The utility of cardiopulmonary exercise testing in difficult asthma

Identifying limitations to exercise with incremental cardiopulmonary exercise testing: a scoping review

Cardiopulmonary exercise testing (CPET) is a comprehensive and invaluable assessment used to identify the mechanisms that limit exercise capacity. However, its interpretation remains poorly standardised. This scoping review aims to investigate which limitations to exercise are differentiated by the use of incremental CPET in literature and which criteria are used to identify them. We performed a systematic, electronic literature search of PubMed, Embase, Cochrane CENTRAL, Web of Science and Scopus. All types of publications that reported identification criteria for at least one limitation to exercise based on clinical parameters and CPET variables were eligible for inclusion. 86 publications were included, of which 57 were primary literature and 29 were secondary literature. In general, at the level of the cardiovascular system, a distinction was often made between a normal physiological limitation and a pathological one. Within the respiratory system, ventilatory limitation, commonly identified by a low breathing reserve, and gas exchange limitation, mostly identified by a high minute ventilation/carbon dioxide production slope and/or oxygen desaturation, were often described. Multiple terms were used to describe a limitation in the peripheral muscle, but all variables used to identify this limitation lacked specificity. Deconditioning was a frequently mentioned exercise limiting factor, but there was no consensus on how to identify it through CPET. There is large heterogeneity in the terminology, the classification and the identification criteria of limitations to exercise that are distinguished using incremental CPET. Standardising the interpretation of CPET is essential to establish an objective and consistent framework.

Analyzing key elements of breathing patterns, deriving remaining variables, and identifying cutoff values in individuals with chronic respiratory disease and healthy subjects

BACKGROUND

Pulmonary physiology encompasses intricate breathing patterns (BPs), characterized by breathing frequency (Bf), volumes, and flows. The complexities intensify in the presence of interstitial lung disease (ILD) and chronic obstructive pulmonary disease (COPD), especially during exercise. This study seeks to identify pivotal factors driving changes among these variables and establish cutoff values, comparing their efficacy in differentiating BPs to traditional methods, specifically a breathing reserve (BR) of 30% and a Bf of 50 bpm.

METHODS

Screening 267 subjects revealed 23 with ILD, 126 with COPD, 33 healthy individuals, and the exclusion of 85 subjects. Lung function tests and ramp-pattern cardiopulmonary exercise testing (CPET) were conducted, identifying crucial BP elements. Changes were compared between groups at peak exercise. The area under the receiver operating characteristic curve (AUC) analysis determined cutoff values.

RESULTS

Inspiratory time (TI) remained constant at peak exercise for all subjects (two-group comparisons, all p=NS). Given known differences in expiratory time (TE) and tidal volume (VT) among ILD, COPD, and healthy states, constant TI could infer patterns for Bf, total breathing cycle time (TTOT=60/Bf), I:E ratio, inspiratory duty cycle (IDC, TI/TTOT), rapid shallow breathing index (Bf/VT), tidal inspiratory and expiratory flows (VT/TI and VT/TE), and minute ventilation (V̇E=Bf×VT) across conditions. These inferences aligned with measurements, with potential type II errors causing inconsistencies. RSBI of 23 bpm/L and VT/TI of 104 L/min may differentiate ILD from control, while V̇E of 54 L/min, BR of 30%, and VT/TE of 108 may differentiate COPD from control. BR of 21%, TE of 0.99 s, and IDC of .45 may differentiate ILD from COPD. The algorithm outperformed traditional methods (AUC 0.84-0.91 versus 0.59-0.90).

CONCLUSION

The quasi-fixed TI, in conjunction with TE and VT, proves effective in inferring time-related variables of BPs. The findings have the potential to significantly enhance medical education in interpreting cardiopulmonary exercise testing. Moreover, the study introduces a novel algorithm for distinguishing BPs among individuals with ILD, COPD, and those who are healthy.

Cardiopulmonary exercise testing in younger patients with persistent dyspnea following acute, outpatient COVID-19 infection

Studies using cardiopulmonary exercise testing (CPET) to evaluate persistent dyspnea following infection with COVID-19 have focused on older patients with co-morbid diseases who are post-hospitalization. Less attention has been given to younger patients with post-COVID-19 dyspnea treated as outpatients for their acute infection. We sought to determine causes of persistent dyspnea in younger patients recovering from acute COVID-19 infection that did not require hospitalization. We collected data on all post-COVID-19 patients who underwent CPET in our clinic in the calendar year 2021. Data on cardiac function and respiratory response were abstracted, and diagnoses were assigned using established criteria. CPET data on 45 patients (238.3 ± 124 days post-test positivity) with a median age of 27.0 (22.0-40.0) were available for analysis. All but two (95.6%) were active-duty service members. The group showed substantial loss of aerobic capacity-average VO2 peak (L/min) was 84.2 ± 23% predicted and 25 (55.2%) were below the threshold for normal. Spirometry, diffusion capacity, high-resolution computed tomography, and echocardiogram were largely normal and were not correlated with VO2 peak. The two most common contributors to dyspnea and exercise limitation following comprehensive evaluation were deconditioning and dysfunctional breathing (DB). Younger active-duty military patients with persistent dyspnea following outpatient COVID-19 infection show a substantial reduction in aerobic capacity that is not driven by structural cardiopulmonary disease. Deconditioning and DB breathing are common contributors to their exercise limitation. The chronicity and severity of symptoms accompanied by DB could be consistent with an underlying myopathy in some patients, a disorder that cannot be differentiated from deconditioning using non-invasive CPET.

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.

A comparative study of dynamic lung hyperinflation and tidal volume to total lung capacity ratios during exercise in patients with chronic respiratory disease and healthy individuals

BACKGROUND

Current measures of tidal volume/forced vital capacity (VT/FVC) and VT/inspiratory capacity (VT/IC) at peak exercise cannot differentiate restrictive from obstructive ventilation patterns. This study aimed to investigate the utility of VT/total lung capacity (VT/TLC) as a marker for dynamic lung hyperinflation (DH) in patients with chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD).

METHODS

267 subjects were screened: 23 ILD, 126 COPD, and 33 healthy individuals were enrolled. Lung function tests and cardiopulmonary exercise tests with repeated IC maneuver were conducted and compared at three exercise efforts: unloaded, middle of exercise, and peak exercise.

RESULTS

During exercise, ILD patients demonstrated normal end-expiratory lung volume/TLC (EELV/TLC) ratios, but elevated end-inspiratory lung volume/TLC (EILV/TLC) ratios, except for peak exercise. COPD patients exhibited elevated ratios for both EELV/TLC and EILV/TLC during exercise with a larger EELV/TLC ratio compared to ILD patients at peak exercise (p < 0.05). The VT/TLC ratio distinguished ILD, COPD, and healthy controls at peak exercise (p < 0.05). A VT/TLC ratio of ≤ 0.22 or ≥ 0.30 indicated airflow obstruction with hyperinflation or normal lung expansion, respectively (AUC: 0.74 or 0.88). Furthermore, VT/TLC outperformed VT/FVC and VT/IC in differentiating lung expansion between ILD and COPD during exercise (all p < 0.05).

CONCLUSION

Exercise-induced DH was absent in ILD patients but observed in COPD patients. Excessive lung expansion occurred in all patients during exercise, except for limited expansion in ILD at peak exercise probably due to specific lung properties. VT/TLC can distinguish between restrictive, obstructive, and normal ventilatory patterns.

Does the severity of asthma affect exercise capacity and daily physical activity?

OBJECTIVE

Exercise capacity, daily physical activity, and psychological profile are crucial aspects in the management of asthmatic patients. Whether these features are expressed in a different way in mild-moderate (MMA) and severe asthma (SA) is unknown.

METHODS

In this observational cross-sectional study, patients matching the American Thoracic Society/European Respiratory Society (ATS/ERS) definition for SA underwent incremental cardiopulmonary exercise testing (CPET), full lung function testing, and an evaluation of daily step count and physical activity. Questionnaires on quality of life, general fatigue, and presence of anxiety and depression traits (Hospital Anxiety and Depression Scale - HADS) were administered. Patients were compared with a cohort of age- and gender-matched MMA patients.

RESULTS

We enrolled 16 SA, 17 MMA patients, and 16 healthy subjects. Compared to MMA, SA subjects showed a median (interquartile range) reduced peak oxygen consumption during CPET (20.4 (17.2-23.3) vs. 25.6 (18.5-30.3) ml/min/kg; p = 0.019), a reduced resting lung function (FEV1% of predicted 77 (67-84) vs. 96 (84-100); p < 0.001) and a pronounced anxiety trait at HADS (9.5 (3-11.7) vs. 4.0 (2.0-7.5); p = 0.023). In addition, SA patients showed a significantly higher reduction in inspiratory capacity from rest to peak (310 (160-520) vs. 110 (-65-325) ml; p = 0.031). We found no significant differences in mean daily step count or quality of life.

CONCLUSIONS

Compared to MMA, SA patients present a reduced exercise capacity and a more pronounced anxiety trait, but not worse daily physical activity or quality of life. These aspects should be considered in the clinical management and research development of SA.

Exercise Limitation in Children and Adolescents With Severe Refractory Asthma: A Lack of Asthma Control?

Background

Patients with severe refractory asthma (SRA), even when using high doses of multiple controller medications in a regular and appropriate way, can have persistent complaints of exercise limitation.

Methods

This was a cross-sectional study involving patients with SRA (treated with ≥ 800 μg of budesonide or equivalent, with ≥ 80% adherence, appropriate inhaler technique, and comorbidities treated), who presented no signs of a lack of asthma control other than exercise limitation. We also evaluated healthy controls, matched to the patients for sex, age, and body mass index. All participants underwent cardiopulmonary exercise testing (CPET) on a cycle ergometer, maximum exertion being defined as ≥ 85% of the predicted heart rate, with a respiratory exchange ratio ≥ 1.0 for children and ≥ 1.1 for adolescents. Physical deconditioning was defined as oxygen uptake (VO₂) < 80% of predicted at peak exercise, without cardiac impairment or ventilatory limitation. Exercise-induced bronchoconstriction (EIB) was defined as a forced expiratory volume in one second ≥ 10% lower than the baseline value at 5, 10, 20, and 30 minutes after CPET.

Results

We evaluated 20 patients with SRA and 19 controls. In the sample as a whole, the mean age was 12.9 ± 0.4 years. The CPET was considered maximal in all participants. In terms of the peak VO₂ (VO_{2 peak}), there was no significant difference between the patients and controls, (P = 0.10). Among the patients, we observed isolated EIB in 30%, isolated physical deconditioning in 25%, physical deconditioning accompanied by EIB in 25%, and exercise-induced symptoms not supported by the CPET data in 15%.

Conclusion and Clinical Relevance

Physical deconditioning, alone or accompanied by EIB, was the determining factor in reducing exercise tolerance in patients with SRA and was not therefore found to be associated with a lack of asthma control.

Determinants of exercise capacity in children and adolescents with severe therapy-resistant asthma

OBJECTIVE

To evaluate the exercise capacity of children and adolescents with severe therapy resistant asthma (STRA) aiming to identify its main determinants.

METHODS

Cross-sectional study including individuals aged 6-18 years with a diagnosis of STRA. Clinical (age and gender), anthropometric (weight, height and body mass index) and disease control data were collected. Lung function (spirometry), cardiopulmonary exercise testing (CPET) and exercise-induced bronchoconstriction (EIB) test were performed.

RESULTS

Twenty-four patients aged 11.5 ± 2.6 years were included. The mean forced expiratory volume in one second (FEV₁) was 91.3 ± 9.2%. EIB occurred in 54.2% of patients. In CPET, the peak oxygen uptake (VO_2peak) was 34.1 ± 7.8 mL kg^-1 min^-1. A significant correlation between ventilatory reserve and FEV₁ (r = 0.57; p = 0.003) was found. Similarly, there was a significant correlation between CPET and percent of FEV₁ fall in the EIB test for both V_E/VO₂ (r = 0.47; p = 0.02) and V_E/VCO₂ (r = 0.46; p = 0.02). Patients with FEV₁<80% had lower ventilatory reserve (p = 0.009). In addition, resting heart rate correlated with VO_2peak (r=-0.40; p = 0.04), V_E/VO₂ (r = 0.46; p = 0.02) and V_E/VCO₂ (r = 0.48; p = 0.01).

CONCLUSIONS

Exercise capacity is impaired in approximately 30% of children and adolescents with STRA. The results indicate that different aspects of aerobic fitness are influenced by distinct determinants, including lung function and EIB.

Cardiopulmonary exercise testing in patients with asthma: What is its clinical value?

Asthma is one of the most common respiratory disorders, characterized by fully or largely reversible airflow limitation. Asthma symptoms can be triggered or magnified during exertion, while physical activity limitation is often present among asthmatic patients. Cardiopulmonary exercise testing (CPET) is a dynamic, non-invasive technique which provides a thorough assessment of exercise physiology, involving the integrative assessment of cardiopulmonary, neuromuscular and metabolic responses during exercise. This review summarizes current evidence regarding the utility of CPET in the diagnostic work-up, functional evaluation and therapeutic intervention among patients with asthma, highlighting its potential role for thorough patient assessment and physician clinical desicion-making.

Systematic Assessment of Difficult-to-Treat Asthma: Principles and Perspectives

Difficult-to-treat asthma affects a minority of adults and children with asthma but represents a challenging mix of misdiagnosis, multimorbidity, inadequate self-management, severe airway pathobiology, and treatment complications. Management of these patients extends beyond asthma pharmacotherapy, because multiple other patient-related domains need to be addressed as well. Such complexity can hinder adequate clinical assessment even when performed in specialist practice. Systematic assessment undertaken by specialized multidisciplinary teams brings a broad range of resources to bear on patients with difficult-to-treat asthma. Although the concept of systematic assessment is not new, practices vary considerably and implementation is not universal. Nevertheless, assessment protocols are already in place in several institutions worldwide, and outcomes after such assessments have been highly encouraging. This review discusses the rationale, components, and benefits of systematic assessment, outlining its clinical utility and the available evidence for improved outcomes. It describes a range of service configurations and assessment approaches, drawing examples from severe asthma centers around the world to highlight common essential elements. It also provides a framework for establishing such services and discusses practical considerations for implementation.

Different endotypes and phenotypes drive the heterogeneity in severe asthma

The identification of sputum eosinophilia indicating corticosteroid responsiveness in subjects with severe asthma heralded the beginning of phenotyping asthmatic subjects based on airways inflammation. Since then, the heterogeneity of severe asthma has been explored and the importance of immunobiology has come sharply into focus with the identification of the key type-2 cytokine pathways driving eosinophilic inflammation. The development of molecules targeting these type-2 pathways has transformed severe asthma treatment, but necessitates robust clinical evaluation, biomarker profiling and assessment of comorbid factors to identify subjects most likely to benefit from these therapies. It has also become clear that targeting these pathways does not eradicate asthma symptoms and exacerbation risk; further work is needed to clarify underlying non-type-2 mechanisms in severe asthma pathways and possible therapeutic targets. This review addresses progress to date in clinical assessment and management of severe asthma and some of the challenges and unmet needs in severe asthma to achieve the goal of delivering individualized patient care.

Developing a New Marker of Dynamic Hyperinflation in Patients with Obstructive Airway Disease - an observational study

Tidal volume at peak exercise and vital capacity ratio (V_Tpeak/VC) and V_Tpeak/inspiratory capacity (IC) were used to differentiate lung expansion in subjects with normal health and chronic obstructive pulmonary disease (COPD) from that in subjects with restrictive ventilation. However, VC and IC variably change due to pseudorestriction of lung volumes. Thus, these variables are currently not recommended. In contrast, total lung capacity (TLC) does little change during exercise. The aims of the study investigated whether V_Tpeak/TLC is more significantly correlated with static air trapping and lung hyperinflation in patients with COPD than V_Tpeak/IC, V_Tpeak/FVC, and V_Tpeak/SVC (study 1), and developed a marker to replace dynamic IC maneuvers by evaluation of the relationship between end-expiratory lung volume (EELV) and V_Tpeak/TLC and identification of a cutoff value for V_Tpeak/TLC (study 2). One hundred adults with COPD (study 1) and 23 with COPD and 19 controls (study 2) were analyzed. Spirometry, lung volume, diffusing capacity, incremental cardiopulmonary exercise tests with dynamic IC maneuvers were compared between groups. An ROC curve was generated to identify a cut off value for V_Tpeak/TLC. In study 1, V_Tpeak/TLC was more significantly associated with airflow obstruction, static air trapping and hyperinflation. In study 2, V_Tpeak/TLC was highly correlated with EELV in the patients (r = -0.83), and V_Tpeak/TLC ≥ 0.27 predicted that 18% of the patients with static air trapping and hyperinflation can expand their V_T equivalent to the controls. In conclusions, V_Tpeak/TLC was superior to other V_Tpeak/capacities. V_Tpeak/TLC may be a marker of dynamic hyperinflation in subjects with COPD, thereby avoiding the need for dynamic IC maneuvers. V_Tpeak/TLC < 0.27 identified approximately 82% of subjects with COPD who could not adequately expand their tidal volume. As most of our participants were male, further studies are required to elucidate whether the results of this study can be applied to female patients with COPD.

Outpatient pulmonary rehabilitation for severe asthma with fixed airway obstruction: Comparison with COPD

Background: The benefit of exercise has been demonstrated in asthma, but the role of pulmonary rehabilitation (PR) in people with severe asthma, especially with airway obstruction, has been less investigated. The activity limitation mechanisms differ in asthma and COPD, so the effect of a PR program not specific to asthma is unclear. Methods: We retrospectively compared the effect of an ambulatory PR program in nonsmoking patients with severe asthma and airway obstruction (FEV1/FVC ratio <70% and FEV1 < 80% measured twice, not under an exacerbation) and sex-, age-, FEV1-, and BMI-matched COPD controls. Results: We included 29 patients, each with asthma and COPD. Airway obstruction was moderate (median FEV1 57% [44-64]). VO₂ at peak was higher for asthma than COPD patients (19.0 [15.7-22.2] vs 16.1 [15.3-19.6] ml.min^-1.kg^-1, p = 0.05). After PR, asthma and COPD groups showed a significant and similar increase in constant work cycling test of 378 [114-831] s and 377 [246-702] s. Changes in Hospital Anxiety and Depression Scale (HAD) total score were similar (-2.5 [-7.0 to 0.0] vs -2.0 [-5.0 to 2.0], p > 0.05). Quality of life on the St. George's Respiratory Questionnaire (SGRQ) was significantly improved in both groups (-14.0 [-17.7 to -2.0], p < 0.005 and -8.3 [-13.0 to -3.6], p < 0.0001). Conclusion: Outpatient PR is feasible and well tolerated in patients with severe asthma with fixed airway obstruction. A nondedicated program strongly improves HAD and SGRQ scores and constant work-rate sub-maximal cycling, with similar amplitude as with COPD.

Cardiopulmonary Exercise Test: Background, Applicability and Interpretation

Cardiopulmonary exercise test (CPET) has been gaining importance as a method of functional assessment in Brazil and worldwide. In its most frequent applications, CPET consists in applying a gradually increasing intensity exercise until exhaustion or until the appearance of limiting symptoms and/or signs. The following parameters are measured: ventilation; oxygen consumption (VO₂); carbon dioxide production (VCO₂); and the other variables of conventional exercise testing. In addition, in specific situations, pulse oximetry and flow-volume loops during and after exertion are measured. The CPET provides joint data analysis that allows complete assessment of the cardiovascular, respiratory, muscular and metabolic systems during exertion, being considered gold standard for cardiorespiratory functional assessment.^1-6

The CPET allows defining mechanisms related to low functional capacity that can cause symptoms, such as dyspnea, and correlate them with changes in the cardiovascular, pulmonary and skeletal muscle systems. Furthermore, it can be used to provide the prognostic assessment of patients with heart or lung diseases, and in the preoperative period, in addition to aiding in a more careful exercise prescription to healthy subjects, athletes and patients with heart or lung diseases.

Similarly to CPET clinical use, its research also increases, with the publication of several scientific contributions from Brazilian researchers in high-impact journals.

Therefore, this study aimed at providing a comprehensive review on the applicability of CPET to different clinical situations, in addition to serving as a practical guide for the interpretation of that test.

Novel assessment tool to detect breathing pattern disorder in patients with refractory asthma

BACKGROUND AND OBJECTIVE

Breathing pattern disorder (BPD) can co-exist with and mimic asthma, acting to amplify symptoms and confound assessment of disease control, resulting in inappropriate treatment escalation. The aim of this research was to report the utility of a novel breathing pattern assessment tool (BPAT) to detect BPD in treatment-refractory asthma.

METHODS

As a component of a multidisciplinary assessment, adult patients referred with treatment-refractory asthma underwent respiratory physiotherapy assessment to diagnose BPD. Based on this assessment, patients were classified as having asthma, asthma + BPD or BPD alone. BPAT data were collected in addition to questionnaire data (Asthma Quality of Life Questionnaire (AQLQ) and Nijmegen Questionnaire (NQ)), pulmonary function and an assessment of exercise capacity.

RESULTS

Data were retrospectively analysed for 150 (female; 69%) patients, mean (SD) age of 43 (14) years; characterized as asthma-only (n = 54, 36%), asthma + BPD (n = 63, 42%) and BPD-only (n = 33, 22%). Of the total population, 113 (76%) had an NQ score ≥23, but of these only 68% had physiotherapy evidence of BPD. Exercise capacity and AQLQ were lower in the asthma + BPD group than in the asthma-only group (P < 0.05), whilst lung function was similar between groups. Sensitivity analysis indicated that a BPAT score of ≥4 corresponded to a sensitivity of 0.92 and a specificity of 0.75 for diagnosis of BPD in this cohort.

CONCLUSION

Breathing pattern irregularities are highly prevalent in individuals referred with treatment-refractory asthma and can be characterized using the BPAT. Further work is needed to determine inter-observer and within-subject variability and ensure the BPAT is a robust clinical tool. Watch the video abstract.

Patterns of Oxygen Pulse Curve in Response to Incremental Exercise in Patients with Chronic Obstructive Pulmonary Disease - An Observational Study

In COPD, pulmonary hyperinflation causes decreased stroke volume thereby decreased oxygen pulse (O₂P). While O₂P flattening is related to myocardial ischemia in cardiac patients, O₂P patterns have seldom been explored in COPD. The aims of the study were to investigate O₂P-curve patterns and associated factors in COPD. Seventy-five patients with stable COPD were enrolled. The demographics, cardiac size, physiological measurements and stress EKG were compared among O₂P-curve pattern groups. An algorithm to identify O₂P-curve patterns was developed in 28 patients. In the remaining 45 patients after excluding two with poor effort, this algorithm revealed 20 (44%) flattening, 16 (36%) increasing, and nine (20%) decreasing patterns. The flattening-type group had lower body mass, cardiac size, and diffusing capacity, and larger lung volumes (p = 0.05–<0.0001) compared to the increasing-type group. During exercise, the flattening-type group had a lower operable O₂P and more hyperventilation and dyspnea (p = 0.02–<0.01). None had ST-T changes. Most differences were related to body mass and mildly to inspiratory fraction. The decreasing-type group performed higher effort than the increasing-type group (p < 0.05). In conclusion, O₂P flattening was common and was associated with reduced body mass and pulmonary hyperinflation rather than with myocardial ischemia. The decreasing-type may be caused by motivation to exercise.

Management of Severe Asthma before Referral to the Severe Asthma Specialist

Severe asthma is associated with significant morbidity and can be challenging to assess and control, due to heterogeneity of disease, complexity of diagnosis, and impact of comorbidities. A structured approach to the assessment and management of severe asthma may be helpful to the practicing clinician. First, it is important to confirm a diagnosis of asthma. In patients who are either not responding to treatment, or who require high doses of medication to control symptoms, it is highly possible that disease mimickers or comorbidities are present and can inhibit therapeutic responsiveness. The assessment and management of common comorbidities of asthma may dramatically impact disease control and thus medication requirement. Determining medication adherence and optimizing drug dose and delivery may separate out truly severe asthmatics from those not using medications regularly or properly. Next, although true personalized medicine for severe asthma is not yet realized, for those individuals with severe asthma, phenotypic characteristics of each patient may guide which therapeutic options may be most effective for that patient. Finally, evaluation and management of severe asthma at a referral center can add additional phenotyping, therapeutic, and diagnostic strategies.

Mechanisms, measurement and management of exertional dyspnoea in asthma: Number 5 in the Series "Exertional dyspnoea" Edited by Pierantonio Laveneziana and Piergiuseppe Agostoni

Asthma is a heterogeneous condition, with dyspnoea during exercise affecting individuals to a variable degree. This narrative review explores the mechanisms and measurement of exertional dyspnoea in asthma and summarises the available evidence for the efficacy of various interventions on exertional dyspnoea. Studies on the mechanisms of dyspnoea in asthma have largely utilised direct bronchoprovocation challenges, rather than exercise, which may invoke different physiological mechanisms. Thus, the description of dyspnoea during methacholine challenge can differ from what is experienced during daily activities, including exercise. Dyspnoea perception during exercise is influenced by many interacting variables, such as asthma severity and phenotype, bronchoconstriction, dynamic hyperinflation, respiratory drive and psychological factors. In addition to the intensity of dyspnoea, the qualitative description of dyspnoea may give important clues as to the underlying mechanism and may be an important endpoint for future interventional studies. There is currently little evidence demonstrating whether pharmacological or non-pharmacological interventions specifically improve exertional dyspnoea, which is an important area for future research.

Advances in the Evaluation of Respiratory Pathophysiology during Exercise in Chronic Lung Diseases

Dyspnea and exercise limitation are among the most common symptoms experienced by patients with various chronic lung diseases and are linked to poor quality of life. Our understanding of the source and nature of perceived respiratory discomfort and exercise intolerance in chronic lung diseases has increased substantially in recent years. These new mechanistic insights are the primary focus of the current review. Cardiopulmonary exercise testing (CPET) provides a unique opportunity to objectively evaluate the ability of the respiratory system to respond to imposed incremental physiological stress. In addition to measuring aerobic capacity and quantifying an individual's cardiac and ventilatory reserves, we have expanded the role of CPET to include evaluation of symptom intensity, together with a simple "non-invasive" assessment of relevant ventilatory control parameters and dynamic respiratory mechanics during standardized incremental tests to tolerance. This review explores the application of the new advances in the clinical evaluation of the pathophysiology of exercise intolerance in chronic obstructive pulmonary disease (COPD), chronic asthma, interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH). We hope to demonstrate how this novel approach to CPET interpretation, which includes a quantification of activity-related dyspnea and evaluation of its underlying mechanisms, enhances our ability to meaningfully intervene to improve quality of life in these pathologically-distinct conditions.

Dysfunctional breathing and reaching one's physiological limit as causes of exercise-induced dyspnoea

Key points

This review provides an overview of the spectrum of conditions that can present as exercise-­induced breathlessness experienced by young subjects participating in sport and aims to promote understanding of the need for accurate assessment of an individual’s symptoms. We will highlight the high incidence of nonasthmatic causes, which simply require reassurance or simple interventions from respiratory physiotherapists or speech pathologists.

Breathlessness: accurate assessment and diagnosis is essential in order to provide correct advice and assistancehttp://ow.ly/4nrW8z

Activity limitation and exertional dyspnea in adult asthmatic patients: What do we know?

Limitation of activity is the most cited symptom described by uncontrolled asthma patients. Assessment of activity limitation can be undertaken through several ways, more or less complex, subjective or objective. Yet little is known about the link between patients sensations and objective measurements. The present review reports the current knowledge regarding activity limitation and symptom perception (i.e., exertional dyspnea) in adult patients with asthma. This work is based on references indexed by PubMed, irrespective of the year of publication. Overall, patients with stable asthma do not have a more sedentary lifestyle than healthy subjects. However, during a cycle ergometric test, the maximal load is reduced when FEV1, FVC and muscle strengths are decreased. Additionally, during the six-minute walking test, mild asthma patients walk less than healthy subjects even if the minimal clinically important difference is not reached. The major complaint of asthma patients when exercising is dyspnea that is mainly related to the inspiratory effort and also to dynamic hyperinflation in some circumstances. Finally, the administration of bronchodilator does not improve the ventilatory pattern and the exercise capacity of asthma patients and little is known on its effect on exertional dyspnea. The present review allows to conclude that until now there is no gold standard test allowing the objective assessment of "activity limitation and exertional dyspnea" in asthma patients.

Protocol for a feasibility study to inform the development of a multicentre randomised controlled trial of asthma-tailored pulmonary rehabilitation versus usual care for individuals with severe asthma

INTRODUCTION

Pulmonary rehabilitation with core components of exercise training and multiprofessional education is an integral part of the management of patients with chronic lung disease. International guidelines for individuals with asthma recommend exercise as exercise improves symptoms, indices of cardiopulmonary efficiency, health status and psychosocial outcome. However, there is little published evidence evaluating safety and acceptability of exercise training for individuals with severe asthma and there are concerns regarding exercise-induced asthma. We propose a feasibility study for a multicentre randomised controlled trial (RCT) of asthma-tailored pulmonary rehabilitation (asthma-tailored PR) versus usual care in individuals with severe asthma.

METHODS AND ANALYSIS

The study will be conducted in three stages. Adults with severe asthma will be included if they have persistent symptoms despite being at step 4 or 5 of the British Thoracic Society guidelines. Stage 1: semistructured interviews will be used in a sample of 20-30 individuals with severe asthma to understand the experience and attitudes of this population towards exercise. Stage 2: eight focus groups of at least six healthcare professionals involved in the care of patients with severe asthma will be conducted to understand their attitudes towards exercise for this population. Stage 3: a small-scale RCT of the proposed multicentre RCT of asthma-tailored PR versus usual care for individuals with severe asthma will be conducted. The primary outcome measures will be recruitment, retention and adverse event rates. Semistructured interviews with participants of stage 3 will be used to identify further barriers or facilitators to participation in PR and the trial. Thematic analysis will be used for the interpretation of all interviews.

ETHICS AND DISSEMINATION

The study results will inform the design of a larger multicentre RCT. The National Research Ethics Service Committee East Midland approved the study protocol.

TRIAL REGISTRATION NUMBER

ISRCTN96143888.

Six-minute walk test and respiratory muscle strength in patients with uncontrolled severe asthma: a pilot study

OBJECTIVE:

To evaluate respiratory muscle strength and six-minute walk test (6MWT) variables in patients with uncontrolled severe asthma (UCSA).

METHODS:

This was a cross-sectional study involving UCSA patients followed at a university hospital. The patients underwent 6MWT, spirometry, and measurements of respiratory muscle strength, as well as completing the Asthma Control Test (ACT). The Mann-Whitney test was used in order to analyze 6MWT variables, whereas the Kruskal-Wallis test was used to determine whether there was an association between the use of oral corticosteroids and respiratory muscle strength.

RESULTS:

We included 25 patients. Mean FEV₁ was 58.8 ± 21.8% of predicted, and mean ACT score was 14.0 ± 3.9 points. No significant difference was found between the median six-minute walk distance recorded for the UCSA patients and that predicted for healthy Brazilians (512 m and 534 m, respectively; p = 0.14). During the 6MWT, there was no significant drop in SpO₂. Mean MIP and MEP were normal (72.9 ± 15.2% and 67.6 ± 22.2%, respectively). Comparing the patients treated with at least four courses of oral corticosteroids per year and those treated with three or fewer, we found no significant differences in MIP (p = 0.15) or MEP (p = 0.45).

CONCLUSIONS:

Our findings suggest that UCSA patients are similar to normal subjects in terms of 6MWT variables and respiratory muscle strength. The use of oral corticosteroids has no apparent impact on respiratory muscle strength.

The impact of exercise-induced bronchoconstriction on athletic performance: a systematic review

BACKGROUND

Exercise-induced bronchoconstriction (EIB) describes the phenomenon of transient airway narrowing in association with physical activity. Although it may seem likely that EIB would have a detrimental impact on athletic performance, this has yet to be established.

OBJECTIVES

The aim of this review is to provide a systematic appraisal of the current status of knowledge regarding EIB and exercise performance and to highlight potential mechanisms by which performance may be compromised by EIB.

DATA SOURCES AND STUDY SELECTION

PubMed/Medline and EBSCO databases were searched up to May 2014 using the search parameter: [('exercise' OR 'athlete') AND ('asthma' OR 'bronchoconstriction' OR 'hypersensitivity') AND 'performance']. This search string returned 243 citations. After systematically reviewing all of the abstracts, 101 duplicate papers were removed, with 132 papers excluded for not including an exercise performance outcome measure.

RESULTS

The remaining ten studies that met the initial criteria were included in this review; six evaluated the performance of physically active individuals with asthma and/or EIB while four assessed the effects of medication on performance in a comparable population.

CONCLUSION

The evidence concludes that whilst it is reasonable to suspect that EIB does impact athletic performance, there is currently insufficient evidence to provide a definitive answer.

Guidelines for the evaluation and treatment of muscle dysfunction in patients with chronic obstructive pulmonary disease

In patients with chronic obstructive pulmonary disease (COPD), skeletal muscle dysfunction is a major comorbidity that negatively impacts their exercise capacity and quality of life. In the current guidelines, the most recent literature on the various aspects of COPD muscle dysfunction has been included. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) scale has been used to make evidence-based recommendations on the different features. Compared to a control population, one third of COPD patients exhibited a 25% decline in quadriceps muscle strength, even at early stages of their disease. Although both respiratory and limb muscles are altered, the latter are usually more severely affected. Numerous factors and biological mechanisms are involved in the etiology of COPD muscle dysfunction. Several tests are proposed in order to diagnose and evaluate the degree of muscle dysfunction of both respiratory and limb muscles (peripheral), as well as to identify the patients' exercise capacity (six-minute walking test and cycloergometry). Currently available therapeutic strategies including the different training modalities and pharmacological and nutritional support are also described.

Cardiovascular and respiratory dysfunction in chronic obstructive pulmonary disease complicated by impaired peripheral oxygenation

Background

Impaired peripheral oxygenation (IPO)-related variables readily achieved with cardiopulmonary exercise testing (CPET) represent cardiovascular dysfunction. These variables include peak oxygen uptake ( (V˙O2)<85% predicted, anaerobic threshold <40%V˙O2max predicted, V˙O2-work rate slope <8.6 mL/watt, oxygen pulse <80% predicted, and ventilatory equivalents for O₂ and CO₂ at nadir of >31 and >34, respectively. Some of these six variables may be normal while the others are abnormal in patients with chronic obstructive pulmonary disease (COPD). This may result in confusion when using the interpretation algorithm for diagnostic purposes. We therefore hypothesized that patients found to have abnormal values for all six variables would have worse cardiovascular function than patients with abnormal values for none or some of these variables.

Methods

In this cross-sectional comparative study, 58 COPD patients attending a university teaching hospital underwent symptom-limited CPET with multiple lactate measurements. Patients with abnormal values in all six IPO-related variables were assigned to an IPO group while those who did not meet the requirements for the IPO group were assigned to a non-IPO group. Cardiovascular function was measured by two-dimensional echocardiography and Δlactate/ΔV˙O2, and respiratory dynamics were compared between the two groups.

Results

Fourteen IPO and 43 non-IPO patients were entered into the study. Both groups were similar with regard to left ventricular ejection fraction and right ventricular morphology (P>0.05 for both). At peak exercise, both groups reached a similar heart rate level and Δlactate/ΔV˙O2. The IPO patients had an unfavorable dead space to tidal volume ratio, mean inspiratory tidal flow, and shallow breathing (P<0.05–P<0.001).

Conclusion

Our IPO and non-IPO patients with COPD had similar cardiovascular performance at rest and at peak exercise, indicating that IPO variables are non-specific for cardiovascular function in these patients. COPD patients with full IPO variables have more deranged ventilatory function.

Getting to grips with 'dysfunctional breathing'

Dysfunctional breathing (DB) is common, frequently unrecognised and responsible for a substantial burden of morbidity. Previously lack of clarity in the use of the term and the use of multiple terms to describe the same condition has hampered our understanding. DB can be defined as an alteration in the normal biomechanical patterns of breathing that result in intermittent or chronic symptoms. It can be subdivided into thoracic and extra thoracic forms. Thoracic DB is characterised by breathing patterns involving relatively inefficient, excessive upper chest wall activity with or without accessory muscle activity. This is frequently associated with increased residual volume, frequent sighing and an irregular pattern of respiratory effort. It may be accompanied by true hyperventilation in the minority of subjects. Extra thoracic forms include paradoxical vocal cord dysfunction and the increasingly recognised supra-glottic 'laryngomalacia' commonly seen in young sportsmen and women. While the two forms would appear to be two discreet entities they often share common factors in aetiology and respond to similar interventions. Hence both forms are considered in this review which aims to generate a more coherent approach to understanding, diagnosing and treating these conditions.

Clinical characteristics and lung function in chronic obstructive pulmonary disease complicated with impaired peripheral oxygenation

During exercise testing, patients with chronic obstructive pulmonary disease (COPD) often present with ventilatory limitations and various combinations of impaired peripheral oxygenation (IPO) to the exercising muscles. The entities of IPO include anemia, circulation impairment and deconditioning. COPD-IPO is not widely accepted as being a subgroup of COPD. Therefore, the aim of this study was to evaluate the clinical features of COPD-IPO patients. Forty-seven COPD patients underwent cardiopulmonary exercise testing. COPD-IPO was identified when all IPO variables had abnormal values. The patients who did not meet the COPD-IPO criteria were defined as the NIPO group. The variables with abnormal values included peak oxygen uptake (VO₂) <85% predicated, anaerobic threshold <40% VO₂max pred, VO₂-work rate slope <8.6 ml/watt, oxygen pulse <80%pred, and ventilatory equivalents for O₂ and CO₂ at nadir (>31 and >34, respectively). Anthropometrics, biochemistry, and lung function were compared between the groups. Forty-six COPD patients were enrolled after excluding one patient who had technical difficulties in performing the exercise tests. Despite FEV1 and FVC being similarly reduced (p = NS) between the groups, the COPD-IPO (n = 13, 28%) patients had lower body mass index and were taller, and had impaired diffusing capacity and larger total lung capacity and air-trapping (all p < 0.05). We concluded that COPD patients with all six variables having abnormal values are a unique subgroup and that identification of these patients is worthwhile for further investigations and management such as exercise training and nutritional supplements.

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.

Eucapnic voluntary hyperventilation is superior to methacholine challenge testing for detecting airway hyperreactivity in nonathletes

INTRODUCTION

Response to eucapnic voluntary hyperventilation (EVH) has not been compared with methacholine challenge testing (MCCT) in nonathletes being evaluated for dyspnea on exertion.

OBJECTIVE

To determine the airway response to EVH and MCCT in a population of nonathletes who exercise regularly but have symptoms with exertion.

METHODS

We reviewed records for all patients with exercise symptoms who underwent both EVH and MCCT. Presenting symptoms, comorbid diseases, and results of bronchoprovocation (BP) testing were recorded. This study was approved by the institutional review board at our hospital.

RESULTS

A total of 131 patients (mean age 32.3 ± 11.6, body mass index (BMI) 27.1 ± 4.7 kg/m(2), 59.5% male) had an EVH, MCCT, and clinical evaluation performed. Overall, 37 (28.2%) patients had positive BP testing and met criteria for exercise-induced bronchoconstriction (EIB). There were 32 (24.4%) patients with a positive EVH, compared with only 11 patients with a positive MCCT (8.4%). There were 26 patients (19.8%) who had a positive EVH but a negative MCCT, and correlation between the two tests was poor to moderate (r = 0.11-0.57). A complaint of chest pain and younger age were independent predictors for a positive EVH, whereas a history of tobacco use and a decreased FEV(1)/FVC (forced expiratory volume in 1 s/forced vital capacity) predicted a positive MCCT. A previous diagnosis of asthma was an independent predictor for a response to either test. Discussion. In a population of nonathletes who exercise regularly and have symptoms with exertion, EIB is common. Correlation between EVH and MCCT in this population is poor, and although the tests are somewhat complementary, a large percentage of patients had a negative MCCT but a positive EVH.

CONCLUSIONS

EIB is common in nonathletes with exercise-induced symptoms, and EVH is the preferred test for this population.

CLINICAL IMPLICATIONS

EIB is common in nonathletes who exercise regularly. In this population, MCCT will miss most patients with EIB, and MCCT and EVH show only poor-to-moderate correlation.

CAPSULE SUMMARY

EVH has not been compared with MCCT in nonathletes without a diagnosis of asthma. Our study shows that the two tests are complementary in this population, but EVH is positive more often.

Asthma and obesity: a known association but unknown mechanism

The obese asthma phenotype is an increasingly common encounter in our clinical practice. Epidemiological data indicate that obesity increases the prevalence and incidence of asthma, and evidence that obesity precedes the development of asthma raises the possibility of a causal association. Obese patients with asthma experience more symptoms and increased morbidity compared with non-obese asthma patients. Despite more than a decade of research into this association, the exact mechanisms that underlie the interaction of obesity with asthma remain unclear. It is unlikely that the asthma-obesity association is simply due to comorbidities such as obstructive sleep apnoea or gastroesophageal reflux disease. Although inflammatory pathways are purported to play a role, there is scant direct evidence in humans that systemic inflammation modulates the behaviour of the asthmatic airway or the expression of symptoms in the obese. The role of non-eosinophilic airway inflammation also requires further study. Obesity results in important changes to the mechanical properties of the respiratory system, and these obesity-related factors appear to exert an additive effect to the asthma-related changes seen in the airways. An understanding of the various physiological perturbations that might be contributing to symptoms in obese patients with asthma will allow for a more targeted and rational treatment approach for these patients.