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

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

Peak oxygen uptake and respiratory muscle performance in patients with chronic obstructive pulmonary disease: Clinical findings and implications

The maximal oxygen uptake (VO2max) is the gold standard measure of aerobic exercise capacity and is an important outcome measure in patients with chronic obstructive pulmonary disease (COPD). And respiratory muscle performance is also an important functional parameter for COPD patients. In addition to the traditional respiratory muscle strength test, the Test of Incremental Respiratory Endurance has recently been introduced and validated in patients with COPD. However, the relationship between VO2 and respiratory muscle performance in COPD is not well understood. Therefore, this study investigated the correlations among VO2 and respiratory muscle performance and other functional markers in COPD. A total of 32 patients with COPD were enrolled. All study participants underwent the following assessments: cardiopulmonary exercise test, pulmonary function test, respiratory muscle strength test, peripheral muscle strength test, and bioelectrical impedance analysis. When comparing VO2peak and respiratory muscle parameters, the sustained maximal inspiratory pressure (SMIP) was the only factor with a significant relationship with VO2peak. Among other functional parameters, the forced expiratory volume in one second (FEV1) showed the strongest correlation with VO2peak. It was followed by phase angle values of lower limbs, leg extension peak torque, age, and total skeletal muscle mass. When comparing respiratory muscle performance with other functional parameters, the SMIP showed the strongest correlation with hand grip strength, followed by peak cough flow, forced vital capacity, maximal inspiratory pressure, and FEV1. The results showed that the SMIP was more significantly correlated with VO2peak than the static measurement of respiratory muscle strength. This suggests that TIRE may be a useful assessment tool for patients with COPD. Additionally, FEV1 and other functional markers were significantly correlated with VO2peak, suggesting that various parameters may be used to evaluate aerobic power indirectly.

Distinguishing exercise intolerance in early-stage pulmonary hypertension with invasive exercise hemodynamics: Rest VE /VCO2 and ETCO2 identify pulmonary vascular disease

BACKGROUND

Among subjects with exercise intolerance and suspected early-stage pulmonary hypertension (PH), early identification of pulmonary vascular disease (PVD) with noninvasive methods is essential for prompt PH management.

HYPOTHESIS

Rest gas exchange parameters (minute ventilation to carbon dioxide production ratio: VE /VCO2 and end-tidal carbon dioxide: ETCO2 ) can identify PVD in early-stage PH.

METHODS

We conducted a retrospective review of 55 subjects with early-stage PH (per echocardiogram), undergoing invasive exercise hemodynamics with cardiopulmonary exercise test to distinguish exercise intolerance mechanisms. Based on the rest and exercise hemodynamics, three distinct phenotypes were defined: (1) PVD, (2) pulmonary venous hypertension, and (3) noncardiac dyspnea (no rest or exercise PH). For all tests, *p < .05 was considered statistically significant.

RESULTS

The mean age was 63.3 ± 13.4 years (53% female). In the overall cohort, higher rest VE /VCO2 and lower rest ETCO2 (mm Hg) correlated with high rest and exercise pulmonary vascular resistance (PVR) (r ~ 0.5-0.6*). On receiver-operating characteristic analysis to predict PVD (vs. non-PVD) subjects with noninvasive metrics, area under the curve for pulmonary artery systolic pressure (echocardiogram) = 0.53, rest VE /VCO2  = 0.70* and ETCO2  = 0.73*. Based on this, optimal thresholds of rest VE /VCO2  > 40 mm Hg and rest ETCO2  < 30 mm Hg were applied to the overall cohort. Subjects with both abnormal gas exchange parameters (n = 12, vs. both normal parameters, n = 19) had an exercise PVR 5.2 ± 2.6* (vs. 1.9 ± 1.2), mPAP/CO slope with exercise 10.2 ± 6.0* (vs. 2.9 ± 2.0), and none included subjects from the noncardiac dyspnea group.

CONCLUSIONS

In a broad cohort of subjects with suspected early-stage PH, referred for invasive exercise testing to distinguish mechanisms of exercise intolerance, rest gas exchange parameters (VE /VCO2  > 40 mm Hg and ETCO2  < 30 mm Hg) identify PVD.

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.

Clinical insights into pulmonary hypertension in chronic obstructive pulmonary disease

Pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD). Little is known about the prevalence and clinical profiles of patients with COPD-PH. We report the clinical characteristics, hemodynamic profiles, and prognosis in a large population of patients with COPD referred for right heart catheterization (RHC). We extracted data from all patients referred for RHC between 1997 and 2017 in Vanderbilt's deidentified medical record. PH was defined as mean pulmonary artery pressure >20 mmHg. Pre- and postcapillary PH were defined according to contemporary guidelines. COPD was identified using a validated rules-based algorithm requiring international classification of diseases codes relevant to COPD. We identified 6065 patients referred for RHC, of whom 1509 (24.9%) had COPD and 1213 had COPD and PH. Patients with COPD-PH had a higher prevalence of diabetes, atrial fibrillation, and heart failure compared with COPD without PH. Approximately 55% of patients with COPD-PH had elevated left ventricle (LV) filling pressure. Pulmonary function testing data from individuals with COPD-PH revealed subtype differences, with precapillary COPD-PH having lower diffusion capacity of the lungs for carbon monoxide (DLCO) values than the other COPD-PH subtypes. Patients with COPD-PH had significantly increased mortality compared with COPD alone (hazard ratio [HR]: 1.70, 95% confidence interval [CI]: 1.28-2.26) with the highest mortality among the combined pre- and postcapillary COPD-PH subgroup (HR: 2.39; 95% CI: 1.64-3.47). PH is common among patients with COPD referred for RHC. The etiology of PH in patients with COPD is often mixed due to multimorbidity and is associated with high mortality, which may have implications for risk factor management.

Making Cardiopulmonary Exercise Testing Interpretable for Clinicians

ABSTRACT

Cardiopulmonary exercise testing (CPET) is a dynamic clinical tool for determining the cause for a person's exercise limitation. CPET provides clinicians with fundamental knowledge of the coupling of external to internal respiration (oxygen and carbon dioxide) during exercise. Subtle perturbations in CPET parameters can differentiate exercise responses among individual patients and disease states. However, perhaps because of the challenges in interpretation given the amount and complexity of data obtained, CPET is underused. In this article, we review fundamental concepts in CPET data interpretation and visualization. We also discuss future directions for how to best use CPET results to guide clinical care. Finally, we share a novel three-dimensional graphical platform for CPET data that simplifies conceptualization of organ system-specific (cardiac, pulmonary, and skeletal muscle) exercise limitations. Our goal is to make CPET testing more accessible to the general medical provider and make the test of greater use in the medical toolbox.

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

Effect of pulmonary hypertension on exercise tolerance in patients with COPD: a prognostic systematic review and meta-analysis

Background

Pulmonary hypertension (PH) is a frequent complication in patients with COPD.

Objective

To determine if, in patients with COPD, the presence of PH decreases exercise tolerance.

Methods

We included studies that analysed exercise tolerance using a cardiopulmonary exercise test (CPET) in patients with COPD with PH (COPD-PH) and without PH (COPD-nonPH). Two independent reviewers analysed the studies, extracted the data and assessed the quality of the evidence.

Results

Of the 4915 articles initially identified, seven reported 257 patients with COPD-PH and 404 patients with COPD-nonPH. The COPD-PH group showed differences in peak oxygen consumption (V′_O2peak), −3.09 mL·kg⁻¹·min⁻¹ (95% CI −4.74 to −1.43, p=0.0003); maximum workload (W_max), −20.5 W (95% CI −34.4 to −6.5, p=0.004); and oxygen pulse (O₂ pulse), −1.24 mL·beat⁻¹ (95% CI −2.40 to −0.09, p=0.03), in comparison to the group with COPD-nonPH. If we excluded studies with lung transplant candidates, the sensitivity analyses showed even bigger differences: V′_O2, −4.26 mL·min⁻¹·kg⁻¹ (95% CI −5.50 to −3.02 mL·kg⁻¹·min⁻¹, p<0.00001); W_max, −26.6 W (95% CI −32.1 to −21.1 W, p<0.00001); and O₂ pulse, −2.04 mL·beat⁻¹ (95% CI −2.92 to −1.15 mL·beat⁻¹, p<0.0001).

Conclusion

Exercise tolerance was significantly lower in patients with COPD-PH than in patients with COPD-nonPH, particularly in nontransplant candidates.

The V′_O2peak, Wmax and O₂ pulse values were significantly lower in patients with COPD-PH than in patients with COPD-nonPH, particularly in nontransplant candidateshttps://bit.ly/3s5dtJ9

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.

The value of cardiopulmonary exercise testing in the diagnosis of pulmonary hypertension

Background

Cardiopulmonary exercise testing (CPET) continuously analyzes the gas exchange of patients during rest, exercise, recovery, and simultaneously records the response of the cardiopulmonary system. This study aimed to observe the characteristics of CPET in patients with pulmonary hypertension (PH) and to explore the cutoff value of CPET variables in detecting PH. The diagnostic value of CPET was also investigated in a subgroup of patients who had an incorrect or missed diagnosis of PH by echocardiography.

Methods

Treatment-naïve patients with suspected PH who were admitted to Fuwai Hospital from January 2017 to August 2018 were consecutively enrolled. The gold standard criterion for PH was defined as mean pulmonary artery pressure (mPAP) ≥25 mmHg at rest, measured by right heart catheterization. General clinical materials, echocardiography, hemodynamics, and CPET data of the patients were collected and compared between groups. Logistic regression analyses were performed to explore the CPET variables that were independently associated with PH. To further validate the value of CPET for diagnosing PH, the CPET cutoff values obtained from receiver operating characteristic (ROC) curve analysis were used in patients who had an incorrect or missed diagnosis by echocardiography.

Results

Five hundred and fifty-nine patients were included in the study. Among them, patients with PH had significantly poorer CPET variables. Multivariate logistic regression analysis showed that peak work rate (WR), peak oxygen uptake (VO₂), and end-tidal carbon dioxide partial pressure (PetCO₂) at the anaerobic threshold (AT) were independently associated with PH after adjustment for age, sex, and body mass index. The above three CPET variables were all negatively correlated with mPAP. The combined CPET variable including peak WR, peak VO₂ and PetCO₂ at AT had the largest area under the ROC curve for the diagnosis of PH (0.890, 95% CI: 0.852–0.927, P<0.001). The cutoff value was 0.86, and the sensitivity and specificity were 81.8% and 86.5%, respectively. Using this cutoff value, 83.7% of patients who were misdiagnosed and 67.9% of patients who had a missed diagnosis by echocardiography were identified.

Conclusions

PH patients have decreased cardiopulmonary reserve, lower exercise tolerance, and increased ineffective ventilation. The combination of peak WR, peakVO₂, and PetCO₂ at AT had increased sensitivity and specificity for the diagnosis of PH, and increased the specificity for identifying patients who had been misdiagnosed as PH by echocardiography.

Comparison of Functional Capacity and Symptoms of COPD Patients with and without Pulmonary Hypertension

OBJECTIVE

Pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD) associated with a decrease in the survival rate of patients with COPD. Our aim was to investigate whether PH impairs the functional capacity and symptoms in patients with COPD. In addition, we aimed to evaluate the correlation between the functional capacity and symptoms score in patients with COPD.

MATERIALS AND METHODS

This prospective cross-sectional study enrolled 64 patients with moderate to severe COPD, prospectively. All patients underwent the pulmonary function test, echocardiography, 6-minute walk test (6MWT), and cardiopulmonary exercise testing (CPET). We applied the modified Medical Research Council (mMRC) dyspnea scale and COPD Assessment Test (CAT) to all patients. The mean pulmonary arterial pressure (mPAP) >30 mmHg with echocardiography was considered as PH. The patients were grouped according to the presence of PH as COPD-PH (n=30) and COPD-nonPH (n=34).

RESULTS

Hospitalization rate was higher in the COPD-PH group than in the COPD-nonPH group (p=0.006). The 6MWT results were lower in the COPD-PH group compared to the COPD-nonPH group (325±61 m vs. 354±46 m, respectively, p=0.025). In the COPD-PH group, the maximum oxygen consumption (VO2max) was lower, but the difference did not reach statistical significance (p=0.118). Although the maximum load and minute ventilation were lower in the COPD-PH group, the end-tidal pressure of CO2 (PETCO2) was higher (p=0.033, p=0.036, and p=0.009, respectively). However, the CAT score and mMRC were similar between the groups (p=0.405 and p=0.238, respectively).

CONCLUSION

An elevated PAP in patients with COPD limits the exercise capacity. Using CPET in the functional evaluation of patients with COPD may be beneficial in the early detection of PH.

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.

The supine position improves but does not normalize the blunted pulmonary capillary blood volume response to exercise in mild COPD

Patients with mild chronic obstructive pulmonary disease (COPD) demonstrate resting pulmonary vascular dysfunction as well as a blunted pulmonary diffusing capacity (DLCO) and pulmonary capillary blood volume (V_C) response to exercise. The transition from the upright to supine position increases central blood volume and perfusion pressure, which may overcome microvascular dysfunction in an otherwise intact alveolar-capillary interface. The present study examined whether the supine position normalized DLCO and V_C responses to exercise in mild COPD. Sixteen mild COPD participants and 13 age-, gender-, and height-matched controls completed DLCO maneuvers at rest and during exercise in the upright and supine position. The multiple FIO2-DLCO method was used to determine DLCO, V_C, and membrane diffusion capacity (D_M). All three variables were adjusted for alveolar volume (DLCOAdj, V_CAdj, and D_MAdj). The supine position reduced alveolar volume similarly in both groups, but oxygen consumption and cardiac output were unaffected. DLCOAdj, D_MAdj, and V_CAdj were all lower in COPD. These same variables all increased with upright and supine exercise in both groups. DLCOAdj was unaffected by the supine position. V_CAdj increased in the supine position similarly in both groups. D_MAdj was reduced in the supine position in both groups. While the supine position increased exercise V_CAdj in COPD, the increase was of similar magnitude to healthy controls; therefore, exercise V_C remained blunted in COPD. The persistent reduction in exercise DLCO and V_C when supine suggests that pulmonary vascular destruction is a contributing factor to the blunted DLCO and V_C response to exercise in mild COPD.NEW & NOTEWORTHY Patients with mild chronic obstructive pulmonary disease demonstrate a combination of reversible pulmonary microvascular dysfunction and irreversible pulmonary microvascular destruction.

Effect of Breathing Oxygen-Enriched Air on Exercise Performance in Patients with Chronic Obstructive Pulmonary Disease: Randomized, Placebo-Controlled, Cross-Over Trial

BACKGROUND

Patients with chronic obstructive pulmonary disease (COPD) experience dyspnea and hypoxemia during exercise.

OBJECTIVE

The aim of this study was to evaluate the effects of breathing oxygen-enriched air on exercise performance and associated physiological changes in patients with COPD.

METHODS

In a randomized, placebo-controlled, single-blind, cross-over trial, 20 patients with COPD (11 women, age 65 ± 6 years, FEV1 64 ± 19% pred., resting SpO2 ≥90%) performed 4 cycle ergospirometries to exhaustion using an incremental exercise test (IET) and a constant work rate (at 75% maximal workload with air) exercise test (CWRET), each with ambient (FiO2 0.21) and oxygen-enriched (FiO2 0.5) air. The main outcomes were the change in maximal workload in the IET and the change in exercise duration in the CWRET with oxygen versus air. Electrocardiogram, pulmonary gas exchange, thoracic volumes by inductance plethysmography, arterial blood gases, and cerebral and quadriceps muscle tissue oxygenation (CTO and MTO) were additionally measured.

RESULTS

In the IET, maximal workload increased from 96 ± 21 to 104 ± 28 W with oxygen. In the CWRET, exercise duration increased from 605 ± 274 to 963 ± 444 s with oxygen. At end-exercise with oxygen, CTO, MTO, PaO2, and PaCO2 were increased, while V'E/V'CO2 was reduced and thoracic volumes were similar. At the corresponding time to end of exercise with ambient air, oxygen decreased heart rate, respiratory rate, minute ventilation, and V'E/V'CO2, while oxygenation was increased.

CONCLUSION

In COPD patients without resting hypoxemia, breathing oxygen-enriched air improves exercise performance. This relates to a higher arterial oxygen saturation promoting oxygen availability to muscle and cerebral tissue and an enhanced ventilatory efficiency. COPD patients may benefit from oxygen therapy during exercise training.

Effects of Pulmonary Hypertension on Exercise Capacity in Patients With Chronic Obstructive Pulmonary Disease

INTRODUCTION

The impact of pulmonary hypertension (PH) on exercise tolerance in chronic obstructive pulmonary disease (COPD) has not been fully elucidated. It is necessary to characterize pulmonary hemodynamics in patients with moderate to severe COPD in order to improve their management. The aim of the study was to determine whether in COPD the presence of PH is associated with reduced exercise tolerance in a cohort of stable COPD patients.

METHODS

Cross-sectional analysis of 174 COPD patients clinically stable: 109 without PH and 65 with PH (COPD-PH). We assessed socio-demographic data, lung function, quality of life, dyspnea, cardiopulmonary exercise testing (CPET), constant workload endurance time (CWET), and six-minute walk test (6MWT). We elaborated a logistic regression model to explore the impact of PH on exercise capacity in COPD patients.

RESULTS

COPD-PH patients showed lower exercise capacity both at maximal (CPET) (43(20) versus 68(27) Watts and 50(19)% versus 71(18)% predicted peak oxygen consumption (VO₂peak), COPD-PH and COPD, respectively), and at submaximal tests (6MWT) (382(94) versus 486(95) m). In addition, the COPD-PH group had lower endurance time than the non-PH COPD group (265(113) s and 295(164) s, respectively).

CONCLUSIONS

The presence of PH is an independent factor that impairs exercise capacity in COPD.

Effect of pre-discharge cardiopulmonary fitness on outcomes in patients with ST-elevation myocardial infarction after percutaneous coronary intervention

BACKGROUND

The purpose of this study was to analyze cardiopulmonary fitness in Phase I cardiac rehabilitation on the prognosis of patients with ST-Elevation Myocardial Infarction (STEMI) after percutaneous coronary intervention (PCI).

METHODS

The study enrolled a total of 499 STEMI patients treated with PCI between January 2015 and December 2015. Patients were assigned to individualized exercise prescriptions (IEP) group and non-individualized exercise prescriptions (NIEP) group according to whether they accept or refuse individualized exercise prescriptions. We compared the incidence of major cardiovascular events between the two groups. IEP group were further divided into two subgroups based on prognosis status, namely good prognosis (GP) group and poor prognosis (PP) group. Key cardio-pulmonary exercise testing (CPX) variables that may affect the prognosis of patients were identified through comparison of the cardio-respiratory fitness (CRF).

RESULTS

There is no significant difference in the incidence of cardio-genetic death, re-hospitalization, heart failure, stroke, or atrial fibrillation between the IEP and the NIEP group. But the incidence of total major adverse cardiac events (MACE) was significantly lower in the IEP group than in the NIEP group (P = 0.039). The oxygen consumption (VO₂) at ventilation threshold (VT), minute CO₂ ventilation (E-VCO₂), margin of minute ventilation carbon dioxide production (△CO₂)_, rest partial pressure of end-tidal carbon dioxide(R-P_ETCO₂), exercise partial pressure of end-tidal carbon dioxide(E-P_ETCO₂) and margin of partial pressure of end-tidal carbon dioxide(△P_ETCO₂) were significantly higher in the GP subgroup than in the PP subgroup; and the slope for minute ventilation/carbon dioxide production (V_E/VCO₂) was significantly lower in GP subgroup than in PP subgroup (P = 0.010). The VO₂ at VT, V_E/VCO₂ slope, E-VCO₂, △CO₂, R-P_ETCO₂, E-P_ETCO₂ and margin of partial pressure of end-tidal carbon dioxide CO₂ (△P_ETCO₂) were predictive of adverse events. The VO₂ at VT was an independent risk factor for cardiovascular disease prognosis.

CONCLUSIONS

Individualized exercise prescription of Phase I cardiac rehabilitation reduced the incidence of cardiovascular events in patients with STEMI after PCI. VO₂ at VT is an independent risk factor for cardiovascular disease prognosis, and could be used as an important evaluating indicator for Phase I cardiac rehabilitation.

Cardiopulmonary exercise test and PaO2 in evaluation of pulmonary hypertension in COPD

Background

Exercise tolerance decreases as COPD progresses. Pulmonary hypertension (PH) is common in COPD and may reduce performance further. COPD patients with and without PH could potentially be identified by cardiopulmonary exercise test (CPET). However, results from previous studies are diverging, and a unified conclusion is missing. We hypothesized that CPET combined with arterial blood gases is useful to discriminate between COPD outpatients with and without PH.

Methods

In total, 93 COPD patients were prospectively included. Pulmonary function tests, right heart catheterization, and CPET with blood gases were performed. The patients were divided, by mean pulmonary artery pressure, into COPD-noPH (<25 mmHg) and COPD-PH (≥25 mmHg) groups. Linear mixed models (LMMs) were fitted to estimate differences when repeated measurements during the course of exercise were considered and adjusted for gender, age, and airway obstruction.

Results

Ventilatory and/or hypoxemic limitation was the dominant cause of exercise termination. In LMM analyses, significant differences between COPD-noPH and COPD-PH were observed for PaO₂, SaO₂, PaCO₂, ventilation, respiratory frequency, and heart rate. PaO₂ <61 mmHg (8.1 kPa) during unloaded pedaling, the only load level achieved by all the patients, predicted PH with a sensitivity of 86% and a specificity of 78%.

Conclusion

During CPET, low exercise performance and PaO₂ strongly indicated PH in COPD patients.

An official European Respiratory Society statement: pulmonary haemodynamics during exercise

There is growing recognition of the clinical importance of pulmonary haemodynamics during exercise, but several questions remain to be elucidated. The goal of this statement is to assess the scientific evidence in this field in order to provide a basis for future recommendations.

Right heart catheterisation is the gold standard method to assess pulmonary haemodynamics at rest and during exercise. Exercise echocardiography and cardiopulmonary exercise testing represent non-invasive tools with evolving clinical applications. The term “exercise pulmonary hypertension” may be the most adequate to describe an abnormal pulmonary haemodynamic response characterised by an excessive pulmonary arterial pressure (PAP) increase in relation to flow during exercise. Exercise pulmonary hypertension may be defined as the presence of resting mean PAP <25 mmHg and mean PAP >30 mmHg during exercise with total pulmonary resistance >3 Wood units. Exercise pulmonary hypertension represents the haemodynamic appearance of early pulmonary vascular disease, left heart disease, lung disease or a combination of these conditions. Exercise pulmonary hypertension is associated with the presence of a modest elevation of resting mean PAP and requires clinical follow-up, particularly if risk factors for pulmonary hypertension are present. There is a lack of robust clinical evidence on targeted medical therapy for exercise pulmonary hypertension.

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

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

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

2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension

Guidelines summarize and evaluate all available evidence on a particular issue at the time of the writing process, with the aim of assisting health professionals in selecting the best management strategies for an individual patient with a given condition, taking into account the impact on outcome, as well as the risk–benefit ratio of particular diagnostic or therapeutic means. Guidelines and recommendations should help health professionals to make decisions in their daily practice. However, the final decisions concerning an individual patient must be made by the responsible health professional(s) in consultation with the patient and caregiver as appropriate.

Use of pulmonary arterial hypertension-approved therapy in the treatment of non-group 1 pulmonary hypertension at US referral centers

Pulmonary hypertension (PH) is a frequent complication of left heart disease and parenchymal lung disease, and it portends increased mortality. A growing number of medications are approved for the treatment of World Health Organization (WHO) group 1 pulmonary arterial hypertension (PAH). However, they are not well studied in PH of other etiologies (WHO groups 2-5). We sought to assess treatment approaches used by PAH referral centers in this diverse group of patients. We developed a semiquantitative online survey designed to evaluate the use of PAH-approved therapy by pulmonary vascular disease centers in the United States for management of non-group 1 PH. Thirty of 50 centers completed the survey. Almost all centers (93%) reported using PAH therapy for patients with non-group 1 PH, including 77% with group 2 PH and 80% with group 3 PH. Elevated transpulmonary gradient or pulmonary vascular resistance and the presence of right ventricular (RV) dysfunction were commonly cited as supporting use of PAH therapy in patients with PH secondary to left heart disease. For patients with PH and concomitant parenchymal lung disease, degree of pulmonary function impairment and RV dysfunction were most important in influencing use of PAH therapy. In conclusion, pulmonary vascular disease treatment centers use PAH-approved therapy for patients with WHO group 2-5 PH, mostly relying on hemodynamics and assessment of RV function to identify candidates for therapy. Clinical trials designed to test the efficacy of PAH therapy in PH due to left heart and lung disease are needed, as clinical practice has extended beyond the evidence for these etiologies of PH.

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

Background

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

Methods

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

Results

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

Conclusion

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

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.

Long-term effect of vasodilator therapy in pulmonary hypertension due to COPD: a retrospective analysis

PURPOSE

Pulmonary hypertension (PH) due to COPD has dismal prognosis. We reviewed the long-term effect of PH-target therapy in severe PH-COPD.

METHOD

Patients attending our PH-clinic were reviewed for PH-COPD receiving PH-target therapy. Baseline characteristics, death/transplantation until 2014, therapy, NYHA functional class, 6 min walk distance (6MWD) and oxygen saturation (SpO(2)) at baseline, 3, 6, 12 and 24 months were analysed.

RESULTS

Of 48 PH-COPD identified 21 were excluded (insufficient data, comorbidity). 27 patients (7 females, 21 smokers, 23 emphysema) with median (quartiles) baseline age 70 (60; 76) years, FEV1 60 (46; 78) %, FEV1/FVC 57 (51; 64) %, DLCO 42 (36; 59) %, mean pulmonary artery pressure 39 (32;44) mmHg under inhaled iloprost (10), subcutaneous prostanoids (2), intravenous prostanoids (3), endothelin receptor antagonists (15) and phosphodiesterase-5-inhibitors (25) were included. Under therapy, NYHA functional class improved from 3.5 (3; 4) to 3 (2; 4) after 3 months and 3 (2; 3.5) after 6 months (p = .02 and .008). The 6MWD improved from 373 (236; 452) to 395 (339; 472), 414 (285; 492) and 396 (308; 497)m at 3, 6 and 12 months (p = .005, .006 and .011) with unchanged resting-SpO(2) but decreased peak-exercise SpO(2). During median follow-up of 5.9 (2.3; 8.4) years, 10 died, 2 were transplanted and 2 were lost to follow-up. Transplant-free survival at 1,2,3 years was 92,69,54 % and was similar for GOLD stages 1-4, but worse for patients with mPAP ≥40 mmHg (p = .026), 6MWD <370 m (p = 0.008), resting SpO(2) <92 % (p = 0.02) and peak-walk SpO(2) <87 % (p = 0.012).

CONCLUSION

PH-target vasodilator therapy improved NYHA functional class and 6MWD up to one year in highly selected patients with severe PH-COPD. Poor exercise capacity, low SpO(2) and high mean pulmonary artery pressure at baseline but not airflow obstruction were associated with unfavourable outcome.

Exercise tolerance, lung function abnormalities, anemia, and cardiothoracic ratio in sickle cell patients

Many patients with sickle cell disease (SCD) have a reduced exercise capacity and abnormal lung function. Cardiopulmonary exercise testing (CPET) can identify causes of exercise limitation. Forty-four consecutive SCD patients (27 HbSS, 11 HbSC, and 6 HbS-beta thalassemia) with a median age (interquartile range) of 26 (21-41) years underwent pulmonary function tests, CPET, chest x-ray, and echocardiography to further characterize exercise limitation in SCD. Peak oxygen uptake (V'O2 -peak), expressing maximum exercise capacity, was decreased in 83% of the studied patients. V'O2 -peak correlated with hemoglobin levels (R = 0.440, P = 0.005), forced vital capacity (FVC) (R = 0.717, P < 0.0001). Cardiothoracic ratio on chest x-ray inversely correlated with FVC (R = -0.637, P < 0.001). According to criteria for exercise limitation, the patients were limited in exercise capacity due to anemia (n = 17), cardiovascular dysfunction (n = 2), musculoskeletal function (n = 10), pulmonary ventilatory abnormalities (n = 1), pulmonary vascular exercise limitation (n = 1), and poor effort (n = 3). In the present study we demonstrate that anemia is the most important determinant of reduced exercise tolerance observed in SCD patients without signs of pulmonary hypertension. We found a strong correlation between various parameters of lung volume and cardiothoracic ratio and we hypothesize that cardiomegaly and relative small chest size may be important causes of the impairment in pulmonary function, that is, reduced long volumes and diffusion capacity, in SCD. Taking into account anthropomorphic differences between SCD patients and controls could help to interpret lung function studies in SCD better.

Chronotropic incompetence predicts mortality in severe obstructive pulmonary disease

We evaluated the prevalence of chronotropic incompetence (CI), a marker of autonomic dysfunction, and its prognostic value in patients with chronic obstructive pulmonary disease (COPD). We performed a retrospective analysis of 449 patients with severe COPD who underwent a cardiopulmonary exercise test, after excluding patients with lung volume reduction surgery, left ventricular dysfunction and those not in sinus rhythm. CI was defined as percent predicted heart rate reserve (%HRR). Events were defined as death or lung transplant during a median follow-up of 68 months. Median age was 61 years; median percent predicted forced expiratory volume in one second (%FEV1) of 25% and median %HRR of 33%. The hazard ratio for an event in the lowest quartile of %HRR, taking the highest quartile as reference, was of 3.2 (95% confidence interval: 2.1-4.8; p<0.001). In a multivariate regression model, %HRR was an independent predictor of events. In conclusion, CI was an independent and powerful outcome predictor in patients with severe COPD.

The influence of systematic pulse-limited physical exercise on the parameters of the cardiovascular system in patients over 65 years of age

INTRODUCTION

The influence of physical exercise on the parameters of the cardiovascular system of elderly persons has not been sufficiently investigated yet. The aim of the study was to assess the influence of regular 6-week physical exercise using the Nordic walking (NW) method in a group of elderly persons on their physical performance and regulation of selected parameters assessing the cardiovascular system.

MATERIAL AND METHODS

Fifty patients over 65 years of age participated in the study. The study encompassed: medical interview, physical examination, resting ECG, spiroergometry examination, 6MWT (6-minute walk test) and 24-hour ambulatory blood pressure monitoring (ABPM). During the exercise programme, the pulse was monitored using pulsometers. After the completion of the training, check-up tests assessing the same parameters were performed. The control group consisted of 18 persons over 65 years of age with similar cardiovascular problems.

RESULTS

In the test group, duration of the physical effort increased by 1.02 min (p = 0.0001), the maximum load increased by 10.68 W (p = 0.0001), values of VO2max by 2.10 (p = 0.0218), distance improved in 6MWT by 75.04 m (p = 0.00001), systolic blood pressure decreased by 5.50 mm Hg (p = 0.035) and diastolic blood pressure by 3.50 mm Hg (p = 0.054) as compared to the control group.

CONCLUSIONS

Systematic NW physical exercise limited by the pulse had a beneficial effect on the physical performance of elderly persons as assessed with main parameters. A short 6-week programme of endurance exercises had a hypotensive effect in elderly persons over 65 years of age.

Ventilatory and cardiocirculatory exercise profiles in COPD: the role of pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) is a well-recognized complication of COPD. The impact of PH on exercise tolerance is largely unknown. We evaluated and compared the circulatory and ventilatory profiles during exercise in patients with COPD without PH, with moderate PH, and with severe PH.

METHODS

Forty-seven patients, GOLD (Global Initiative for Chronic Obstructive Lung Disease)stages II to IV, underwent cardiopulmonary exercise testing and right-sided heart catheterization at rest and during exercise. Patients were divided into three groups based on mean pulmonary artery pressure (mPAP) at rest: no PH (mPAP, < 25 mm Hg), moderate PH (mPAP, 25-39 mm Hg),and severe PH (mPAP, ≥ 40 mm Hg). Mixed venous oxygen saturation (S VO 2 ) was used for evaluating the circulatory reserve. Pa CO 2 and the calculated breathing reserve were used for evaluation of the ventilatory reserve.

RESULTS

Patients without PH (n = 24) had an end-exercise S VO 2 of 48%± 9%, an increasing Pa CO 2 with exercise, and a breathing reserve of 22% ± 20%. Patients with moderate PH (n = 14) had an exercise S VO 2 of 40% ± 8%, an increasing Pa CO 2 , and a breathing reserve of 26% ± 15%. Patients with severe PH (n =9) had a significantly lower end-exercise S VO 2 (30% ± 6%), a breathing reserve of 37% ± 11%, and an absence of Pa CO 2 accumulation.

CONCLUSION

Patients with severe PH showed an exhausted circulatory reserve at the end of exercise.A profile of circulatory reserve in combination with ventilatory impairments was found inpatients with COPD and moderate or no PH. The results suggest that pulmonary vasodilation might only improve exercise tolerance in patients with COPD and severe PH.

Pulmonary Hypertension Secondary to COPD

The development of pulmonary hypertension in COPD adversely affects survival and exercise capacity and is associated with an increased risk of severe acute exacerbations. Unfortunately not all patients with COPD who meet criteria for long term oxygen therapy benefit from it. Even in those who benefit from long term oxygen therapy, such therapy may reverse the elevated pulmonary artery pressure but cannot normalize it. Moreover, the recent discovery of the key roles of endothelial dysfunction and inflammation in the pathogenesis of PH provides the rationale for considering specific pulmonary vasodilators that also possess antiproliferative properties and statins.

Exercise intolerance in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is associated with symptoms of dyspnea and fatigue, which contribute to exercise limitation. The origins and significance of dyspnea and fatigue in PAH are not completely understood. This has created uncertainly among healthcare professionals regarding acceptable levels of these symptoms, on exertion, for patients with PAH. Dysfunction of the right ventricle (RV) contributes to functional limitation and mortality in PAH; however, the role of the RV in eliciting dyspnea and fatigue has not been thoroughly examined. This paper explores the contribution of the RV and systemic and peripheral abnormalities to exercise limitation and symptoms in PAH. Further, it explores the relationship between exercise abnormalities and symptoms, the utility of the cardiopulmonary exercise test in identifying RV dysfunction, and offers suggestions for further research.

Right ventricular dysfunction in chronic lung disease

Right ventricular (RV) dysfunction arises in chronic lung disease when chronic hypoxemia and disruption of pulmonary vascular beds increase ventricular afterload. RV dysfunction is defined by hypertrophy with preserved myocardial contractility and cardiac output. RV hypertrophy seems to be a common complication of chronic and advanced lung disease. RV failure is rare, except during acute exacerbations of chronic lung disease or when multiple comorbidities are present. Treatment is targeted at correcting hypoxia and improving pulmonary gas exchange and mechanics. There are no data supporting the use of pulmonary hypertension-specific therapies for patients with RV dysfunction secondary to chronic lung disease.

Cardiopulmonary exercise testing in the assessment of pulmonary hypertension

The assessment of patients with suspected or confirmed pulmonary arterial hypertension (PAH) and secondary pulmonary hypertension (PH) continues to evolve and, in recent years, evidence demonstrating that cardiopulmonary exercise testing (CPX) provides valuable information has grown at an impressive rate. The key premise supporting the use of CPX is that certain variables obtained provide insight into the degree of ventilation/perfusion mismatching secondary to altered pulmonary hemodynamics. In this article, we discuss the pathophysiology of PAH and secondary PH and its impact on cardiac function, review the clinical presentation of patients with elevated pulmonary pressures and outline a case for the use of CPX as an integral assessment technique, discuss CPX technology and testing procedures, and review the current state of available evidence and provide clinical recommendations for CPX in the setting of known or suspected PAH and secondary PH.

COPD/emphysema: The vascular story

In this perspective, we review published data which support the concept that many or most chronic and progressive lung diseases also involve the lung vessels and that microvascular abnormalities and endothelial cell death contribute to the pathobiology of emphysema. Lung vessel maintenance depends on Vascular Endothelial Growth Factor signaling and both are compromised in the emphysematous lung tissue. Although hypoxic pulmonary vasoconstriction has been considered as an important factor contributing to the vascular remodeling in chronic obstructive pulmonary disease (COPD) (COPD/emphysema, it is now clear that inhaled cigarette smoke can damage the lung vessels independent of the lung vascular tone. We propose that a "sick lung circulation" rather than the right heart afterload may better explain the cardiac abnormalities in COPD patients which are usually summarized with the term "cor pulmonale." The mechanisms and causes of pulmonary hypertension are likely complex and include vessel loss, in situ thrombosis, and endothelial cell dysfunction. Assessment of the functional importance of pulmonary hypertension in COPD requires hemodynamic measurements during exercise.

Cardiopulmonary exercise testing: relevant but underused

Cardiopulmonary exercise testing (CPX) is a relatively old technology, but has sustained relevance for many primary care clinical scenarios in which it is, ironically, rarely considered. Advancing computer technology has made CPX easier to administer and interpret at a time when our aging population is more prone to comorbidities and higher prevalence of nonspecific symptoms of exercise intolerance and dyspnea, for which CPX is particularly useful diagnostically and prognostically. These discrepancies in application are compounded by patterns in which CPX is often administered and interpreted by cardiology, pulmonary, or exercise specialists who limit their assessments to the priorities of their own discipline, thereby missing opportunities to distinguish symptom origins. When used properly, CPX enables the physician to assess fitness and uncover cardiopulmonary issues at earlier phases of work-up, which would therefore be especially useful for primary care physicians. In this article, we provide an overview of CPX principles and testing logistics, as well as some of the clinical contexts in which it can enhance patient care.

Walk-run transition in young and older adults: with special reference to the cardio-respiratory responses

Cardio-respiratory responses of young and older subjects performing walking and running protocols at the walk-run transition speed (WRT) were compared. A total of 26 volunteers assigned to younger (YG, 24 +/- 3 years) and older (OG, 64 +/- 6 years) groups underwent a protocol to determine the WRT used in 6-min walking and running protocols. Oxygen uptake (VO(2)), ventilation (V (E)), expired carbon dioxide (VCO(2)), heart rate (HR) and perceived exertion (RPE) were assessed. Oxygen pulse (O(2) pulse) and respiratory exchange ratio (RER) were calculated. The WRT was not different between groups (OG: 6.84 +/- 0.69 km h(-1) vs. YG: 7.04 +/- 0.77 km h(-1), P = 0.62). No between-group differences were found within a given gait pattern for VO(2) (P = 0.061) and VCO(2) (P = 0.076). However, VO(2) (P = 0.0022) and VCO(2) (P = 0.0041) increased in OG when running, remaining stable in YG (VO(2): P = 0.622; VCO(2): P = 0.412). The VE was higher in OG compared to YG in walking (P = 0.030) and running (P = 0.004) protocols. No age-related (P = 0.180) or locomotion (P = 0.407) effects were found for RER. The HR increased in OG and between-group difference was detected while running (P = 0.003). No within- (P = 0.447) or between-group (P = 0.851) difference was found for O(2) pulse. The net VO(2) increased from walking to running in OG (P < 0.0001) but not in YG (P = 0.53), while RPE was lower in YG (P = 0.041) but stable in OG (P = 0.654). In conclusion, the WRT speed was similar across the age groups. However, the VO(2) and VCO(2) increase from walking to running was larger for OG than YG. The HR, VE and RPE were also higher when running in OG compared to YG. Therefore, the locomotion strategy had different impacts on the metabolic demand of older and younger subjects.