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

Beyond Spirometry: Linking Wasted Ventilation to Exertional Dyspnea in the Initial Stages of COPD

Exertional dyspnea, a key complaint of patients with chronic obstructive pulmonary disease (COPD), ultimately reflects an increased inspiratory neural drive to breathe. In non-hypoxemic patients with largely preserved lung mechanics - as those in the initial stages of the disease - the heightened inspiratory neural drive is strongly associated with an exaggerated ventilatory response to metabolic demand. Several lines of evidence indicate that the so-called excess ventilation (high ventilation-CO2 output relationship) primarily reflects poor gas exchange efficiency, namely increased physiological dead space. Pulmonary function tests estimating the extension of the wasted ventilation and selected cardiopulmonary exercise testing variables can, therefore, shed unique light on the genesis of patients' out-of-proportion dyspnea. After a succinct overview of the basis of gas exchange efficiency in health and inefficiency in COPD, we discuss how wasted ventilation translates into exertional dyspnea in individual patients. We then outline what is currently known about the structural basis of wasted ventilation in "minor/trivial" COPD vis-à-vis the contribution of emphysema versus a potential impairment in lung perfusion across non-emphysematous lung. After summarizing some unanswered questions on the field, we propose that functional imaging be amalgamated with pulmonary function tests beyond spirometry to improve our understanding of this deeply neglected cause of exertional dyspnea. Advances in the field will depend on our ability to develop robust platforms for deeply phenotyping (structurally and functionally), the dyspneic patients showing unordinary high wasted ventilation despite relatively preserved FEV1.

Functional Measures in Non-COPD Chronic Respiratory Diseases: A Systematic Review

Background/Objectives: The extensive range of instruments designed for evaluating functional performance (FP) in chronic respiratory diseases (CRD) other than chronic obstructive pulmonary disease (COPD) presents a challenge in selecting the most appropriate one. Therefore, this systematic review aimed to summarise FP instruments, their measurement properties, their minimum clinically important differences, and their associations with CRD course-related events or prognosis in non-COPD CRD. Methods: Studies employing patient-reported or performance-based instruments to assess FP in non-COPD CRD were systematically identified in the PubMed, PEDro, Embase, and Cochrane Library databases. COPD-exclusive studies or those solely reporting exercise capacity tests were excluded. Examination focused on measurement properties and associations with CRD course-related events or prognosis. The risk of bias was evaluated using the COSMIN, Downs and Black, and PEDro checklists based on the study design. Results: A total of 216 studies across seven CRD categories [asthma, bronchiectasis, cystic fibrosis, interstitial lung disease (ILD), pulmonary arterial hypertension (PAH), pre-/post-lung-transplantation] from various study types were included. Thirty-three instruments were identified, with the SF-36 questionnaire's physical function domain being the most commonly used patient-reported tool. The 1 min sit-to-stand test was the most extensively studied performance-based measure, with its measurement properties frequently reported in non-COPD CRD studies. Associations with events were infrequently documented, primarily in ILD and PAH studies related to mortality. Conclusions: Despite the prevalent use of FP instruments, limited information exists concerning their measurement properties and clinical implications. This review furnishes a concise summary of available evidence, aiding informed clinical decisions when selecting FP tools for non-COPD CRD.

Maximal exercise capacity, peripheral muscle strength, sleep quality, and quality of life in adult patients with stable asthma

OBJECTIVE

The prevalence of asthma is increasing gradually worldwide. The pathophysiological process of asthma causes some alterations in the respiratory system and decreases oxygen-carbon dioxide exchange and respiration volume. These alterations may affect maximal exercise capacity, peripheral muscle strength, sleep quality, and disease-specific quality of life but have yet to be comprehensively investigated. To compare maximal exercise capacity, pulmonary function, peripheral muscle strength, dyspnea, sleep quality, and quality of life in adult patients with asthma, healthy controls were aimed.

METHODS

Forty-one adult stable asthmatic patients (GINA I-III) and 41 healthy subjects were compared. Exercise capacity (cardiopulmonary exercise test [CPET]), pulmonary function (spirometry), peripheral muscle strength (dynamometer), dyspnea (modified Medical Research Council [mMRC] dyspnea scale), quality of life (Asthma Quality of Life Questionnaire [AQLQ]) and sleep quality (Pittsburgh Sleep Quality Index [PSQI]) were evaluated.

RESULTS

Peak VO2, VO2kg, MET, VE, HR, %VE, %HR, VCO2 parameters of CPET, FVC, FEV1, FEF25-75%, and FEV1/FVC and quadriceps femoris, shoulder abductors, and hand grip muscle strength were significantly decreased in patients with asthma (p < 0.05). MMRC dyspnea scale score was increased, and AQLQ and PSQI scores decreased in asthma patients (p < 0.05).

CONCLUSIONS

Cardiac and pulmonary system responses to peak exercise worsened, and maximal exercise capacity and peripheral muscle strength decreased in adult patients with stable asthma. In addition, dyspnea during daily activities increases, and quality of life and sleep quality are impaired. A variety of exercise training that would benefit asthmatic patients' outcomes should be investigated.

Screening and diagnosis of pulmonary hypertension associated with chronic lung disease (PH-CLD): A consensus statement from the pulmonary vascular research institute's innovative drug development initiative-group 3 pulmonary hypertension

Pulmonary hypertension (PH) is a frequent complication of chronic lung disease (CLD). However, PH is difficult to diagnose early since accompanying symptoms overlap and are similar to those of the underlying CLD. In most cases the PH is mild to moderate and therefore physical signs may be absent or subtle. This consensus paper provides insight into the clues that might suggest the presence of occult PH in patients with CLD. An overview of current diagnostic tools and emerging diagnostic technologies is provided as well as guidance for the work-up and diagnosis of PH in patients with CLD.

Differences of ventilatory muscle recruitment and work of breathing in COPD and interstitial lung disease during exercise: a comprehensive evaluation

Introduction

COPD and interstitial lung disease (ILD) are significant chronic respiratory disorders, impacting quality of life. Respiratory muscle roles and differences remain not entirely clear. The objective of the present study was to evaluate the degree of recruitment of the respiratory muscles and the work of breathing in COPD and ILD during exercise.

Methods

We compared the sensory-mechanical relationships in COPD, ILD and healthy controls (n=20 each). They performed pulmonary function, noninvasive and invasive respiratory muscle strength, surface electromyography and work-of-breathing assessments.

Results

COPD and ILD did not show lower static muscle strength compared to controls, but did show poor performance in the exercise test with increased transdiaphragmatic pressure (P di). In ILD, there was a higher increase in oesophageal pressure and a lower gastric pressure (P ga) on inspiration; in COPD, there was a significant increase in P ga on inspiration. In ILD, there is greater recruitment of accessory inspiratory muscles, whereas in COPD, there is marked use of both inspiratory and expiratory muscles. The neuromechanical inefficiency (increased neural respiratory drive without the corresponding tidal volume) was found in both diseases. In COPD, there is a considerable increase in elastic work to overcome intrinsic positive end-expiratory pressure (PEEPi) and expiratory work of breathing, whereas in ILD, non-PEEPi elastic work of breathing is the highest part of the total work of breathing.

Conclusions

Early and increased activity of the respiratory muscles and work-of-breathing components significantly contribute to dyspnoea, exercise intolerance and neuromechanical inefficiency of ventilation in COPD and ILD. The mechanisms of P di generation were different between diseases.

Nonlinear correlation and mediation effects between serum 25-hydroxyvitamin D levels and all-cause mortality in COPD patients

Background

Numerous studies have shown that low levels of vitamin D are linked to a higher risk of inflammatory diseases and their progression. However, how vitamin D levels affect mortality in chronic obstructive pulmonary disease (COPD) patients is still unclear. Thus, this study aimed to explore the relationship between serum 25-hydroxyvitamin D [25(OH)D] levels and the risk of death from all causes in U.S. adults with COPD.

Methods

This study analyzed 1,876 adults with COPD from the National Health and Nutrition Examination Survey (2005-2018). Mortality data up to December 31, 2019, were obtained from the National Death Index (NDI) records. Participants were categorized into three groups according to their 25(OH)D levels: Q1 (<50.0 nmol/L) for deficiency; Q2 (50.0-74.9 nmol/L) for insufficiency; and Q3 (≥75.0 nmol/L) for adequacy. A weighted Cox regression model assessed the link between 25(OH)D levels and mortality. Kaplan-Meier survival curves, subgroup, and sensitivity analyses were conducted. Additionally, the relationship between 25(OH)D and the hazard ratio (HR) was detailed through restricted cubic spline analysis. Mediation analysis revealed how 25(OH)D mediates the relationship between Dietary Inflammatory Index and mortality.

Results

There were 395 all-cause deaths during the follow-up, resulting in a mortality rate of 21.06%. After adjusting for potential confounders, higher 25(OH)D levels significantly correlated with a lower risk of all-cause mortality in COPD patients (HR = 0.52, 95% CI: 0.37-0.72, p < 0.001). Restricted cubic spline analysis indicated a non-linear relationship between 25(OH)D levels and all-cause mortality (p for nonlinear = 0.023), with levels below 63.4 nmol/L posing an independent risk for all-cause mortality in COPD patients (HR = 0.98, 95% CI: 0.97-0.99, p = 0.005). Sensitivity and subgroup analyses confirmed our results' robustness, with mediation analysis showing 25(OH)D's 22% mediating effect on diet-induced inflammation and all-cause mortality in COPD patients.

Conclusion

25(OH)D independently lowers the risk of all-cause mortality in COPD patients, with a non-linear L-shaped correlation, and mediates the effect of Dietary Inflammatory Index on mortality, suggesting new therapeutic possibilities.

Characteristics of Skeletal Muscle Strength in Subjects With Interstitial Lung Disease

OBJECTIVES

To investigate muscle strength and the prevalence of muscle weakness in adults with interstitial lung diseases (ILDs) compared to healthy subjects.

DESIGN

Cross-sectional (description of clinical features).

SETTING

Public referral center (University Hospital).

PARTICIPANTS

One hundred and twelve adults with ILD (n=48, 60±10yr, 68% female) and healthy counterparts (control group, n=64, 57±10yr, 58% female) (N=112).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE(S)

Muscle strength and prevalence of muscle weakness in adults with ILD. Muscle strength was assessed via maximal isometric voluntary contraction of dominant upper and lower limb muscle groups. Data from the control group were used to generate reference equations. Muscle weakness was defined as a muscle strength value below the lower limit of normal calculated using data from the control group. Data were expressed as mean ± SD or median [interquartile range] according to the data distribution.

RESULTS

Compared to the control group, adults with ILD had lower muscle strength for all muscle groups assessed (values presented as %predicted: pectoralis major 75[57-86]%; quadriceps 72[58-87]%; latissimus dorsi 76[57-103]%; deltoid 74[64-98]%; biceps brachii 78[64-91]%; triceps brachii 84[62-101]%; P≤.001 for all). Prevalence of muscle weakness in people with ILD was 40% for pectoralis major, 25% for latissimus dorsi, 16% for triceps brachii, 20% for biceps brachii, 27% for deltoid and 46% for quadriceps.

CONCLUSIONS

Adults with ILD present a generalised reduction in peripheral Muscle strength, ranging between 20% to 46% of people depending on the muscle group assessed. and it was more prevalent in lower limb muscles.

Effects of prehabilitation resistance training in mild to moderate clinically frail patients awaiting coronary artery bypass graft surgery

Coronary artery disease is one of the main causes of mortality and morbidity among chronic heart diseases worldwide. Patients reported chronic chest pain as the primary symptom of coronary artery disease. Due to its progressive nature, it affects the health status and functional capacity of the patients. The current study was planned to compare the effects of prehabilitation resistance training in mild to moderate clinically frail patients awaiting coronary artery bypass graft (CABG). A randomized controlled trial was conducted on 74 patients awaiting CABG at the Faisalabad Institute of Cardiology, Faisalabad, Pakistan. A Modified Healthy Heart Questionnaire was used for screening of the patients. Interventions applied were resistance training by using cuff weights/dumbbells at light intensity (40%-50%) of a maximum of one repetition (10-15 repetitions for one to three times a day) per major muscle groups of upper and lower limbs of the body on weekly basis. The main outcome measures were the 6-minute walk test (6MWT), the New York Heart Association (NYHA) for heart failure, the clinical frailty score, and the essential frailty toolset. Significant differences between group A (resistance training group) and group B (conventional physical therapy group) patients were observed. The mean ranks for 6MWT in group A and group B were 1.70 and 1.55, respectively. The mean ranks of NYHA in group A and group B were 1.68 and 2.84, respectively. Clinical frailty scores in group A and group B were 2.68 and 2.74, respectively, with the essential frailty toolset in group A and group B were 1.14 and 1.11, respectively. There were significant (p < 0.05) differences within and between groups for prehabilitation resistance training after CABG. The study showed that the resistance training group had improved the clinical frailty score, strength, endurance, and functional capacity in patients who underwent elective CABG.

Ultrasound evaluation of diaphragmatic function in patients with idiopathic pulmonary fibrosis: a retrospective observational study

INTRODUCTION

The diaphragm function assessed by ultrasound has been well-studied in COPD, asthma, and intensive care. However, there are only a few studies on diffuse interstitial lung disease, while dyspnea and quality of life are major issues in the management that may depend on the diaphragm.

METHODS

We retrospectively included idiopathic pulmonary fibrosis (IPF) patients followed in our center (Marseille, France) between January 2020 and February 2023 who underwent diaphragmatic ultrasound. Our objectives were to describe the diaphragmatic function of IPFs compared to healthy controls and to correlate with clinical, functional, and lung density on CT-scan.

RESULTS

24 IPF patients and 157 controls were included. The diaphragmatic amplitude in IPF was increased at rest (median of 2.20 cm vs 1.88 cm on the right, p < 0.007, and 2.30 cm vs 1.91 cm on the left, p < 0.03, in IPF and controls respectively) and decreased in deep breathing (median of 4.85 cm vs 5.45 cm on the right, p < 0.009, and 5.10 cm vs 5.65 cm on the left, p < 0.046, in IPF and controls respectively). Diaphragmatic thickness was significantly reduced at rest on the right side (median of 1.75 mm vs 2.00 mm, p < 0.02, in IPF and controls respectively) and in deep breathing on both sides compared to controls (mean of 3.82 mm vs 4.15 mm on the right, p < 0.02, and 3.53 mm vs 3.94 mm, on the left, p < 0.009, in IPF and controls respectively). Diaphragmatic amplitude in deep breathing was moderate to strongly correlated with FVC, DLCO, and 6MWT and negatively correlated with the dyspnea and lung density on CT scan.

CONCLUSION

The diaphragmatic amplitude and thickness were impaired in IPF compared to controls. Diaphragmatic amplitude is the parameter best correlated with clinical, functional, and lung density criteria. Further studies are needed to determine if diaphragmatic amplitude can be a prognostic factor in IPF.

Counseling Patients with Chronic Obstructive Pulmonary Disease Traveling to High Altitude

Bloch, Konrad E., Talant M. Sooronbaev, Silvia Ulrich, Mona Lichtblau, and Michael Furian. Clinician's corner: counseling patients with chronic obstructive pulmonary disease traveling to high altitude. High Alt Med Biol. 24:158-166, 2023.-Mountain travel is increasingly popular also among patients with chronic obstructive pulmonary disease (COPD), a highly prevalent condition often associated with cardiovascular and systemic manifestations. Recent studies have shown that nonhypercapnic and only mildly hypoxemic lowlanders with moderate to severe airflow obstruction owing to COPD experience dyspnea, exercise limitation, and sleep disturbances when traveling up to 3,100 m. Altitude-related adverse health effects (ARAHE) in patients with COPD include severe hypoxemia, which may be asymptomatic but expose patients to the risk of excessive systemic and pulmonary hypertension, cardiac arrhythmia, and even myocardial or cerebral ischemia. In addition, hypobaric hypoxia may impair postural control, psycho-motor, and cognitive performance in patients with COPD during altitude sojourns. Randomized, placebo-controlled trials have shown that preventive treatment with oxygen at night or with acetazolamide reduces the risk of ARAHE in patients with COPD while preventive dexamethasone treatment improves oxygenation and altitude-induced excessive sleep apnea, and lowers systemic and pulmonary artery pressure. This clinical review provides suggestions for pretravel assessment and preparations and measures during travel that may reduce the risk of ARAHE and contribute to pleasant mountain journeys of patients with COPD.

Cardiopulmonary exercise testing applied to respiratory medicine: Myths and facts

Cardiopulmonary exercise testing (CPET) remains poorly understood and, consequently, largely underused in respiratory medicine. In addition to a widespread lack of knowledge of integrative physiology, several tenets of CPET interpretation have relevant controversies and limitations which should be appropriately recognized. With the intent to provide a roadmap for the pulmonologist to realistically calibrate their expectations towards CPET, a collection of deeply entrenched beliefs is critically discussed. They include a) the actual role of CPET in uncovering the cause(s) of dyspnoea of unknown origin, b) peak O₂ uptake as the key metric of cardiorespiratory capacity, c) the value of low lactate ("anaerobic") threshold to differentiate cardiocirculatory from respiratory causes of exercise limitation, d) the challenges of interpreting heart rate-based indexes of cardiovascular performance, e) the meaning of peak breathing reserve in dyspnoeic patients, f) the merits and drawbacks of measuring operating lung volumes during exercise, g) how best interpret the metrics of gas exchange inefficiency such as the ventilation-CO₂ output relationship, h) when (and why) measurements of arterial blood gases are required, and i) the advantages of recording submaximal dyspnoea "quantity" and "quality". Based on a conceptual framework that links exertional dyspnoea to "excessive" and/or "restrained" breathing, I outline the approaches to CPET performance and interpretation that proved clinically more helpful in each of these scenarios. CPET to answer clinically relevant questions in pulmonology is a largely uncharted research field: I, therefore, finalize by highlighting some lines of inquiry to improve its diagnostic and prognostic yield.

Does inspiratory muscle training provide additional benefits during pulmonary rehabilitation in people with interstitial lung disease? A randomized control trial

BACKGROUND

Interstitial lung disease (ILD) encompasses a diverse group of chronic lung conditions which is often characterized by inspiratory muscle weakness (IMW). Despite the potential importance of inspiratory muscle dysfunction in ILD, the effect of inspiratory muscle training (IMT) added to pulmonary rehabilitation (PR) in ILD largely remains unknown.

OBJECTIVE

The primary objective of the present study was to evaluate the benefits of IMT added to PR on inspiratory muscle strength and secondary objectives were to assess its effects on functional capacity, health-related quality of life (HRQoL), pulmonary function test (PFT) and dyspnea in ILD along with IMW.

METHODS

Fifty-one participants were randomly allocated into two groups; PR + IMT (n = 26) or PR alone (n = 25). The primary outcome [maximal inspiratory pressure (PI_max)] and secondary outcomes [6-min walk distance (6MWD), St. George's Respiratory Questionnaire (SGRQ), PFT and modified Medical Research Council dyspnea scale (mMRC)] were evaluated before and after the 8-weeks intervention. Independent t-test or Mann Whitney-U test was applied for between-group comparisons while for within-group comparison Wilcoxon's Sign Rank test or paired t test was performed.

RESULTS

At the end of 8 weeks exercise intervention inspiratory muscle strength (PI_max + 11.10 cm H₂O, p< .001), functional capacity (6MWD, + 47.90 m, p= .001), HRQoL (SGRQ-total - 4 points, p= .038) and dyspnea (mMRC dyspnea scale, -1.27, p< .001) improved significantly in PR+IMT group alone.

CONCLUSION

Inclusion of IMT to PR may have superior benefits as compared to PR alone in ILD accompanied with IMW.

Differential control of respiratory frequency and tidal volume during exercise

The lack of a testable model explaining how ventilation is regulated in different exercise conditions has been repeatedly acknowledged in the field of exercise physiology. Yet, this issue contrasts with the abundance of insightful findings produced over the last century and calls for the adoption of new integrative perspectives. In this review, we provide a methodological approach supporting the importance of producing a set of evidence by evaluating different studies together-especially those conducted in 'real' exercise conditions-instead of single studies separately. We show how the collective assessment of findings from three domains and three levels of observation support the development of a simple model of ventilatory control which proves to be effective in different exercise protocols, populations and experimental interventions. The main feature of the model is the differential control of respiratory frequency (f_R) and tidal volume (V_T); f_R is primarily modulated by central command (especially during high-intensity exercise) and muscle afferent feedback (especially during moderate exercise) whereas V_T by metabolic inputs. Furthermore, V_T appears to be fine-tuned based on f_R levels to match alveolar ventilation with metabolic requirements in different intensity domains, and even at a breath-by-breath level. This model reconciles the classical neuro-humoral theory with apparently contrasting findings by leveraging on the emerging control properties of the behavioural (i.e. f_R) and metabolic (i.e. V_T) components of minute ventilation. The integrative approach presented is expected to help in the design and interpretation of future studies on the control of f_R and V_T during exercise.

Hierarchical stratification of the factors related to exertional dyspnoea and exercise intolerance in male COPD patients

BACKGROUND

The order and extent of interactions across the factors affecting exertional dyspnoea (ED) and exercise intolerance (EI) in patients with chronic obstructive pulmonary disease (COPD) are not clear. We hypothesized that lung and non-lung variables were the primary variables, ED was the secondary variable and EI was the tertiary variable.

METHODS

Data on demographics, blood tests, cardiac imaging, lung function tests and invasive dead space fractions (V_D/V_T) during incremental exercise test of 46 male COPD subjects were obtained. These variables were categorized by factor analysis and pair-wise correlation analysis was conducted. The best factor of each category was selected and then multivariate regression was conducted.

RESULTS

Peak tidal inspiratory flow (V_T/T_Ipeak), V_D/V_Tpeak and tidal lung expansion capability, and resting diffusing capacity of the lungs (D_LCO)% predicted were the primary pulmonary factors most related to ED, whereas body mass index (BMI), haemoglobin and cholesterol levels were the primary non-pulmonary factors. In multivariate regression analysis, V_T/T_Ipeak, V_D/V_Tpeak and D_LCO% were the primary factors most related to ED (r² = 0.69); ED was most related to EI (r = -0.74 to -0.83).

CONCLUSION

Using hierarchical stratification and statistical methods may improve understanding of the pathophysiology of ED and EI in patients with COPD. KEY MESSAGESThe pathophysiology of exertional dyspnoea (ED) and exercise intolerance (EI) in chronic obstructive pulmonary disease (COPD) is complex. The order and extent of interactions across factors are not clear. In multivariate regression analysis, we found that tidal inspiratory flow, dead space fraction and resting diffusing capacity of the lungs % but not the non-pulmonary factors affected ED.Using correlation coefficients, we further found that ED was the secondary variable and EI was the tertiary variable.Hierarchical stratification of the important factors associated with ED and EI in patients with COPD clarifies their relationships and could be incorporated into management programmes and outcome studies for these patients.

Effect of pulmonary hypertension on exercise capacity and gas exchange in patients with chronic obstructive pulmonary disease living at high altitude

Background: Pulmonary hypertension (PH) is associated with decreased exercise tolerance in chronic obstructive pulmonary disease (COPD) patients, but in the altitude the response to exercise in those patients is unknown. Our objective was to compare exercise capacity, gas exchange and ventilatory alterations between COPD patients with PH (COPD-PH) and without PH (COPD-nonPH) residents at high altitude (2640 m). Methods: One hundred thirty-two COPD-nonPH, 82 COPD-PH, and 47 controls were included. Dyspnea by Borg scale, oxygen consumption (VO₂), work rate (WR), ventilatory equivalents (VE/VCO₂), dead space to tidal volume ratio (V_D/V_T), alveolar-arterial oxygen tension gradient (AaPO₂), and arterial-end-tidal carbon dioxide pressure gradient (Pa-ETCO₂) were measurement during a cardiopulmonary exercise test. For comparison of variables between groups, Kruskal-Wallis or one-way ANOVA tests were used, and stepwise regression analysis to test the association between PH and exercise capacity. Results: All COPD patients had a lower exercise capacity and higher PaCO₂, A-aPO₂ and V_D/V_T than controls. The VO₂ % predicted (61.3 ± 20.6 vs 75.3 ± 17.9; p < 0.001) and WR % predicted (65.3 ± 17.9 vs 75.3 ± 17.9; p < 0.001) were lower in COPD-PH than in COPD-nonPH. At peak exercise, dyspnea was higher in COPD-PH (p = 0.011). During exercise, in COPD-PH, the PaO₂ was lower (p < 0.001), and AaPO₂ (p < 0.001), Pa-ETCO₂ (p = 0.033), VE/VCO₂ (p = 0.019), and V_D/V_T (p = 0.007) were higher than in COPD-nonPH. In the multivariate analysis, PH was significantly associated with lower peak VO₂ and WR (p < 0.001). Conclusion: In COPD patients residing at high altitude, the presence of PH was an independent factor related to the exercise capacity. Also, in COPD-PH patients there were more dyspnea and alterations in gas exchange during the exercise than in those without PH.

The Exercising Brain: An Overlooked Factor Limiting the Tolerance to Physical Exertion in Major Cardiorespiratory Diseases?

“Exercise starts and ends in the brain”: this was the title of a review article authored by Dr. Bengt Kayser back in 2003. In this piece of work, the author highlights that pioneer studies have primarily focused on the cardiorespiratory-muscle axis to set the human limits to whole-body exercise tolerance. In some circumstances, however, exercise cessation may not be solely attributable to these players: the central nervous system is thought to hold a relevant role as the ultimate site of exercise termination. In fact, there has been a growing interest relative to the “brain” response to exercise in chronic cardiorespiratory diseases, and its potential implication in limiting the tolerance to physical exertion in patients. To reach these overarching goals, non-invasive techniques, such as near-infrared spectroscopy and transcranial magnetic stimulation, have been successfully applied to get insights into the underlying mechanisms of exercise limitation in clinical populations. This review provides an up-to-date outline of the rationale for the “brain” as the organ limiting the tolerance to physical exertion in patients with cardiorespiratory diseases. We first outline some key methodological aspects of neuromuscular function and cerebral hemodynamics assessment in response to different exercise paradigms. We then review the most prominent studies, which explored the influence of major cardiorespiratory diseases on these outcomes. After a balanced summary of existing evidence, we finalize by detailing the rationale for investigating the “brain” contribution to exercise limitation in hitherto unexplored cardiorespiratory diseases, an endeavor that might lead to innovative lines of applied physiological research.

Exercise hyperventilation and pulmonary gas exchange in chronic thromboembolic pulmonary hypertension: Effects of balloon pulmonary angioplasty

BACKGROUND

Excessive ventilation (V̇E) and abnormal gas exchange during exercise are features of chronic thromboembolic pulmonary hypertension (CTEPH). In selected CTEPH patients, balloon pulmonary angioplasty (BPA) improves symptoms and exercise capacity. How BPA affects exercise hyperventilation and gas exchange is poorly understood.

METHODS

In this longitudinal observational study, symptom-limited cardiopulmonary exercise tests and carbon monoxide lung diffusion (DLCO) were performed before and after BPA (interval, mean (SD): 3.1 (2.4) months) in 36 CTEPH patients without significant cardiac and/or pulmonary comorbidities.

RESULTS

Peak work rate improved by 20% after BPA whilst V̇E at peak did not change despite improved ventilatory efficiency (lower V̇E with respect to CO₂ output [V̇CO₂]). At the highest identical work rate pre- and post-BPA (75 (30) watts), V̇E and alveolar-arterial oxygen gradient (P(Ai-a)O₂) decreased by 17% and 19% after BPA, respectively. The physiological dead space fraction of tidal volume (VD/VT), calculated from measurements of arterial and mixed expired CO₂, decreased by 20%. In the meantime, DLCO did not change. The best correlates of P(Ai-a)O₂ measured at peak exercise were physiological VD/VT before BPA and DLCO after BPA.

CONCLUSIONS

Ventilatory efficiency, physiological VD/VT, and pulmonary gas exchange improved after BPA. The fact that DLCO did not change suggests that the pulmonary capillary blood volume and probably the true alveolar dead space were unaffected by BPA. The correlation between DLCO measured before BPA and P(Ai-a)O₂ measured after BPA suggests that DLCO may provide an easily accessible marker to predict the response to BPA in terms of pulmonary gas exchange.

Physical Function and Health-Related Quality of Life after Surgery for Nontuberculous Mycobacterium Pulmonary Disease: A Prospective Cohort Study

Purpose: To investigate the exercise capacity and health-related quality of life (HRQOL) of surgical patients with nontuberculous mycobacterial pulmonary disease (NTM-PD) preoperatively versus 6 months postoperatively.

Methods: This prospective observational study included patients with NTM-PD and was conducted at a single center. The intervention was surgical resection plus perioperative and post-discharge physical therapy. The physical function was assessed preoperatively and 6 months postoperatively using the 6-minute walk test (6MWT). HRQOL was assessed preoperatively and 6 months postoperatively using the Short-Form 36 (SF-36) health survey questionnaire and St. George’s Respiratory Questionnaire. The postoperative HRQOL was compared between patients with and without preoperative clinical symptoms.

Results: In total, 35 patients were analyzed. The preoperatively symptomatic group had significantly lower preoperative HRQOL than the preoperatively asymptomatic group (p <0.05). Compared with preoperatively, there were significant improvements at 6 months postoperatively in the 6MWT (p <0.01) and HRQOL, mainly in the SF-36 mental component summary (p <0.01). The SF-36 mental component summary in the preoperatively symptomatic group was very significantly improved from preoperatively to 6 months postoperatively (p <0.05).

Conclusion: The combination of surgical treatment and physical therapy for NTM-PD contributes to improvements in physical function and HRQOL.

Identifying Appropriate Delivery of and Referral to Pulmonary Rehabilitation in Uganda: A Survey Study of People Living with Chronic Respiratory Disease and Health Care Workers

Introduction

Pulmonary rehabilitation (PR) is a low cost, high impact intervention that ameliorates the disability associated with chronic respiratory diseases (CRD). PR is becoming increasingly recognized in low resource settings where the burden of CRD is rapidly increasing. To aid the implementation of PR in Uganda, we conducted a study to assess the attitudes and opinions towards PR among patients with CRD in Uganda and explore barriers faced by health care workers (HCWs) in referring to PR.

Methods

A cross-sectional study comprising two survey populations: people living with CRD and HCWs regarded as potential PR referrers and PR deliverers. This exploratory study sought initial opinions and thoughts regarding PR, as well as baseline knowledge and potential barriers faced in the referral process.

Results

Overall, 30 HCWs (53% female, 43% doctors) and 51 adults with CRD (63% female) participated in the survey. Among those with CRD, the majority reported breathlessness as a major problem (86%) and breathlessness affected their ability to do paid and unpaid work (70%). Interest in PR was high amongst adults with CRD (92%) with preference for a hospital-based programme (67%) as opposed to community-based (16%) or home-based (17%). All HCWs considered PR important in lung disease management, but 77% do not refer patients due to a lack of information about PR. HCWs' free-text responses identified the need for training in PR, patient education and streamlining the referral process as key elements to develop successful PR referral services.

Conclusion

To successfully set up a PR service for people with CRD in Uganda, there is a great need for appropriately tailored training and education of prospective referrers about CRD and PR programs. Educating patients about the benefits of PR as well as streamlining the referral process is critical in expanding PR services across Uganda to fulfill this unmet need.

Comparative effects of capsaicin in chronic obstructive pulmonary disease and asthma (Review)

Chronic obstructive pulmonary disease (COPD) and asthma are chronic respiratory diseases with high prevalence and mortality that significantly alter the quality of life in affected patients. While the cellular and molecular mechanisms engaged in the development and evolution of these two conditions are different, COPD and asthma share a wide array of symptoms and clinical signs that may impede differential diagnosis. However, the distinct signaling pathways regulating cough and airway hyperresponsiveness employ the interaction of different cells, molecules, and receptors. Transient receptor potential cation channel subfamily V member 1 (TRPV1) plays a major role in cough and airway inflammation. Consequently, its agonist, capsaicin, is of substantial interest in exploring the cellular effects and regulatory pathways that mediate these respiratory conditions. Increasingly more studies emphasize the use of capsaicin for the inhalation cough challenge, yet the involvement of TRPV1 in cough, bronchoconstriction, and the initiation of inflammation has not been entirely revealed. This review outlines a comparative perspective on the effects of capsaicin and its receptor in the pathophysiology of COPD and asthma, underlying the complex entanglement of molecular signals that bridge the alteration of cellular function with the multitude of clinical effects.

Factors influencing self-selected walking speed in fibrotic interstitial lung disease

This study aimed to investigate the walking economy and possible factors influencing self-selected walking speed (SSWS) in patients with fibrotic interstitial lung disease (ILD) compared to controls. In this study, 10 patients with ILD (mean age: 63.8 ± 9.2 years, forced expiratory volume in the first second: 56 ± 7% of predicted) and 10 healthy controls underwent resting pulmonary function tests, cardiopulmonary exercise, and submaximal treadmill walking tests at different speeds. The walking economy was assessed by calculating the cost-of-transport (CoT). Dynamic stability was assessed by stride-to-stride fluctuations using video recordings. Patients with ILD showed reduced peak oxygen uptake with a tachypneic breathing pattern and significant oxygen desaturation during exercise. The CoT did not differ between the groups (p = 0.680), but dyspnea and SpO₂ were higher and lower, respectively, in patients with ILD at the same relative speeds. SSWS was reduced in ILD patients (2.6 ± 0.9 vs. 4.2 ± 0.4 km h^-1 p = 0.001) and did not correspond to the energetically optimal walking speed. Dynamic stability was significantly lower in patients with ILD than in healthy controls, mainly at lower speeds. Patients with ILD presented a similar cost of transport compared to healthy controls; however, they chose lower SSWS despite higher walking energy expenditure. Although walking stability and dyspnea were negatively affected, these factors were not associated with the slower walking speed chosen by individuals with ILD.

Acute effects of expiratory positive airway pressure on exercise tolerance in patients with COPD

Objective: To evaluate the acute effects of expiratory positive airway pressure (EPAP) on exercise tolerance, dyspnea, leg discomfort, and breathing pattern in patients with COPD. Methods: Fifteen patients with COPD were assessed with the following three different protocols: EPAP of 7.5 cmH₂O used during a constant cycle ergometer exercise test (Protocol-1); EPAP of 7.5 cmH₂O used for 15 minutes before the test (Protocol-2); and a sham system without pressure used for 15 minutes before the test (Protocol-3). Dyspnea and leg discomfort were assessed using Borg scale, whereas breathing pattern by optoelectronic plethysmography. Statistical analyses were performed using generalized estimating equations and Bonferroni tests (α = 5%), considering the protocols (1, 2, and 3) and moment (resting and the end of exercise). Results: Exercise tolerance was lower in protocol 1: 108 ± 45 seconds compared to protocols 2: 187 ± 99 seconds (p= .011) and 3: 183 ± 101 seconds (p= .021). No difference was observed between protocols 2 and 3 (p> .999). Dyspnea in protocol 1: 7.0 ± 2.08 was higher than protocols 2: 4.10 ± 2.45 (p= .001) and 3: 3.90 ± 2.21 (p< .001), but no differences were observed between protocols 2 and 3 (p> .999). No significant difference was observed for leg discomfort among the protocols (p= .137). There were no statistically significant differences for most variables of breathing pattern among the protocols. Conclusion: A reduction on exercise tolerance and an increase in dyspnea were found with EPAP of 7.5 cm H₂O during a constant cycle ergometer exercise test in patients with COPD.

Thoracoabdominal asynchrony associates with exercise intolerance in fibrotic interstitial lung diseases

BACKGROUND AND OBJECTIVE

The precise coordination of respiratory muscles during exercise minimizes work of breathing and avoids exercise intolerance. Fibrotic interstitial lung disease (f-ILD) patients are exercise-intolerant. We assessed whether respiratory muscle incoordination and thoracoabdominal asynchrony (TAA) occur in f-ILD during exercise, and their relationship with pulmonary function and exercise performance.

METHODS

We compared breathing pattern, respiratory mechanics, TAA and respiratory muscle recruitment in 31 f-ILD patients and 31 healthy subjects at rest and during incremental cycle exercise. TAA was defined as phase angle (PhAng) >20°.

RESULTS

During exercise, when compared with controls, f-ILD patients presented increased and early recruitment of inspiratory rib cage muscle (p < 0.05), and an increase in PhAng, indicating TAA. TAA was more frequent in f-ILD patients than in controls, both at 50% of the maximum workload (42.3% vs. 10.7%, p = 0.01) and at the peak (53.8% vs. 23%, p = 0.02). Compared with f-ILD patients without TAA, f-ILD patients with TAA had lower lung volumes (forced vital capacity, p < 0.01), greater dyspnoea (Medical Research Council > 2 in 64.3%, p = 0.02), worse exercise performance (lower maximal work rate % predicted, p = 0.03; lower tidal volume, p = 0.03; greater desaturation and dyspnoea, p < 0.01) and presented higher oesophageal inspiratory pressures with lower gastric inspiratory pressures and higher recruitment of scalene (p < 0.05).

CONCLUSION

Exercise induces TAA and higher recruitment of inspiratory accessory muscle in ILD patients. TAA during exercise occurred in more severely restricted ILD patients and was associated with exertional dyspnoea, desaturation and limited exercise performance.

Clinical Interpretation of Cardiopulmonary Exercise Testing: Current Pitfalls and Limitations

Several shortcomings on cardiopulmonary exercise testing (CPET) interpretation have shed a negative light on the test as a clinically useful tool. For instance, the reader should recognize patterns of dysfunction based on clusters of variables rather than relying on rigid interpretative algorithms. Correct display of key graphical data is of foremost relevance: prolixity and redundancy should be avoided. Submaximal dyspnea ratings should be plotted as a function of work rate (WR) and ventilatory demand. Increased work of breathing and/or obesity may normalize peak oxygen uptake (V̇O₂) despite a low peak WR. Among the determinants of V̇O₂, only heart rate is measured during non-invasive CPET. It follows that in the absence of findings suggestive of severe impairment in O₂ delivery, the boundaries between inactivity and early cardiovascular disease are blurred in individual subjects. A preserved breathing reserve should not be viewed as evidence that "the lungs" are not limiting the subject. In this context, measurements of dynamic inspiratory capacity are key to uncover abnormalities germane to exertional dyspnea. A low end-tidal partial pressure for carbon dioxide may indicate either increased "wasted" ventilation or alveolar hyperventilation; thus, direct measurements of arterial (or arterialized) PO₂ might be warranted. Differentiating a chaotic breathing pattern from the normal breath-by-breath noise might be complex if the plotted data are not adequately smoothed. A sober recognition of these limitations, associated with an interpretation report free from technicalities and convoluted terminology, is crucial to enhance the credibility of CPET in the eyes of the practicing physician.

Pulmonology approach in the investigation of chronic unexplained dyspnea

Chronic unexplained dyspnea and exercise intolerance represent common, distressing symptoms in outpatients. Clinical history taking and physical examination are the mainstays for diagnostic evaluation. However, the cause of dyspnea may remain elusive even after comprehensive diagnostic evaluation-basic laboratory analyses; chest imaging; pulmonary function testing; and cardiac testing. At that point (and frequently before), patients are usually referred to a pulmonologist, who is expected to be the main physician to solve this conundrum. In this context, cardiopulmonary exercise testing (CPET), to assess physiological and sensory responses from rest to peak exercise, provides a unique opportunity to unmask the mechanisms of the underlying dyspnea and their interactions with a broad spectrum of disorders. However, CPET is underused in clinical practice, possibly due to operational issues (equipment costs, limited availability, and poor remuneration) and limited medical education regarding the method. To counter the latter shortcoming, we aspire to provide a pragmatic strategy for interpreting CPET results. Clustering findings of exercise response allows the characterization of patterns that permit the clinician to narrow the list of possible diagnoses rather than pinpointing a specific etiology. We present a proposal for a diagnostic workup and some illustrative cases assessed by CPET. Given that airway hyperresponsiveness and pulmonary vascular disorders, which are within the purview of pulmonology, are common causes of chronic unexplained dyspnea, we also aim to describe the role of bronchial challenge tests and the diagnostic reasoning for investigating the pulmonary circulation in this context.

Estimation of minimal clinically important difference for quadriceps and inspiratory muscle strength in older outpatients with chronic obstructive pulmonary disease: a prospective cohort study

OBJECTIVE

To estimate the minimal clinically important difference (MCID) of quadriceps and inspiratory muscle strength after a home-based pulmonary rehabilitation program (PRP) in chronic obstructive pulmonary disease (COPD).

METHOD

Eighty-five COPD patients were included. Quadriceps maximal voluntary contraction (QMVC) was measured. We measured maximal inspiratory mouth pressure (PImax), the 6-minute walk distance (6MWD), the chronic respiratory questionnaire (CRQ) and the modified Medical Research Council dyspnoea score (mMRC). All measurements were conducted at baseline and at the end of the PRP. The MCID was calculated using anchor-based (using 6MWD, CRQ, and mMRC as possible anchor variables) and distribution-based (half standard deviation and 1.96 standard error of measurement) approaches. Changes in the five variables were compared in patients with and without changes in QMVC or PImax >MCID for each variable.

RESULTS

Sixty-nine COPD patients (age 75±6 years) were analysed. QMVC improved by 2.4 (95%CI 1.1-3.7) kgf, PImax by 5.8 (2.7-8.8) cmH₂O, 6MWD by 21 (11-32) meters and CRQ by 3.9 (1.6-6.3) points. The MCID of QMVC and PImax was 3.3-7.5 kgf and 17.2-17.6 cmH₂O, respectively. The MCID of QMVC (3.3 kgf) could differentiate individuals with significant improvement in 6MWD and PImax from those without.

CONCLUSION

The MCID of QMVC (3.3 kgf) can identify a meaningful change in quadriceps muscle strength after a PRP. The MCID of PImax (17.2 cmH₂O) should be used with careful consideration, because the value is estimated using distributionbased method.

Corticosteroids are associated with reduced skeletal muscle function in interstitial lung disease patients with mild dyspnea

BACKGROUND

Interstitial lung diseases (ILDs) patients receiving steroid treatment tend to be immobilized by dyspnea and muscle weakness as the disease progresses. We therefore expected that steroid treatment for ILDs would have a greater effect on muscle function under severe dyspnea. To test this hypothesis, we evaluated whether the effect of corticosteroid treatment on peripheral muscle force and exercise capacity varied according to patients' dyspnea severity.

METHODS

In this retrospective cross-sectional study of 87 ILD patients enrolled between 2008 and 2017, quadriceps force (QF), handgrip force (HF), and 6-min walk distance (6 MWD) were compared between a low (grades 0-2) and a high (grades 3-4) modified-Medical Research Council (mMRC) dyspnea scale score group.

RESULTS

In patients with lower levels of dyspnea, corticosteroid treatments were associated with lower QF and HF (20.0 vs. 30.0 kgf, p = 0.01; 22.5 vs. 28.4 kgf, p = 0.03, respectively) values; however, no significant differences were observed between the corticosteroid and control subgroups in the high mMRC group (QF: 18.5 vs. 17.3 kgf, p = 0.64; HF: 21.0 vs. 17.1 kgf, p = 0.24, respectively). Analysis of covariance indicated that both corticosteroid treatment and mMRC dyspnea scale interacted with QF, HF, and 6 MWD. The effects of the corticosteroid treatment varied according to the level of dyspnea (interaction β = 7.52, p = 0.034; interaction β = 8.78, p = 0.048; interaction β = 131.08, p < 0.001).

CONCLUSIONS

Muscle weakness and exercise capacity in ILD patients in the low mMRC group were associated with corticosteroid treatment.

Responses to progressive exercise in subjects with chronic dyspnea and inspiratory muscle weakness

INTRODUCTION

Inspiratory muscle weakness (IMW) is a potential cause of exertional dyspnea frequently under-appreciated in clinical practice. Cardiopulmonary exercise testing (CPET) is usually requested as part of the work-up for unexplained breathlessness, but the specific pattern of exercise responses ascribed to IMW is insufficiently characterized.

OBJECTIVES

To identify the physiological and sensorial responses to progressive exercise in dyspneic patients with IMW without concomitant cardiorespiratory or neuromuscular diseases.

METHODS

Twenty-three subjects (18 females, 55.2 ± 16.9 years) complaining of chronic daily life dyspnea (mMRC = 3 [2-3]) plus maximal inspiratory pressure < the lower limit of normal and 12 matched controls performed incremental cycling CPET. FEV₁/FVC<0.7, significant abnormalities in chest CT or echocardiography, and/or an established diagnosis of neuromuscular disease were among the exclusion criteria.

RESULTS AND CONCLUSION

Patients presented with reduced aerobic capacity (peak V̇O₂: 79 ± 26 vs 116 ± 21 %predicted), a tachypneic breathing pattern (peak breathing frequency/tidal volume = 38.4 ± 22.7 vs 21.7 ± 14.2 breaths/min/L) and exercise-induced inspiratory capacity reduction (-0.17 ± 0.33 vs 0.10 ± 0.30 L) (all P < .05) compared to controls. In addition, higher ventilatory response (ΔV̇_E/ΔV̇CO₂ = 34.1 ± 6.7 vs 27.0 ± 2.3 L/L) and symptomatic burden (dyspnea and leg discomfort) to the imposed workload were observed in patients. Of note, pulse oximetry was similar between groups. Reduced aerobic capacity in the context of a tachypneic breathing pattern, inspiratory capacity reduction and preserved oxygen exchange during progressive exercise should raise the suspicion of inspiratory muscle weakness in subjects with otherwise unexplained breathlessness.

Therapeutic effect of budesonide, montelukast and azithromycin on post-infectious bronchiolitis obliterans in children

Optimal treatment options for post-infectious bronchiolitis obliterans (PIBO) have not yet been established. The present study retrospectively analyzed the effect of budesonide, montelukast and azithromycin on treating PIBO in children <5 years old.. Based on treatment regimen, the cohort was divided into group A and group B. Group A received a combination of budesonide, montelukast and azithromycin for at least 3 months and group B received unconventional treatment (budesonide for nebulization intermittently, prednisone, montelukast and antibiotics if necessary) compared with standard treatment. Tidal pulmonary function and symptoms assessment were performed at diagnosis and after 3 months of therapy. There were no significant differences in the sex, age, pulmonary function and symptoms assessment between groups A and B at diagnosis. However, following 3 months of treatment, the time to peak tidal expiratory flow as a proportion of expiratory time, and volume to peak expiratory flow as a proportion of exhaled volume in group A were significantly higher compared with those in group B. The respiratory rate in group A was significantly lower compared with group B. The symptoms assessment score in group A was significantly higher compared with that of group B. In conclusion, the present study demonstrates that combination therapy with budesonide, montelukast and azithromycin improves pulmonary function and respiratory symptoms in PIBO children <5 years old. The present study was retrospectively registered on March 22, 2020 with register no. YY202003-008-HB03.

Interchangeability between two breath-by-breath O2 uptake calculation algorithms in asthmatic and healthy volunteers

INTRODUCTION

The interchangeability analysis has been recently proposed to objectively assess whether a newly developed measurement tool can substitute the older ones; this analysis assumes that the measures yielded by the compared tools should differ less than a maximum acceptable value. We aimed to assess the interchangeability rate (IR) of the breath-by-breath O₂ uptake data calculated with the "Independent breath" (IND) and the "Expiration-only" (EXP) algorithms.

METHODS

Oxygen, carbon dioxide fractions, and ventilatory flow were recorded continuously over 26 min in 18 asthmatic and 20 well-matched healthy volunteers at rest, during cycling, and recovery; oxygen uptake (V'O₂) was calculated with the two algorithms under comparison. Coefficients of variation (CVs) of all the steady-state condition were modeled as a function of the average V'O₂ values and IR was calculated accordingly.

RESULTS

CVs were significantly greater in the asthmatic volunteers (F = 5.97, p < 0.05), being lower for IND compared to EXP (F > 7.04, p < 0.02). CVs decreased as a function of the reciprocal of the square root of the average V'O₂. The IR, calculated on the basis of this relationship, was not significantly different in the two groups of volunteers (F = 0.77, p = 0.385); taking as reference method the IND, or EXP algorithms, the IR values were significantly different (F = 58.6, p < 0.001), amounting to 97.4 ± 2.2% or to 98.2 ± 1.7%, respectively.

CONCLUSION

The relative noise of V'O₂ was greater in the asthmatic volunteers compared to the healthy ones and was lower for IND compared to EXP. The interchangeability analysis suggested that IND might be a better substitute for EXP than the opposite.

Combining Dynamic Hyperinflation with Dead Space Volume during Maximal Exercise in Patients with Chronic Obstructive Pulmonary Disease

Physiological dead space volume (VD) and dynamic hyperinflation (DH) are two different types of abnormal pulmonary physiology. Although they both involve lung volume, their combination has never been advocated, and thus their effect and implication are unclear. This study aimed (1) to combine VD and DH, and (2) investigate their relationship and clinical significance during exercise, as well as (3) identify a noninvasive variable to represent the VD fraction of tidal volume (VD/VT). Forty-six male subjects with chronic obstructive pulmonary disease (COPD) and 34 healthy male subjects matched for age and height were enrolled. Demographic data, lung function, and maximal exercise were investigated. End-expiratory lung volume (EELV) was measured for the control group and estimated for the study group using the formulae reported in our previous study. The VD/VT ratio was measured for the study group, and reference values of VD/VT were used for the control group. In the COPD group, the DHpeak/total lung capacity (TLC, DHpeak%) was 7% and the EELVpeak% was 70%. After adding the VDpeak% (8%), the VDDHpeak% was 15% and the VDEELVpeak% was 78%. Both were higher than those of the healthy controls. In the COPD group, the VDDHpeak% and VDEELVpeak% were more correlated with dyspnea score and exercise capacity than that of the DHpeak% and EELV%, and had a similar strength of correlation with minute ventilation. The VTpeak/TLC (VTpeak%), an inverse marker of DH, was inversely correlated with VD/VT (R2 ≈ 0.50). Therefore, we recommend that VD should be added to DH and EELV, as they are physiologically meaningful and VTpeak% represents not only DH but also dead space ventilation. To obtain VD, the VD/VT must be measured. Because obtaining VD/VT requires invasive arterial blood gases, further studies on noninvasive predicting VD/VT is warranted.

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.

Cardiopulmonary exercise testing in chronic obstructive pulmonary disease: An update on its clinical value and applications

Chronic obstructive pulmonary disease is a debilitating disorder, characterized by airflow limitation, exercise impairment, reduced functional capacity and significant systemic comorbidity, which complicates the course of the disease. The critical inspiratory constraint to tidal volume expansion during exercise (that may be further complicated by the presence of dynamic hyperinflation), abnormalities in oxygen transportation and gas exchange abnormalities are the major pathophysiological mechanisms of exercise intolerance in COPD patients, and thus, exercise testing has been traditionally used for the functional evaluation of these patients. Compared to various laboratory and field exercise tests, cardiopulmonary exercise testing (CPET) provides a thorough assessment of exercise physiology, involving the integrative respiratory, cardiovascular, muscle and metabolic responses to exercise. This review highlights the clinical utility of CPET in COPD patients, as it provides important information for the determination of the major factors that limit exercise among patients with several comorbidities, allows the assessment of the severity of dynamic hyperinflation, provides valuable prognostic information and can be used to evaluate the response to several therapeutic interventions.

Pulmonary Limitations in Heart Failure

The heart and lungs are intimately linked. Hence, impaired function of one organ may lead to changes in the other. Accordingly, heart failure is associated with airway obstruction, loss of lung volume, impaired gas exchange, and abnormal ventilatory control. Cardiopulmonary exercise testing is an excellent tool for evaluation of gas exchange and ventilatory control. Indeed, many parameters routinely measured during cardiopulmonary exercise testing, including the level of minute ventilation per unit of carbon dioxide production and the presence of exercise oscillatory ventilation, have been found to be strongly associated with prognosis in patients with heart failure.

Exercise Pathophysiology in Interstitial Lung Disease

Interstitial lung disease (ILD) is a heterogeneous group of disorders that primarily affect the lung parenchyma. Patients with ILD have reduced lung volumes, impaired pulmonary gas exchange, and decreased cardiovascular function. These pathologic features of ILD become exacerbated during physical exertion, leading to exercise intolerance and abnormally high levels of exertional dyspnea. In this review, the authors summarize the primary pathophysiologic features of patients with ILD and their effect on the integrative response to exercise.

Enhanced External Counterpulsation Efficacy on Exercise Endurance in COPD Patients and Healthy Subjects: A Pilot Randomized Clinical Trial

Purpose

Enhanced external counterpulsation (EECP) is popular in China for the treatment of coronary heart diseases, but it may be an effective treatment for other populations. This study aimed to explore the effect of EECP on exercise endurance of healthy people and chronic obstructive pulmonary disease (COPD) patients and provide intervention measures to improve their physical condition.

Patients and methods

Patients were enrolled in this pilot randomized controlled trial at Jiangbin Hospital, China, between March 1st and May 30th, 2018. They were randomly divided into the EECP and non-EECP groups. According to their maximal oxygen uptake, the volunteers were also sub-grouped into the normal, low exercise endurance, and COPD subgroups. Differences in exercise endurance were evaluated between the EECP and non-EECP groups before and after treatment. Cardiopulmonary exercise testng included anaerobic threshold oxygen uptake (AT-VO₂Kg), maximum oxygen uptake (Max-VO₂Kg), anaerobic threshold pulse (AT-O₂puls), anaerobic threshold metabolic equivalent (AT-Mets), and maximum metabolic equivalent (Max-Mets).

Results

72 volunteers were enrolled. The EECP and non-EECP groups were similar in terms of age, sex, body mass index, blood pressure, heart rate, breathing frequency, AT-VO₂Kg, Max-VO₂Kg, AT-O₂puls, AT-Mets, and Max-Mets (P > 0.05) before treatment. EECP significantly improved AT-VO₂Kg, Max-VO₂Kg, AT-O₂puls, AT-Mets, and Max-Mets compared with the non-EECP group (P<0.05). When analyzed according to sub-groups, the AT-VO₂Kg, Max-VO₂Kg, AT-O₂puls, AT-Mets, and Max-Mets of the normal, low exercise endurance, and COPD subgroups were all significantly increased after EECP (P<0.05).

Conclusion

EECP significantly improved the exercise endurance of normal adults, low endurance adults, and COPD patients.

Registration number

ChiCTR1900021993.

Diaphragmatic ultrasound findings correlate with dyspnea, exercise tolerance, health-related quality of life and lung function in patients with fibrotic interstitial lung disease

BACKGROUND

Fibrotic interstitial lung disease (FILD) patients are typically dyspneic and exercise-intolerant with consequent impairment of health-related quality of life (HRQoL). Respiratory muscle dysfunction is among the underlying mechanisms of dyspnea and exercise intolerance in FILD but may be difficult to diagnose. Using ultrasound, we compared diaphragmatic mobility and thickening in FILD cases and healthy controls and correlated these findings with dyspnea, exercise tolerance, HRQoL and lung function.

METHODS

We measured diaphragmatic mobility and thickness during quiet (QB) and deep breathing (DB) and calculated thickening fraction (TF) in 30 FILD cases and 30 healthy controls. We correlated FILD cases' diaphragmatic findings with dyspnea, exercise tolerance (six-minute walk test), lung function and HRQoL (St. George's Respiratory Questionnaire).

RESULTS

Diaphragmatic mobility was similar between groups during QB but was lower in FILD cases during DB when compared to healthy controls (3.99 cm vs 7.02 cm; p <  0.01). FILD cases showed higher diaphragm thickness during QB but TF was lower in FILD when compared to healthy controls (70% vs 188%, p <  0.01). During DB, diaphragmatic mobility and thickness correlated with lung function, exercise tolerance and HRQoL, but inversely correlated with dyspnea. Most FILD cases (70%) presented reduced TF, and these patients had higher dyspnea and exercise desaturation, lower HRQoL and lung function.

CONCLUSION

Compared to healthy controls, FILD cases present with lower diaphragmatic mobility and thickening during DB that correlate to increased dyspnea, decreased exercise tolerance, worse HRQoL and worse lung function. FILD cases with reduced diaphragmatic thickening are more dyspneic and exercise-intolerant, have lower HRQoL and lung function.

Interval aerobic exercise in individuals with advanced interstitial lung disease: a feasibility study

Background: Aerobic exercise is used in the rehabilitation setting in people with interstitial lung disease (ILD), however little is known about interval exercise as a training strategy. The aim of this study was to compare the cardiorespiratory responses and preferences of a single bout of interval exercise with continuous exercise in individuals with advanced ILD. Methods: Peak work (Wpeak) was obtained from a cardiopulmonary exercise test (CPET). The total volume of prescribed exercise was matched between a bout of interval cycling (alternating 30 seconds at 100% of Wpeak: 30 seconds total rest × 20 min) and continuous cycling (50% of Wpeak × 20 min). Results: Nine lung transplant candidates with ILD were included: 4 men; 62 (6) years; forced vital capacity (FVC) 60% of predicted; and all using supplemental oxygen. Eight (89%) participants reported a preference for interval exercise and one reported no preference (p = .01). One participant required two unintended breaks during continuous exercise. There were no large differences between interval and continuous exercise although some trends emerged. Interval exercise resulted in a lower peak heart rate (124 (12) vs. 132 (15), p = .04) and a trend toward less oxygen desaturation (drop of 8 (4)% vs. 11 (5)%, p = .05) and lower end-exercise Borg leg fatigue (3.8 (2) vs. 4.4 (2), p = .05). End-exercise dyspnea was similar between both exercise modes. Conclusions: Interval exercise was well tolerated and preferred by participants with advanced ILD.

Activity-related dyspnea in chronic obstructive pulmonary disease: physical and psychological consequences, unmet needs, and future directions

Dyspnea is a distressing, debilitating, and near-ubiquitous symptom affecting patients with COPD. In addition to the functional consequences of dyspnea, which include activity limitation and reduced exercise tolerance, it is important to consider its psychological impact on patients with COPD, such as onset of depression or anxiety. Moreover, the anticipation of dyspnea itself can have a significant effect on patients' emotions and behavior, with patients frequently self-limiting physical activity to avoid what has become the hallmark symptom of COPD. Dyspnea is, therefore, a key target for COPD treatments. Pharmacologic treatments can optimize respiratory mechanics, provide symptom relief, and reduce patients' increased inspiratory neural drive to breathe. However, it is important to acknowledge the value of non-pharmacologic interventions, such as pulmonary rehabilitation and patient self-management education, which have proven to be invaluable tools for targeting the affective components of dyspnea. Furthermore, it is important to encourage maintenance of physical activity to optimize long-term patient outcomes. Here, we review the physiological and psychological consequences of activity-related dyspnea in COPD, assess the efficacy of modern management strategies in improving this common respiratory symptom, and discuss key unmet clinical and research needs that warrant further immediate attention.

Anxiety Sensitivity is Associated with Lower Enjoyment and an Anxiogenic Response to Physical Activity in Smokers

Background

The subjective affective response to, and enjoyment of, physical activity are strong predictors of engagement in physical activity. Anxiety sensitivity, the fear of bodily sensations, is a cognitive factor that may inhibit the pleasurable affective experience of physical activity, possibly contributing to low levels of physical activity. The current study evaluated anxiety sensitivity in relation to PA enjoyment and affective experience before and after exercise in smokers.

Method

Participants were low-active treatment-seeking smokers (n = 201) enrolled in a smoking cessation intervention. At baseline, participants completed self -report assessments of anxiety sensitivity, cigarette dependence, and physical activity enjoyment. State affect was also reported before and after a submaximal exercise test to index pre-exercise activity affect and affective response to exercise.

Results

Anxiety sensitivity was significantly negatively correlated with physical activity enjoyment, specifically lower enjoyable physical feelings of physical activity. Anxiety sensitivity was significantly correlated with lower state mood and higher state anxiety prior to the submaximal exercise test, and higher anxiety immediately after the exercise test. Additionally, anxiety sensitivity predicted increased anxiety, but not lower mood, in response to the submaximal exercise test.

Conclusions

This is the first study to document an association of anxiety sensitivity with affective determinants of physical activity behavior in smokers. Anxiety sensitivity was associated with lower physical activity enjoyment, higher negative affect prior to after exercise testing, and an anxiogenic response to exercise. Future work is needed to understand how the current findings generalize beyond smokers.

Cardiopulmonary exercise testing for identification of patients with hyperventilation syndrome

Introduction

Measurement of ventilatory efficiency, defined as minute ventilation per unit carbon dioxide production (V_E/VCO₂), by cardiopulmonary exercise testing (CPET) has been proposed as a screen for hyperventilation syndrome (HVS). However, increased V_E/VCO₂ may be associated with other disorders which need to be distinguished from HVS. A more specific marker of HVS by CPET would be clinically useful. We hypothesized ventilatory control during exercise is abnormal in patients with HVS.

Methods

Patients who underwent CPET from years 2015 through 2017 were retrospectively identified and formed the study group. HVS was defined as dyspnea with respiratory alkalosis (pH >7.45) at peak exercise with absence of acute or chronic respiratory, heart or psychiatric disease. Healthy patients were selected as controls. For comparison the Student t-test or Mann-Whitney U test were used. Data are summarized as mean ± SD or median (IQR); p<0.05 was considered significant.

Results

Twenty-nine patients with HVS were identified and 29 control subjects were selected. At rest, end-tidal carbon dioxide (P_ETCO₂) was 27 mmHg (25–30) for HVS patients vs. 30 mmHg (28–32); in controls (p = 0.05). At peak exercise P_ETCO₂ was also significantly lower (27 ± 4 mmHg vs. 35 ± 4 mmHg; p<0.01) and V_E/VCO₂ higher ((38 (35–43) vs. 31 (27–34); p<0.01)) in patients with HVS. In contrast to controls, there were minimal changes of P_ETCO₂ (0.50 ± 5.26 mmHg vs. 6.2 ± 4.6 mmHg; p<0.01) and V_E/VCO₂ ((0.17 (-4.24–6.02) vs. -6.6 (-11.4-(-2.8)); p<0.01)) during exercise in patients with HVS. The absence of V_E/VCO₂ and P_ETCO₂ change during exercise was specific for HVS (83% and 93%, respectively).

Conclusion

Absence of V_E/VCO₂ and P_ETCO₂ change during exercise may identify patients with HVS.

Meta-analysis of the Effect of a Pulmonary Rehabilitation Program on Respiratory Muscle Strength in Patients with Chronic Obstructive Pulmonary Disease

PURPOSE

Pulmonary rehabilitation (PR) programs are important in the treatment of patients with chronic obstructive pulmonary disease (COPD) but vary widely in type, duration, and efficacy. This meta-analysis investigated the effect of PR programs on respiratory muscle strength in patients with COPD.

METHODS

PubMed, Embase, and CINAHL were searched. The primary outcome variables were maximal expiratory pressure (MEP) and maximal inspiratory pressure (MIP). The secondary outcome variables were the modified Borg score after the 6-min walking test, percent predicted forced expiratory volume in 1 second (FEV₁%pred), and percent FEV₁/forced volume capacity (FVC). Comprehensive Meta-Analysis, version 3.0, was used to analyze the data. The effect size was calculated using the standardized mean difference (SMD) and 95% confidence interval (CI).

RESULTS

Twenty randomized controlled trials (with 992 participants) were included in the analysis. The PR programs had a significant effect on the MEP (SMD, 0.87; 95% CI, 0.42-1.32; p < .001), MIP (SMD, 0.53; 95% CI, 0.13-0.93; p = .009), and modified Borg score (SMD, -0.37; 95% CI, -0.52 to -0.22; p < .001) in patients with COPD. There was no effect on FEV₁%pred (SMD, 0.09; 95% CI, -0.12 to 0.30; p = .406) or FEV₁/FVC% (SMD, 0.04; 95% CI, -0.17 to 0.26; p = .702).

CONCLUSION

PR programs improve respiratory muscle strength in patients with COPD. Strategies for selecting a suitable PR program need to be developed, and future studies should evaluate the long-term effects of such programs on pulmonary function.