiopulmonary exercise tests (CPETs) during 2012-2018. The tests were classified as those demonstrating DH non-DH. Demographic, genetic, and clinical data until 12.2022 were extracted from patient charts.

RESULTS

A total of 33 patients aged 10-61 years performed 41 valid CPETs with valid DH measurements; sixteen (39%) demonstrated DH. At the time of the CPETs, there was no difference in the FEV1% measurements between the DH and non-DH groups (median 83.5% vs. 87.6%, respectively; p = 0.174). The FEV1% trend over 4 years showed a decline in the DH group compared to the non-DH group (p = 0.009). A correlation was found between DH and the lung clearance index (LCI), as well as the FEV1% (r = 0.36 and p = 0.019 and r = -0.55 and p = 0.004, respectively). Intravenous (IV) antibiotic courses during the 4 years after the CPETs were significantly more frequent in the DH group (p = 0.046). The peak VO2 also correlated with the FEV1% and LCI (r = 0.36 and p = 0.02 and r = -0.46 and p = 0.014, respectively) as well as with the IV antibiotic courses (r = -0.46 and p = 0.014).

CONCLUSIONS

In our cohort, the DH and peak VO2 were both associated with lung function deterioration and more frequent pulmonary exacerbations. DH may serve as a marker to predict pulmonary deterioration in people with CF.

Relationship of Exercise Capacity, Physical Function, and Frailty Measures With Clinical Outcomes and Healthcare Utilization in Lung Transplantation: A Scoping Review

Measures of exercise capacity, frailty, and physical function are commonly used in lung transplant candidates and recipients to evaluate their physical limitations and the effects of exercise training and to select candidates for transplantation. It is unclear how these measures are related to clinical outcomes and healthcare utilization before and after lung transplantation. The purpose of this scoping review was to describe how measures of exercise capacity, physical function, and frailty are related to pre- and posttransplant outcomes.

The feasibility of collecting the physiotherapy outcomes airway clearance, physical activity and fitness for the Australian Cystic Fibrosis Data Registry

BACKGROUND

Physiotherapy-related data, such as airway clearance techniques (ACTS), physical activity and aerobic fitness are not consistently included in international cystic fibrosis (CF) data registries. This study aimed to pilot the collection of ACTS, physical activity and fitness in a hospital CF clinic, as a step towards informing future national implementation.

METHODS

This study was undertaken in a CF clinic within a major tertiary hospital. Patients and families were invited to participate. Participants completed self-report questionnaires on ACT use and those aged ≥ 10 years completed a physical activity questionnaire (Core Indicators and Measures of Youth Health Survey) and aerobic fitness test (the A-STEP test). Participants also completed a survey to explore the tolerance and acceptability of the fitness test, and the perceived accuracy of the self-reported data collection.

RESULTS

Forty patients agreed to participate in the study (mean age = 9.8, SD = 4.1 years old; 52.5% female). All patients and/or families that were approached agreed to participate and completion rate for the ACTs and physical activity surveys was 98% and 100% (respectively). Completion rate for the fitness test was 55%, due to time constraints. Most participants agreed (≥ 90%) they could accurately provide ACT and physical activity data, and the assessments were tolerable and acceptable.

CONCLUSIONS

Patients with CF and their families are able to and can acceptably provide physiotherapy-related data, and collecting self-report ACTs and physical activity data is highly feasibly during routine CF clinic visits. However, aerobic fitness testing using the A-STEP test may be less feasible in clinic environments, due to time constraints.

Ventilatory efficiency and its clinical and prognostic value in adults with cystic fibrosis

Cystic fibrosis, due to the absence or abnormal function of the cystic fibrosis transmembrane conductance regulator, is the most common life-limiting autosomal recessive genetic disorder among the Caucasian population. The lungs are particularly affected due to thick and tenacious mucus causing parenchymal anomalies ranging from bronchiectasis, progressive airflow limitation, respiratory infections, lung destruction and ultimately respiratory failure. Despite the remarkable advances in treatment that have greatly improved survival, most patients experience progressive exercise curtailment, with the consequence that a growing number of patients with cystic fibrosis will be referred for exercise-based evaluations in the forthcoming years. Cardiopulmonary exercise testing, in particular, is a useful tool to assess the mechanisms of exercise intolerance in individual patients that may have treatment and prognostic implications. In this review, we will focus on ventilatory efficiency and its clinical and prognostic value in adults with cystic fibrosis.

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.

Emerging non-pulmonary complications for adults with cystic fibrosis

Improved treatments of cystic fibrosis (CF) related lung disease have resulted in increased longevity, but also increasing prevalence and severity of extrapulmonary manifestations of CF, treatment related complications, age-related conditions and psychosocial effects of longstanding chronic disease. Likewise, the recognition of mild CF phenotypes has changed the landscape of CF disease. This review outlines our current understanding of the common extrapulmonary complications of CF, as well as the changing landscape and future directions of the extrapulmonary complications experienced by patients with CF.

Should the physiotherapy outcomes airway clearance, physical activity and fitness be recorded on the Australian Cystic Fibrosis Data Registry? A consensus approach

BACKGROUND

Physiotherapy is a cornerstone of cystic fibrosis (CF) management, yet the Australian CF Data Registry (ACFDR) currently does not record physiotherapy-related data. This study aimed to gather opinions from lead Australian CF physiotherapists regarding the importance and feasibility of collecting physiotherapy-related data on the ACFDR.

METHODS

A three-round online Delphi survey was conducted to gather expert stakeholder opinion and consensus agreement. Lead physiotherapists from all 23 Australian CF centres were invited to participate. Round one explored the potential benefits, barriers and importance of recording three physiotherapy-related domains on the ACFDR: airway clearance, physical activity and fitness. Subsequent rounds were developed based on the findings from the previous round and sought consensus (80% agreement) for the inclusion of physiotherapy-related data on the ACFDR and for the most appropriate methods of collecting such data.

RESULTS

The response rate was > 80% for all rounds. Participants agreed that collection of airway clearance, physical activity and fitness data on the ACFDR was important and feasible. Findings suggested that airway clearance and physical activity should be collected using self-reported questionnaires, while fitness should be measured using a field-based test.

CONCLUSIONS

Australian lead CF physiotherapists believe that collection of airway clearance, physical activity and fitness on the ACFDR is important and feasible. Future work is needed to pilot the data collection procedure to examine its feasibility in real-world clinical settings. This study demonstrates how Delphi methodology can provide a contemporary summary of expert clinicians' opinion that may underpin nation-wide health service improvement.

The Fitter the Better? Cardiopulmonary Exercise Testing Can Predict Pulmonary Exacerbations in Cystic Fibrosis

Background: The role of cardiopulmonary exercise testing (CPET) in the assessment of prognosis in CF (cystic fibrosis) is crucial. However, as the overall survival of the disease becomes better, the need for examinations that can predict pulmonary exacerbations (PEx) and subsequent deterioration becomes evident. Methods: Data from a 10-year follow up with CPET and spirometry of CF patients were used to evaluate whether CPET-derived parameters can be used as prognostic indexes for pulmonary exacerbations in patients with CF. Pulmonary exacerbations were recorded. We used a survival analysis through Cox Regression to assess the prognostic role of CPET parameters for PeX. CPET parameters and other variables such as sputum culture, age, and spirometry measurements were tested via multivariate cox models. Results: During a 10-year period (2009–2019), 78 CF patients underwent CPET. Cox regression analysis revealed that VO₂peak% (peak Oxygen Uptake predicted %) predicted (hazard ratio (HR), 0.988 (0.975, 1.000) p = 0.042) and PetCO₂ (end-tidal CO₂ at peak exercise) (HR 0.948 (0.913, 0.984) p = 0.005), while VE/VO₂ and (respiratory equivalent for oxygen at peak exercise) (HR 1.032 (1.003, 1.062) p = 0.033) were significant predictors of pulmonary exacerbations in the short term after the CPET. Additionally, patients with VO₂peak% predicted <60% had 4.5-times higher relative risk of having a PEx than those with higher exercise capacity. Conclusions: CPET can provide valuable information regarding upcoming pulmonary exacerbation in CF. Patients with VO₂peak <60% are at great risk of subsequent deterioration. Regular follow up of CF patients with exercise testing can highlight their clinical image and direct therapeutic interventions.

The correlation between 6-min walk test and respiratory parameters in children with cystic fibrosis

BACKGROUND

The 6-min walk test (6MWT) is a sub-maximal exercise test and has been widely used for evaluating of exercise capacity of patients with cystic fibrosis (CF) in recent years. Few studies have examined the relationship between 6MWT and parameters used to assess the severity of the disease in children with CF. In this study, we have examined this relationship to find out if 6MWT can be a marker of the severity of cystic fibrosis.

METHODS

A cross-sectional study was done to analyze the correlations among spirometry parameters, body mass index (BMI), chest tomography (CT), and 6MWT. CF patients, aged 7-14 years, were involved.

RESULTS

Seventy-six patients, 32F/44M, mean age 10.49 ± 3.18 years, were studied. The mean distance in 6MWT was 447 ± 84.1. The following correlations versus distance were found: FEV1 (r = 0.255, p = 0.026), FVC(r = 0.285, p = 0.013), FEF25-75% (r = 0.546, p < 0.001), BMI (r = 0.163, p = 0.160), and CT (r = 0.075, p = 0.520).The following correlations versus O₂ saturation (SpO₂) decline were found: FEV1 (r = -0.393, p < 0.001), FVC (r = -0.431, p < 0.001), FEF25-75% (r = -0.296, p = 0.010), BMI (r = 0.042, p = 0.721), and CT (r = -0.196, p = 0.090). There was a significant correlation between 6MWT (distance and SpO₂ decline) and pulmonary function test. There was no significant correlation between BMI, chest CT, and 6MWT.

CONCLUSIONS

6MWT can be applied beside spirometry and chest CT for CF patients follow up.

Toward the Establishment of New Clinical Endpoints for Cystic Fibrosis: The Role of Lung Clearance Index and Cardiopulmonary Exercise Testing

As Cystic Fibrosis (CF) treatment advances, research evidence has highlighted the value and applicability of Lung Clearance Index and Cardiopulmonary Exercise Testing as endpoints for clinical trials. In the context of these new endpoints for CF trials, we have explored the use of these two test outcomes for routine CF care. In this review we have presented the use of these methods in assessing disease severity, disease progression, and the efficacy of new interventions with considerations for future research.

VO2max as an exercise tolerance endpoint in people with cystic fibrosis: Lessons from a lumacaftor/ivacaftor trial

BACKGROUND

The impact of lumacaftor/ivacaftor on exercise tolerance in people with cystic fibrosis (CF) has not been thoroughly studied.

METHODS

We conducted a multisite Phase 4 trial comparing the impact of lumacaftor/ivacaftor on exercise tolerance with that of placebo in participants ≥ 12 years of age with CF homozygous for F508del-CFTR. The primary endpoint was relative change from baseline in maximum oxygen consumption (VO_2max) during cardiopulmonary exercise testing (CPET) at Week 24. The key secondary endpoint was relative change from baseline in exercise duration during CPET at Week 24. Other secondary endpoints included changes in other indices of exercise tolerance and changes in CF assessments; safety and tolerability were assessed as an endpoint.

RESULTS

Seventy participants were randomized to receive lumacaftor/ivacaftor (n = 34) or placebo (n = 36). The least-squares mean difference for lumacaftor/ivacaftor versus placebo in relative change in VO_2max from baseline at Week 24 was -3.2% (95% CI: -9.2, 2.9; P=0.3021); the least-squares mean difference in relative change from baseline in exercise duration at Week 24 was -3.2% (95% CI: -8.0, 1.6). Safety results were consistent with the known lumacaftor/ivacaftor safety profile.

CONCLUSIONS

Definitive conclusions regarding the impact of lumacaftor/ivacaftor on exercise tolerance cannot be drawn from these results; however, multicenter studies using CPETs can be reliably performed with multiple time points and conventional methods, provided that calibration can be achieved. Future studies of exercise tolerance may benefit from lessons learned from this study. NCT02875366.

New strategies of physical activity assessment in cystic fibrosis: a pilot study

Background

Regular physical activity (PA) is a valued part of cystic fibrosis (CF) care. Although the accelerometer, SenseWear Armband (SWA), accurately measures habitual PA in CF, it is mostly used for research purposes. For the first time, we analyzed different methods of measuring PA in daily life by the use of smartphones and other electronic devices such as smartwatch and Fitbit.

Methods

Twenty-four stable adults with CF (mean age 37.5 ± 11.5SD yrs.; FEV₁ 58 ± 19% predicted, BMI 22.9 ± 3.2) were studied. Daily PA was monitored for seven consecutive days. All patients wore the accelerometer SWA and at the same time they monitored PA with the electronic device they used routinely. They were allocated into one of four arms according to their device: Smartwatch, Fitbit, Android smartphones and iOS smartphones. PA related measurements included: duration of PA, energy expenditure, number of steps.

Results

There was a good agreement between SWA and Fitbit for number of steps (p = 0.605) and energy expenditure (p = 0.143). iOS smartphones were similar to SWA in monitoring the number of steps (p = 0.911). Significant differences were found between SWA and both Smartwatch and Android smartphones.

Conclusions

Fitbit and iOS smartphones seem to be a valuable approach to monitor daily PA. They provide a good performance to measure step number compared to SWA.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12890-020-01313-5.

Exercise capacity and ventilation inhomogeneity in cystic fibrosis: A cross-sectional study

BACKGROUND

Lung clearance index (LCI_2.5 ) is a marker of overall lung ventilation inhomogeneity and has proven to be able to detect early peripheral damage in subjects with cystic fibrosis (CF), with greater sensitivity than conventional spirometry. Combining its sensitivity with the output of an incremental exercise testing, we hypothesized that any sign of ventilation inhomogeneity in subjects without severe airflow obstruction and with a normal exercise tolerance could be relevant for the CF team, tracking early lung disease and potential exercise limiting factors.

METHODS

Patients with CF in clinical stable conditions were recruited between 2015 and 2017. Available spirometry, nitrogen multiple-breath washout test and symptoms-limited exercise testing performed as parts of patients' annual routine evaluation were considered for this cross-sectional study. To describe the relationship between exercise intensity and ventilation inhomogeneity, a linear regression analysis was performed using backward elimination based on Akaike information criteria.

RESULTS

Seventy-seven patients (38 females) were included. S_acin and LCI_2.5 were significantly higher in patients with an overall reduced exercise tolerance. Peak work developed during exercise was associated with body mass index (b = 5.25; 95% confidence interval [CI] = 1.53-8.98), forced expiratory volume in 1 second (FEV₁ ; b = 3.71; 95% CI = 1.96-5.46), Pseudomonas aeruginosa chronic infection (b = -8.84; 95% CI = -15.84 to -1.84) but not with LCI_2.5 .

CONCLUSION

Exercise capacity and airflow obstruction are associated in this Italian CF cohort. Considering the greater discriminatory power of LCI_2.5 over FEV₁ and peak work, the Godfrey protocol without gas analysis cannot provide detailed information about lung function or efficiency. However, this incremental protocol without gas exchange measures can still provide the CF team with information about exercise tolerance and disability.

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.

Minimal detectable change in six-minute walk test in children and adolescents with cystic fibrosis

PURPOSE

To provide test-retest reliability for the 6-min walk test and the physiological variables obtained during the test, and to establish the minimal detectable change for the distance walked in children and adolescents with cystic fibrosis.

METHODS

40 patients performed two 6-min walk tests on the same day (separated by 30-min of rest). The perceived breathlessness and fatigue in the legs were assessed with the modified Borg scale. The peripheral muscle strength was assessed using a hand dynamometer device, the medicine ball throw test and the horizontal jump test.

RESULTS

The test-retest reliability of the distance walked, dyspnea and fatigue in the legs were good for children (minimal detectable change_90-95: 59.39-70.55 m) and for adolescents (minimal detectable change_90-95: 47.81-56.8 m) with cystic fibrosis. Exercise tolerance is more related to 6-min walk work (distance walked x body weight) than to the distance walked alone and showed a positive association with peripheral muscle strength and forced vital capacity.

CONCLUSIONS

The 6-min walk test is a reproducible and reliable tool to measure exercise tolerance for children and adolescents with cystic fibrosis. The minimal detectable changes reported for the distances achieved by these patients will be useful to identify the effectiveness of therapies aimed at alleviating or improving impaired physical capacity.IMPLICATIONS FOR REHABILITATIONThe 6-min walk test could be used to measure exercise tolerance for children and adolescents with cystic fibrosis, as it is a reliable test over time.An increase in the distance covered in the 6-min walk test that exceeds the minimum detectable change is recommended to determine improved exercise tolerance for children and adolescents with cystic fibrosis.The use of the 6-min walk work (distance walked x body weight) is recommended because it correlates better with exercise tolerance than the distance alone in children and adolescents with cystic fibrosis.

Reduced exercise ventilatory efficiency in adults with cystic fibrosis and normal to moderately impaired lung function

Despite being a hallmark and an independent prognostic factor in several cardiopulmonary diseases, ventilatory efficiency-i.e., minute ventilation/carbon dioxide output relationship (V̇e/V̇co₂)-has never been systematically explored in cystic fibrosis (CF). To provide a comprehensive frame of reference regarding measures of ventilatory efficiency in CF adults with normal to moderately impaired lung function and to confirm the hypothesis that V̇e/V̇co₂ is a sensitive marker of early lung disease. CF patients were divided into three groups, according to their spirometry: normal (G₁), mild impairment (G₂), and moderate impairment (G₃) in lung function. All participants underwent incremental cardiopulmonary exercise testing on a cycle ergometer. Lowest V̇e/V̇co₂ ratio (nadir) and the slope and the intercept of the linear region of the V̇e/V̇co₂ relationship were contrasted in a two-center retrospective analysis, involving 72 CF patients and 36 healthy controls (HC). Compared with HC, CF patients had significantly higher V̇e/V̇co₂ nadir, slope, and intercept (P < 0.001, P < 0.001, and P = 0.049, respectively). Subgroup analysis revealed significant differences in nadir (P = 0.001) and slope (P = 0.012) values even between HC and G₁. Dynamic hyperinflation related negatively with slope (P = 0.045) and positively with intercept (P = 0.001), while no impact on nadir was observed. Ventilatory inefficiency is a clear feature of adults with CF, even among patients with normal spirometry. V̇e/V̇co₂ nadir seems to be the most reliable metric to describe ventilatory efficiency in CF adults. Further prospective studies are needed to clarify whether V̇e/V̇co₂ could represent a useful marker in the evaluation of early lung disease in CF.NEW & NOTEWORTHY This is the first study to investigate ventilatory efficiency in a cohort of adult cystic fibrosis (CF) patients with nonsevere lung disease. The finding of impaired ventilatory efficiency in patients with normal lung function confirms the higher sensitivity of exercise testing in detecting early lung disease compared with spirometry. Dynamic hyperinflation plays a significant role in determining the behavior of V̇e/V̇co₂ slope and intercept values with increasing lung function impairment. Apparently free from interference from mechanical constraints, V̇e/V̇co₂ nadir seems the most reliable parameter to evaluate ventilatory efficiency in CF adults.

Prediction of peak oxygen uptake using the modified shuttle test in children and adolescents with cystic fibrosis

BACKGROUND

Several tests may be used to assess exercise intolerance in cystic fibrosis (CF), including the gold standard cardiopulmonary exercise test (CPET) and the Modified Shuttle Test (MST).

OBJECTIVE

To evaluate the use of the MST as a predictor of peak oxygen uptake (VO₂ peak) and to compare VO₂ peak and maximal heart rate (HRmax) obtained in both tests.

METHODS

Cross-sectional study including individuals with CF aged between 6 and 20 years old. Participants who were unable to perform the tests and/or presented signs of pulmonary exacerbation were excluded. Demographic, anthropometric, clinical and spirometric values ​​were collected. CPET and the MST were performed in two consecutive outpatient visits. HRmax, peripheral oxygen saturation, dyspnea, and VO₂ peak measured and estimated were compared.

RESULTS

Twenty-four patients, mean age 15.7 ± 4.2 years and FEV₁ (% predicted) 76.4 ± 23.8, were included. Mean values ​​of HRmax (bpm) and HRmax in percent of predicted (HRmax%) were lower (P = 0.01) in the MST (171.6 ± 14.5 and 87.1 ± 7.5) compared to CPET (180.9 ± 10.0 and 91.9 ± 5.4). However, there was no significant differences between tests in the variation (delta) for HRmax and HRmax% (P = 0.17). A strong correlation (r = 0.79; P < 0.0001) was found between distance achieved (MST) and VO₂ peak (CPET). The regression model to estimate VO₂ peak resulted in the following equation: VO₂ (mL · kg^-1 · min^-1 ) = 20.301 + 0.019 × MST distance (meters). There was no difference (P = 0.50) between VO₂ peak measured (CPET) and estimated by the equation.

CONCLUSION

The MST may be an alternative method to evaluate exercise capacity and to predict VO₂ peak in children and adolescents with CF.

Airway clearance physiotherapy improves ventilatory dynamics during exercise in patients with cystic fibrosis: a pilot study

BACKGROUND

Airflow limitation and dynamic hyperinflation may limit exercise capacity in patients with cystic fibrosis (CF). The aim was to investigate whether the undertaking of airway clearance physiotherapy (ACT) prior to cardiopulmonary exercise testing (CPET) results in improvements in exercise capacity.

METHODS

A prospective randomised, cross-over pilot study was performed in children aged >9 years. Spirometry, plethysmography and CPET were performed on two separate occasions-one test with ACT prior to CPET and the other without.

RESULTS

12 patients with CF were included in the study with a mean (SD) age of 12.83 (1.85) years. No significant difference in peak oxygen uptake (VO₂) was found between the tests. However, lower minute ventilation (V_E) and ventilatory equivalents (V_EVO₂ and V_EVCO₂) at ventilatory threshold (VT) were noted when ACT was undertaken prior to CPET. The mean(SD) V_E (L/min) at VT was 26.67 (5.49) vs 28.92 (6.3) (p=0.05), V_EVO₂ (L/min) at VT was 24.5 (1.75) vs 26.05 (2.5) (p=0.03) and V_EVCO₂ (L/min) at VT was 26.58 (2.41) vs 27.98 (2.11) (p=0.03).

CONCLUSIONS

These pilot data suggest that ACT prior to exercise may lead to improved ventilatory dynamics during exercise in individuals with CF.

Is daily physical activity affected by dynamic hyperinflation in adults with cystic fibrosis?

Background

The aim of this study was to investigate the relationship between dynamic hyperinflation and daily physical activity (DPA) in adults with cystic fibrosis (CF).

Methods

Thirty-four clinically stable CF were studied. All patients undertook incremental cardiopulmonary exercise testing (CPET). CPET-related measurements included: oxygen uptake (V’O₂), carbon dioxide production (V’CO₂), ventilatory profile, work rate (W), inspiratory capacity (IC), end-expiratory lung volume (EELV). PA was assessed using the accelerometer SenseWear Pro3 Armband.

Results

Exercise tolerance was reduced in most of patients and the mean V’O_2,peak value was 75.2% of predicted (28.5 ± 4.8 ml/min/kg). Seventy % of patients responded to CPET with dynamic hyperinflation. Higher incidence of dynamic hyperinflation was found in CF males compared to CF females (p = 0.026). Patients who developed dynamic hyperinflation during CPET had higher vigorous PA (p = 0.01) and more total energy expenditure (p = 0.006) than patients who did not. EELVΔ was related to activities requiring vigorous intensity and total energy expenditure (R = 0.46, p = 0.001; R = 0.57, p <  0.001).

Conclusions

In adults with CF and mild to moderate lung impairment, DPA might not be limited by dynamic hyperinflation.

Electronic supplementary material

The online version of this article (10.1186/s12890-018-0623-7) contains supplementary material, which is available to authorized users.

Six-minute walk test as a determinant of the functional capacity of children and adolescents with cystic fibrosis: A systematic review

Cystic Fibrosis (CF) is a multisystem disorder. The involvement of the respiratory system is frequent and culminates in dyspnea and exercise intolerance. Functional capacity is an important diagnostic tool, because it reflects the cardiorespiratory status, quality of life and prognosis. This systematic review aims to assess the reproducibility and validity of the six minute walk test (6MWT) to reflect the functional capacity of children and adolescents with cystic fibrosis, and also the correlation between 6MWT and lung function. Searches for articles were performed in eight databases using MeSH/DeCS keywords. A total of 695 articles were found and, after verifying all eligibility criteria, six articles were included for analysis and scoring regarding the methodological quality according to the QUADAS scale (Quality Assessment of Diagnostic Accuracy Studies). All articles had good methodology (QUADAS between 9 and 11 points). The 6MWT is not correlated with lung function. There is a strong indication that the 6MWT is a reproducible test to assess the functional capacity of children and adolescents with CF. The validity assessment could not be reached because the studies included in this systematic review did not use adequate statistical tools to carry out such an evaluation.

Ventilatory response to exercise in cardiopulmonary disease: the role of chemosensitivity and dead space

The lungs and heart are irrevocably linked in their oxygen (O₂) and carbon dioxide (CO₂) transport functions. Functional impairment of the lungs often affects heart function and vice versa The steepness with which ventilation (V'_E) rises with respect to CO₂ production (V'_CO2 ) (i.e. the V'_E/V'_CO2 slope) is a measure of ventilatory efficiency and can be used to identify an abnormal ventilatory response to exercise. The V'_E/V'_CO2 slope is a prognostic marker in several chronic cardiopulmonary diseases independent of other exercise-related variables such as peak O₂ uptake (V'_O2 ). The V'_E/V'_CO2 slope is determined by two factors: 1) the arterial CO₂ partial pressure (P_aCO2 ) during exercise and 2) the fraction of the tidal volume (V_T) that goes to dead space (V_D) (i.e. the physiological dead space ratio (V_D/V_T)). An altered P_aCO2 set-point and chemosensitivity are present in many cardiopulmonary diseases, which influence V'_E/V'_CO2 by affecting P_aCO2 Increased ventilation-perfusion heterogeneity, causing inefficient gas exchange, also contributes to the abnormal V'_E/V'_CO2 observed in cardiopulmonary diseases by increasing V_D/V_T During cardiopulmonary exercise testing, the P_aCO2 during exercise is often not measured and V_D/V_T is only estimated by taking into account the end-tidal CO₂ partial pressure (P_ETCO2 ); however, P_aCO2 is not accurately estimated from P_ETCO2 in patients with cardiopulmonary disease. Measuring arterial gases (P_aO2 and P_aCO2 ) before and during exercise provides information on the real (and not "estimated") V_D/V_T coupled with a true measure of gas exchange efficiency such as the difference between alveolar and arterial O₂ partial pressure and the difference between arterial and end-tidal CO₂ partial pressure during exercise.

Improvement in exercise duration, lung function and well-being in G551D-cystic fibrosis patients: a double-blind, placebo-controlled, randomized, cross-over study with ivacaftor treatment

G551D, a mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, results in impaired chloride channel function in cystic fibrosis (CF) with multiple end-organ manifestations. The effect of ivacaftor, a CFTR-potentiator, on exercise capacity in CF is unknown. Twenty G551D-CF patients were recruited to a single-centre, double-blind, placebo-controlled, 28-day crossover study of ivacaftor. Variables measured included percentage change from baseline (%Δ) of VO_2max (maximal oxygen consumption, primary outcome) during cardiopulmonary exercise testing (CPET), relevant other CPET physiological variables, lung function, body mass index (BMI), sweat chloride and disease-specific health related quality of life (QOL) measures (CFQ-R and Alfred Wellness (AWEscore)). %ΔVO_2max was unchanged compared with placebo as was %Δminute ventilation. However, %Δexercise time (mean 7.3, CI 0.5-14,1, P=0.0222) significantly increased as did %ΔFEV₁ (11.7%, range 5.3-18.1, P<0·005) and %ΔBMI (1.2%, range 0.1-2.3, P=0·0393) whereas sweat chloride decreased (mean -43.4; range -55.5-18.1 mmol·l^-1, P<0·005). Total and activity based domains in both CFQ-R and AWEscore also increased. A positive treatment effect on spirometry, BMI (increased), SCT (decreased) and total and activity based CF-specific QOL measures was expected. However, the lack of discernible improvement in VO_2max and VE despite other positive changes including spirometric lung function and exercise time with a 28-day ivacaftor intervention suggests that ventilatory parameters are not the sole driver of change in exercise capacity in this study cohort. Investigation over a more prolonged period may delineate the potential interdependencies of the observed discordances over time.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov-NCT01937325.

Pulmonary Pseudomonas aeruginosa infection induces autophagy and proteasome proteolytic pathways in skeletal muscles: effects of a pressurized whey protein-based diet in mice

Background: Pulmonary Pseudomonas aeruginosa infection in cystic fibrosis patients is associated with skeletal muscle atrophy. In this study, we investigated the effects of P. aeurginosa infection and a whey protein-rich diet on skeletal muscle proteolytic pathways.

Design: An agar bead model of pulmonary P. aeurginosa infection was established in adult C57/Bl6 mice. Protein ubiquitinaiton, lipidation of LC3B protein and expressions of autophagy-related genes and ubiquitin E3 ligases were quantified using immunoblotting and qPCR. The effects of pressure-treated whey protein diet on muscle proteolysis were also evaluated.

Results: Pulmonary P. aeurginosa infection reduced diaphragm, tibialis anterior, and soleus muscle weights and increased protein ubiquitination, LC3B protein lipidation, and the expressions of Lc3b, Gabarapl1, Bnip3, Parkin, Atrogin-1, and MuRF1 genes in each muscle. These changes were greater in the tibialis as compared to soleus and diaphragm. Proteolysis indicators increased within one day of infection but were not evident after seven days of infection. A pressurized whey diet attenuated LC3B protein lipidation, expressions of autophagy-related genes (BNIP3), pro-inflammatory cytokines, and protein ubiquitination.

Conclusions: We conclude that pulmonary P. aeruginosa infection activates the autophagy, and the proteasome pathways in skeletal muscles and that a pressurized whey protein diet attenuates muscle proteolysis in this model.

Respiratory muscle training improves respiratory muscle endurance but not exercise tolerance in children with cystic fibrosis

BACKGROUND

Respiratory muscle endurance (RME) training has been shown to increase exercise endurance and lung function in adults with cystic fibrosis (CF). We conducted an interventional study to investigate the effectiveness of RME training on CF-related health outcomes in children.

METHODS

In a crossover trial, 22 children, aged 9-18 years, with CF performed 8 weeks of RME training and standard chest physiotherapy in a randomized sequence separated by a 1 week washout period. All children underwent training sessions using the RME training device before beginning the study. The primary outcomes were RME (in minutes) and exercise endurance (in minutes). Data were analyzed according to the intention-to-treat principle.

RESULTS

Sixteen of 22 children (73%) completed the study. Study dropouts tended to be older with more advanced lung disease. After RME training, respiratory muscle endurance significantly increased by 7.03 ± 8.15 min (mean ± standard deviation, P < 0.001), whereas exercise endurance was unchanged by RME training (0.80 ± 2.58 min, P = 0.169). No significant improvement in secondary outcomes (lung function, CF quality of life, and CF clinical score) were observed. The small sample size and short intervention time have to be acknowledged as limitations of our study.

CONCLUSIONS

RME training led to a significant increase in respiratory muscle endurance in children with CF. However, RME training did not improve exercise endurance or other CF-related health outcomes. Thus, our results do not support the routine use of RME training in the care of children with CF. Future studies in larger populations and with prolonged intervention time may overcome the limitations of our study. Pediatr Pulmonol. 2017;52:331-336. © 2017 Wiley Periodicals, Inc.

The Coupling of Peripheral Blood Pressure and Ventilatory Responses during Exercise in Young Adults with Cystic Fibrosis

PURPOSE

Cystic fibrosis (CF) is commonly recognized as a pulmonary disease associated with reduced airway function. Another primary symptom of CF is low exercise capacity where ventilation and gas-exchange are exacerbated. However, an independent link between pathophysiology of the pulmonary system and abnormal ventilatory and gas-exchange responses during cardiopulmonary exercise testing (CPET) has not been established in CF. Complicating this understanding, accumulating evidence suggests CF demonstrate abnormal peripheral vascular function; although, the clinical implications are unclear. We hypothesized that compared to controls, relative to total work performed (WorkTOT), CF would demonstrate increased ventilation accompanied by augmented systolic blood pressure (SBP) during CPET.

METHODS

16 CF and 23 controls (age: 23±4 vs. 27±4 years, P = 0.11; FEV1%predicted: 73±14 vs. 96±5, P<0.01) participated in CPET. Breath-by-breath oxygen uptake ([Formula: see text]), ventilation ([Formula: see text]), and carbon dioxide output ([Formula: see text]) were measured continuously during incremental 3-min stage step-wise cycle ergometry CPET. SBP was measured via manual sphygmomanometry. Linear regression was used to calculate [Formula: see text] slope from rest to peak-exercise.

RESULTS

Compared to controls, CF performed less WorkTOT during CPET (90±19 vs. 43±14 kJ, respectively, P<0.01). With WorkTOT as a covariate, peak [Formula: see text] (62±8 vs. 90±4 L/min, P = 0.76), [Formula: see text] (1.8±0.3 vs. 2.7±0.1 L/min, P = 0.40), and SBP (144±13 vs. 152±6 mmHg, P = 0.88) were similar between CF and controls, respectively; whereas CF demonstrated increased [Formula: see text] slope (38±4 vs. 28±2, P = 0.02) but lower peak [Formula: see text] versus controls (22±5 vs. 33±4 mL/kg/min, P<0.01). There were modest-to-moderate correlations between peak SBP with [Formula: see text] (r = 0.30), [Formula: see text] (r = 0.70), and [Formula: see text] (r = 0.62) in CF.

CONCLUSIONS

These data suggest that relative to WorkTOT, young adults with mild-to-moderate severity CF demonstrate augmented [Formula: see text] slope accompanied by increased SBP during CPET. Although the underlying mechanisms remain unclear, the coupling of ventilatory inefficiency with increased blood pressure suggest important contributions from peripheral pathophysiology to low exercise capacity in CF.

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.

Exercise as medicine - evidence for prescribing exercise as therapy in 26 different chronic diseases

This review provides the reader with the up-to-date evidence-based basis for prescribing exercise as medicine in the treatment of 26 different diseases: psychiatric diseases (depression, anxiety, stress, schizophrenia); neurological diseases (dementia, Parkinson's disease, multiple sclerosis); metabolic diseases (obesity, hyperlipidemia, metabolic syndrome, polycystic ovarian syndrome, type 2 diabetes, type 1 diabetes); cardiovascular diseases (hypertension, coronary heart disease, heart failure, cerebral apoplexy, and claudication intermittent); pulmonary diseases (chronic obstructive pulmonary disease, asthma, cystic fibrosis); musculo-skeletal disorders (osteoarthritis, osteoporosis, back pain, rheumatoid arthritis); and cancer. The effect of exercise therapy on disease pathogenesis and symptoms are given and the possible mechanisms of action are discussed. We have interpreted the scientific literature and for each disease, we provide the reader with our best advice regarding the optimal type and dose for prescription of exercise.

Exercise responses are related to structural lung damage in CF pulmonary disease

INTRODUCTION

Early detection of lung disease is a primary objective in monitoring patients with Cystic Fibrosis (CF); High-Resolution-Computed-Tomography (HRCT) assesses structural damage. Spirometry and cardiopulmonary exercise testing are used for functional evaluation of CF lung disease.

AIM

To evaluate the deterioration of exercise testing parameters over a 2-year period compared to the change of spirometry and HRCT parameters among CF patients.

METHODS

Twenty-eight CF patients were evaluated with HRCT, spirometry, and exercise testing; 15 had two assessments with an interval of 2 years. Correlation analyses between Bhalla score parameters and functional measures were performed.

RESULTS

Twenty-eight patients with CF (mean age 14.9 years, mean forced expiratory volume in 1 sec [FEV1 ] 83.2%) were evaluated. FEV1 was not found to change significantly in the 2-year period (P = 0.612). Both mean Bhalla score and mean peak oxygen consumption (VO2 peak %) deteriorated significantly (P = 0.014 and P = 0.026, respectively). VO2 peak and respiratory equivalents for O2 and CO2 at peak exercise were found to be significant predictors of Bhalla score (r = -0.477, P = 0.010; r = 0.461, P = 0.018; r = 0.402; P = 0.042, respectively). Anaerobic threshold was associated with changes in Bhalla score over the following 2 years.

CONCLUSIONS

Exercise testing is more sensitive than spirometry to detect structural changes in CF lungs. Pediatr Pulmonol. 2016; 51:914-920. © 2016 Wiley Periodicals, Inc.

Physiological responses during exercise with video games in patients with cystic fibrosis: A systematic review

BACKGROUND

Interactive video games are recently being used as an exercise tool in cystic fibrosis (CF). This study aimed to assess the literature describing whether video games generate a physiological response similar to the exercise intensity needed for training in CF.

METHODS

An online search in PubMed, Embase, Cochrane, SciELO, LILACS and PEDro databases was conducted and original studies describing physiological responses of the use of video games as exercise in CF were included.

RESULTS

In four, out of five studies, the heart rate achieved during video games was within the standards recommended for training (60-80%). Two studies assessed VO₂ and showed higher levels compared to the six-minute walk test. No desaturation was reported. Most games were classified as moderate intensity. Only one study used a maximum exercise test as comparator.

CONCLUSION

Interactive video games generate a heart rate response similar to the intensity required for training in CF patients.

The relationship between cardiac hemodynamics and exercise tolerance in cystic fibrosis

BACKGROUND

Individuals with cystic fibrosis (CF) have reduced pulmonary function and exercise tolerance. Additionally, these individuals may develop abnormal cardiac function. The implications of abnormal cardiac function on exercise tolerance are unclear in CF.

OBJECTIVE

Study relationships between exercise cardiac hemodynamics and exercise tolerance in CF.

METHODS

17 CF and 25 controls participated in cardiopulmonary exercise testing to measure exercise duration and peak workload (PW). Cardiac index (QI) was measured using acetylene rebreathe and oxygen uptake (VO2) breath-by-breath. Forced expiratory volume in 1-second (FEV1) was performed at rest.

RESULTS

Peak QI was 6.7 ± 0.5 vs. 9.1 ± 0.3 mL/min/m(2), CF vs. controls, respectively (P < 0.05). Linear regressions between QI (R(2) = 0.63 and 0.51) and exercise duration or PW were stronger than VO2 (R(2) = 0.35 and 0.37) or FEV1 (R(2) = 0.34 and 0.36) in CF, respectively (P < 0.05).

CONCLUSION

These data are clinically relevant suggesting attenuated cardiac function in addition to low airway function relate to exercise tolerance in CF.

Evidence of microvascular dysfunction in patients with cystic fibrosis

Cystic fibrosis (CF) is a genetic, multisystemic disorder with broad clinical manifestations apart from the well-characterized pulmonary dysfunction. Recent findings have described impairment in conduit vessel function in patients with CF; however, whether microvascular function is affected in this population has yet to be elucidated. Using laser-Doppler imaging, we evaluated microvascular function through postocclusive reactive hyperemia (PORH), local thermal hyperemia (LTH), and iontophoresis with acetylcholine (ACh). PORH [518 ± 174% (CF) and 801 ± 125% (control), P = 0.039], LTH [1,338 ± 436% (CF) and 1,574 ± 620% (control), P = 0.045], and iontophoresis with ACh [416 ± 140% (CF) and 617 ± 143% (control), P = 0.032] were significantly lower in patients with CF than control subjects. In addition, the ratio of PORH to LTH was significantly (P = 0.043) lower in patients with CF (55.3 ± 5.1%) than control subjects (68.8 ± 3.1%). Significant positive correlations between LTH and forced expiratory volume in 1 s (%predicted) (r = 0.441, P = 0.013) and between the PORH-to-LTH ratio and exercise capacity (r = 0.350, P = 0.049) were observed. These data provide evidence of microvascular dysfunction in patients with CF compared with control subjects. In addition, our data demonstrate a complex relationship between microvascular function and classical markers of disease severity (i.e., pulmonary function and exercise capacity) in CF.

Use of exercise testing in the evaluation of interventional efficacy: an official ERS statement

This document reviews 1) the measurement properties of commonly used exercise tests in patients with chronic respiratory diseases and 2) published studies on their utilty and/or evaluation obtained from MEDLINE and Cochrane Library searches between 1990 and March 2015.

Exercise tests are reliable and consistently responsive to rehabilitative and pharmacological interventions. Thresholds for clinically important changes in performance are available for several tests. In pulmonary arterial hypertension, the 6-min walk test (6MWT), peak oxygen uptake and ventilation/carbon dioxide output indices appear to be the variables most responsive to vasodilators. While bronchodilators do not always show clinically relevant effects in chronic obstructive pulmonary disease, high-intensity constant work-rate (endurance) tests (CWRET) are considerably more responsive than incremental exercise tests and 6MWTs. High-intensity CWRETs need to be standardised to reduce interindividual variability. Additional physiological information and responsiveness can be obtained from isotime measurements, particularly of inspiratory capacity and dyspnoea. Less evidence is available for the endurance shuttle walk test. Although the incremental shuttle walk test and 6MWT are reliable and less expensive than cardiopulmonary exercise testing, two repetitions are needed at baseline. All exercise tests are safe when recommended precautions are followed, with evidence suggesting that no test is safer than others.

Relationship between daily physical activity and aerobic fitness in adults with cystic fibrosis

Background

The best clinical practice to investigate aerobic fitness includes measurements obtained during cardiopulmonary exercise testing (CPET), however it remains an underutilised clinical measure in cystic fibrosis (CF). To investigate this further, different methods of quantifying exercise capacity in CF are required. The possibility that measuring physical activity (PA) by a portable accelerometer could be used to assess the CF aerobic state and could be added among the CPET surrogates has not been investigated. The aim of this study was to examine the relationship between PA and exercise fitness both at submaximal and maximal levels in clinically stable adults with CF.

Methods

Thirty CF patients (FEV₁ 71 ± 19% predicted) and fifteen healthy controls undertook an incremental CPET on a cycle ergometer. CPET-related measurements included: oxygen uptake (V’O₂), carbon dioxide production (V’CO₂), ventilatory profile, heart rate (HR) and oxygen pulse (V’O₂/HR) throughout exercise and at lactic threshold (LT) and peak. LT measures represent submaximal exercise related data. PA was assessed using the accelerometer SenseWear Pro3 Armband.

Results

Moderate (>4.8 metabolic equivalents (METS)) and moderate + vigorous (>7.2 METS) PA was related to V’O₂ (p = 0.005 and p = 0.009, respectively) and work rate (p = 0.004 and p = 0.002, respectively) at LT. Moderate PA or greater was positively related to peak V’O₂ (p = 0.005 and p = 0.003, respectively). Daily PA levels were similar in CF and healthy controls. Except for peak values, V’O₂ profile and the V’O₂ at LT were comparable between CF and healthy controls.

Conclusions

In adult CF patients daily PA positively correlated with aerobic capacity. PA measurements are a valuable tool in the assessment of exercise performance in an adult CF population and could be used for interventional exercise trials to optimize exercise performance and health status. PA levels and parameters obtained at submaximal exercise are similar in CF and in healthy controls.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-015-0036-9) contains supplementary material, which is available to authorized users.

Aerobic fitness is associated with lower risk of hospitalization in children with cystic fibrosis

BACKGROUND

Children with cystic fibrosis (CF) often have to be hospitalized because of acute exacerbation of their respiratory symptoms. Given the fact that improved peak oxygen uptake (VO2peak ) is positively associated with lung function and overall health in children with CF, this study examined the association between VO2peak and the need for hospitalization in a cohort of pediatric CF patients.

METHODS

In a 3-year study, 77 CF children with mild-to-moderately severe CF (forced expiratory volume in 1 sec [FEV1 ] ≥ 50%) underwent a maximal exercise test to determine VO2peak . Anthropometric, lung function and muscle strength measurements were also conducted and dates of hospitalization were recorded for the study period. Associations were then determined between the variables recorded and hospitalization by univariate and multivariate Cox proportional hazards regression analyses.

RESULTS

VO2peak was 38.6 ± 6.7 ml kg(-1)  min(-1) for boys and 31.9 ± 6.9 ml kg(-1)  min(-1) for girls. In multivariate analyses, VO2peak was the only variable significantly associated with time to hospitalization (hazard ratio 0.91, P = 0.03).

CONCLUSION

A significant association was detected between greater aerobic fitness, and lower risk of hospitalization. Because hospitalization due to respiratory exacerbation is a powerful prognostic factor, our findings provide further support for the importance of aerobic fitness evaluation in the management of children with mild-to-moderately severe CF.

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.

Effects of noninvasive ventilation on treadmill 6-min walk distance and regional chest wall volumes in cystic fibrosis: randomized controlled trial

BACKGROUND

Dyspnea and exercise intolerance are the symptoms that most affect the quality of life of children and adolescents with respiratory disorders resulting from cystic fibrosis (CF).

OBJECTIVE

To evaluate the effect of noninvasive ventilation (NIV) on treadmill 6-min walk distance and regional chest wall volumes in cystic fibrosis patients.

METHOD

Crossover clinical trial, randomized, controlled and open with 13 children and adolescents with CF, aged 7-16 years, with pulmonary impairment (NTC01987271). The patients performed a treadmill walking test (TWT) during 6 min, with and without NIV on a BiLEVEL mode, an interval of 24-48 h between tests. Before and after each test, patients were assessed by spirometry and optoelectronic plethysmography.

RESULTS

Walking distance in TWT with NIV was significantly higher that without ventilatory support (mean ± sd: 0.41 ± 0.08 vs. 0.39 ± 0.85 km, p = 0.039). TWT with NIV increase forced expiratory volume on 1 s (FEV1; p = 0.036), tidal volume (Vt; p = 0.005), minute ventilation (MV; p = 0.013), pulmonary rib cage volume (Vrcp; p = 0.011), and decrease the abdominal volume (Vab; p = 0.013) after test. There was a significant reduction in oxygen saturation (p = 0.018) and permanent increase in respiratory rate after 5 min (p = 0.021) after the end test without NIV.

CONCLUSION

During the walking test on the treadmill, the NIV change thoracoabdominal kinematics and lung function in order to optimized ventilation and tissue oxygenation, with improvement of walk distance. Consequently, NIV is an effective tool to increase functional capacity in children and adolescents with cystic fibrosis.

Estimating peak oxygen uptake in adolescents with cystic fibrosis

OBJECTIVES

To predict peak oxygen uptake (VO2 peak) from the peak work rate (W peak) obtained during a cycle ergometry test using the Godfrey protocol in adolescents with cystic fibrosis (CF), and assess the accuracy of the model for prognostication clustering.

METHODS

Out of our database of anthropometric, spirometric and maximal exercise data from adolescents with CF (N=363; 140 girls and 223 boys; age 14.77 ± 1.73 years; mean expiratory volume in 1 s (FEV1%pred) 86.82 ± 17.77%), a regression equation was developed to predict VO2 peak (mL/min). Afterwards, this prediction model was validated with cardiopulmonary exercise data from another 60 adolescents with CF (28 girls, 32 boys; mean age 14.6 ± 1.67 years; mean FEV1%pred 85.43 ± 20.01%).

RESULTS

We developed a regression model VO2 peak (mL/min)=216.3-138.7 × sex (0=male; 1=female)+11.5 × W peak; R(2)=0.91; SE of the estimate (SEE) 172.57. A statistically significant difference (107 mL/min; p<0.001) was found between predicted VO2 peak and measured VO2 peak in the validation group. However, this difference was not clinically relevant because the difference was within the SEE of the model. Furthermore, we found high positive predictive and negative predictive values for the model for prognostication clustering (PPV 50-87% vs NPV 82-94%).

CONCLUSIONS

In the absence of direct VO2 peak assessment it is possible to estimate VO2 peak in adolescents with CF using only a cycle ergometer. Furthermore, the regression model showed to be able to discriminate patients in different prognosis clusters based on exercise capacity.