Physiological responses to linear treadmill and cycle ergometer exercise in COPD

Evaluating current assessment techniques of cardiorespiratory fitness

INTRODUCTION

Considerable and convincing global data from cohorts across the health spectrum (i.e. apparently healthy to known disease) indicate that cardiorespiratory fitness (CRF) is a major predictor of overall and cardiovascular disease (CVD)-survival, seemingly with greater prognostic resolution compared to other traditional CVD risk factors. Therefore, the assessment of CRF in research and clinical settings is of major importance.

AREAS COVERED

In this manuscript, we review the technology of measuring CRF assessed by the 'gold standard,' cardiopulmonary exercise testing (CPET), as well as with various other methods (e.g. estimated metabolic equivalents, 6-minute walk tests, shuttle tests, and non-exercise equations that estimate CRF), all of which provide significant prognostic information for CVD- and all-cause survival. The literature through May 2024 has been cited.

EXPERT OPINION

The promotion of physical activity in efforts to improve levels of CRF is needed throughout the world to improve lifespan and, more importantly, healthspan. The routine assessment of CRF should be considered a vital sign that is routinely assessed in clinical practice.

Utility of Cardiopulmonary Exercise Testing in Chronic Obstructive Pulmonary Disease: A Review

Chronic obstructive pulmonary disease (COPD) is a disease defined by airflow obstruction with a high morbidity and mortality and significant economic burden. Although pulmonary function testing is the cornerstone in diagnosis of COPD, it cannot fully characterize disease severity or cause of dyspnea because of disease heterogeneity and variable related and comorbid conditions affecting cardiac, vascular, and musculoskeletal systems. Cardiopulmonary exercise testing (CPET) is a valuable tool for assessing physical function in a wide range of clinical conditions, including COPD. Familiarity with measurements made during CPET and its potential to aid in clinical decision-making related to COPD can thus be useful to clinicians caring for this population. This review highlights pulmonary and extrapulmonary impairments that can contribute to exercise limitation in COPD. Key elements of CPET are identified with an emphasis on measurements most relevant to COPD. Finally, clinical applications of CPET demonstrated to be of value in the COPD setting are identified. These include quantifying functional capacity, differentiating among potential causes of symptoms and limitation, prognostication and risk assessment for operative procedures, and guiding exercise prescription.

Melatonin supplementation enhances pulmonary rehabilitation outcomes in COPD: a randomized, double-blind, placebo-controlled study

Melatonin (MLT), the main product of the pineal gland, is involved in muscle tissue repair and regeneration, besides several other important physiologic functions. In COPD, MLT administration can improve lung oxidative stress and sleep quality, but its potential effects on the outcomes of pulmonary rehabilitation (PR) have not been previously investigated. A randomized controlled trial was undertaken to test the hypothesis that a combined approach of rehabilitative exercise training and MLT supplementation could maximize functional performance, health status and quality of life in patients with COPD. Thirty-nine individuals with COPD referred to a supervised PR program at the Federal University of Ceara, Brazil, were randomized to receive MLT (3 mg/day; n = 18) or placebo (n = 21). Exercise capacity (6-min walk test - 6MWT), health status (COPD assessment test), and quality of life (airways questionnaire 20) were investigated as primary outcomes. No differences were observed at baseline in demographic, anthropometric and clinical characteristics between MLT and placebo groups. At the end of PR, superiority of the MLT group was demonstrated in improvement in the distance covered in the 6MWT (71 ± 26 vs. 25 ± 36 m; p < 0.01), health status (-11 ± 6 vs. -3 ± 5; p < 0.01), and quality of life (-6.9 ± 3.0 vs. -1.9 ± 2.4; p < 0.01), compared to the placebo group. In conclusion, MLT supplementation during the course of 12 weeks of PR can improve functional capacity, health status and quality of life in patients with COPD. These findings may have significant implications for the management of this condition.

Exercise Physiology and Cardiopulmonary Exercise Testing

Aerobic, or endurance, exercise is an energy requiring process supported primarily by energy from oxidative adenosine triphosphate synthesis. The consumption of oxygen and production of carbon dioxide in muscle cells are dynamically linked to oxygen uptake (V̇O2) and carbon dioxide output (V̇CO2) at the lung by integrated functions of cardiovascular, pulmonary, hematologic, and neurohumoral systems. Maximum oxygen uptake (V̇O2max) is the standard expression of aerobic capacity and a predictor of outcomes in diverse populations. While commonly limited in young fit individuals by the capacity to deliver oxygen to exercising muscle, (V̇O2max) may become limited by impairment within any of the multiple systems supporting cellular or atmospheric gas exchange. In the range of available power outputs, endurance exercise can be partitioned into different intensity domains representing distinct metabolic profiles and tolerances for sustained activity. Estimates of both V̇O2max and the lactate threshold, which marks the upper limit of moderate-intensity exercise, can be determined from measures of gas exchange from respired breath during whole-body exercise. Cardiopulmonary exercise testing (CPET) includes measurement of V̇O2 and V̇CO2 along with heart rate and other variables reflecting cardiac and pulmonary responses to exercise. Clinical CPET is conducted for persons with known medical conditions to quantify impairment, contribute to prognostic assessments, and help discriminate among proximal causes of symptoms or limitations for an individual. CPET is also conducted in persons without known disease as part of the diagnostic evaluation of unexplained symptoms. Although CPET quantifies a limited sample of the complex functions and interactions underlying exercise performance, both its specific and global findings are uniquely valuable. Some specific findings can aid in individualized diagnosis and treatment decisions. At the same time, CPET provides a holistic summary of an individual's exercise function, including effects not only of the primary diagnosis, but also of secondary and coexisting conditions.

The six-minute walk test - a reliable test for detection of exercise-related desaturation in patients with chronic obstructive pulmonary disease

INTRODUCTION

Exercise-induced desaturation is common in patients with moderate to severe chronic obstructive pulmonary disease (COPD). It provides additional information about physical capacity and disease evolution, and it is an important predictor of mortality.

In adults with advanced lung disease, the 1-minute sit-to-stand test underestimates exertional desaturation compared with the 6-minute walk test: an observational study

QUESTION

In adults with advanced lung disease, do the 6-minute walk test (6MWT) and 1-minute sit-to-stand test (1minSTS) elicit similar cardiorespiratory responses? Can the 6-minute walk distance (6MWD) be estimated from the 1minSTS result?

DESIGN

Prospective observational study using data collected during routine clinical practice.

PARTICIPANTS

Eighty adults (43 males) with advanced lung disease, a mean age of 64 years (SD 10) and a mean forced expiratory volume in 1 second of 1.65 L (SD 0.77).

OUTCOME MEASURES

Participants completed a 6MWT and a 1minSTS. During both tests, oxygen saturation (SpO2), pulse rate, dyspnoea and leg fatigue (Borg 0 to 10) were recorded.

RESULTS

Compared with the 6MWT, the 1minSTS resulted in higher nadir SpO2 (MD 4%, 95% CI 3 to 5), lower end-test pulse rate (MD -4 beats/minute, 95% CI -6 to -1), similar dyspnoea (MD -0.3, 95% CI -0.6 to 0.1) and greater leg fatigue (MD 1.1, 95% CI 0.6 to 1.6). Among the participants who demonstrated severe desaturation (SpO2 nadir < 85%) on the 6MWT (n = 18), five and ten participants were classified as moderate (nadir 85 to 89%) or mild desaturators (nadir ≥ 90%), respectively, on the 1minSTS. The relationship between the 6MWD and 1minSTS was: 6MWD (m) = 247 + (7 × number of transitions achieved during the 1minSTS) with poor predictive ability (r2 = 0.44).

CONCLUSION

The 1minSTS elicited less desaturation than the 6MWT and classified a smaller proportion of people as 'severe desaturators' on exertion. It is therefore inappropriate to use the nadir SpO2 recorded during a 1minSTS to make decisions about whether strategies are needed to prevent severe transient exertional desaturation during walking-based exercise. Further, the extent to which performance on the 1minSTS can estimate a person's 6MWD is poor. For these reasons, the 1minSTS is unlikely to be helpful when prescribing walking-based exercise.

Using Cardiopulmonary Exercise Testing to Understand Dyspnea and Exercise Intolerance in Respiratory Disease

A cardiopulmonary exercise test (CPET) is ideally suited to quantify exercise tolerance and evaluate the pathophysiological mechanism(s) of dyspnea and exercise limitation in people with chronic respiratory disease. Although there are several statements on CPET and many outstanding resources detailing the cardiorespiratory and perceptual responses to exercise, limited information is available to support the health care provider in conducting a practical CPET evaluation. This article provides the health care provider with practical and timely information on how to use CPET data to understand dyspnea and exercise intolerance in people with chronic respiratory diseases. Information on CPET protocol, as well as how to evaluate maximal patient effort, peak rate of oxygen consumption, ventilatory demand, pulmonary gas exchange, ventilatory reserve, operating lung volumes, and exertional dyspnea, is presented. Two case examples are also described to highlight how these parameters are evaluated to provide a clinical interpretation of CPET data.

Dynamic physiological responses in obese and non-obese adults submitted to cardiopulmonary exercise test

PURPOSE

Obese individuals have reduced performance in cardiopulmonary exercise testing (CPET), mainly considering peak values of variables such as oxygen uptake ([Formula: see text]), carbon dioxide production ([Formula: see text]), tidal volume (Vt), minute ventilation ([Formula: see text]) and heart rate (HR). The CPET interpretation and prognostic value can be improved through submaximal ratios analysis of key variables like [Formula: see text], [Formula: see text], [Formula: see text] [Formula: see text] and oxygen uptake efficiency slope (OUES). The obesity influence on these responses has not yet been investigated. Our purpose was to evaluate the influence of adulthood obesity on maximal and submaximal physiological responses during CPET, emphasizing the analysis of submaximal dynamic variables.

METHODS

We analyzed 1,594 CPETs of adults (755 obese participants, Body Mass Index ≥ 30 kg/m2) and compared the obtained variables among non-obese (normal weight and overweight) and obese groups (obesity classes I, II and III) through multivariate covariance analyses.

RESULT

Obesity influenced the majority of evaluated maximal and submaximal responses with worsened CPET performance. Cardiovascular, metabolic and gas exchange variables were the most influenced by obesity. Other maximal and submaximal responses were altered only in morbidly obese. Only a few cardiovascular and ventilatory variables presented inconsistent results. Additionally, Vtmax, [Formula: see text], Vt/Inspiratory Capacity, Vt/Forced Vital Capacity, Lowest [Formula: see text], [Formula: see text], and the y-intercepts of [Formula: see text] did not significantly differ regardless of obesity.

CONCLUSION

Obesity expressively influences the majority of CPET variables. However, the prognostic values of the main ventilatory efficiency responses remain unchanged. These dynamic responses are not dependent on maximum effort and may be useful in detecting incipient ventilatory disorder. Our results present great practical applicability in identifying exercise limitation, regardless of overweight and obesity.

Effects of a Rehabilitation Programme Using a Nasal Inspiratory Restriction Device in COPD

Chronic obstructive pulmonary disease (COPD) patients are characterised for presenting dyspnea, which reduces their physical capacity and tolerance to physical exercise. The aim of this study was to analyse the effects of adding a Feel-Breathe (FB) device for inspiratory muscle training (IMT) to an 8-week pulmonary rehabilitation programme. Twenty patients were randomised into three groups: breathing with FB (FBG), oronasal breathing without FB (ONBG) and control group (CG). FBG and ONBG carried out the same training programme with resistance, strength and respiratory exercises for 8 weeks. CG did not perform any pulmonary rehabilitation programme. Regarding intra group differences in the value obtained in the post-training test at the time when the maximum value in the pre-training test was obtained (Post_PRE), FBG obtained lower values in oxygen consumption (VO₂, mean = -435.6 mL/min, Bayes Factor (BF₁₀) > 100), minute ventilation (VE, -8.5 L/min, BF₁₀ = 25), respiratory rate (RR, -3.3 breaths/min, BF₁₀ = 2), heart rate (HR, -13.7 beats/min, BF₁₀ > 100) and carbon dioxide production (VCO₂, -183.0 L/min, BF₁₀ = 50), and a greater value in expiratory time (Tex, 0.22 s, BF₁₀ = 12.5). At the maximum value recorded in the post-training test (Post_FINAL), FBG showed higher values in the total time of the test (T_t, 4.3 min, BF₁₀ = 50) and respiratory exchange rate (RER, 0.05, BF₁₀ = 1.3). Regarding inter group differences at Pre_POST, FBG obtained a greater negative increment than ONBG in the ventilatory equivalent of CO₂ (EqCO₂, -3.8 L/min, BF₁₀ = 1.1) and compared to CG in VE (-8.3 L/min, BF₁₀ = 3.6), VCO₂ (-215.9 L/min, BF₁₀ = 3.0), EqCO2 (-3.7 L/min, BF₁₀ = 1.1) and HR (-12.9 beats/min, BF₁₀ = 3.4). FBG also showed a greater Pre_POST positive increment in Tex (0.21 s, BF₁₀ = 1.4) with respect to CG. At Pre_FINAL, FBG presented a greater positive increment compared to CG in T_t (4.4 min, BF₁₀ = 3.2) and negative in VE/VCO₂ intercept (-4.7, BF₁₀ = 1.1). The use of FB added to a pulmonary rehabilitation programme in COPD patients could improve tolerance in the incremental exercise test and energy efficiency. However, there is only a statically significant difference between FBG and ONBG in EqCO₂. Therefore, more studies are necessary to reach a definitive conclusion about including FB in a pulmonary rehabilitation programme.

Evaluation of Dynamic Respiratory Mechanical Abnormalities During Conventional CPET

Assessment of the ventilatory response to exercise is important in evaluating mechanisms of dyspnea and exercise intolerance in chronic cardiopulmonary diseases. The characteristic mechanical derangements that occur during exercise in chronic respiratory conditions have previously been determined in seminal studies using esophageal catheter pressure-derived measurements. In this brief review, we examine the emerging role and clinical utility of conventional assessment of dynamic respiratory mechanics during exercise testing. Thus, we provide a physiologic rationale for measuring operating lung volumes, breathing pattern, and flow-volume loops during exercise. We consider standardization of inspiratory capacity-derived measurements and their practical implementation in clinical laboratories. We examine the evidence that this iterative approach allows greater refinement in evaluation of ventilatory limitation during exercise than traditional assessments of breathing reserve. We appraise the available data on the reproducibility and responsiveness of this methodology. In particular, we review inspiratory capacity measurement and derived operating lung volumes during exercise. We demonstrate, using recent published data, how systematic evaluation of dynamic mechanical constraints, together with breathing pattern analysis, can provide valuable insights into the nature and extent of physiological impairment contributing to exercise intolerance in individuals with common chronic obstructive and restrictive respiratory disorders.

Physiological rationale of commonly used clinical exercise tests

In order to measure cardiopulmonary performance for clinical and investigation purposes we need standardized tests which allow the comparison with standard values, between people, or individuals with themselves over time. The quest for the ideal exercise test has led to the development of several formats, the so called laboratory and field tests. Incremental exercise tests allow measurement of maximal exercise capacity and a host of submaximal variables of great interest. The physiological rationale of the tests and of the detection of interesting submaximal variables can be explained from the oxygen uptake and carbon dioxide output kinetic response to constant power exercise. When the muscles have to produce very high energy, the exercise is physiologically limited to relatively short duration. The minimum power at which an exercise can no longer be sustained for long periods of time is called critical power. Above critical power the time-power function shows a hyperbolic shape. This shape provides the rationale for understanding the properties, limitations and responsiveness to interventions of endurance tests such as constant power test on a cycle-ergometer or treadmill, endurance shuttle walk test and six-minute walk test.

Physiologic Effects of Oxygen Supplementation During Exercise in Chronic Obstructive Pulmonary Disease

Supplemental long-term oxygen therapy (LTOT) is a well-established therapy that improves mortality in patients with chronic obstructive pulmonary disease (COPD) with resting hypoxemia. In the large number of patients with COPD who do not have severe resting hypoxemia but who desaturate with exercise, the clinical benefits that can be obtained by supplemental O₂ therapy during exercise is an area of interest and active research. A summary of current evidence for benefits of supplemental O₂ therapy and a review of physiologic mechanisms underlying published observations are reviewed in this article.

ERS statement on standardisation of cardiopulmonary exercise testing in chronic lung diseases

The objective of this document was to standardise published cardiopulmonary exercise testing (CPET) protocols for improved interpretation in clinical settings and multicentre research projects. This document: 1) summarises the protocols and procedures used in published studies focusing on incremental CPET in chronic lung conditions; 2) presents standard incremental protocols for CPET on a stationary cycle ergometer and a treadmill; and 3) provides patients' perspectives on CPET obtained through an online survey supported by the European Lung Foundation. We systematically reviewed published studies obtained from EMBASE, Medline, Scopus, Web of Science and the Cochrane Library from inception to January 2017. Of 7914 identified studies, 595 studies with 26 523 subjects were included. The literature supports a test protocol with a resting phase lasting at least 3 min, a 3-min unloaded phase, and an 8- to 12-min incremental phase with work rate increased linearly at least every minute, followed by a recovery phase of at least 2–3 min. Patients responding to the survey (n=295) perceived CPET as highly beneficial for their diagnostic assessment and informed the Task Force consensus. Future research should focus on the individualised estimation of optimal work rate increments across different lung diseases, and the collection of robust normative data.

The document facilitates standardisation of conducting, reporting and interpreting cardiopulmonary exercise tests in chronic lung diseases for comparison of reference data, multi-centre studies and assessment of interventional efficacy.http://bit.ly/31SXeB5

Exercise Training Modalities for People with Chronic Obstructive Pulmonary Disease

Exercise training confers health benefits for people with chronic obstructive pulmonary disease (COPD). This article reviews the evidence for several exercise training modalities shown to be beneficial among individuals with COPD. These modalities include aerobic, resistance, nonlinear periodized, upper limb and balance training, as well as yoga, Tai Chi, inspiratory muscle training, whole body vibration training and neuromuscular electrical stimulation. The literature pertaining to each modality was critically reviewed, and information on the rationale, mechanism(s) of action (where known), benefits, and exercise prescription is described to facilitate easy implementation into clinical practice.

Incremental step test in patients with pulmonary hypertension

Cardiopulmonary exercise testing (CPET) on a treadmill or cycle ergometer provides an integrated assessment of the cardiorespiratory system during exertion and is widely used in clinical practice. An incremental step test (IST) can be an alternative for eliciting maximal exercise responses. Therefore, 20 patients with pre-capillary PH (65% female, 41 ± 15 yrs) randomly performed a symptom-limited CPET on a cycle ergometer and IST. Metabolic, cardiovascular, ventilatory and gas exchange variables were recorded during both tests. There was a greater desaturation and higher V̇O_2PEAK in IST compared to CPET. The V̇O_2GET, HR _PEAK (% pred), ΔV̇E/ΔV̇CO₂ and ΔHR/ΔV̇O₂ were similar in both IST and CPET. By linear regression analyses, the work performed on IST [W = (mass × 9,8 m/s2 x vertical distance)] was a predictor of peak V̇O₂ independent of the gender and age (r² = 077, p = 0001). In conclusion, IST elicited higher peak cardiopulmonary responses and has a good agreement with known severity markers in patients with pre-capillary PH.

A systematic review of surgical treatment for supraglottic exercise-induced laryngeal obstruction

Objectives

Exercise‐induced laryngeal obstruction (EILO) is a condition causing breathing difficulties and stridor during exercise. The condition has in severe cases been treated surgically with supraglottoplasty. The purpose of this systematic review is to assess the evidence and recommendations for surgical intervention in treating patients with EILO.

Methods

A systematic search was performed in PubMed and Embase to identify relevant studies describing surgical treatment of patients diagnosed with severe EILO. According to eligibility criteria, data were independently extracted by two reviewers. To assess the risk of bias of each included study, the Newcastle‐Ottawa scale (NOS) was used.

Results

The screening process identified 11 observational studies with a total of 75 patients. Findings indicated that many beneficial outcomes are to be found in surgical treatment for EILO. These indications were found both on visual verification of improvement of the laryngeal obstruction during exercise and patient self‐reported symptom severity. The average NOS score (4.3) indicated low level of evidence in the included studies.

Conclusion

Studies reporting effects of surgical treatment of EILO have shown promising results in patients with laryngeal obstruction. However, the heterogeneity of study methodologies and the level of evidence precludes definitive recommendations for or against supraglottoplasty at this time; prospective and methodologically robust studies are now needed.

Level of Evidence

4

Faster oxygen uptake, heart rate, and ventilatory kinetics in stepping compared with cycle ergometry in patients with COPD during moderate-intensity exercise

Step tests are a stressful and feasible cost-effective modality to evaluate aerobic performance. However, the eccentric in addition to concentric muscle contractions of the legs on stepping emerge as a potential speeding factor for cardioventilatory and metabolic adjustments towards a steady-state, since eccentric contractions would prompt an earlier and stronger mechanoreceptor activation, as well as higher heart rate/cardiac output adjustments to the same metabolic demand. Moreover, shorter tests are ideal for exercise-limited subjects. Nine subjects with chronic obstructive pulmonary disease were invited to participate in comprehensive lung function tests and constant work tests performed on different days at a 90% gas exchange threshold for 6 min, in single-step tests or cycle ergometry. After careful monoexponential regression modelling, statistically relevant faster phase II time constants for oxygen uptake (45 ± 18 s vs 53 ± 17 s, p = 0.017) and minute ventilation (61 ± 13 s vs 74 ± 17 s, p = 0.027) were observed in the 6-min step tests compared with cycle ergometry, respectively. Despite an absence of heart rate time constant difference (43 ± 20 s vs 69 ± 46 s, p = 0.167), there was a significantly faster rate constant toward a steady state for heart rate (p = 0.02). In addition, 4-min compared with 6-min analysis presented similar results (p > 0.05), providing an appropriate steady-state. We conclude that step tests might elicit faster time constants compared with cycle ergometry, at the same average metabolic level, and 4-min analysis has similar mean errors compared with 6-min analysis within an acceptable range. New studies, comprising mechanisms and detailed physiological backgrounds, are necessary.

Cardiorespiratory Response to Different Exercise Tests in Interstitial Lung Disease

INTRODUCTION

The 6-min stepper test (6MST) has been used as an alternative to the 6-min walk test (6MWT) to assess exercise tolerance in patients with interstitial lung disease (ILD). Recent data suggest that the tests may involve different energy pathways and cardiorespiratory responses. We thus aimed to compare the cardiorespiratory responses of ILD patients during the 6MWT and the 6MST.

METHODS

Thirty-one patients with ILD were randomized to perform both tests in the order 6MST → 6MWT (n = 16) or 6MWT → 6MST (n = 15). Gas exchange, HR, and pulse O2 saturation (SpO2) were measured continuously, and dyspnoea, leg discomfort, and blood lactate concentration were assessed before and immediately after each test.

RESULTS

Oxygen uptake (V˙O2) was lower (P = 0.002) and respiratory equivalent ratio for O2 (V˙E/V˙O2) and RER were higher (both P < 0.001) during the 6MST compared with the 6MWT. The 6MST was also associated with higher blood lactate concentrations (6MST, 4.16 ± 1.95 mmol·L; 6MWT, 2.84 ± 1.17 mmol·L; P = 0.01), higher leg discomfort scores (6MST 5 ± 3 points, 6MWT 3 ± 2 points; P < 0.001), and smaller decreases in SpO2 (6MST -5% ± 5%, 6MWT -9% ± 6%; P < 0.001).

CONCLUSIONS

ILD patients exhibited greater ventilatory responses and lower arterial O2 desaturation during the 6MST compared with the 6MWT. The higher lactate concentrations and perceived muscle fatigue observed during the 6MST may indicate the presence of intertest differences in active muscle metabolism that could contribute to the distinct cardiorespiratory responses.

Exertional dyspnoea in COPD: the clinical utility of cardiopulmonary exercise testing

Activity-related dyspnoea is often the most distressing symptom experienced by patients with chronic obstructive pulmonary disease (COPD) and can persist despite comprehensive medical management. It is now clear that dyspnoea during physical activity occurs across the spectrum of disease severity, even in those with mild airway obstruction. Our understanding of the nature and source of dyspnoea is incomplete, but current aetiological concepts emphasise the importance of increased central neural drive to breathe in the setting of a reduced ability of the respiratory system to appropriately respond. Since dyspnoea is provoked or aggravated by physical activity, its concurrent measurement during standardised laboratory exercise testing is clearly important. Combining measurement of perceptual and physiological responses during exercise can provide valuable insights into symptom severity and its pathophysiological underpinnings. This review summarises the abnormal physiological responses to exercise in COPD, as these form the basis for modern constructs of the neurobiology of exertional dyspnoea. The main objectives are: 1) to examine the role of cardiopulmonary exercise testing (CPET) in uncovering the physiological mechanisms of exertional dyspnoea in patients with mild-to-moderate COPD; 2) to examine the escalating negative sensory consequences of progressive respiratory impairment with disease advancement; and 3) to build a physiological rationale for individualised treatment optimisation based on CPET.

Is the six-minute walk test a useful tool to prescribe high-intensity exercise in patients with chronic obstructive pulmonary disease?

BACKGROUND

It is not yet completely known whether the 6MWT can be used to prescribe high-intensity exercise for patients with COPD.

OBJECTIVE

To evaluate the ability of the six-minute walk test (6MWT) to prescribe high-intensity exercise for patients with chronic obstructive pulmonary disease (COPD).

METHODS

Lung function, maximal inspiratory strength, symptoms and exercise capacity were evaluated in patients with COPD (n = 27) before and after a 12-week high-intensity exercise program. Criteria for high-intensity training were: 1) ≥75% of the 6MWT average speed; 2) American Thoracic Society/European Respiratory Society (ATS/ERS) criteria (≥60% of the maximal incremental shuttle walk test speed).

RESULTS

The 6MWT showed good positive and negative predictive values (0.69 and 0.71, respectively), and accuracy (0.70), good reliability (ICC 0.70 [95%CI 0.45-0.85]) and moderate agreement (k 0.41 [95%CI 0.13-0.67]) with the ATS/ERS criteria.

CONCLUSION

The 6MWT has good predictive ability and accuracy in relation to high-intensity exercise for patients with COPD.

Comparison of the six-minute walk test with a cycle-based cardiopulmonary exercise test in people following curative intent treatment for non-small cell lung cancer

This study is aimed to (i) compare both the magnitude of impairment in exercise capacity and exercise responses measured during the six-minute walk test (6MWT) and the cardiopulmonary exercise test (CPET) and (ii) investigate the effect of test repetition on six-minute walk distance (6MWD) in people following curative intent treatment for non-small cell lung cancer (NSCLC). Twenty participants (67 ± 10 years; 14 females), 6-10 weeks following lobectomy, underwent a CPET and two 6MWTs. Peak exercise responses, dyspnoea and leg fatigue, as well as heart rate (HR) and oxygen saturation (SpO2) during the 6MWT, were compared to those during the CPET. Compared with exercise capacity when expressed as peak rate of oxygen consumption (%pred) measured during the CPET, exercise capacity when expressed as 6MWD (%pred) was less impaired (81 ± 10 vs. 63 ± 15 %pred; p < 0.001). Compared with the CPET, the 6MWT elicited lower peak HR (119 ± 15 vs. 128 ± 18 beats minute(-1); p = 0.02), lower SpO2 (93 ± 2 vs. 95 ± 3%; p < 0.05), less dyspnoea (3.1 ± 1.6 vs. 6.9 ± 2.6; p < 0.01) and less leg fatigue (2.0 ± 1.9 vs. 6.8 ± 2.4; p < 0.01). The 6MWD increased 19 ± 19 metre (4 ± 4%) with test repetition (p < 0.001). In people following curative intent treatment for NSCLC, the 6MWT appears to elicit sub-maximal exercise responses when compared with the CPET. There is a significant effect of test repetition on 6MWD.

Comparison of laboratory- and field-based exercise tests for COPD: a systematic review

Exercise tests are often used to evaluate the functional status of patients with COPD. However, to the best of our knowledge, a comprehensive systematic comparison of these tests has not been performed. We systematically reviewed studies reporting the repeatability and/or reproducibility of these tests, and studies comparing their sensitivity to therapeutic intervention. A systematic review identified primary manuscripts in English reporting relevant data on the following exercise tests: 6-minute walk test (6MWT) and 12-minute walk test, incremental and endurance shuttle walk tests (ISWT and ESWT, respectively), incremental and endurance cycle ergometer tests, and incremental and endurance treadmill tests. We identified 71 relevant studies. Good repeatability (for the 6MWT and ESWT) and reproducibility (for the 6MWT, 12-minute walk test, ISWT, ESWT, and incremental cycle ergometer test) were reported by most studies assessing these tests, providing patients were familiarized with them beforehand. The 6MWT, ISWT, and particularly the ESWT were reported to be sensitive to therapeutic intervention. Protocol variations (eg, track layout or supplemental oxygen use) affected performance significantly in several studies. This review shows that while the validity of several tests has been established, for others further study is required. Future work will assess the link between these tests, physiological mechanisms, and patient-reported measures.

Characteristics and determinants of endurance cycle ergometry and six-minute walk distance in patients with COPD

Background

Exercise tolerance can be assessed by the cycle endurance test (CET) and six-minute walk test (6MWT) in patients with Chronic Obstructive Pulmonary Disease (COPD). We sought to investigate the characteristics of functional exercise performance and determinants of the CET and 6MWT in a large clinical cohort of COPD patients.

Methods

A dataset of 2053 COPD patients (43% female, age: 66.9 ± 9.5 years, FEV₁% predicted: 48.2 ± 23.2) was analyzed retrospectively. Patients underwent, amongst others, respiratory function evaluation; medical tests and questionnaires, one maximal incremental cycle test where peak work rate was determined and two functional exercise tests: a CET at 75% of peak work rate and 6MWT. A stepwise multiple linear regression was used to assess determinants.

Results

On average, patients had impaired exercise tolerance (peak work rate: 56 ± 27% predicted, 6MWT: 69 ± 17% predicted). A total of 2002 patients had CET time of duration (CET-T_end) less than 20 min while only 51 (2.5%) of the patients achieved 20 min of CET-T_end . In former patients, the percent of predicted peak work rate achieved differed significantly between men (48 ± 21% predicted) and women (67 ± 31% predicted). In contrast, CET-T_end was longer in men (286 ± 174 s vs 250 ± 153 s, p < 0.001). Also, six minute walking distance (6MWD) was higher in men compared to women, both in absolute terms as in percent of predicted (443 m, 67%predicted vs 431 m, 72%predicted, p < 0.05). Gender was associated with the CET-T_end but BMI, FEV₁ and FRC were related to the 6MWD highlighting the different determinants of exercise performance between CET and 6MWT.

Conclusions

CET-T_end is a valuable outcome of CET as it is related to multiple clinical aspects of disease severity in COPD. Gender difference should temper the interpretation of CET.

The continuum of physiological impairment during treadmill walking in patients with mild-to-moderate COPD: patient characterization phase of a randomized clinical trial

BACKGROUND

To have a better understanding of the mechanisms of exercise limitation in mild-to-moderate chronic obstructive pulmonary disease (COPD), we compared detailed respiratory physiology in patients with COPD and healthy age- and sex-matched controls.

METHODS

Data were collected during the pre-treatment, patient characterization phase of a multicenter, randomized, double-blind, crossover study. Patients with COPD met Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 or 2 spirometric criteria, were symptomatic, and had evidence of gas trapping during exercise. All participants completed pulmonary function and symptom-limited incremental treadmill exercise tests.

RESULTS

Chronic activity-related dyspnea measured by Baseline Dyspnea Index was similarly increased in patients with GOLD 1 (n = 41) and 2 (n = 63) COPD compared with controls (n = 104). Plethysmographic lung volumes were increased and lung diffusing capacity was decreased in both GOLD groups. Peak oxygen uptake and work rate were reduced in both GOLD groups compared with controls (p<0.001). Submaximal ventilation, dyspnea, and leg discomfort ratings were higher for a given work rate in both GOLD groups compared with controls. Resting inspiratory capacity, peak ventilation, and tidal volume were reduced in patients with GOLD 2 COPD compared with patients with GOLD 1 COPD and controls (p<0.001).

CONCLUSIONS

Lower exercise tolerance in patients with GOLD 1 and 2 COPD compared with controls was explained by greater mechanical abnormalities, greater ventilatory requirements, and increased subjective discomfort. Lower resting inspiratory capacity in patients with GOLD 2 COPD was associated with greater mechanical constraints and lower peak ventilation compared with patients with GOLD 1 COPD and controls.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01072396.

Exercise: Kinetic considerations for gas exchange

The activities of daily living typically occur at metabolic rates below the maximum rate of aerobic energy production. Such activity is characteristic of the nonsteady state, where energy demands, and consequential physiological responses, are in constant flux. The dynamics of the integrated physiological processes during these activities determine the degree to which exercise can be supported through rates of O₂ utilization and CO₂ clearance appropriate for their demands and, as such, provide a physiological framework for the notion of exercise intensity. The rate at which O₂ exchange responds to meet the changing energy demands of exercise--its kinetics--is dependent on the ability of the pulmonary, circulatory, and muscle bioenergetic systems to respond appropriately. Slow response kinetics in pulmonary O₂ uptake predispose toward a greater necessity for substrate-level energy supply, processes that are limited in their capacity, challenge system homeostasis and hence contribute to exercise intolerance. This review provides a physiological systems perspective of pulmonary gas exchange kinetics: from an integrative view on the control of muscle oxygen consumption kinetics to the dissociation of cellular respiration from its pulmonary expression by the circulatory dynamics and the gas capacitance of the lungs, blood, and tissues. The intensity dependence of gas exchange kinetics is discussed in relation to constant, intermittent, and ramped work rate changes. The influence of heterogeneity in the kinetic matching of O₂ delivery to utilization is presented in reference to exercise tolerance in endurance-trained athletes, the elderly, and patients with chronic heart or lung disease.

Abnormal heart rate recovery and chronotropic incompetence on exercise in chronic obstructive pulmonary disease

Chronotropic incompetence (CI; failure to reach the targeted heart rate (HR) on exercise) and a delayed HR recovery (HRR; ≤12 beats decline within the first minute after cessation) reflect autonomic dysfunction (AD) and predict adverse cardiac prognosis. As chronic obstructive pulmonary disease (COPD) is known to be associated with AD, we hypothesized that these patients may manifest these responses on exercise. The prevalence and predictors of these responses in COPD and their association with its severity have not been evaluated. Normoxemic, stable male patients with COPD ( n = 39) and 11 healthy controls underwent lung function testing and incremental leg ergometry. HR responses were monitored during exercise and recovery to compute the HRR and CI. Of all the patients, 33 (84.6%) had at least one of the two exercise responses as abnormal, with the majority (23, 58.9%) having both an abnormal HRR and CI. The frequency of abnormal responses increased with increasing Global Initiative for Chronic Obstructive Lung Disease stage and body mass index, airflow obstruction, dyspnoea and exercise capacity index. After adjusting for smoking history and post-bronchodilator forced expiratory volume in 1 second, only a reduced diffusion capacity for carbon monoxide predicted abnormal HRR, though weakly. We concluded that abnormal HRR and CI are common in patients with COPD. These responses are observed with increasing frequency as the severity of disease increases.

Xbox Kinect™ represents high intensity exercise for adults with cystic fibrosis

BACKGROUND

Exercise is important for patients with cystic fibrosis (CF). Interactive gaming consoles are a new trend in exercise. This study sought to determine the exercise intensity of training using the Xbox Kinect(™).

METHODS

Participants with CF completed two sessions separated by ≤10 days. The first session involved a cardiopulmonary exercise test (CPET) to measure peak exercise capacity. The second session involved 20 min of exercise using the Xbox Kinect™.

RESULTS

Ten participants (median [interquartile range] FEV1 58 [46]%, 29 [6] years, 6 males) completed the study. The average heart rate over the final 10 min of exercise using the Xbox Kinect™, expressed as a percentage of the peak heart rate achieved on the CPET, was 86% (95% confidence interval, 81 to 92%).

CONCLUSIONS

Training using the Xbox Kinect™ represents high intensity exercise for adults with CF and may be a suitable alternative to conventional exercise modalities.

Inspiratory Capacity during Exercise: Measurement, Analysis, and Interpretation

Cardiopulmonary exercise testing (CPET) is an established method for evaluating dyspnea and ventilatory abnormalities. Ventilatory reserve is typically assessed as the ratio of peak exercise ventilation to maximal voluntary ventilation. Unfortunately, this crude assessment provides limited data on the factors that limit the normal ventilatory response to exercise. Additional measurements can provide a more comprehensive evaluation of respiratory mechanical constraints during CPET (e.g., expiratory flow limitation and operating lung volumes). These measurements are directly dependent on an accurate assessment of inspiratory capacity (IC) throughout rest and exercise. Despite the valuable insight that the IC provides, there are no established recommendations on how to perform the maneuver during exercise and how to analyze and interpret the data. Accordingly, the purpose of this manuscript is to comprehensively examine a number of methodological issues related to the measurement, analysis, and interpretation of the IC. We will also briefly discuss IC responses to exercise in health and disease and will consider how various therapeutic interventions influence the IC, particularly in patients with chronic obstructive pulmonary disease. Our main conclusion is that IC measurements are both reproducible and responsive to therapy and provide important information on the mechanisms of dyspnea and exercise limitation during CPET.

Exercise and COPD: therapeutic responses, disease-related outcomes, and activity-promotion strategies

Chronic obstructive pulmonary disease (COPD) reduces patients' exercise capacities and their abilities to perform daily physical activities, thereby increasing morbidity and mortality rates. The cycle of dyspnea, deconditioning, and declining physical activity not only accelerates the progression of COPD but also increases the risk for developing or aggravating metabolic and cardiovascular diseases. Cardiovascular and metabolic comorbidities also limit physical function, and their disabling effects in combination with COPD may be greater than the effects of each disease alone. The impact of COPD and its treatment on the ability to exercise, and the degree of physical activity in daily life, can be measured by field-based tests (eg, the 6-minute walk test or incremental and endurance shuttle-walk test), laboratory-based tests (eg, incremental or constant work-rate treadmill and cycle-ergometer tests), and physical activity assessments (eg, questionnaires and accelerometers). Walking tests increase oxygen consumption and desaturation in patients with COPD more than cycling tests with similar work-rate profiles and may more closely resemble patients' normal activities. Despite the questionable relevance of exercise testing to patients' daily functionality, exercise parameters remain important predictors of survival in patients with COPD. Treatment of COPD (pharmacotherapy, pulmonary rehabilitation, or both) can increase exercise capacity and physical activity in daily life, which potentially slows the decline of lung function, reduces the frequencies of exacerbations and hospitalizations, decreases mortality, slows the progression of comorbidities, improves health-related quality of life, and increases the activity reserve for routine function. This article examines the interactions of reduced physical activity and decreased exercise capacity with the progression of COPD, comorbidities, and mortality. The article also describes the available exercise tests for patients with COPD and reviews the evidence indicating that treating COPD improves exercise capacity. Notably, it appears that even mild COPD reduces exercise capacity and daily physical activity, indicating the need for early intervention.

Responsiveness of Various Exercise-Testing Protocols to Therapeutic Interventions in COPD

Exercise intolerance is a key element in the pathophysiology and course of Chronic Obstructive Pulmonary Disease (COPD). As such, evaluating exercise tolerance has become an important part of the management of COPD. A wide variety of exercise-testing protocols is currently available, each protocol having its own strengths and weaknesses relative to their discriminative, methodological, and evaluative characteristics. This paper aims to review the responsiveness of several exercise-testing protocols used to evaluate the efficacy of pharmacological and nonpharmacological interventions to improve exercise tolerance in COPD. This will be done taking into account the minimally important difference, an important concept in the interpretation of the findings about responsiveness of exercise testing protocols. Among the currently available exercise-testing protocols (incremental, constant work rate, or self-paced), constant work rate exercise tests (cycle endurance test and endurance shuttle walking test) emerge as the most responsive ones for detecting and quantifying changes in exercise capacity after an intervention in COPD.

Pulmonary rehabilitation: a review of the recent literature

Pulmonary rehabilitation (PR) is an evidence-based, multidisciplinary, comprehensive intervention that can be integrated into the management of individuals with chronic lung disease. It aims to reduce symptoms, optimize function, increase participation in daily life, and reduce health-care resource utilization. In this review, we summarize the new developments in PR over the past 5 years. Issues related to patient assessment include a comparison of cycle- and walking-based measures of exercise capacity, the emergence of multidimensional indices, the refinement of the minimal clinically important difference, and the importance of assessing physical activity. Issues related to exercise training focus on strategies to optimize the training load. We also comment on the acquisition of self-management skills, balance training, optimizing access, and maintaining gains following completion of PR.

Respiratory Consequences of Mild-to-Moderate Obesity: Impact on Exercise Performance in Health and in Chronic Obstructive Pulmonary Disease

In many parts of the world, the prevalence of obesity is increasing at an alarming rate. The association between obesity, multiple comorbidities, and increased mortality is now firmly established in many epidemiological studies. However, the link between obesity and exercise intolerance is less well studied and is the focus of this paper. Although exercise limitation is likely to be multifactorial in obesity, it is widely believed that the respiratory mechanical constraints and the attendant dyspnea are important contributors. In this paper, we examined the evidence that critical ventilatory constraint is a proximate source of exercise limitation in individuals with mild-to-moderate obesity. We first reviewed existing information on exercise performance, including ventilatory and perceptual response patterns, in obese individuals who are otherwise healthy. We then considered the impact of obesity in patients with preexisting respiratory mechanical abnormalities due to chronic obstructive pulmonary disease (COPD), with particular reference to the effect on dyspnea and exercise performance. Our main conclusion, based on the existing and rather sparse literature on the subject, is that abnormalities of dynamic respiratory mechanics are not likely to be the dominant source of dyspnea and exercise intolerance in otherwise healthy individuals or in patients with COPD with mild-to-moderate obesity.

Transcriptional profiling of CD133(+) cells in coronary artery disease and effects of exercise on gene expression

BACKGROUND AIMS

Bone marrow (BM)-derived progenitor cells are under investigation for cardiovascular repair but may be altered by disease. Our aim was to identify differences in gene expression in CD133(+) cells of patients with coronary artery disease (CAD) and healthy controls, and determine whether exercise modifies gene expression.

METHODS

CD133(+) cells were flow-sorted from 10 CAD patients and four controls, and total RNA was isolated for microarray-based gene expression profiling. Genes that were found to be differentially regulated in patients were analyzed further to investigate whether exercise had any normalizing effect on CD133(+) cells in CAD patients following 3 months of an exercise program.

RESULTS

Improvement in effort tolerance and increases in the number of CD133(+) cells were observed in CAD patients after 3 months of exercise. Gene expression analysis of the CD133(+) cells identified 82 differentially expressed genes (2-fold cut-off, 25% false-discovery rate and % present calls) in patients compared with controls, of which 59 were found to be up-regulated and 23 down-regulated. These genes were found to be involved in carbohydrate metabolism, cell cycle, cellular development and signaling, and molecular transport. Following completion of the exercise program, gene expression patterns resembled those of controls in seven of 10 patients.

CONCLUSIONS

Alterations in gene expression of BM-derived CD133(+) progenitor cells were found in CAD patients, which in part may be normalized by exercise.

State of the art: how to set up a pulmonary rehabilitation program

Pulmonary rehabilitation plays an essential role in the management of symptomatic patients with COPD. The benefits of rehabilitation include a decrease in dyspnoea and fatigue, and improvements in exercise tolerance and health-related quality of life. Importantly, rehabilitation reduces hospitalization for acute exacerbations and is cost-effective. Although most of the evidence for pulmonary rehabilitation has been obtained in patients with COPD, symptomatic individuals with other respiratory diseases have been shown to benefit. In this review we outline a stepwise approach to establish, deliver and evaluate a pulmonary rehabilitation program (PRP) that would be feasible in most settings. Throughout the review we have specified the minimum requirements for a PRP to facilitate the establishment of programs using limited resources. Recommendations for staffing and other resources required for a PRP are presented in the first section. Exercise training is a focus of the section on program delivery as this is the component of rehabilitation that has the strongest level of evidence for benefit. Program considerations for patients with respiratory conditions other than COPD are described. Different approaches for delivering the education component of a PRP are outlined and recommendations are made regarding topics for group and individual sessions. The problems commonly encountered in pulmonary rehabilitation, together with recommendations to avoid these problems and strategies to assist in their resolution, are discussed. The review concludes with recommendations for evaluating a PRP.

Mechanism of greater oxygen desaturation during walking compared with cycling in patients with COPD

BACKGROUND

Patients with COPD exhibit greater oxyhemoglobin desaturation during walking than with cycling. The purpose of this investigation was to investigate differences in ventilatory responses and gas exchange as proposed mechanisms for this observation.

METHODS

Arterial blood gas and lactate levels were measured in 12 patients with COPD (aged 68 ± 6 years) during incremental treadmill and cycle exercise. The primary outcome to assess the ventilatory response to exercise was Pao₂. The primary outcome to assess impairment in exercise gas exchange was the difference between partial pressures of alveolar and arterial oxygen (Pao₂ - Pao₂).

RESULTS

Pao₂ in patients was significantly lower at peak exercise for treadmill walking (51.4 ± 6.8 mm Hg) compared with cycling (60.4 ± 10.7 mm Hg) (P = .002). The initial increase in Pao₂ with cycling occurred prior to the onset of the anaerobic threshold. At peak exercise, Pao₂ was significantly higher with cycling compared with walking (P = .004). The anaerobic threshold occurred at a lower oxygen consumption during cycling than walking (P = .001), and peak lactate levels were higher with cycling (P = .019). With progressive exercise, Pao₂ - Pao₂ increased similarly during treadmill and cycle exercise.

CONCLUSIONS

The higher Pao₂ during cycling minimized the magnitude of oxyhemoglobin desaturation compared with walking. The enhanced respiratory stimulation during cycling appears due to an initial neurogenic process, possibly originating in receptors of exercising muscles, and a subsequent earlier onset of anaerobic metabolism with higher lactate levels during cycling.

Development and implementation of treadmill exercise testing protocols in COPD

BACKGROUND

Because treadmill exercise testing is more representative of daily activity than cycle testing, we developed treadmill protocols to be used in various clinical settings as part of a two-year, multicenter, chronic obstructive pulmonary disease (COPD) trial evaluating the effect of tiotropium on exercise.

METHODS

We enrolled 519 COPD patients aged 64.6 ± 8.3 years with a postbronchodilator forced expiratory volume in one second (FEV(1)) of 1.25 ± 0.42 L, 44.3% ± 11.9% predicted. The patients performed symptom-limited treadmill tests where work rate (Ẇ) was increased linearly using speed and grade adjustments every minute. On two subsequent visits, they performed constant Ẇ tests to exhaustion at 90% of maximum Ẇ from the incremental test.

RESULTS

Mean incremental test duration was 522 ± 172 seconds (range 20-890), maximum work rate 66 ± 34 watts. For the first and second constant Ẇ tests, both at 61 ± 33 watts, mean endurance times were 317 ± 61 seconds and 341 ± 184 seconds, respectively. The mean of two tests had an intraclass correlation coefficient of 0.85 (P < 0.001). During the second constant Ẇ test, 88.2% of subjects stopped exercise because of breathing discomfort; 87.1% for Global Initiative for Chronic Obstructive Lung Disease (GOLD) Stage II, 88.5% for GOLD Stage III, and 90.2% for GOLD Stage IV.

CONCLUSION

The symptom-limited incremental and constant work treadmill protocol was well tolerated and appeared to be representative of the physiologic limitations of COPD.