Comparison of cardiopulmonary exercise testing variables in COPD patients with and without coronary artery disease

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

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

Comparable Ventilatory Inefficiency at Maximal and Submaximal Performance in COPD vs. CHF subjects: An Innovative Approach

BACKGROUND

Currently, excess ventilation has been grounded under the relationship between minute-ventilation/carbon dioxide output ( V ˙ E - V ˙ CO 2 ). Alternatively, a new approach for ventilatory efficiency ( η E V ˙ ) has been published.

OBJECTIVE

Our main hypothesis is that comparatively low levels of η E V ˙ between chronic heart failure (CHF) and chronic obstructive pulmonary disease (COPD) are attainable for a similar level of maximum and submaximal aerobic performance, conversely to long-established methods ( V ˙ E - V ˙ CO 2 slope and intercept).

METHODS

Both groups performed lung function tests, echocardiography, and cardiopulmonary exercise testing. The significance level adopted in the statistical analysis was 5%. Thus, nineteen COPD and nineteen CHF-eligible subjects completed the study. With the aim of contrasting full values of V ˙ E - V ˙ CO 2 and η V ˙ E for the exercise period (100%), correlations were made with smaller fractions, such as 90% and 75% of the maximum values.

RESULTS

The two groups attained matched characteristics for age (62±6 vs. 59±9 yrs, p>.05), sex (10/9 vs. 14/5, p>0.05), BMI (26±4 vs. 27±3 Kg m2, p>0.05), and peak V ˙ O 2 (72±19 vs. 74±20 %pred, p>0.05), respectively. The V ˙ E - V ˙ CO 2 slope and intercept were significantly different for COPD and CHF (27.2±1.4 vs. 33.1±5.7 and 5.3±1.9 vs. 1.7±3.6, p<0.05 for both), but η V ˙ E average values were similar between-groups (10.2±3.4 vs. 10.9±2.3%, p=0.462). The correlations between 100% of the exercise period with 90% and 75% of it were stronger for η V ˙ E (r>0.850 for both).

CONCLUSION

The η V ˙ E is a valuable method for comparison between cardiopulmonary diseases, with so far distinct physiopathological mechanisms, including ventilatory constraints in COPD.

Predictors of cardiopulmonary exercise testing in COPD patients according to the Weber classification

BACKGROUND

Weber classification stratifies cardiac patients based on peak oxygen consumption (V̇O2), the gold-standard measure of exercise capacity.

OBJECTIVE

To determine if Weber classification is a useful tool to discriminate clinical phenotypes in COPD patients and to evaluate if disease severity and other clinical measures can predict V̇O2peak.

METHODS

Three hundred and six COPD patients underwent cardiopulmonary exercise testing (CPX) and were divided according to Weber class: 1) Weber A (n = 34); 2) Weber B (n = 88); 3) Weber C (n = 138); and 4) Weber D (n = 46).

RESULTS

Weber class D patients demonstrated a reduced V̇O2 peak, heart rate (HR), minute ventilation (V̇E), oxygen (O2) pulse, circulatory power (CP), oxygen uptake efficiency slope (OUES), oxygen saturation (SpO2%), delta (Δ)HR and ΔSpO2 when compared to Weber A and B (p<0.05). Moreover, Dyspnea and the V̇E/carbon dioxide production (V̇CO2) slope were higher in Weber D compared with Weber C and A (p<0.001). Hierarchical regression analysis demonstrated significant predictors of V̇O2peak (R2= 0.131; Adj R 2 = 1.25), including HR (β=0.5757; t = 5.7; P<0.001) and forced expiratory volume in one second (FEV1) (β=0.119; t = 2.16; P<0.03). Among the Weber C + D groups, predictors of V̇O2peak (R = 0.78; R2= 0.60; Adj R2 =0.59), dyspnea (β=0.076; t = 1.111; P<0.27) and maximal voluntary ventilation (MVV) (β=0.75; t = 1.14; P<0.00).

CONCLUSION

Weber classification may be a useful tool to stratify cardiorespiratory fitness in COPD patients. Other clinical measures may be useful in predicting peak V̇O2 in mild-to-severe COPD, moreover different phenotypes may be important tool to improve physical capacity of chronic disease patients.

Exertional ventilation/carbon dioxide output relationship in COPD: from physiological mechanisms to clinical applications

There is well established evidence that the minute ventilation (V′_E)/carbon dioxide output (V′_CO2) relationship is relevant to a number of patient-related outcomes in COPD. In most circumstances, an increased V′_E/V′_CO2 reflects an enlarged physiological dead space (“wasted” ventilation), although alveolar hyperventilation (largely due to increased chemosensitivity) may play an adjunct role, particularly in patients with coexistent cardiovascular disease. The V′_E/V′_CO2 nadir, in particular, has been found to be an important predictor of dyspnoea and poor exercise tolerance, even in patients with largely preserved forced expiratory volume in 1 s. As the disease progresses, a high nadir might help to unravel the cause of disproportionate breathlessness. When analysed in association with measurements of dynamic inspiratory constraints, a high V′_E/V′_CO2 is valuable to ascertain a role for the “lungs” in limiting dyspnoeic patients. Regardless of disease severity, cardiocirculatory (heart failure and pulmonary hypertension) and respiratory (lung fibrosis) comorbidities can further increase V′_E/V′_CO2. A high V′_E/V′_CO2 is a predictor of poor outcome in lung resection surgery, adding value to resting lung hyperinflation in predicting all-cause and respiratory mortality across the spectrum of disease severity. Considering its potential usefulness, the V′_E/V′_CO2 should be valued in the clinical management of patients with COPD.

The minute ventilation/carbon dioxide production relationship is relevant to a number of patient-related outcomes in COPD. Minute ventilation/carbon dioxide production, therefore, should be valued in the clinical management of these patients.https://bit.ly/3df2upH

Intercept of minute ventilation versus carbon dioxide output relationship as an index of ventilatory inefficiency in chronic obstructive pulmonary disease

Background

Ventilatory inefficiency contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). The intercept of the minute ventilation (V^˙_E) vs. carbon dioxide output (V^˙ CO₂) plot is a key ventilatory inefficiency parameter. However, its relationships with lung hyperinflation (LH) and airflow limitation are not known. This study aimed to evaluate correlations between the V^˙_E/V^˙ CO₂ intercept and LH and airflow limitation to determine its physiological interpretation as an index of functional impairment in COPD.

Methods

We conducted a retrospective analysis of data from 53 COPD patients and 14 healthy controls who performed incremental cardiopulmonary exercise tests (CPETs) and resting pulmonary function assessment. Ventilatory inefficiency was represented by parameters reflecting the V^˙_E/V^˙ CO₂ nadir and slope (linear region) and the intercept of V^˙_E/V^˙ CO₂ plot. Their correlations with measures of LH and airflow limitation were evaluated.

Results

Compared to control, the slope (30.58±3.62, P<0.001) and intercept (4.85±1.11 L/min, P<0.05) were higher in COPD_stages1-2, leading to a higher nadir (31.47±4.47, P<0.01). Despite an even higher intercept in COPD_stages3-4 (7.16±1.41, P<0.001), the slope diminished with disease progression (from 30.58±3.62 in COPD_stages1-2 to 26.84±4.96 in COPD_stages3-4, P<0.01). There was no difference in nadir among COPD groups and higher intercepts across all stages. The intercept was correlated with peak V^˙_E/maximal voluntary ventilation (MVV) (r=0.489, P<0.001) and peak V^˙ O₂/Watt (r=0.354, P=0.003). The intercept was positively correlated with residual volume (RV) % predicted (r=0.571, P<0.001), RV/total lung capacity (TLC) (r=0.588, P<0.001), peak tidal volume (V_T)/FEV₁ (r=0.482, P<0.001) and negatively correlated with rest inspiratory capacity (IC)/TLC (r=−0.574, P<0.001), peak V_T/TLC (r=−0.585, P<0.001), airflow limitation forced expiratory volume in 1 s (FEV₁) % predicted (r=−0.606, P<0.001), and FEV₁/forced vital capacity (FVC) (r=−0.629, P<0.001).

Conclusions

V^˙_E/V^˙ CO₂ intercept was consistently correlated with worsening static and dynamic LH, pulmonary gas exchange, and airflow limitation in COPD. The V^˙_E/V^˙ CO₂ intercept emerged as a useful index of ventilatory inefficiency in COPD patients.

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.

Incorporating Lung Diffusing Capacity for Carbon Monoxide in Clinical Decision Making in Chest Medicine

Lung diffusing capacity for carbon monoxide (Dlco) remains the only noninvasive pulmonary function test to provide an integrated picture of gas exchange efficiency in human lungs. Due to its critical dependence on the accessible "alveolar" volume (Va), there remains substantial misunderstanding on the interpretation of Dlco and the diffusion coefficient (Dlco/Va ratio, Kco). This article presents the physiologic and methodologic foundations of Dlco measurement. A clinically friendly approach for Dlco interpretation that takes those caveats into consideration is outlined. The clinical scenarios in which Dlco can effectively assist the chest physician are discussed and illustrative clinical cases are presented.

Exercise ventilatory inefficiency in heart failure and chronic obstructive pulmonary disease

BACKGROUND

Dyspnea on exertion is common to both heart failure (HF) and chronic obstructive pulmonary disease (COPD), and it is important to discriminate whether symptoms are caused by HF or COPD in clinical practice. The ventilatory equivalent for carbon dioxide (V̇_E/V̇CO₂) slope and V̇_E intercept (a reflection of pulmonary dead space) are two candidate non-invasive indices that could be used for this purpose. Thus, we compared non-invasive indexes of ventilatory efficiency in patients with HF and preserved or reduced ejection fraction (HFpEF and HFrEF, respectively) or COPD.

METHODS

Patients with HFpEF (n = 21), HFrEF (n = 20), and COPD (n = 22) patients performed cardiopulmonary exercise testing to volitional fatigue. V̇_E and gas exchange were measured via breath-by-breath open circuit spirometry. All data from rest to peak exercise were used to calculate V̇_E/V̇CO₂ slope and V̇_E intercept using linear regression. Receiver operating characteristic (ROC) curves were constructed to determine optimized cutoffs for V̇_E/V̇CO₂ slope and V̇_E intercept to discriminate HFpEF and HFrEF from COPD.

RESULTS

HFrEF patients had a greater V̇_E/V̇CO₂ slope than HFpEF and COPD patients (HFrEF: 40 ± 9; HFpEF: 32 ± 7; COPD: 32 ± 7) (p < 0.01). COPD patients had a greater V̇_E intercept than HFpEF and HFrEF patients (COPD: 3.32 ± 1.66; HFpEF: 0.77 ± 1.23; HFrEF: 1.28 ± 1.19 L/min) (p < 0.01). A V̇_E intercept of 2.64 L/min discriminated COPD from HF patients (AUC: 0.88, p < 0.01), while V̇_E/V̇CO₂ slope did not (p = 0.11).

CONCLUSION

These findings demonstrate that V̇_E intercept, not V̇_E/V̇CO₂ slope, may discriminate COPD from both HFpEF and HFrEF patients.

Estimates of Medication Expenditure for Ischemic Heart Disease Accompanying Chronic Obstructive Pulmonary Disease

Ischemic heart disease (IHD) is a frequent accompaniment of chronic obstructive pulmonary disease (COPD). Co-occurrence of these two diseases is associated with many risk factors, difficulties in implementing appropriate therapies, numerous complications, and high spending for treatment. All these elements significantly reduce the quality of life of patients. The aim of this study was to estimate the expenditure for medications involved with IHD pharmacotherapy in the course of COPD. This retrospective study was based on the review of medical files of 57 patients, 27 women and 30 men, diagnosed with IHD, according to the severity classification, in the course of COPD which was staged according to the GOLD criteria. We found a considerable increase in per capita per year retail spending for drugs. The spending increased with the severity class of IHD; from 27.41 EUR in Class I to 142.30 EUR in Class IV. This spending did not include the treatment cost for the basic disease, i.e., COPD. A high individual cost burden was decreased by a discounting intervention of the National Health Fund. Despite a relatively high drug expenditure, we consider the treatment being cost-effective since we noticed a reduction in the classical risk factors for IHD, related to metabolic disturbances and lifestyle features, as soon as 2 months after treatment initiation. This study confirms that heart disease accompanying COPD is a frequent occurrence, generating high costs of treatment, which relates to the severity of this comorbidity.

Physiological and clinical relevance of exercise ventilatory efficiency in COPD

Exercise ventilation (V'_E) relative to carbon dioxide output (V'_CO2 ) is particularly relevant to patients limited by the respiratory system, e.g. those with chronic obstructive pulmonary disease (COPD). High V'_E-V'_CO2 (poor ventilatory efficiency) has been found to be a key physiological abnormality in symptomatic patients with largely preserved forced expiratory volume in 1 s (FEV₁). Establishing an association between high V'_E-V'_CO2 and exertional dyspnoea in mild COPD provides evidence that exercise intolerance is not a mere consequence of detraining. As the disease evolves, poor ventilatory efficiency might help explaining "out-of-proportion" breathlessness (to FEV₁ impairment). Regardless, disease severity, cardiocirculatory co-morbidities such as heart failure and pulmonary hypertension have been found to increase V'_E-V'_CO2 In fact, a high V'_E-V'_CO2 has been found to be a powerful predictor of poor outcome in lung resection surgery. Moreover, a high V'_E-V'_CO2 has added value to resting lung hyperinflation in predicting all-cause and respiratory mortality across the spectrum of COPD severity. Documenting improved ventilatory efficiency after lung transplantation and lung volume reduction surgery provides objective evidence of treatment efficacy. Considering the usefulness of exercise ventilatory efficiency in different clinical scenarios, the V'_E-V'_CO2 relationship should be valued in the interpretation of cardiopulmonary exercise tests in patients with mild-to-end-stage COPD.

Emphysema on Thoracic CT and Exercise Ventilatory Inefficiency in Mild-to-Moderate COPD

There is growing evidence that emphysema on thoracic computed tomography (CT) is associated with poor exercise tolerance in COPD patients with only mild-to-moderate airflow obstruction. We hypothesized that an excessive ventilatory response to exercise (ventilatory inefficiency) would underlie these abnormalities. In a prospective study, 19 patients (FEV₁ = 82 ± 13%, 12 Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 1) and 26 controls underwent an incremental exercise test. Ventilatory inefficiency was assessed by the ventilation ([Formula: see text]E)/CO₂ output ([Formula: see text]CO₂) nadir. Pulmonary blood flow (PBF) in a submaximal test was calculated by inert gas rebreathing. Emphysema was quantified as % of attenuation areas below 950 HU. Patients typically presented with centrilobular emphysema (76.8 ± 10.1% of total emphysema) in the upper lobes (upper/total lung ratio = 0.82 ± 0.04). They had lower peak oxygen uptake ([Formula: see text]O₂), higher [Formula: see text]E/[Formula: see text]CO₂ nadir, and greater dyspnea scores than controls (p < 0.05). Lower peak [Formula: see text]O₂ and worse dyspnea were found in patients with higher [Formula: see text]E/[Formula: see text]CO₂ nadirs (≥30). Patients had blunted increases in PBF from rest to iso-[Formula: see text]O₂ exercise (p < 0.05). Higher [Formula: see text]E/[Formula: see text]CO₂ nadir in COPD was associated with emphysema severity (r = 0.63) which, in turn, was related to reduced lung diffusing capacity (r = -0.72) and blunted changes in PBF from rest to exercise (r = -0.69) (p < 0.01). Ventilation "wasted" in emphysematous areas is associated with impaired exercise ventilatory efficiency in mild-to-moderate COPD. Exercise ventilatory inefficiency links structure (emphysema) and function (D_LCO) to a key clinical outcome (poor exercise tolerance) in COPD patients with only modest spirometric abnormalities.

Changes in Hepatic Venous Pressure Gradient Induced by Physical Exercise in Cirrhosis: Results of a Pilot Randomized Open Clinical Trial

OBJECTIVES

Exercise has been scarcely studied in patients with cirrhosis, and prior evidence showed hepatic venous pressure gradient (HVPG) to be increased in response to exercise. The aim of this study was to investigate the effects of a supervised physical exercise program (PEP) in patients with cirrhosis.

METHODS

In an open-label, pilot clinical trial, patients with cirrhosis were randomized to PEP (cycloergometry/kinesiotherapy plus nutritional therapy, n=14) or control (nutritional therapy, n=15); for 14 weeks. Primary outcomes were: the effect of PEP in HVPG, and quality of life (chronic liver disease questionnaire, CLDQ). As secondary outcomes we investigated changes in physical fitness (cardiopulmonary exercise testing), nutritional status (phase angle-bioelectrical impedance), ammonia levels, and safety.

RESULTS

Twenty-two patients completed the study (11 each). HVPG decreased in subjects allocated to PEP (-2.5 mm Hg (interquartile range: -5.25 to 2); P=0.05), and increased in controls (4 mm Hg (0-5); P=0.039), with a significant between-groups difference (P=0.009). No major changes were noted in CLDQ in both groups. There was significant improvement in ventilatory efficiency (VE/VCO2) in PEP group (-1.9 (-3.12 to -0.1); P=0.033), but not in controls (-0.4 (-5.7 to 1.4); P=0.467). Phase angle improvement and a less-pronounced exercise-induced hyperammonemia were noted only in PEP group. No episodes of variceal bleeding or hepatic encephalopathy were observed.

CONCLUSIONS

A supervised PEP in patients with cirrhosis decreases the HVPG and improves nutritional status with no changes in quality of life. Further studies evaluating physical training in cirrhosis are eagerly awaited in order to better define the benefits of sustained exercise. ClinicalTrials.gov:NCT00517738.

Chronic obstructive pulmonary disease and ischemic heart disease comorbidity: overview of mechanisms and clinical management

In the last few years, many studies focused their attention on the relationship between chronic obstructive pulmonary disease (COPD) and ischemic heart disease (IHD), showing that these diseases are mutually influenced. Many different biological processes such as hypoxia, systemic inflammation, endothelial dysfunction, heightened platelet reactivity, arterial stiffness and right ventricle modification interact in the development of the COPD-IHD comorbidity, which therefore deserves special attention in early diagnosis and treatment. Patients with COPD-IHD comorbidity have a worst outcome, when compared to patients with only COPD or only IHD. These patients showed a significant increase on risk of adverse events and of hospital readmissions for recurrent myocardial infarction, heart failure, coronary revascularization, and acute exacerbation of COPD. Taken together, these complications determine a significant increase in mortality. In most cases death occurs for cardiovascular cause, soon after an acute exacerbation of COPD or a cardiovascular adverse event. Recent data regarding incidence, mechanisms and prognosis of this comorbidity, along with the development of new drugs and interventional approaches may improve the management and long-term outcome of COPD-IHD patients. The aim of this review is to describe the current knowledge on COPD-IHD comorbidity. Particularly, we focused our attention on underlying pathological mechanisms and on all treatment and strategies that may improve and optimize the clinical management of COPD-IHD patients.

CO2 pulse and acid-base status during increasing work rate exercise in health and disease

The CO2 pulse (VCO2/heart rate), analogous to the O2 pulse (VO2/heart rate), was calculated during cardiopulmonary exercise testing and evaluated in normal and diseased states. Our aim was to define its application in its release in excess of that from VCO2/heart rate in the presence of impaired cardiovascular and lung function. In the current study, forty-five patients were divided into six physiological states: normal, exercise-induced myocardial ischemia, chronic heart failure, pulmonary vasculopathy, chronic obstructive pulmonary disease, and interstitial lung disease. We subtracted the O2 pulse from the CO2 pulse to determine the exhaled CO2 that could be attributed to CO2 pulse of buffering of lactic acid. The difference between the CO2 pulse and O2 pulse (VCO2/heart rate-VO2/heart rate) includes CO2 generated from HCO3(-) buffering of lactic acid. The accumulated CO2 per body mass was found to be significantly correlated with the corresponding [HCO3(-)] decrease (R(2)=0.72; P<0.0001). In summary, the increase in CO2 pulse over the O2 pulse accounted for the anaerobically-generated excess-CO2 in each of the physiological states and correlated with the decreases in the arterial Bicarbonate concentration.

Exercise ventilatory inefficiency in mild to end-stage COPD

Ventilatory inefficiency during exercise is a key pathophysiological feature of chronic obstructive pulmonary disease. Currently, it is unknown how this physiological marker relates to clinically relevant outcomes as resting ventilatory impairment progresses across disease stages.

Slope and intercept of the linear region of the ventilation–carbon dioxide output relationship and the ratio between these variables, at the lowest point (nadir), were contrasted in 316 patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages 1–4 (forced expiratory volume in 1 s, ranging from 148% pred to 12% pred) and 69 aged- and gender-matched controls,

Compared to controls, slope and intercept were higher in GOLD stages 1 and 2, leading to higher nadirs (p<0.05). Despite even larger intercepts in GOLD stages 3 and 4, slopes diminished as disease evolved (from mean±sd35±6 in GOLD stage 1 to 24±5 in GOLD stage 3, p<0.05). As a result, there were no significant differences in nadirs among patient groups. Higher intercepts, across all stages (p<0.01), and to a lesser extent lower slopes in GOLD stages 2–4 (p<0.05), were related to greater mechanical constraints, worsening pulmonary gas exchange, higher dyspnoea scores, and poorer exercise capacity.

Increases in the ventilation intercept best indicate the progression of exercise ventilatory inefficiency across the whole spectrum of chronic obstructive pulmonary disease severity.