Right ventricular dysfunction and the exercise limitation of chronic obstructive pulmonary disease

Haemodynamic compensations for exercise tissue oxygenation in early stages of COPD: an integrated cardiorespiratory assessment study

BACKGROUND

Cardiovascular comorbidities are increasingly being recognised in early stages of chronic obstructive pulmonary disease (COPD) yet complete cardiorespiratory functional assessments of individuals with mild COPD or presenting with COPD risk factors are lacking. This paper reports on the effectiveness of the cardiocirculatory-limb muscles oxygen delivery and utilisation axis in smokers exhibiting no, or mild to moderate degrees of airflow obstruction using standardised cardiopulmonary exercise testing (CPET).

METHODS

Post-bronchodilator spirometry was used to classify participants as 'ever smokers without' (n=88), with 'mild' (n=63) or 'mild-moderate' COPD (n=56). All underwent CPET with continuous concurrent monitoring of oxygen uptake (V'O2) and of bioimpedance cardiac output (Qc) enabling computation of arteriovenous differences (a-vO2). Mean values of Qc and a-vO2 were mapped across set ranges of V'O2 and Qc isolines to allow for meaningful group comparisons, at same metabolic and circulatory requirements.

RESULTS

Peak exercise capacity was significantly reduced in the 'mild-moderate COPD' as compared with the two other groups who showed similar pulmonary function and exercise capacity. Self-reported cardiovascular and skeletal muscle comorbidities were not different between groups, yet disease impact and exercise intolerance scores were three times higher in the 'mild-moderate COPD' compared with the other groups. Mapping of exercise Qc and a-vO2 also showed a leftward shift of values in this group, indicative of a deficit in peripheral O2 extraction even for submaximal exercise demands. Concurrent with lung hyperinflation, a distinctive blunting of exercise stroke volume expansion was also observed in this group.

CONCLUSION

Contrary to the traditional view that cardiovascular complications were the hallmark of advanced disease, this study of early COPD spectrum showed a reduced exercise O2 delivery and utilisation in individuals meeting spirometry criteria for stage II COPD. These findings reinforce the preventive clinical management approach to preserve peripheral muscle circulatory and oxidative capacities.

Effect of Dynamic Hyperinflation on Cardiac Response to Exercise of Patients With Chronic Obstructive Pulmonary Disease

INTRODUCTION

Although the major limitation to exercise performance in patients with COPD is dynamic hyperinflation (DH), little is known about its relation with cardiac response to exercise. Our objectives were to compare the exercise response of stroke volume (SV) and cardiac output (CO) between COPD patients with or without DH and control subjects, and to assess the main determinants.

METHODS

Fifty-seven stable COPD patients without cardiac comorbidity and 25 healthy subjects were recruited. Clinical evaluation, baseline function tests, computed tomography and echocardiography were conducted in all subjects. Patients performed consecutive incremental exercise tests with measurement of operating lung volumes and non-invasive measurement of SV, CO and oxygen uptake (VO₂) by an inert gas rebreathing method. Biomarkers of systemic inflammation and oxidative stress, tissue damage/repair, cardiac involvement and airway inflammation were measured.

RESULTS

COPD patients showed a lower SV/VO₂ slope than control subjects, while CO response was compensated by a higher heart rate increase. COPD patients with DH experienced a reduction of SV/VO₂ and CO/VO₂ compared to those without DH. In COPD patients, the end-expiratory lung volume (EELV) increase was related to SV/VO₂ and CO/VO₂ slopes, and it was the only independent predictor of cardiac response to exercise. However, in the regression models without EELV, plasma IL-1β and high-sensitivity cardiac troponin T were also retained as independent predictors of SV/VO₂ slope.

CONCLUSION

Dynamic hyperinflation decreases the cardiac response to exercise of COPD patients. This effect is related to systemic inflammation and myocardial stress but not with left ventricle diastolic dysfunction.

Renin-Angiotensin-Aldosterone System Inhibitor Use and Mortality in Pulmonary Hypertension: Insights From the Veterans Affairs Clinical Assessment Reporting and Tracking Database

BACKGROUND

The renin-angiotensin-aldosterone system (RAAS) contributes to pulmonary hypertension (PH) pathogenesis. Although animal data suggest that RAAS inhibition attenuates PH, it is unknown if RAAS inhibition is beneficial in PH patients.

RESEARCH QUESTION

Is RAAS inhibitor use associated with lower mortality in a large cohort of patients with hemodynamically confirmed PH?

STUDY DESIGN AND METHODS

We used the Department of Veterans Affairs Clinical Assessment Reporting and Tracking Database to study retrospectively relationships between RAAS inhibitors (angiotensin converting enzyme inhibitors [ACEIs], angiotensin receptor blockers [ARBs], and aldosterone antagonists [AAs]) and mortality in 24,221 patients with hemodynamically confirmed PH. We evaluated relationships in the full and in propensity-matched cohorts. Analyses were adjusted for demographics, socioeconomic status, comorbidities, disease severity, and comedication use in staged models.

RESULTS

ACEI and ARB use was associated with improved survival in unadjusted Kaplan-Meier survival analyses in the full cohort and the propensity-matched cohort. This relationship was insensitive to adjustment, independent of pulmonary artery wedge pressure, and also was observed in a cohort restricted to individuals with precapillary PH. AA use was associated with worse survival in unadjusted Kaplan-Meier survival analyses in the full cohort; however, AA use was associated less robustly with mortality in the propensity-matched cohort and was not associated with worse survival after adjustment for disease severity, indicating that AAs in real-world practice are used preferentially in sicker patients and that the unadjusted association with increased mortality may be an artifice of confounding by indication of severity.

INTERPRETATION

ACEI and ARB use is associated with lower mortality in veterans with PH. AA use is a marker of disease severity in PH. ACEIs and ARBs may represent a novel treatment strategy for diverse PH phenotypes.

Effect of Dynamic Hyperinflation on Cardiac Response to Exercise of Patients With Chronic Obstructive Pulmonary Disease

INTRODUCTION

Although the major limitation to exercise performance in patients with COPD is dynamic hyperinflation (DH), little is known about its relation with cardiac response to exercise. Our objectives were to compare the exercise response of stroke volume (SV) and cardiac output (CO) between COPD patients with or without DH and control subjects, and to assess the main determinants.

METHODS

Fifty-seven stable COPD patients without cardiac comorbidity and 25 healthy subjects were recruited. Clinical evaluation, baseline function tests, computed tomography and echocardiography were conducted in all subjects. Patients performed consecutive incremental exercise tests with measurement of operating lung volumes and non-invasive measurement of SV, CO and oxygen uptake (VO₂) by an inert gas rebreathing method. Biomarkers of systemic inflammation and oxidative stress, tissue damage/repair, cardiac involvement and airway inflammation were measured.

RESULTS

COPD patients showed a lower SV/VO₂ slope than control subjects, while CO response was compensated by a higher heart rate increase. COPD patients with DH experienced a reduction of SV/VO₂ and CO/VO₂ compared to those without DH. In COPD patients, the end-expiratory lung volume (EELV) increase was related to SV/VO₂ and CO/VO₂ slopes, and it was the only independent predictor of cardiac response to exercise. However, in the regression models without EELV, plasma IL-1β and high-sensitivity cardiac troponin T were also retained as independent predictors of SV/VO₂ slope.

CONCLUSION

Dynamic hyperinflation decreases the cardiac response to exercise of COPD patients. This effect is related to systemic inflammation and myocardial stress but not with left ventricle diastolic dysfunction.

Sex, Gender, and Sex Hormones in Pulmonary Hypertension and Right Ventricular Failure

Pulmonary hypertension (PH) encompasses a syndrome of diseases that are characterized by elevated pulmonary artery pressure and pulmonary vascular remodeling and that frequently lead to right ventricular (RV) failure and death. Several types of PH exhibit sexually dimorphic features in disease penetrance, presentation, and progression. Most sexually dimorphic features in PH have been described in pulmonary arterial hypertension (PAH), a devastating and progressive pulmonary vasculopathy with a 3-year survival rate <60%. While patient registries show that women are more susceptible to development of PAH, female PAH patients display better RV function and increased survival compared to their male counterparts, a phenomenon referred to as the "estrogen paradox" or "estrogen puzzle" of PAH. Recent advances in the field have demonstrated that multiple sex hormones, receptors, and metabolites play a role in the estrogen puzzle and that the effects of hormone signaling may be time and compartment specific. While the underlying physiological mechanisms are complex, unraveling the estrogen puzzle may reveal novel therapeutic strategies to treat and reverse the effects of PAH/PH. In this article, we (i) review PH classification and pathophysiology; (ii) discuss sex/gender differences observed in patients and animal models; (iii) review sex hormone synthesis and metabolism; (iv) review in detail the scientific literature of sex hormone signaling in PAH/PH, particularly estrogen-, testosterone-, progesterone-, and dehydroepiandrosterone (DHEA)-mediated effects in the pulmonary vasculature and RV; (v) discuss hormone-independent variables contributing to sexually dimorphic disease presentation; and (vi) identify knowledge gaps and pathways forward. © 2020 American Physiological Society. Compr Physiol 10:125-170, 2020.

Assessment of Right Ventricular Function in the Research Setting: Knowledge Gaps and Pathways Forward. An Official American Thoracic Society Research Statement

BACKGROUND

Right ventricular (RV) adaptation to acute and chronic pulmonary hypertensive syndromes is a significant determinant of short- and long-term outcomes. Although remarkable progress has been made in the understanding of RV function and failure since the meeting of the NIH Working Group on Cellular and Molecular Mechanisms of Right Heart Failure in 2005, significant gaps remain at many levels in the understanding of cellular and molecular mechanisms of RV responses to pressure and volume overload, in the validation of diagnostic modalities, and in the development of evidence-based therapies.

METHODS

A multidisciplinary working group of 20 international experts from the American Thoracic Society Assemblies on Pulmonary Circulation and Critical Care, as well as external content experts, reviewed the literature, identified important knowledge gaps, and provided recommendations.

RESULTS

This document reviews the knowledge in the field of RV failure, identifies and prioritizes the most pertinent research gaps, and provides a prioritized pathway for addressing these preclinical and clinical questions. The group identified knowledge gaps and research opportunities in three major topic areas: 1) optimizing the methodology to assess RV function in acute and chronic conditions in preclinical models, human studies, and clinical trials; 2) analyzing advanced RV hemodynamic parameters at rest and in response to exercise; and 3) deciphering the underlying molecular and pathogenic mechanisms of RV function and failure in diverse pulmonary hypertension syndromes.

CONCLUSIONS

This statement provides a roadmap to further advance the state of knowledge, with the ultimate goal of developing RV-targeted therapies for patients with RV failure of any etiology.

Exercise gas exchange in continuous-flow left ventricular assist device recipients

Exercise ventilation/perfusion matching in continuous-flow left ventricular assist device recipients (LVAD) has not been studied systematically. Twenty-five LVAD and two groups of 15 reduced ejection fraction chronic heart failure (HFrEF) patients with peak VO₂ matched to that of LVAD (HFrEF-matched) and ≥14 ml/kg/min (HFrEF≥14), respectively, underwent cardiopulmonary exercise testing with arterial blood gas analysis, echocardiogram and venous blood sampling for renal function evaluation. Arterial-end-tidal PCO₂ difference (P(a-ET)CO₂) and physiological dead space-tidal volume ratio (VD/VT) were used as descriptors of alveolar and total wasted ventilation, respectively. Tricuspid annular plane systolic excursion/pulmonary artery systolic pressure ratio (TAPSE/PASP) and blood urea nitrogen/creatinine ratio were calculated in all patients and used as surrogates of right ventriculo-arterial coupling and circulating effective volume, respectively. LVAD and HFrEF-matched showed no rest-to-peak change of P(a-ET)CO₂ (4.5±2.4 vs. 4.3±2.2 mm Hg and 4.1±1.4 vs. 3.8±2.5 mm Hg, respectively, both p >0.40), whereas a decrease was observed in HFrEF≥14 (6.5±3.6 vs. 2.8±2.0 mm Hg, p <0.0001). Rest-to-peak changes of P(a-ET)CO₂ correlated to those of VD/VT (r = 0.70, p <0.0001). Multiple regression indicated TAPSE/PASP and blood urea nitrogen/creatinine ratio as independent predictors of peak P(a-ET)CO₂. LVAD exercise gas exchange is characterized by alveolar wasted ventilation, i.e. hypoperfusion of ventilated alveoli, similar to that of advanced HFrEF patients and related to surrogates of right ventriculo-arterial coupling and circulating effective volume.

The Link between Reduced Inspiratory Capacity and Exercise Intolerance in Chronic Obstructive Pulmonary Disease

Low inspiratory capacity (IC), chronic dyspnea, and reduced exercise capacity are inextricably linked and are independent predictors of increased mortality in chronic obstructive pulmonary disease. It is no surprise, therefore, that a major goal of management is to improve IC by reducing lung hyperinflation to improve respiratory symptoms and health-related quality of life. The negative effects of lung hyperinflation on respiratory muscle and cardiocirculatory function during exercise are now well established. Moreover, there is growing appreciation that a key mechanism of exertional dyspnea in chronic obstructive pulmonary disease is critical mechanical constraints on tidal volume expansion during exercise when resting IC is reduced. Further evidence for the importance of lung hyperinflation comes from multiple studies, which have reported the clinical benefits of therapeutic interventions that reduce lung hyperinflation and increase IC. A reduced IC in obstructive pulmonary disease is further eroded by exercise and contributes to ventilatory limitation and dyspnea. It is an important outcome for both clinical and research studies.

Diagnostic workup, etiologies and management of acute right ventricle failure : A state-of-the-art paper

INTRODUCTION

This is a state-of-the-art article of the diagnostic process, etiologies and management of acute right ventricular (RV) failure in critically ill patients. It is based on a large review of previously published articles in the field, as well as the expertise of the authors.

RESULTS

The authors propose the ten key points and directions for future research in the field. RV failure (RVF) is frequent in the ICU, magnified by the frequent need for positive pressure ventilation. While no universal definition of RVF is accepted, we propose that RVF may be defined as a state in which the right ventricle is unable to meet the demands for blood flow without excessive use of the Frank-Starling mechanism (i.e. increase in stroke volume associated with increased preload). Both echocardiography and hemodynamic monitoring play a central role in the evaluation of RVF in the ICU. Management of RVF includes treatment of the causes, respiratory optimization and hemodynamic support. The administration of fluids is potentially deleterious and unlikely to lead to improvement in cardiac output in the majority of cases. Vasopressors are needed in the setting of shock to restore the systemic pressure and avoid RV ischemia; inotropic drug or inodilator therapies may also be needed. In the most severe cases, recent mechanical circulatory support devices are proposed to unload the RV and improve organ perfusion CONCLUSION: RV function evaluation is key in the critically-ill patients for hemodynamic management, as fluid optimization, vasopressor strategy and respiratory support. RV failure may be diagnosed by the association of different devices and parameters, while echocardiography is crucial.

Sex-based differences in veterans with pulmonary hypertension: Results from the veterans affairs-clinical assessment reporting and tracking database

Women have an increased risk of pulmonary hypertension (PH) but better survival compared to men. Few studies have explored sex-based differences in population-based cohorts with PH. We sought to determine whether sex was associated with hemodynamics and survival in US veterans with PH (mean pulmonary artery pressure [mPAP] ≥ 25 mm Hg) from the Veterans Affairs Clinical Assessment, Reporting, and Tracking database. The relationship between sex and hemodynamics was assessed with multivariable linear mixed modeling. Cox proportional hazards models were used to compare survival by sex for those with PH and precapillary PH (mPAP ≥ 25 mm Hg, pulmonary artery wedge pressure [PAWP] ≤ 15 mm Hg and pulmonary vascular resistance [PVR] > 3 Wood units) respectively. The study population included 15,464 veterans with PH, 516 (3%) of whom were women; 1,942 patients (13%) had precapillary PH, of whom 120 (6%) were women. Among those with PH, women had higher PVR and pulmonary artery pulse pressure, and lower right atrial pressure and PAWP (all p <0.001) compared with men. There were no significant differences in hemodynamics according to sex in veterans with precapillary PH. Women with PH had 18% greater survival compared to men with PH (adjusted HR 0.82, 95% CI 0.69-0.97, p = 0.020). Similarly, women with precapillary PH were 29% more likely to survive as compared to men with PH (adjusted HR 0.71, 95% CI 0.52-0.98, p = 0.040). In conclusion, female veterans with PH have better survival than males despite higher pulmonary afterload.

Emerging role of angiogenesis in adaptive and maladaptive right ventricular remodeling in pulmonary hypertension

Right ventricular (RV) function is the primary prognostic factor for both morbidity and mortality in pulmonary hypertension (PH). RV hypertrophy is initially an adaptive physiological response to increased overload; however, with persistent and/or progressive afterload increase, this response frequently transitions to more pathological maladaptive remodeling. The mechanisms and disease processes underlying this transition are mostly unknown. Angiogenesis has recently emerged as a major modifier of RV adaptation in the setting of pressure overload. A novel paradigm has emerged that suggests that angiogenesis and angiogenic signaling are required for RV adaptation to afterload increases and that impaired and/or insufficient angiogenesis is a major driver of RV decompensation. Here, we summarize our current understanding of the concepts of maladaptive and adaptive RV remodeling, discuss the current literature on angiogenesis in the adapted and failing RV, and identify potential therapeutic approaches targeting angiogenesis in RV failure.

Influence of resting lung diffusion on exercise capacity in patients with COPD

Background

Lung diffusing capacity for carbon monoxide (DLCO) gives an overall assessment of functional lung surface area for gas exchange and can be assessed using various methods. DLCO is an important factor in exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). We investigated if the intra-breath (IBDLCO) method may give a more sensitive measure of available gas exchange surface area than the more typical single breath (SBDLCO) method and if COPD subjects with the largest resting DLCO relative to pulmonary blood flow (Qc) would have a more preserved exercise capacity.

Methods

Informed consent, hemoglobin, spirometry, SBDLCO, IBDLCO, and Qc during IBDLCO were performed in moderate to severe COPD patients, followed by progressive cycle ergometry to exhaustion with measures of oxygen saturation (SaO₂) and expired gases.

Results

Thirty two subjects (47% female, age 66 ± 9 yrs., BMI 30.4 ± 6.3 kg/m², smoking hx 35 ± 29 pkyrs, 2.3 ± 0.8 on the 0-4 GOLD classification scale) participated. The majority used multiple inhaled medications and 20% were on oral steroids. Averages were: FEV₁/FVC 58 ± 10%Pred, peak VO₂ 11.4 ± 3.1 ml/kg/min, and IBDLCO 72% of the SBDLCO (r = 0.88, SB vs IB methods). Using univariate regression, both the SB and IBDLCO (% predicted but not absolute) were predictive of VO₂peak in ml/kg/min; SBDLCO/Qc (r = 0.63, p < 0.001) was the best predictor of VO₂peak; maximal expiratory flows over the mid to lower lung volumes were the most significantly predictive spirometric measure (r = 0.49, p < 0.01). However, in multivariate models only BMI added additional predictive value to the SBDLCO/Qc for predicting aerobic capacity (r = 0.73). Adjusting for current smoking status and gender did not significantly change the primary results.

Conclusion

In patients with moderate to severe COPD, preservation of lung gas exchange surface area as assessed using the resting SBDLCO/Qc appears to be a better predictor of exercise capacity than more classic measures of lung mechanics.

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

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

Oestradiol metabolism and androgen receptor genotypes are associated with right ventricular function

Sex hormones are linked to right ventricular (RV) function, but the relationship between genetic variation in these pathways and RV function is unknown.We performed a cross-sectional study of 2761 genotyped adults without cardiovascular disease. The relationships between RV measures and single nucleotide polymorphisms (SNPs) in 10 candidate genes were assessed. Urinary oestradiol (E2) metabolites produced by cytochrome P4501B1 (CYP1B1) and serum testosterone were measured in women and men respectively.In African-American (AA) women, the CYP1B1 SNP rs162561 was associated with RV ejection fraction (RVEF), such that each copy of the A allele was associated with a 2.0% increase in RVEF. Haplotype analysis revealed associations with RVEF in AA (global p<7.2×10(-6)) and white (global p=0.05) women. In white subjects, higher E2 metabolite levels were associated with significantly higher RVEF. In men, androgen receptors SNPs (rs1337080; rs5918764) were significantly associated with all RV measures and modified the relationship between testosterone and RVEF.Genetic variation in E2 metabolism and androgen signalling was associated with RV morphology in a sex-specific manner. The CYP1B1 SNP identified is in tight linkage disequilibrium with SNPs associated with pulmonary hypertension and oncogenesis, suggesting these pathways may underpin sexual dimorphism in RV failure.

Lung hyperinflation in chronic obstructive pulmonary disease: mechanisms, clinical implications and treatment

Lung hyperinflation is highly prevalent in patients with chronic obstructive pulmonary disease and occurs across the continuum of the disease. A growing body of evidence suggests that lung hyperinflation contributes to dyspnea and activity limitation in chronic obstructive pulmonary disease and is an important independent risk factor for mortality. In this review, we will summarize the recent literature on pathogenesis and clinical implications of lung hyperinflation. We will outline the contribution of lung hyperinflation to exercise limitation and discuss its impact on symptoms and physical activity. Finally, we will examine the physiological rationale and efficacy of selected pharmacological and non-pharmacological 'lung deflating' interventions aimed at improving symptoms and physical functioning.

Factors limiting exercise tolerance in chronic lung diseases

The major limitation to exercise performance in patients with chronic lung diseases is an issue of great importance since identifying the factors that prevent these patients from carrying out activities of daily living provides an important perspective for the choice of the appropriate therapeutic strategy. The factors that limit exercise capacity may be different in patients with different disease entities (i.e., chronic obstructive, restrictive or pulmonary vascular lung disease) or disease severity and ultimately depend on the degree of malfunction or miss coordination between the different physiological systems (i.e., respiratory, cardiovascular and peripheral muscles). This review focuses on patients with chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD) and pulmonary vascular disease (PVD). ILD and PVD are included because there is sufficient experimental evidence for the factors that limit exercise capacity and because these disorders are representative of restrictive and pulmonary vascular disorders, respectively. A great deal of emphasis is given, however, to causes of exercise intolerance in COPD mainly because of the plethora of research findings that have been published in this area and also because exercise intolerance in COPD has been used as a model for understanding the interactions of different pathophysiologic mechanisms in exercise limitation. As exercise intolerance in COPD is recognized as being multifactorial, the impacts of the following factors on patients' exercise capacity are explored from an integrative physiological perspective: (i) imbalance between the ventilatory capacity and requirement; (ii) imbalance between energy demands and supplies to working respiratory and peripheral muscles; and (iii) peripheral muscle intrinsic dysfunction/weakness.

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.

Mechanisms of non-pharmacologic adjunct therapies used during exercise in COPD

Individuals with chronic obstructive pulmonary disease (COPD) are often limited in their ability to perform exercise due to a heightened sense of dyspnea and/or the occurrence of leg fatigue associated with a reduced ventilatory capacity and peripheral skeletal muscle dysfunction, respectively. Pulmonary rehabilitation programs have been shown to improve exercise tolerance and health related quality of life. Additional therapeutic approaches such as non-invasive ventilatory support (NIVS), heliox (He-O(2)) and supplemental oxygen have been used as non-pharmacologic adjuncts to exercise to enhance the ability of patients with COPD to exercise at a higher exercise-intensity and thus improve the physiological benefits of exercise. The purpose of the current review is to examine the pathophysiology of exercise limitation in COPD and to explore the physiological mechanisms underlying the effect of the adjunct therapies on exercise in patients with COPD. This review indicates that strategies that aim to unload the respiratory muscles and enhance oxygen saturation during exercise alleviate exercise limiting factors and improve exercise performance in patients with COPD. However, available data shows significant variability in the effectiveness across patients. Further research is needed to identify the most appropriate candidates for these forms of therapies.

Resting handgrip force and impaired cardiac function at rest and during exercise in COPD patients

BACKGROUND

Cardiac function measured as the oxygen pulse (O(2) pulse) is impaired during exercise (CPET) in patients with COPD. We investigated the relationship between handgrip force and O(2) pulse in COPD and controls.

METHODS

We measured anthropometrics, lung function, respiratory muscle force, handgrip (HG) force and fat free mass (FFM) at rest in 18 men with COPD (FEV(1)%=45±20) and 15 controls. We then performed a symptom limited cardiopulmonary exercise test (CPET) with similar load and used heart rate, and oxygen pulse (VO(2)/HR) to express cardiac function at rest and during exercise. We corrected the O(2) pulse by FFM.

RESULTS

Patients and controls were similar in BMI and FFM. COPD patients had lower handgrip (37.8±7 vs. 55±2) kg. O(2) pulse and HG were associated (r=0.665). At rest, COPD patients had faster heart rate (76±11 vs. 61±5) and lower oxygen pulse. COPD patients had lower oxygen pulse mL/beat at exercise isotime (10.6±3.7 vs. 14.3±2.7), even adjusted by muscle mass.

CONCLUSION

Handgrip is associated with impaired heart function at rest and during exercise in COPD patients even adjusting for muscle mass differences. Lower handgrip may be a marker of impaired cardiac function in COPD patients.

Echocardiographic abnormalities and their correlation with bronchiectasis score in primary antibody deficiencies

BACKGROUND

Primary antibody deficiencies are characterized by defective antibody production and recurrent infections. Patients usually present with recurrent respiratory tract infections with consequent chronic pulmonary damage and bronchiectasis, which could potentially influence cardiac function. Our aim was to assess noninvasively the cardiac complications due to pulmonary disease in patients with primary antibody deficiency.

METHODS

A cross-sectional series of patients with primary antibody deficiency syndromes from our referral immunology center were recruited. Individuals undergoing high-resolution computed tomography (HRCT) and transthoracic echocardiography were reviewed.

RESULTS

Thirty primary immunodeficient patients aged 5-55 years of age (21 males and 9 females) were enrolled in this study. Half of the patients (50%) were found to have bronchiectasis in HRCT imaging. In echocardiographic examination, 20 patients (67%) had at least one abnormality; among which pulmonary hypertension was the most common (33%). Patients with bronchiectasis had higher pulmonary artery pressures and HRCT bronchiectasis score was strongly correlated with pulmonary artery pressure (regression R = 0.59, P value = 0.001).

CONCLUSION

Echocardiographic evaluation of right ventricular function and noninvasive estimation of pulmonary artery pressure could have an important diagnostic role in the follow-up and therapeutic management of patients with primary immune deficiency.

Acute effects of sildenafil on exercise pulmonary hemodynamics and capacity in patients with COPD

BACKGROUND

We investigated in chronic obstructive pulmonary disease (COPD) patients whether a single dose of sildenafil can attenuate the exercise-induced increase in pulmonary artery pressure, thereby allowing augmentation of stroke volume (SV), and improving maximal exercise capacity.

METHODS

Eighteen COPD patients (GOLD II-IV) underwent right heart catheterization at rest and submaximal exercise. Mean pulmonary artery pressure (mPpa) and cardiac output (CO) were assessed. Resting and exercise measurements were repeated 60 min after oral intake of 50mg sildenafil. Also, on different days, patients performed two maximal exercise tests (CPET) randomly, 1h after placebo and after 50mg sildenafil.

RESULTS

Five COPD patients had pulmonary hypertension (PH) at rest (mPpa >25 mmHg) and six developed PH during exercise (mPpa >30 mmHg). In all patients, mPpa increased from rest to submaximal exercise (23+/-10-35+/-14 mmHg). After sildenafil mPpa at rest was 20+/-10 mmHg, in exercise mPpa was increased less to 30+/-14 mmHg (p<0.01). The reduced augmentation in mPpa was not accompanied by an increased SV and CO. In COPD patients with PH the percentage increase in mPpa to submaximal exercise was 68% before, and 51% after oral intake of sildenafil (p=0.07). In COPD without PH, these values were 46% and 41% (ns), respectively. Maximal exercise capacity and CPET characteristics were unchanged after sildenafil.

CONCLUSION

Regardless of mPpa at rest, sildenafil attenuates the increase in mPpa during submaximal exercise in COPD. This attenuated increase is neither accompanied by enhanced SV and CO, nor by improved maximal exercise capacity.

Tricuspid Annular Systolic Velocity: A Useful Measurement in Determining Right Ventricular Systolic Function Regardless of Pulmonary Artery Pressures

Assessment of right ventricular (RV) systolic function can be somewhat difficult, particularly in pulmonary hypertension (PH). RV fractional area change (FAC) and tricuspid valve annular motion (TAPSE) although useful in the assessment of RV performance, their use can be sometimes limited and tedious. Thus, a quicker but yet reliable alternative is needed. Accordingly, we compared peak tricuspid annulus systolic (TA Sa) velocities derived from Doppler tissue imaging (DTI) with both RVFAC and TAPSE to estimate RV function in 52 patients (53 +/- 16 years) with varying degrees of PH. In this group, mean was RVFAC 49 +/- 20, TAPSE was 2.3 +/- 0.7 cm, peak TA Sa velocity by DTI was 10.4 +/- 3.8 cm/s, left ventricular systolic function was 57 +/- 18%, and pulmonary artery systolic pressure was 47 +/- 28 mmHg. An excellent correlation was noted between TAPSE and RVFAC (r = 0.91, P < 0.001). Similar correlations were noted between peak TA Sa velocity and RVFAC (r = 0.84, P < 0.001) and between peak TA Sa velocity and TAPSE (r = 0.90, P < 0.001). A TA Sa >10.5 cm/s identified individuals with both a normal RV function and without significant PH. Therefore, we conclude that TA Sa velocity, an easily obtainable DTI measure, that has an excellent correlation with more time-consuming methods to assess RV systolic function regardless of the degree of PH should be routinely assessed during the initial evaluation and eventual follow-up of patients either at risk or with documented PH.

Pathophysiology of exercise dyspnea in healthy subjects and in patients with chronic obstructive pulmonary disease (COPD)

In patients with a number of cardio-respiratory disorders, breathlessness is the most common symptom limiting exercise capacity. Increased respiratory effort is frequently the chosen descriptor cluster both in normal subjects and in patients with chronic obstructive pulmonary disease (COPD) during exercise. The body of evidence indicates that dyspnea may be due to a central perception of an overall increase in central respiratory motor output directed preferentially to the rib cage muscles. On the other hand, the disparity between respiratory motor output and mechanical response of the system is also thought to play an important role in the increased perception of exercise in patients. The expiratory muscles also contribute to exercise dyspnea: a decrease in Borg scores is related to a decrease in end-expiratory lung volume and to a decrease in end-expiratory gastric pressure at isowork after lung volume reduction surgery. Changes in respiratory mechanics and intrathoracic pressure surrounding the heart can reduce cardiac output by affecting the return of blood to the heart from the periphery, or by interfering with the ability of the heart to eject blood into the peripheral circulation. Change in arterial blood gas content may affect breathlessness via direct or indirect effects. Old and more recent data have demonstrated that hypercapnia makes an independent contribution to breathlessness. In hypercapnic COPD patients an increase in PaCO2 seems to be the most important stimulus overriding all other inputs for dyspnea. Hypoxia may act indirectly by increasing ventilation (VE), and directly, independent of change in VE. Finally, chemical (metabolic) ventilatory stimuli do not have a specific effect on breathlessness other than via their stimulation of VE. We conclude that exercise provides a stimulus contributing to dyspnea, which can be applied to many diseases.

Influence of expiratory flow-limitation during exercise on systemic oxygen delivery in humans

To determine the effects of exercise with expiratory flow-limitation (EFL) on systemic O(2) delivery, seven normal subjects performed incremental exercise with and without EFL at approximately 0.8 l s(-1) (imposed by a Starling resistor in the expiratory line) to determine maximal power output under control (W'(max,c)) and EFL (W'(max,e)) conditions. W'(max,e) was 62.5% of W'(max,c), and EFL exercise caused a significant fall in the ventilatory threshold. In a third test, after exercising at W'(max,e) without EFL for 4 min, EFL was imposed; exercise continued for 4 more minutes or until exhaustion. O(2) consumption (V'(O)(2)) was measured breath-by-breath for the last 90 s of control, and for the first 90 s of EFL exercise. Assuming that the arterio-mixed venous O(2) content remained constant immediately after EFL imposition, we used V'(O)(2) as a measure of cardiac output (Q'(c)). Q'(c) was also calculated by the pulse contour method with blood pressure measured continuously by a photo-plethysmographic device. Both sets of data showed a decrease of Q'(c) due to a decrease in stroke volume by 10% (p < 0.001 for V'(O)(2)) with EFL and remained decreased for the full 90 s. Concurrently, arterial O(2) saturation decreased by 5%, abdominal, pleural and alveolar pressures increased, and duty cycle decreased by 43%. We conclude that this combination of events led to a decrease in venous return secondary to high expiratory pressures, and a decreased duty cycle which decreased O(2) delivery to working muscles by approximately 15%.

Exercise training improves exertional dyspnea in patients with COPD: evidence of the role of mechanical factors

BACKGROUND

To our knowledge, no data have been reported on the effects of exercise training (EXT) on central respiratory motor output or neuromuscular coupling (NMC) of the ventilatory pump, and their potential association with exertional dyspnea. Accurate assessment of these important clinical outcomes is integral to effective management of breathlessness of patients with COPD.

MATERIAL AND METHODS

Twenty consecutive patients with stable moderate-to-severe COPD were tested at 6-week intervals at baseline, after a nonintervention control period (pre-EXT), and after EXT. Patients entered an outpatient pulmonary rehabilitation program involving regular exercise on a bicycle. Incremental symptom-limited exercise testing (1-min increments of 10 W) was performed on an electronically braked cycle ergometer. Oxygen uptake (O(2)), carbon dioxide output (CO(2)), minute ventilation (E), time, and volume components of the respiratory cycle and, in six patients, esophageal pressure swings (Pessw), both as actual values and as percentage of maximal (most negative in sign) esophageal pressure during sniff maneuver (Pessn), were measured continuously over the runs. Exertional dyspnea and leg effort were evaluated by administering a Borg scale.

RESULTS

Measurements at baseline and pre-EXT were similar. Significant increase in exercise capacity was found in response to EXT: (1) peak work rate (WR), O(2), CO(2), E, tidal volume (VT), and heart rate increased, while peak exertional dyspnea and leg effort did not significantly change; (2) exertional dyspnea/O(2) and exertional dyspnea/CO(2) decreased while E/O(2) and E/CO(2) remained unchanged. The slope of both exertional dyspnea and leg effort relative to E fell significantly after EXT; (3) at standardized WR, E, and CO(2), exertional dyspnea and leg effort decreased while inspiratory capacity (IC) increased. Decrease in E was accomplished primarily by decrease in respiratory rate (RR) and increase in both inspiratory time (TI) and expiratory time; VT slightly increased, while inspiratory drive (VT/TI) and duty cycle (TI/total time of the respiratory cycle) remained unchanged. The decrease in Pessw and the increase in VT were associated with lower exertional dyspnea after EXT; (4) at standardized E, VT, RR, and IC, Pessw and Pessw(%Pessn)/VT remained unchanged while exertional dyspnea and leg effort decreased with EXT.

CONCLUSION

In conclusion, increases in NMC, aerobic capacity, and tolerance to dyspnogenic stimuli and possibly breathing retraining are likely to contribute to the relief of both exertional dyspnea and leg effort after EXT.

Cardiovascular limitations in chronic pulmonary disease

Chronic lung disease has significant impact on cardiovascular function. Much of this effect is because of increased right ventricular afterload caused by increased pulmonary vascular resistance resulting from structural changes in the pulmonary circulation, and because of hypoxic pulmonary vasoconstriction. In the case of chronic obstructive diseases, there may be additional increases in afterload resulting from dynamic hyperinflation. These processes can lead to structural changes in the heart (cor pulmonale), including right ventricular dilatation and hypertrophy, to maintain right ventricular output. In most ambulatory patients with chronic obstructive disease, it appears that cardiac output may be maintained at levels that are similar to normal both at rest and during exercise, with no consistent improvement in maximal exercise function afforded by interventions that increase blood flow. In contrast, diseases characterized by fibrosis or infiltration of the lung parenchyma may be associated with a disproportionate increase in pulmonary vascular resistance and more pronounced cardiovascular impairment, particularly with exercise.

Chronic obstructive pulmonary disease: capillarity and fiber-type characteristics of skeletal muscle

BACKGROUND

The purpose of this investigation was to compare capillarity and fiber type proportions of the vastus lateralis muscle between patients with chronic obstructive pulmonary disease (COPD) and healthy subjects.

METHODS

Fifteen male subjects were included in the study (8 COPD: 61.0 +/- 1.8 years [mean +/- SEM]; forced expiratory volume in 1 second 42.0 +/- 2.1% predicted; 7 N: age 54.0 +/- 1.1). Subjects were submitted to a symptom-limited maximal exercise test on ergocycle. After a transcutaneous biopsy of the vastus lateralis muscle, sections were cut 8 to 10 microns thick and stained with the Andersen method for capillarity and Stevens method for fiber typing.

RESULTS

Patients with COPD had a decrease in peak oxygen consumption compared with healthy subjects (1.2 +/- 0.1 versus 3.0 +/- 0.2 L/min). Number of capillaries per square millimeter was lower in patients with COPD versus healthy subjects (92.6 +/- 16.1 and 213.3 +/- 33.5, P < 0.001); percentages of fiber types were 43.5 +/- 5.5% type I, 56.5 +/- 5.5% type II in COPD, and 56.7 +/- 3.4% type I, 43.2 +/- 3.4% type II in healthy subjects (P < 0.05). In addition, capillaries/fiber ratio was 0.83 +/- 0.05 in COPD, and 1.56 +/- 0.10 in healthy subjects (P < 0.001).

CONCLUSION

As expected, patients with COPD showed a decrease in exercise capacity. The muscle analysis results indicate that patients with COPD have a greater proportion of type II fibers and a much lower capillaries/fiber ratio than normal subjects. We conclude that COPD adversely affects fiber type and capillarization of the lower limbs. This could be partly caused by deconditioning in these patients.

Metabolic and hemodynamic responses of lower limb during exercise in patients with COPD

Premature lactic acidosis during exercise in patients with chronic obstructive pulmonary disease (COPD) may play a role in exercise intolerance. In this study, we evaluated whether the early exercise-induced lactic acidosis in these individuals can be explained by changes in peripheral O2 delivery (O2). Measurements of leg blood flow by thermodilution and of arterial and femoral venous blood gases, pH, and lactate were obtained during a standard incremental exercise test to capacity in eight patients with severe COPD and in eight age-matched controls. No significant difference was found between the two groups in leg blood flow at rest or during exercise at the same power outputs. Blood lactate concentrations and lactate release from the lower limb were greater in COPD patients at all submaximal exercise levels (all P < 0.05). Leg D02 at a given power output was not significantly different between the two groups, and no significant correlation was found between this parameter and blood lactate concentrations. COPD patients had lower arterial and venous pH at submaximal exercise, and there was a significant positive correlation between venous pH at 40 W and the peak O2 uptake (r = 0.91, P < 0.0001). The correlation between venous pH and peak O2 uptake suggests that early muscle acidosis may be involved in early exercise termination in COPD patients. The early lactate release from the lower limb during exercise could not be accounted for by changes in peripheral O2. The present results point to skeletal muscle dysfunction as being responsible for the early onset of lactic acidosis in COPD.

Disparate effects of out-patient cardiac and pulmonary rehabilitation programs on work efficiency and peak aerobic capacity in patients with coronary disease or severe obstructive pulmonary disease

BACKGROUND

Exercise intolerance is an integral component of chronic obstructive pulmonary disease (COPD) and coronary heart disease (CHD) and is caused by several mechanisms that ultimately impact overall functional capacity. We assessed various components of exercise function in patients with CHD and COPD during the course of cardiac and pulmonary rehabilitation to evaluate changes unique to each condition.

METHODS

Work efficiency (WEf, defined as delta watts/delta VO2) and peak VO2 were measured and compared at baseline and after 3 months (36 sessions) of outpatient cardiac and pulmonary rehabilitation programs in 25 patients (mean age = 66 +/- 7 years) with severe COPD (mean FEV1.0 = 0.90 +/- 0.35 L) and in 25 patients (mean age = 65 +/- 8 years) with CHD.

RESULTS

At baseline, patients with COPD had significantly reduced values of WEf (2.04 +/- 0.86 versus 3.23 +/- 1.38 watts/mL/kg/min; P = 0.004) and peak VO2 (13.2 +/- 3.9 versus 17.1 +/- 3.9 mL/kg/min; P = 0.005) compared with patients with CHD. After rehabilitation, patients with CHD increased peak VO2 by 12% (17.1 +/- 3.9 to 19.1 +/- 4.9 mL/kg/min; P = 0.01) with no change in WEf (3.23 +/- 1.38 to 3.32 +/- 1.43 watts/mL/kg/min; P = not significant). In contrast, patients with COPD increased peak VO2 by only 5% (13.2 +/- 3.9 to 13.9 +/- 3.8 mL/kg/min; P = 0.0008), but WEf increased by 36% (2.04 +/- 0.86 to 2.78 +/- 0.84 watts/mL/kg/min; P = 0.0002). Subjective measures of functional status improved similarly in both groups.

CONCLUSIONS

In contrast to patients with CHD, work inefficiency contributes significantly to exercise intolerance in patients with severe COPD. Outpatient rehabilitation programs enhance functional status in patients with CHD and COPD by differing mechanisms, depending on the underlying disease. These data show the disparate effects of out-patient rehabilitation on peak VO2 and WEf in cardiac and pulmonary patients.

Early and long-term functional outcomes following lung volume reduction surgery

In the past 3 years, lung volume reduction surgery has become the most controversial topic in the clinical management of patients with emphysema. Although literature has added to the understanding of the procedure, many important issues remain unclear. This article emphasizes functional and basic physiologic changes that occur following lung volume reduction surgery in patients with emphysema.

[Right ventricular function and pulmonary hypertension]

BACKGROUND

Hypothetically the right ventricular function measured by Equilibrium Radionuclide Ventriculography (RNV) is determined by the right ventricular ejection fraction and depends on the afterload. We investigated the possibility to evaluate the increased pulmonary artery pressure (PAP) by using this method.

PATIENTS AND METHOD

We examined 109 patients (54.6 +/- 11 years) with chronic obstructive pulmonary disease (COPD). Lung function test, analysis of blood gases, pulmonary artery catheterisation and RNV were done within one week.

RESULTS

There are 52 patients with non. 37 with labile and 20 with fixed pulmonary hypertension. Patients with normal PAP and nearly normal RVEF (49.2 +/- 8) were used as control group. Patients with pulmonary hypertension have had a lower mean RVEF, but there was no significant difference to the control group. Furthermore there was no significant correlation between mean PAP and RVEF detectable. By using RNV we diagnosed fixed pulmonary hypertension with a sensitivity of 95% and a specificity of 33% reduced RVEF and partial respiratory failure as a second noninvasive parameter achieved a more precise but not sufficient prediction of pulmonary hypertension, tested in Chi Square-Test. Obviously the RVEF depends not only on the afterload but also on the preload and contractility. However, influences on contractility are multidimensional and difficult to assess and to determine.

CONCLUSION

Eventually it is not possible to use the RNV for measuring RVEF to diagnose pulmonary hypertension in COPD.

Role of pulmonary vascular disorder in determining exercise capacity in patients with severe chronic obstructive pulmonary disease

In patients with chronic obstructive pulmonary disease (COPD), the primary cardiovascular complication is the development of pulmonary hypertension, especially during exercise. The purpose of this study was to determine whether pulmonary vascular disorder plays an important role in determining exercise capacity in patients with severe COPD. Twenty-one male patients with severe COPD (mean FEV1 = 0.91 +/- 0.26 1) performed a progressive incremental exercise test, until symptom-limited maximum, to determine maximal exercise capacity, and then a constant-load exercise test for 5 min at a workload (20-60 W) corresponding to 60% of maximal workload during right heart catheterization to characterize the haemodynamic behavior of pulmonary circulation during exercise. The severity of the pulmonary vascular disorder was assessed using the slope of the mean pulmonary arterial pressure (PAP) - cardiac index (CI) relationship during constant-load exercise (P-Q slope). A significant inverse correlation was found between the maximal oxygen consumption (VO2max) and P-Q slope (r = -0.669), but not between VO2max and indices of expiratory airflow obstruction. In addition, the P-Q slope was inversely correlated with mixed venous oxygen tension (PvO2) at the end of constant-load exercise (r = -0.679) and with the change in oxygen delivery relative to oxygen consumption (delta DO2/delta VO2) during constant-load exercise (r = -0.671). These findings suggest that in patients with COPD, the functional impairment of the pulmonary vasculature is associated with disturbance in oxygen transport to the peripheral muscle during exercise, resulting in reduction of exercise capacity. We conclude that pulmonary vascular disorder may be an important factor in determining the exercise capacity of patients with severe COPD.

Left ventricular dysfunction in deteriorating patients with chronic obstructive pulmonary disease

OBJECTIVE

To evaluate the effectiveness of simple clinical variables and radionuclide ventriculogram in separating those patients with isolated chronic obstructive pulmonary disease (COPD) from those with COPD and coexisting left ventricular dysfunction (LVD).

DESIGN

Retrospective record review of 77 patients with increasing dyspnea, defined as recent deterioration in exercise tolerance, new use of corticosteroids, or recent hospital admission for COPD; referred to the outpatient Pulmonary Rehabilitation Program at the Cincinnati Veterans Affairs Medical Center from July 1987 to October 1992.

SETTING

Outpatient medical clinic.

PATIENTS

Veterans who were referred to the Pulmonary Rehabilitation Program.

MEASUREMENTS

History and physical findings, pulmonary function tests, arterial blood gases, distance achieved in a 12-min walk, dyspnea score, electrocardiogram, chest radiograph, and radionuclide multigated ventriculography.

RESULTS

Twenty-five of 77 patients evaluated in the Pulmonary Rehabilitation Program for increasing dyspnea were functionally more limited (12-min walk 10.4 vs 13.9 laps; MRC score 2.68 vs 2.06; p < 0.05) and had left ventricular dysfunction (LVD) (left ventricular ejection fraction < 40%) associated with wall motion abnormalities on radionuclide ventriculogram. Careful standard clinical evaluation did not separate those patients with COPD from those with both COPD and LVD.

CONCLUSIONS

LVD was found in 32% of patients with COPD presenting with symptomatic deterioration. Since the therapeutic approach to these two disorders differs, the identification of patients with LVD is important. Prospective studies are needed to identify the most cost-effective approach to this problem of coexisting disease and to evaluate the benefit from therapy.

Normal right ventricular systolic and diastolic function assessed by krypton-81m equilibrium ventriculography

Krypton-81m equilibrium ventriculography was used to study right ventricular function in 23 healthy male volunteers. Technetium-99m lung perfusion scintigraphy was employed to subtract radionuclide activity within lung during image analysis thereby enhancing image quality. The imaging technique was used to generate a time-activity curve for the right ventricle allowing the definition of indices of normal systolic and diastolic function for the right ventricle. At rest, indices of systolic ejection and diastolic filling were comparable to those previously reported for the left ventricle. Using the imaging technique, movement artifact during exercise reduces image quality and limits accurate measurement of these indices to resting studies.

Right ventricular function at rest and during exercise in chronic obstructive pulmonary disease. Comparison of two radionuclide techniques

Right ventricular function was assessed in 24 patients with COPD, at rest and during submaximal exercise, using both technetium-99m (99mTc) blood-pool and krypton-81m (81mKr) equilibrium ventriculography. Technetium-99m right ventricular ejection fraction (RVEF) at rest was lower than 81mKr RVEF (0.39 +/- 0.12 and 0.54 +/- 0.08, respectively; p < 0.001). During submaximal exercise, there was no increase in RVEF using either imaging technique. This observation contrasted with an increase in RVEF in a group of age-comparable normal subjects during modest submaximal exercise. An inability to obtain spatial separation of right heart structures using 99mTc imaging leads to a value for RVEF that is consistently lower than that measured using 81mKr ventriculography. Resting RVEF is well preserved at rest in most patients with COPD. In contrast to normal subjects, many show an inability to augment right ventricular function during exercise that may contribute to the reduced exercise capacity observed in these patients.

Increased exercise capacity in hypoxemic patients after long-term oxygen therapy

Low-flow continuous oxygen can lead to significant improvement in exercise capacity in selected patients with stable hypoxemic pulmonary disease. Although the mechanisms of improvement are incompletely understood, two tenable hypotheses are (1) the relief of hypoxic pulmonary vasoconstriction and (2) improved peripheral oxygen delivery. This prospective study was performed to examine these two hypotheses. Stable patients with hypoxemic lung disease performed symptom-limited ergometry with hemodynamic monitoring before and after greater than one month of long-term home oxygen therapy. There were 22 patients who increased exercise capacity by greater than 100 KPM/min and greater than 4 min duration and 11 patients who did not increase their exercise capacity greater than 2 min or in KPM/min. Neither the responders nor the nonresponders had significant changes in pulmonary pressures or resistances or effective arterial volume elastances at exercise after long-term O2 therapy. The responders had significant increases in oxygen delivery during exercise (148 +/- 33 ml/min vs 184 +/- 51 ml/min, p = 0.004), cardiac output (7.7 +/- 1.6 L/min vs 8.7 +/- 2.1 L/min, p = 0.003), and arterial oxygen content (18.6 +/- 2.6 ml/dl vs 20.2 +/- 2.8 ml/dl, p = 0.02). The nonresponders had no significant changes in these parameters during exercise. Increased exercise capacity in response to long-term O2 therapy is associated with increased O2 delivery not relief of hypoxic vasoconstriction (in terms of pressure or resistance or arterial elastance). Increased O2 delivery can accrue from both increased cardiac output and increased arterial O2 content. Increase in arterial O2 content is unique to O2 relative to all vasodilator drugs.

Exercise Doppler: functional evaluation of right heart dynamics

Exercise echocardiography is a versatile technique that includes not only two-dimensional imaging, but also Doppler of aortic, mitral, and tricuspid valves. Doppler echocardiography can be useful in the evaluation of global left ventricular systolic and diastolic function, valvular function, transvalvular gradients, and pulmonary artery pressure. The technique lends itself to the study of the cardiac response to exercise in a variety of disease states, including pulmonary, coronary artery, valvular, and congenital heart disease. We review our experience using agitated saline-enhanced Doppler of tricuspid insufficiency to determine pulmonary artery pressure throughout exercise in chronic lung disease.