Optimizing the evaluation of excess exercise ventilation for prognosis assessment in pulmonary arterial hypertension

Ventilatory efficiency in long-term dyspnoeic patients following COVID-19 pneumonia

BACKGROUND

Long COVID is defined as persistency of symptoms, such as exertional dyspnea, twelve weeks after recovery from SARS-CoV-2 infection.

OBJECTIVES

To investigate ventilatory efficiency by the use of cardiopulmonary exercise testing (CPET) in patients with exertional dyspnea despite normal basal spirometry after 18 (T18) and 36 months (T36) from COVID-19 pneumonia.

METHODS

One hundred patients with moderate-critical COVID-19 were prospectively enrolled in our Long COVID program. Medical history, physical examination and lung high-resolution computed tomography (HRCT) were obtained at hospitalization (T0), 3 (T3) and 15 months (T15). All HRCTs were revised using a semi-quantitative CT severity score (CSS). Pulmonary function tests were obtained at T3 and T15. CPET was performed in a subset of patients with residual dyspnea (mMRC ≥ 1), at T18 and at T36.

RESULTS

Remarkably, at CPET, ventilatory efficiency was reduced both at T18 (V'E/V'CO2 slope = 31.4±3.9 SD) and T36 (V'E/V'CO2 slope = 31.28±3.70 SD). Furthermore, we identified positive correlations between V'E/V'CO2 slope at T18 and T36 and both percentage of involvement and CSS at HRCT at T0, T3 and T15. Also, negative linear correlations were found between V'E/V'CO2 slope at T18 and T36 and DLCO at T3 and T15.

CONCLUSIONS

At eighteen months from COVID-19 pneumonia, 20 % of subjects still complains of exertional dyspnea. At CPET this may be explained by persistently reduced ventilatory efficiency, possibly related to the degree of lung parenchymal involvement in the acute phase of infection, likely reflecting a damage in the pulmonary circulation.

The Current Role of Cardiopulmonary Exercise Test in the Diagnosis and Management of Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a poor prognosis if left untreated. Despite remarkable achievements in understanding disease pathophysiology, specific treatments, and therapeutic strategies, we are still far from a definitive cure for the disease, and numerous evidences have underlined the importance of early diagnosis and treatment to improve the prognosis. Cardiopulmonary exercise testing (CPET) is the gold standard for assessing functional capacity and evaluating the pathophysiological mechanisms underlying exercise limitation. As effort dyspnea is the earliest and one of the main clinical manifestations of PAH, CPET has been shown to provide valid support in early detection, differential diagnosis, and prognostic stratification of PAH patients, being a useful tool in both the first approach to patients and follow-up. The purpose of this review is to present the current applications of CPET in pulmonary hypertension and to propose possible future utilization to be further investigated.

Excess ventilation and exertional dyspnoea in heart failure and pulmonary hypertension

Increased ventilation relative to metabolic demands, indicating alveolar hyperventilation and/or increased physiological dead space (excess ventilation), is a key cause of exertional dyspnoea. Excess ventilation has assumed a prominent role in the functional assessment of patients with heart failure (HF) with reduced (HFrEF) or preserved (HFpEF) ejection fraction, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). We herein provide the key pieces of information to the caring physician to 1) gain unique insights into the seeds of patients' shortness of breath and 2) develop a rationale for therapeutically lessening excess ventilation to mitigate this distressing symptom. Reduced bulk oxygen transfer induced by cardiac output limitation and/or right ventricle-pulmonary arterial uncoupling increase neurochemical afferent stimulation and (largely chemo-) receptor sensitivity, leading to alveolar hyperventilation in HFrEF, PAH and small-vessel, distal CTEPH. As such, interventions geared to improve central haemodynamics and/or reduce chemosensitivity have been particularly effective in lessening their excess ventilation. In contrast, 1) high filling pressures in HFpEF and 2) impaired lung perfusion leading to ventilation/perfusion mismatch in proximal CTEPH conspire to increase physiological dead space. Accordingly, 1) decreasing pulmonary capillary pressures and 2) mechanically unclogging larger pulmonary vessels (pulmonary endarterectomy and balloon pulmonary angioplasty) have been associated with larger decrements in excess ventilation. Exercise training has a strong beneficial effect across diseases. Addressing some major unanswered questions on the link of excess ventilation with exertional dyspnoea under the modulating influence of pharmacological and nonpharmacological interventions might prove instrumental to alleviate the devastating consequences of these prevalent diseases.

Impaired Ventilatory Efficiency, Dyspnea and Exercise Intolerance in Chronic Obstructive Pulmonary Disease: Results from the CanCOLD Study

RATIONALE

Impaired exercise ventilatory efficiency (high ventilatory requirements for CO2 [V̇E/V̇CO2]) provides an indication of pulmonary gas exchange abnormalities in chronic obstructive pulmonary disease (COPD).

OBJECTIVES

To determine: 1) the association between high V̇E/V̇CO2 and clinical outcomes (dyspnea and exercise capacity) and its relationship to lung function and structural radiographic abnormalities; and 2) its prevalence in a large population-based cohort.

METHODS

Participants were recruited randomly from the population and underwent clinical evaluation, pulmonary function, cardiopulmonary exercise testing and chest computed tomography (CT). Impaired exercise ventilatory efficiency was defined by a nadir V̇E/V̇CO2 above the upper limit of normal (V̇E/V̇CO2>ULN), using population-based normative values.

MEASUREMENTS AND MAIN RESULTS

Participants included 445 never-smokers, 381 ever-smokers without airflow obstruction, 224 with GOLD 1 COPD, and 200 with GOLD 2-4 COPD. Participants with V̇E/V̇CO2>ULN were more likely to have activity-related dyspnea (Medical Research Council dyspnea scale≥2, odds ratio=1.77[1.31-2.39]) and abnormally low peak oxygen uptake (V̇O2peak<LLN, odds ratio=4.58[3.06-6.86]). The carbon monoxide transfer coefficient (KCO) had a stronger correlation with nadir V̇E/V̇CO2 (r=-0.38, p<0.001) than other relevant lung function and CT metrics. The prevalence of V̇E/V̇CO2>ULN was 24% in COPD (similar in GOLD 1 and 2-4), which was greater than in never-smokers (13%) and ever-smokers (12%).

CONCLUSIONS

V̇E/V̇CO2>ULN was associated with greater dyspnea and low VO2peak and was present in 24% of all participants with COPD, regardless of GOLD stage. The results show the importance of recognizing impaired exercise ventilatory efficiency as a potential contributor to dyspnea and exercise limitation, even in mild COPD.

ROLE OF CARDIOPULMONARY EXERCISE TEST IN THE PREDICTION OF HEMODYNAMIC IMPAIRMENT IN PATIENTS WITH PULMONARY ARTERIAL HYPERTENSION

Periodic repetition of right heart catheterization (RHC) in pulmonary arterial hypertension (PAH) can be challenging. We evaluated the correlation between RHC and cardiopulmonary exercise test (CPET) aiming at CPET use as a potential noninvasive tool for hemodynamic burden evaluation. One hundred and forty‐four retrospective PAH patients who had performed CPET and RHC within 2 months were enrolled. The following analyses were performed: (a) CPET parameters in hemodynamic variables tertiles; (b) position of hemodynamic parameters in the peak end‐tidal carbon dioxide pressure (P_ETCO₂) versus ventilation/carbon dioxide output (VE/VCO₂) slope scatterplot, which is a specific hallmark of exercise respiratory abnormalities in PAH; (c) association between CPET and a hemodynamic burden score developed including mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR), cardiac index, and right atrial pressure. VE/VCO₂ slope and peak P_ETCO₂ significantly varied in mPAP and PVR tertiles, while peak oxygen uptake (peak VO₂) and O₂ pulse varied in the tertiles of all hemodynamic parameters. P_ETCO₂ versus VE/VCO₂ slope showed a strong hyperbolic relationship (R² = 0.7627). Patients with peak P_ETCO₂ > median (26 mmHg) and VE/VCO₂ slope < median (44) presented lower mPAP and PVR (p < 0.005) than patients with peak P_ETCO₂ < median and VE/VCO₂ slope > median. Multivariate analysis individuated peak VO₂ (p = 0.0158) and peak P_ETCO₂ (p = 0.0089) as hemodynamic score independent predictors; the formula 11.584 − 0.0925 × peak VO₂ − 0.0811 × peak P_ETCO₂ best predicts the hemodynamic score value from CPET data. A significant correlation was found between estimated and calculated scores (p < 0.0001), with a precise match for patients with mild‐to‐moderate hemodynamic burden (76% of cases). The results of the present study suggest that CPET could allow to estimate the hemodynamic burden in PAH patients.

Ventilatory efficiency in pulmonary vascular diseases

Cardiopulmonary exercise testing (CPET) is a frequently used tool in the differential diagnosis of dyspnoea. Ventilatory inefficiency, defined as high minute ventilation (V′_E) relative to carbon dioxide output (V′_CO2), is a hallmark characteristic of pulmonary vascular diseases, which contributes to exercise intolerance and disability in these patients. The mechanisms of ventilatory inefficiency are multiple and include high physiologic dead space, abnormal chemosensitivity and an altered carbon dioxide (CO₂) set-point. A normal V′_E/V′_CO2 makes a pulmonary vascular disease such as pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH) unlikely. The finding of high V′_E/V′_CO2 without an alternative explanation should prompt further diagnostic testing to exclude PAH or CTEPH, particularly in patients with risk factors, such as prior venous thromboembolism, systemic sclerosis or a family history of PAH. In patients with established PAH or CTEPH, the V′_E/V′_CO2 may improve with interventions and is a prognostic marker. However, further studies are needed to clarify the added value of assessing ventilatory inefficiency in the longitudinal follow-up of patients.

Ventilatory inefficiency is a hallmark feature of PH that reflects abnormal ventilation/perfusion matching, chemosensitivity and an altered CO₂ set-point. Minute ventilation/CO₂ production is useful in the diagnosis, management and prognostication of PH.https://bit.ly/3jnNdUG

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 Breathing Oxygen-Enriched Air on Exercise Performance in Patients With Pulmonary Hypertension Due to Heart Failure With Preserved Ejection Fraction: A Randomized, Placebo-Controlled, Crossover Trial

Objective: To evaluate the effects of breathing oxygen-enriched air (oxygen) on exercise performance in patients with pulmonary hypertension due to heart failure with preserved ejection fraction (PH-HFpEF).

Methods: Ten patients with PH-HFpEF (five women, age 60 ± 9 y, mPAP 37 ± 14 mmHg, PAWP 18 ± 2 mmHg, PVR 3 ± 3 WU, resting SpO₂ 98 ± 2%) performed two-cycle incremental exercise tests (IET) and two constant-work-rate exercise test (CWRET) at 75% maximal work-rate (W_max), each with ambient air (FiO₂ 0.21) and oxygen (FiO₂ 0.5) in a randomized, single-blinded, cross-over design. The main outcomes were the change in W_max (IET) and cycling time (CWRET) with oxygen vs. air. Blood gases at rest and end-exercise, dyspnea by Borg CR10 score at end-exercise; continuous SpO₂, minute ventilation (V'E), carbon dioxide output (V'CO₂), and cerebral and quadricep muscle tissue oxygenation (CTO and QMTO) were measured.

Results: With oxygen vs. air, W_max (IET) increased from 94 ± 36 to 99 ± 36 W, mean difference (95% CI) 5.4 (0.9–9.8) W, p = 0.025, and cycling time (CWRET) from 532 ± 203 to 680 ± 76 s, +148 (31.8–264) s, p = 0.018. At end-exercise with oxygen, Borg dyspnea score and V'E/V'CO₂ were lower, whereas PaO₂ and end-tidal PaCO₂ were higher. Other parameters were unchanged.

Conclusion: Patients with PH-HFpEF not revealing resting hypoxemia significantly improved their exercise performance while breathing oxygen-enriched air along with less subjective dyspnea sensation, a better blood oxygenation, and an enhanced ventilatory efficiency. Future studies should investigate whether prolonged training with supplemental oxygen would increase the training effect and, potentially, daily activity for PH-HFpEF patients.

Clinical Trial Registration: [clinicaltrials.gov], identifier [NCT04157660].

Ventilation/carbon dioxide output relationships during exercise in health

“Ventilatory efficiency” is widely used in cardiopulmonary exercise testing to make inferences regarding the normality (or otherwise) of the arterial CO₂ tension (P_aCO2) and physiological dead-space fraction of the breath (V_D/V_T) responses to rapid-incremental (or ramp) exercise. It is quantified as: 1) the slope of the linear region of the relationship between ventilation (V′_E) and pulmonary CO₂ output (V′_CO2); and/or 2) the ventilatory equivalent for CO₂ at the lactate threshold (V′_E/V′_CO2) or its minimum value (V′_E/V′_CO2min), which occurs soon after but before respiratory compensation. Although these indices are normally numerically similar, they are not equally robust. That is, high values for V′_E/V′_CO2 and V′_E/V′_CO2min provide a rigorous index of an elevated V_D/V_T when P_aCO2 is known (or can be assumed) to be regulated. In contrast, a high V′_E–V′_CO2 slope on its own does not, as account has also to be taken of the associated normally positive and small V′_E intercept. Interpretation is complicated by factors such as: the extent to which P_aCO2 is actually regulated during rapid-incremental exercise (as is the case for steady-state moderate exercise); and whether V′_E/V′_CO2 or V′_E/V′_CO2min provide accurate reflections of the true asymptotic value of V′_E/V′_CO2, to which the V′_E–V′_CO2 slope approximates at very high work rates.

The efficiency of CO₂ clearance at the lungs in exercise is estimated from the relationship between ventilation and CO₂ elimination rate. It is compromised in lung and cardiovascular disease, stressing breathing and shortness of breath, and therefore impairing exercise capacity.https://bit.ly/3gYY866

Residual Exertional Dyspnea in Cardiopulmonary Disease

In cardiopulmonary medicine, residual exertional dyspnea (RED) can be defined by the persistence of limiting breathlessness in a patient who is already under the best available therapy for the underlying heart and/or lung disease. RED is a challenge to the pulmonologist because the patient (and the referring physician) assumes that the "lung doctor" should invariably provide a successful plan to fight the symptom. After presenting a simplified framework to understand the neurobiological underpinnings of dyspnea in cardiorespiratory disease, I discuss the seeds of RED associated with 1) increased metabolic cost of work, 2) increased inspiratory constraints, 3) diaphragm dysfunction, 4) impaired right ventricle preload, 5) increased central and/or peripheral chemosensitivity, 6) increased physiological dead space, 7) increased pulmonary venous and/or high left ventricle filling pressures, 8) impaired chronotropic response to exertion, and 9) increased activation of the cortical-limbic circuits. I finalize by outlining the following two common coexistence of diseases in which these multiple mechanisms interact to produce severe RED: chronic obstructive pulmonary disease-heart failure with reduced ejection fraction and chronic pulmonary fibrosis-emphysema. RED exposes the important limitations of the current reductionist approach focused only on the (over)treatment of the poorly reversible cardiopulmonary disease(s). Conversely, recognizing the existence of RED sets the stage for a more holistic approach toward one of the most devastating symptoms known to man.

Clinical utility of ventilatory and gas exchange evaluation during low-intensity exercise for risk stratification and prognostication in pulmonary arterial hypertension

BACKGROUND AND OBJECTIVE

Peak oxygen consumption (pVO₂ ), determined from CPET, provides a valuable indication of PAH severity and patient prognosis. However, CPET is often contraindicated in severe PAH and frequently terminated prior to achievement of a sufficient exercise effort. We sought to determine whether in PAH low-intensity [i.e. freewheeling exercise (FW)] exercise reveals abnormal V_E /VCO₂ and P_ET CO₂ responses that are associated with pVO₂ and serve as indices of PAH risk stratification and mortality.

METHODS

Retrospective analysis of CPET from 97 PAH patients and 20 age-matched controls was undertaken. FW V_E /VCO₂ and P_ET CO₂ were correlated with pVO₂ % age-predicted. Prognostication analysis was conducted using pVO₂  > 65% age-predicted, as known to represent a low mortality risk. Primary outcome was mortality from any cause.

RESULTS

FW P_ET CO₂ was correlated with pVO₂ (P < 0.0001; r = 0.52), while FW V_E /VCO₂ was not (P = 0.13; r = -0.16). ROC curve analyses showed that FW P_ET CO₂ (AUC = 0.659), but not FW V_E /VCO₂ (AUC = 0.587), provided predictive information identifying pVO₂  > 65% age-predicted (best cut-off value of 28 mm Hg). By Cox analysis, FW P_ET CO₂  < 28 mm Hg remained a predictor of mortality after adjusting for age and PAH aetiology (HR: 2.360, 95% CI: 1.144-4.866, P = 0.020).

CONCLUSION

Low P_ET CO₂ during FW is associated with reduced pVO₂ in PAH and provides predictive information for PAH risk stratification and prognostication.

Prognostic value of six-minute walk distance at a South American pulmonary hypertension referral center

Six-minute walk distance (6MWD) assessment is recommended for pulmonary arterial hypertension multidimensional risk stratification. However, current 6MWD cut-off values were mainly derived from North American and European pulmonary arterial hypertension registries. Therefore, it is unknown if such cut-off values broadly apply to other geographical populations. In this study, we aimed to identify 6MWD cut-off values for Brazilian pulmonary arterial hypertension patients and to contrast our findings to current international Pulmonary Hypertension guidelines recommendations. One-hundred four consecutive pulmonary arterial hypertension patients were allocated in groups according to their 6MWD, considering 50 m as a clinically relevant 6MWD difference. Next, patients were categorized into different 6MWD ranges based on similar survival rates in each group: < 250 m, 250–400 m, and >400 m. The study outcome was all-cause mortality and transplantation according to the 6MWD range. Survival was truncated at five years. Median follow-up period was 4.35 years (0.48–5.00). Survival rates at 1, 2, 3, and 5 years were 96%, 89%, 81%, and 73%, respectively. Cox analyses adjusted for age, sex, and pulmonary arterial hypertension etiology showed that 6MWD < 250 m and >400 m were associated with higher and lower risk of all-cause mortality and transplantation. According to Harrell's c-statistic, the prognostic discrimination of the 6MWD cut-off value identified by the current study was 0.70 while international Pulmonary Hypertension guidelines 6MWD cut-offs value was 0.61. In conclusion, our findings suggest that 6MWD geographical variations should be considered when assessing risk stratification in pulmonary arterial hypertension.

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.

The role of cardiopulmonary exercise testing and training in patients with pulmonary hypertension: making the case for this assessment and intervention to be considered a standard of care

Introduction: Pulmonary hypertension (PH) is a broad pathophysiological disorder primarily characterized by increased pulmonary vascular resistance due to multiple possible etiologies. Patients typically present with multiple complaints that worsen as disease severity increases. Although initially discouraged due to safety concerns, exercise interventions for patients with PH have gained wide interest and multiple investigations have established the effective role of exercise training in improving the clinical profile, exercise tolerance, and overall quality of life.Areas covered: In this review, we discuss the pathophysiology of PH during rest and exercise, the role of cardiopulmonary exercise testing (CPX) in the diagnosis and prognosis of PAH, the role of exercise interventions in this patient population, and the expected physiological adaptations to exercise training.Expert opinion: Exercise testing, in particular CPX, provides a wealth of clinically valuable information in the PH population. Moreover, the available evidence strongly supports the safety and efficacy of exercise training as a clinical tool in improving exercise tolerance and quality of life. Although clinical trials investigating the role of exercise in this PH population are relatively few compared to other chronic conditions, current available evidence supports the clinical implementation of exercise training as a safe and effective treatment modality.

Incremental step test in patients with pulmonary hypertension

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

Exercise physiology in pulmonary hypertension patients with and without congenital heart disease

Background

Cardiopulmonary exercise testing allows the assessment of integrative cardiopulmonary response to exercise.

Aims

The aim of the study was to better understand the exercise physiology in pulmonary arterial hypertension related to adult congenital heart disease compared to non-adult congenital heart disease patients by means of cardiopulmonary exercise testing parameters.

Methods

The present is a multicentre retrospective study which includes pulmonary hypertension group 1 and group 4 patients. All subjects underwent full clinical and instrumental evaluation, including cardiopulmonary exercise testing and right heart catheterization.

Results

One hundred and sixty-seven pulmonary hypertension patients (93 women and 74 men, 57 adult congenital heart disease and 110 non-adult congenital heart disease) were enrolled. Adult congenital heart disease patients had higher pulmonary pressure (mean pulmonary arterial pressure: 59.8 ± 19.5 mmHg vs 44.6 ± 16.5 mmHg, p < 0.001) and lower pulmonary blood flow (pulmonary blood flow: 3.3 (2.1–4.3) l/min vs 4.5 (3.8–5.4) l/min, p < 0.001). At cardiopulmonary exercise testing they had lower peak oxygen uptake/kg (12.8 ± 3.8 ml/kg/min vs 15.5 ± 4.2 ml/kg/min, p < 0.001) and higher ventilation/carbon dioxide elimination slope (53.2 (43.3–64.8) vs 44.0 (34.6–51.6), p < 0.001). When patients were paired for gender and peak oxygen uptake ( ± 1 ml/kg/min), obtaining 44 pairs, adult congenital heart disease patients had higher pulmonary pressure (mean pulmonary arterial pressure: 58.4 ± 20.2 mmHg vs 42.8 ± 16.8 mmHg, p < 0.001) and ventilation/carbon dioxide elimination slope (51.2 (43.4–63.6) vs 44.9 (35.4–55.1), p = 0.033).

Conclusions

In pulmonary arterial hypertension-adult congenital heart disease patients, pulmonary pressure and ventilation/carbon dioxide elimination slope are higher compared to non-adult congenital heart disease pulmonary hypertension patients, while pulmonary blood flow and peak oxygen uptake are lower. After matching patients for gender and peak oxygen uptake, pulmonary pressure and ventilation/carbon dioxide elimination remain higher in adult congenital heart disease patients suggesting that the long-term adaptation to high pulmonary pressure, hypoxia and low pulmonary blood flow, as well as a persisting shunt has, at least partially, preserved exercise performance of pulmonary arterial hypertension-adult congenital heart disease patients.

Cardiopulmonary exercise testing reveals subclinical abnormalities in chronic kidney disease

Background

Reductions in exercise capacity associated with exercise intolerance augment cardiovascular disease risk and predict mortality in chronic kidney disease. This study utilized cardiopulmonary exercise testing to (a) investigate mechanisms of exercise intolerance; (b) unmask subclinical abnormalities that may precede cardiovascular disease in chronic kidney disease.

Design

The design of this study was cross-sectional.

Methods

Cardiopulmonary exercise testing was carried out in 31 Stage 3–4 chronic kidney disease patients (60 ± 11 years; estimated glomerular filtration rate 43 ± 13 ml/min/1.73 m2) and 21 matched healthy individuals (healthy controls; 56 ± 5 years; estimated glomerular filtration rate>90 ml/min/1.73 m2) on a cycle ergometer with workload increased by 15 W every minute until volitional fatigue. Breath-by-breath respiratory gas analysis was performed with an automated gas analyzer and averaged over 10 s intervals.

Results

Peak oxygen uptake was reduced in chronic kidney disease compared to healthy controls (17.43 ± 1.03 vs 28 ± 2.05 ml/kg/min; p < 0.01), as was oxygen uptake at the ventilatory threshold (9.44 ± 0.53 vs15.55 ± 1.34 ml/kg/min; p < 0.01). A steeper minute ventilation rate/carbon dioxide production slope (32 ± 0.8 vs 28 ± 1; p < 0.01) and a lower expired carbon dioxide pressure in chronic kidney disease (27 ± 0.6 vs 31 ± 0.9 vs 0.9; p < 0.01) indicated ventilation perfusion mismatching in these patients. The ventilatory cost of oxygen uptake was higher in chronic kidney disease (37 ± 0.8 vs 33 ± 1; p < 0.01). Maximum heart rate (134 ± 5 vs 159 ± 3 bpm) and one-minute heart rate recovery (15 ± 1 vs 20 ± 2 bpm) were reduced in chronic kidney disease ( p < 0.01).

Conclusion

This study suggests that both central and peripheral limitations likely contribute to reduced exercise capacity in non-dialysis chronic kidney disease. Additionally, cardiopulmonary exercise testing revealed subclinical cardiopulmonary abnormalities in these patients in the absence of overt cardiovascular disease. Cardiopulmonary exercise testing could potentially be a tool for unmasking cardiopulmonary abnormalities preceding cardiovascular disease in chronic kidney disease.

The role of cardiopulmonary exercise tests in pulmonary arterial hypertension

Despite recent advances in the therapeutic management of patients affected by pulmonary arterial hypertension (PAH), survival remains poor. Prompt identification of the disease, especially in subjects at increased risk of developing PAH, and prognostic stratification of patients are a necessary target of clinical practice but remain challenging. Cardiopulmonary exercise test (CPET) parameters, particularly peak oxygen uptake, end-tidal carbon dioxide tension and the minute ventilation/carbon dioxide production relationship, emerged as new prognostic tools for PAH patients. Moreover, CPET provides a comprehensive pathophysiological evaluation of patients' exercise limitation and dyspnoea, which are the main and early symptoms of the disease. This review focuses on the role of CPET in the management of PAH patients, reporting guideline recommendations for CPET and discussing the pathophysiology of exercise limitation and the most recent use of CPET in the diagnosis, prognosis and therapeutic targeting of PAH.

Peak circulatory power is a strong prognostic factor in patients with idiopathic pulmonary arterial hypertension

BACKGROUND

Studies have shown that peak circulatory power (peak CircP; peak oxygen uptake × peak systolic blood pressure) is a variable predictor of prognosis in patients with left heart failure. It remains unknown whether peak CircP also predicts outcome in patients with idiopathic pulmonary arterial hypertension (IPAH).

METHODS

Patients with newly diagnosed IPAH who underwent symptom-limited cardiopulmonary exercise testing (CPET) from 1 January 2011 to 1 January 2014 in Fuwai Hospital were prospectively enrolled and followed for up to 66 months for cardiac events (mortality and lung transplantation).

RESULTS

One hundred forty patients with IPAH (104 female, mean age: 33 ± 11 years) were studied. During follow-up (mean: 42 ± 14 months), 24 patients died and 1 patient underwent lung transplantation. In the univariate analysis, peak oxygen uptake(VO₂), oxygen uptake at anaerobic threshold, ventilation (VE)/carbon dioxide output (VCO₂) slope, end-tidal partial pressure of carbon dioxide at anaerobic threshold, peak systolic blood pressure (SBP), the change of SBP, the change of heart rate, peak work rate, peak CircP, pulmonary vascular resistance, cardiac index and World Health Organization functional class were predictive of cardiac events (all P < .05).In the multivariate analysis, Peak CircP in the fourth model had the highest significance compared with peak VO₂ and VE/VCO₂ slope in the second and third model (chi-square = 5.26, P < .02, HR: 0.99, 95% CI: 0.99 to 1.00).

CONCLUSIONS

Peak CircP, better than peak VO₂ and VE/VCO₂slope, was a strong predictor of cardiac events among exercise parameters in patients with IPAH.

Effect of breathing oxygen-enriched air on exercise performance in patients with precapillary pulmonary hypertension: randomized, sham-controlled cross-over trial

Aims

The purpose of the current trial was to test the hypothesis that breathing oxygen-enriched air increases exercise performance of patients with pulmonary arterial or chronic thrombo-embolic pulmonary hypertension (PAH/CTEPH) and to investigate involved mechanisms.

Methods and results

Twenty-two patients with PAH/CTEPH, eight women, means ± SD 61 ± 14 years, resting mPAP 35 ± 9mmHg, PaO2 ambient air >7.3 kPa, underwent four bicycle ergospirometries to exhaustion on different days, while breathing oxygen-enriched (FiO2 0.50, hyperoxia) or ambient air (FiO2 0.21, normoxia) using progressively increased or constant load protocols (with 75% maximal work rate under FiO2 0.21), according to a randomized, sham-controlled, single-blind, cross-over design. ECG, pulmonary gas-exchange, arterial blood gases, cerebral and quadriceps muscle tissue oxygenation (CTO and QMTO) by near-infrared spectroscopy were measured. In ramp exercise, maximal work rate increased from 113 ± 38 W with normoxia to 132 ± 48 W with hyperoxia, mean difference 19.7 (95% CI 10.5-28.9) W, P < 0.001. Constant load exercise endurance increased from 571 ± 443 to 1242 ± 514 s, mean difference 671 (95% CI 392-951) s, P < 0.001. At end-exercise with hyperoxia PaO2, CTO, QMTO, and PaCO2 were increased, and ventilatory equivalents for CO2 were reduced while the physiological dead space/tidal volume ratio remained unchanged.

Conclusion

In patients with PAH/CTEPH, breathing oxygen-enriched air provides major increases in exercise performance. This is related to an improved arterial oxygenation that promotes oxygen availability in muscles and brain and to a reduction of the excessive ventilatory response to exercise thereby enhancing ventilatory efficiency. Patients with PAH/CTEPH may therefore benefit from oxygen therapy during daily physical activities and training.

Trial registration

clinicaltrials.gov Identifier: NCT01748474.

Oxygen Uptake Efficiency Slope Predicts Poor Outcome in Patients With Idiopathic Pulmonary Arterial Hypertension

BACKGROUND

Few published studies have evaluated the power of the oxygen uptake efficiency slope (OUES) to predict outcomes in patients with idiopathic pulmonary arterial hypertension (IPAH), who typically die of right-sided heart failure. Our study sought to evaluate the power of OUES to predict clinical worsening and mortality in patients with IPAH.

METHODS AND RESULTS

Patients with newly diagnosed IPAH who underwent symptom-limited cardiopulmonary exercise testing from November 11, 2010, to June 25, 2015, in our hospital were prospectively enrolled and followed for up to 66 months. Clinical worsening and mortality were recorded. A total of 210 patients with IPAH (159 women; mean age, 32±10 years) were studied with a median follow-up of 41 months. Thirty-one patients died, 1 patient underwent lung transplantation, and 85 patients presented with clinical worsening. The univariate analysis revealed that OUES, OUESI (OUESI=OUES/body surface area), peak oxygen uptake (V˙O2), peak V˙O2/kg, ventilation (V˙E)/carbon dioxide output (V˙CO2) slope, peak systolic blood pressure, heart rate recovery, pulmonary vascular resistance, cardiac index, N-terminal prohormone brain natriuretic peptide, and World Health Organization functional class were all predictive of clinical worsening and mortality (all P<0.05). Multivariate analysis demonstrated that OUESI and cardiac index were independently predictive of clinical worsening, and OUESI and N-terminal prohormone brain natriuretic peptide were independently predictive of mortality. Patients with OUESI ≤0.52 m-2 had a worse 5-year survival rate than patients with OUESI >0.52 m-2 (41.9% versus 89.8%, P<0.0001).

CONCLUSIONS

The OUES, a submaximal parameter obtained from cardiopulmonary exercise testing, provides prognostic information for predicting clinical worsening and mortality in patients with IPAH.

Physiological and clinical relevance of exercise ventilatory efficiency in COPD

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

Frequent coexistence of chronic heart failure and chronic obstructive pulmonary disease in respiratory and cardiac outpatients: Evidence from SUSPIRIUM, a multicentre Italian survey

Background Chronic heart failure (CHF) and chronic obstructive pulmonary disease (COPD) frequently coexist but concurrent COPD + CHF has been little investigated. Design This multicentre survey (SUSPIRIUM) was designed to evaluate: the prevalence of COPD in stable CHF and CHF in stable COPD; diagnostic/therapeutic work-up for concurrent COPD + CHF; clinical profile of patients with COPD + CHF; predictors of COPD in CHF and CHF in COPD. Methods A 5-month-long cross-sectional prospective observational survey was conducted in 10 cardiac and 10 respiratory connected outpatient units. Results The prevalence of CHF in the 378 surveyed COPD patients was 11.9% (95% confidence interval 8.8-16.6) and the prevalence of COPD in 375 CHF patients was 31.5% (95% confidence interval 26.8-36.4). Diagnostic tests for suspected comorbidity were prescribed in 21.6% and 22.9% of COPD and CHF patients, respectively. Patients with coexisting CHF + COPD had a higher incidence of hypertension, physical inactivity and more frequently a GOLD score of 3 or greater. Compared to CHF only, CHF + COPD patients were significantly older, more frequently smokers, at worse respiratory risk and in a higher New York Heart Association class. Conversely, hypercholesterolaemia, a family history of ischaemic heart disease, fluid retention and comorbidities were more frequent in COPD + CHF than COPD-only patients. At multivariate analysis, a GOLD score of 3 or greater in CHF strongly predicted coexistent COPD (odds ratio 8.985, P < 0.0001) as did a history of other respiratory diseases (5.184, P < 0.0001). A history of ischaemic heart disease (4.868, P < 0.0001), atrial fibrillation (3.302, P < 0.0001) and sedentary lifestyle (2.814, P < 0.004) predicted coexistent CHF in COPD. Conclusion The high prevalence of COPD + CHF calls for integrated disease management between cardiologists and pulmonologists. SUSPIRIUM identifies which cardiac/pulmonary outpatients should be screened for the respective comorbidity.

Clinical usefulness of end-tidal CO2 profiles during incremental exercise in patients with chronic thromboembolic pulmonary hypertension

INTRODUCTION

Great ventilation to carbon dioxide output (ΔV˙E/ΔV˙CO₂) and reduced end-tidal partial pressures for CO₂ (PetCO₂) during incremental exercise are hallmarks of chronic thromboembolic pulmonary hypertension (CTEPH) and idiopathic pulmonary arterial hypertension (IPAH). However, CTEPH is more likely to involve proximal arteries, which may lead to poorer right ventricle-pulmonary vascular coupling and worse gas exchange abnormalities. Therefore, abnormal PetCO₂ profiles during exercise may be more prominent in patients with CTEPH and could be helpful to indicate disease severity.

METHODS

Seventy patients with CTEPH and 34 with IPAH underwent right heart catheterization and cardiopulmonary exercise testing. According to PetCO₂ pattern during exercise, patients were classified as having an increase or stabilization in PetCO₂ up to the gas exchange threshold (GET), an abrupt decrease in the rest-exercise transition or a progressive and slow decrease throughout exercise. A subgroup of patients with CTEPH underwent a constant work rate exercise test to obtain arterial blood samples during steady-state exercise.

RESULTS

Multivariate logistic regression analyses showed that progressive decreases in PetCO₂ and SpO₂ were better discriminative parameters than ΔV˙E/ΔV˙CO₂ to distinguish CTEPH from IPAH. This pattern of PetCO₂ was associated with worse functional impairment and greater reduction in PaCO₂ during exercise.

CONCLUSION

Compared to patients with IPAH, patients with CTEPH present more impaired gas exchange during exercise, and PetCO₂ abnormalities may be used to identify more clinically and hemodynamically severe cases.

Cerebral microvascular blood flow and CO2 reactivity in pulmonary arterial hypertension

Hypocapnia and endothelial dysfunction might impair microvascular cerebral blood flow (CBF_micr) and cerebrovascular reactivity to CO₂ (CVR_CO2). Pulmonary arterial hypertension (PAH) is characteristically associated with chronic alveolar hyperventilation and microvascular endothelial dysfunction. We therefore determined CBF_micr (pre-frontal blood flow index (BFI) by the indocyanine green-near infrared spectroscopy methodology) during hypocapnia and hypercapnia in 25 PAH patients and 10 gender- and age-matched controls. Cerebral BFI was lower in patients than controls at similar transcutaneous PCO₂ (PtcCO₂) levels in both testing conditions. In fact, while BFI increased from hypocapnia to hypercapnia in all controls, it failed to increase in 17/25 (68%) patients. Thus, BFI increased to a lesser extent from hypo to hypercapnia ("Δ") in patients, i.e., they showed lower Δ BFI/Δ PtcCO₂ ratios than controls. In conclusion, CBF_micr and CVR_CO2 are lessened in clinically stable, mildly-impaired patients with PAH. These abnormalities might be associated with relevant clinical outcomes (hyperventilation and dyspnea, cognition, cerebrovascular disease) being potentially amenable to pharmacological treatment.

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.