Ventilatory response to exercise in cardiopulmonary disease: the role of chemosensitivity and dead space

Cardiopulmonary Exercise Testing in Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is a progressive pulmonary vascular disease that has a high impact on patients' quality of life, morbidity and mortality. PAH is characterized by extensive pulmonary vascular remodeling that results in an increase in pulmonary vascular resistance and right ventricular afterload, and can lead to right heart failure. Patients with PAH exhibit inefficient ventilation, high dead space ventilation, dynamic hyperinflation, and ventricular-arterial uncoupling, which can contribute to high dyspnea and low exercise tolerance. Cardiopulmonary exercise testing can help to diagnose PAH, define prognosis and treatment response in PAH, as well as discriminate between different pulmonary vascular diseases.

Advancing Cardiac Amyloidosis Care Through Insights from Cardiopulmonary Exercise Testing

Cardiac amyloidosis, encompassing both transthyretin (ATTR) and light-chain (AL) types, poses considerable challenges in patient management due to its intricate pathophysiology and progressive course. This narrative review elucidates the pivotal role of cardiopulmonary exercise testing (CPET) in the assessment of these patients. CPET is essential for evaluating disease progression by measuring cardio-respiratory performance and providing prognostic insights. This functional test is crucial not only for tracking the disease trajectory, but also for assessing the effectiveness of disease-modifying therapies. Moreover, CPET facilitates the customization of therapeutic strategies based on individual patient performance, enhancing personalized care. By objectively measuring parameters such as peak oxygen uptake (VO2 peak), ventilatory efficiency, and exercise capacity, clinicians can gain a deeper understanding of the degree of functional impairment and make informed decisions regarding treatment initiation, adjustment, and anticipated outcomes. This review emphasizes the importance of CPET in advancing personalized medicine approaches, ultimately striving to improve the quality of life and clinical outcomes for patients with cardiac amyloidosis.

Gas exchange efficiency slopes to assess exercise tolerance in chronic obstructive pulmonary disease

BACKGROUND

In patients with chronic obstructive pulmonary disease (COPD), the clinical use of the minute ventilation-carbon dioxide production ([Formula: see text]E-[Formula: see text]CO2) slope has been reported as a measure of exercise efficiency, but the oxygen uptake efficiency slope (OUES), i.e., the slope of oxygen uptake ([Formula: see text]O2) versus the logarithmically transformed [Formula: see text]E, has rarely been reported.

METHODS

We hypothesized that the [Formula: see text]E-[Formula: see text]CO2 slope is more useful than OUES in clinical use for the pathophysiological evaluation of COPD. Then, we investigated the cardiopulmonary exercise testing parameters affecting each of these slopes in 122 patients with all Global Initiative for Chronic Obstructive Lung Disease (GOLD) COPD grades selected from our database.

RESULTS

Compared with the GOLD I-II group (n = 51), peak [Formula: see text]O2 (p < 0.0001), OUES (p = 0.0161), [Formula: see text]E at peak exercise (p < 0.0001), and percutaneous oxygen saturation (SpO2) at peak exercise (p = 0.0004) were significantly lower in the GOLD III-IV group (n = 71). The GOLD III-IV group was divided into two groups by the exertional decrease in SpO2 from rest to peak exercise: 3% or less (the non-desaturation group: n = 23), or greater than 3% (the desaturation group: n = 48). OUES correlated only weakly with peak [Formula: see text]O2, [Formula: see text]E at peak exercise, and the difference between inspired and expired mean O2 concentrations (ΔFO2) at peak exercise, i.e., an indicator of oxygen consumption ability throughout the body, in the GOLD III-IV group with exertional hypoxemia. In contrast, the [Formula: see text]E-[Formula: see text]CO2 slope was significantly correlated with ΔFO2 at peak exercise, regardless of the COPD grade and exertional desaturation. Across all COPD stages, there was no correlation between the [Formula: see text]E-[Formula: see text]CO2 slope and [Formula: see text]E at peak exercise, and stepwise analysis identified peak [Formula: see text]O2 (p = 0.0345) and ΔFO2 (p < 0.0001) as variables with a greater effect on the [Formula: see text]E-[Formula: see text]CO2 slope.

CONCLUSIONS

The OUES may be less useful in advanced COPD with exertional hypoxemia. The [Formula: see text]E-[Formula: see text]CO2 slope, which is independent of [Formula: see text]E, focuses on oxygen consumption ability and exercise tolerance in COPD, regardless of the exertional hypoxemia level and COPD grade. Therefore, the [Formula: see text]E-[Formula: see text]CO2 slope might be useful in establishing or evaluating tailor-made therapies for individual patient's pathologies in COPD as an indicator focusing on oxygen consumption ability.

Improved exercise ventilatory efficiency with nasal compared to oral breathing in cardiac patients

Objectives: To assess whether nasal breathing improves exercise ventilatory efficiency in patients with heart failure (HF) or chronic coronary syndromes (CCS). Background: Exercise inefficient ventilation predicts disease progression and mortality in patients with cardiovascular diseases. In healthy people, improved ventilatory efficiency with nasal compared to oral breathing was found. Methods: Four study groups were recruited: Patients with HF, patients with CCS, old (age≥45 years) and young (age 20-40 years) healthy control subjects. After a 3-min warm-up, measurements of 5 min with once nasal and once oral breathing were performed in randomized order at 50% peak power on cycle ergometer. Ventilation and gas exchange parameters measured with spiroergometry were analysed by Wilcoxon paired-sample tests and linear mixed models adjusted for sex, height, weight and test order. Results: Groups comprised 15 HF, CCS, and young control and 12 old control. Ventilation/carbon dioxide production (V ˙ E/V ˙ CO2), ventilation (V ˙ E), breathing frequency (fR), and end-tidal oxygen partial pressure (PETO2) were significantly lower and tidal volume and end-tidal carbon dioxide partial pressure (PETCO2) significantly higher during nasal compared to oral breathing in all groups, with large effect sizes for most parameters. For patients with HF, medianV ˙ E/V ˙ CO2 was 35% lower, fR 26% lower, and PETCO2 10% higher with nasal compared to oral breathing, respectively. Exercise oscillatory ventilation (EOV) was present in 6 patients and markedly reduced with nasal breathing. Conclusion: Nasal breathing during submaximal exercise significantly improved ventilatory efficiency and abnormal breathing patterns (rapid shallow breathing and EOV) in 80% of our patients with HF and CCS.

Mechanisms and consequences of excess exercise ventilation in fibrosing interstitial lung disease

The causes and consequences of excess exercise ventilation (EEV) in patients with fibrosing interstitial lung disease (f-ILD) were explored. Twenty-eight adults with f-ILD and 13 controls performed an incremental cardiopulmonary exercise test. EEV was defined as ventilation-carbon dioxide output (⩒E-⩒CO2) slope ≥36 L/L. Patients showed lower pulmonary function and exercise capacity compared to controls. Lower DLCO was related to higher ⩒E-⩒CO2 slope in patients (P<0.05). 13/28 patients (46.4%) showed EEV, reporting higher dyspnea scores (P=0.033). Patients with EEV showed a higher dead space (VD)/tidal volume (VT) ratio while O2 saturation dropped to a greater extent during exercise compared to those without EEV. Higher breathing frequency and VT/inspiratory capacity ratio were observed during exercise in the former group (P<0.05). An exaggerated ventilatory response to exercise in patients with f-ILD is associated with a blunted decrease in the wasted ventilation in the physiological dead space and greater hypoxemia, prompting higher inspiratory constraints and breathlessness.

Persisting exercise ventilatory inefficiency in subjects recovering from COVID-19. Longitudinal data analysis 34 months post-discharge

BACKGROUND

SARS-CoV-2 infection has raised concerns about long-term health repercussions. Exercise ventilatory inefficiency (EVin) has emerged as a notable long-term sequela, potentially impacting respiratory and cardiovascular health. This study aims to assess the long-term presence of EVin after 34 months and its association with cardiorespiratory health in post-COVID patients.

METHODS

In a longitudinal study on 32 selected post-COVID subjects, we performed two cardiopulmonary exercise tests (CPETs) at 6 months (T0) and 34 months (T1) after hospital discharge. The study sought to explore the long-term persistence of EVin and its correlation with respiratory and cardiovascular responses during exercise. Measurements included also V̇O2peak, end-tidal pressure of CO2 (PETCO2) levels, oxygen uptake efficiency slope (OUES) and other cardiorespiratory parameters, with statistical significance set at p < 0.05. The presence of EVin at both T0 and T1 defines a persisting EVin (pEVin).

RESULTS

Out of the cohort, five subjects (16%) have pEVin at 34 months. Subjects with pEVin, compared to those with ventilatory efficiency (Evef) have lower values of PETCO2 throughout exercise, showing hyperventilation. Evef subjects demonstrated selective improvements in DLCO and oxygen pulse, suggesting a recovery in cardiorespiratory function over time. In contrast, those with pEvin did not exhibit these improvements. Notably, significant correlations were found between hyperventilation (measured by PETCO2), oxygen pulse and OUES, indicating the potential prognostic value of OUES and Evin in post-COVID follow-ups.

CONCLUSIONS

The study highlights the clinical importance of long-term follow-up for post-COVID patients, as a significant group exhibit persistent EVin, which correlates with altered and potentially unfavorable cardiovascular responses to exercise. These findings advocate for the continued investigation into the long-term health impacts of COVID-19, especially regarding persistent ventilatory inefficiencies and their implications on patient health outcomes.

The value of cardiopulmonary comorbidity in patients with acute large vessel occlusion stroke undergoing endovascular thrombectomy: a retrospective, observational cohort study

BACKGROUND

Chronic lung and heart diseases are more likely to lead an intensive end point after stroke onset. We aimed to investigate characteristics and outcomes of endovascular thrombectomy (EVT) in patients with acute large vessel occlusion stroke (ALVOS) and identify the role of comorbid chronic cardiopulmonary diseases in ALVOS pathogenesis.

METHODS

In this single-center retrospective study, 191 consecutive patients who underwent EVT due to large vessel occlusion stroke in neurological intensive care unit were included. The chronic cardiopulmonary comorbidities and several conventional stroke risk factors were assessed. The primary efficacy outcome was functional independence (defined as a mRS of 0 to 2) at day 90. The primary safety outcomes were death within 90 days and the occurrence of symptomatic intracranial hemorrhage(sICH). Univariate analysis was applied to evaluate the relationship between factors and clinical outcomes, and logistic regression model were developed to predict the prognosis of ALVOS.

RESULTS

Endovascular therapy in ALVOS patients with chronic cardiopulmonary diseases, as compared with those without comorbidity, was associated with an unfavorable shift in the NHISS 24 h after EVT [8(4,15.25) versus 12(7.5,18.5), P = 0.005] and the lower percentage of patients who were functionally independent at 90 days, defined as a score on the modified Rankin scale of 0 to 2 (51.6% versus 25.4%, P = 0.000). There was no significant between-group difference in the frequency of mortality (12.1% versus 14.9%, P = 0.580) and symptomatic intracranial hemorrhage (13.7% versus 19.4%, P = 0.302) or of serious adverse events. Moreover, a prediction model showed that existence of cardiopulmonary comorbidities (OR = 0.456, 95%CI 0.209 to 0.992, P = 0.048) was independently associated with functional independence at day 90.

CONCLUSIONS

EVT was safe in ALVOS patients with chronic cardiopulmonary diseases, whereas the unfavorable outcomes were achieved in such patients. Moreover, cardiopulmonary comorbidity had certain clinical predictive value for worse stroke prognosis.

Cardiac magnetic resonance ventricular parameters correlate with cardiopulmonary fitness in patients with functional single ventricle

Owing to advances in medical and surgical fields, patients with single ventricle (SV) have a greatly improved life expectancy. However, progressive functional deterioration is observed over time, with a decrease in cardiopulmonary fitness. This study aimed to identify, in patients with SV, the association between cardiac magnetic resonance imaging (CMR) parameters and change in cardiopulmonary fitness assessed by cardiopulmonary exercise test (CPET), and if certain thresholds could anticipate a decline in aerobic fitness. Patients with an SV physiology were retrospectively screened from 2011 and 2021 in a single-centre observational study. We evaluated (1) the correlation between baseline CMR and CPET parameters, (2) the association between baseline CMR results and change in peak oxygen uptake (peak VO2), and (3) the cut-off values of end-diastolic and end-systolic volume index in patients with an impaired cardiopulmonary fitness (low peak VO2 and/or high VE/VCO2 slope). 32 patients were included in the study. End-systolic volume index (r = 0.37, p = 0.03), end-diastolic volume index (r = 0.45, p = 0.01), and cardiac index (r = 0.46, p = 0.01) correlated with the VE/VCO2 slope. End-systolic ventricular volume (r = - 0.39, p = 0.01), end-diastolic ventricular volume (r = - 0.38, p = 0.01), and cardiac output (r = - 0.45, p < 0.01) inversely correlated with the peak VO2. In multivariate analysis, the cardiac index obtained from baseline CMR was inversely associated with the change in peak VO2 (p < 0.01). An end-diastolic volume index > 101 ml/m2 and an end-systolic volume index > 47 ml/m2 discriminated patients with impaired cardiopulmonary fitness. CMR parameters correlate with cardiopulmonary fitness in patients with SV and can therefore be useful for follow-up and therapeutic management of these patients.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Postoperative esketamine improves ventilation after video-assisted thoracoscopic lung resection: A double-blinded randomized controlled trial

Background

Pain management after lung resection plays a crucial role in reducing postoperative pulmonary complications (PPCs). This study aimed to examine the effect of postoperative esketamine infusion as an adjunct to opioid analgesia on ventilation and pulmonary complications in patients underwent lung resection.

Methods

Patients undergoing video-assisted thoracoscopic lung resection were randomly assigned to either the esketamine group or the control group. The esketamine group received a 24-h infusion of 1.5 mcg/ml sufentanil combined with 0.75 mcg/ml esketamine after surgery, while the control group received 1.5 mcg/ml sufentanil alone. The primary outcome measure was low minute ventilation, and the secondary outcome measures were hypoxemia, PaO2/FiO2 levels, postoperative pulmonary complications, hospital stay duration, ambulation time, Visual Analogue Scale (VAS) score, depression and anxiety levels, sleep quality, and analgesia satisfaction.

Results

80 patients were randomly divided into two groups: the esketamine group (n = 40) and the control group (n = 40). The esketamine group exhibited notably reduced incidence of low minute ventilation (P = 0.014), lower occurrence of postoperative pulmonary complications (PPCs) compared to the control group (P = 0.039), and decreased incidence of hypoxemia (P = 0.003). Furthermore, the esketamine group showed improved outcomes with lower VAS scores on the second postoperative day and enhanced sleep quality (P < 0.001) after the surgery.

Conclusions

Postoperative esketamine infusion with opioids improved ventilation and reduced PPCs after lung resection, warranting further clinical studies.

Trial registration

This study was registered on ClinicalTrials.gov (Trial ID: NCT05458453, https://clinicaltrials.gov/ct2/show/NCT05458453).

Shedding Light on Latent Pulmonary Vascular Disease in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Among patients with heart failure with preserved ejection fraction (HFpEF), a distinct hemodynamic phenotype has been recently described, ie, latent pulmonary vascular disease (HFpEF-latentPVD), defined by exercise pulmonary vascular resistance (PVR) >1.74 WU.

OBJECTIVES

This study aims to explore the pathophysiological significance of HFpEF-latentPVD.

METHODS

The authors analyzed a cohort of patients who had undergone supine exercise right heart catheterization with cardiac output (CO) measured by direct Fick method, between 2016 and 2021. HFpEF-latentPVD patients were compared with HFpEF control patients.

RESULTS

Out of 86 HFpEF patients, 21% qualified as having HFpEF-latentPVD, 78% of whom had PVR >2 WU at rest. Patients with HFpEF-latentPVD were older, with a higher pretest probability of HFpEF, and more frequently experienced atrial fibrillation and at least moderate tricuspid regurgitation (P < 0.05). PVR trajectories differed between HFpEF-latentPVD patients and HFpEF control patients (Pinteraction = 0.008), slightly increasing in the former and reducing in the latter. HFpEF-latentPVD patients displayed more frequent hemodynamically significant tricuspid regurgitation during exercise (P = 0.002) and had more impaired CO and stroke volume reserve (P < 0.05). Exercise PVR was correlated with mixed venous O2 tension (R2 = 0.33) and stroke volume (R2 = 0.31) in HFpEF-latentPVD patients. The HFpEF-latentPVD patients had had higher dead space ventilation during exercise and higher PaCO2 (P < 0.05), which correlated with resting PVR (R2 = 0.21). Event-free survival was reduced in HFpEF-latentPVD patients (P < 0.05).

CONCLUSIONS

The results suggest that when CO is measured by direct Fick, few HFpEF patients have isolated latent PVD (ie, normal PVR at rest, becoming abnormal during exercise). HFpEF-latentPVD patients present with CO limitation to exercise, associated with dynamic tricuspid regurgitation, altered ventilatory control, and pulmonary vascular hyperreactivity, portending a poor prognosis.

Reference Values of Cardiopulmonary Exercise Test Parameters in the Contemporary Paediatric Population

BACKGROUND

The evaluation of health status by cardiopulmonary exercise test (CPET) has shown increasing interest in the paediatric population. Our group recently established reference Z-score values for paediatric cycle ergometer VO_2max, applicable to normal and extreme weights, from a cohort of 1141 healthy children. There are currently no validated reference values for the other CPET parameters in the paediatric population. This study aimed to establish, from the same cohort, reference Z-score values for the main paediatric cycle ergometer CPET parameters, apart from VO_2max.

RESULTS

In this cross-sectional study, 909 healthy children aged 5-18 years old underwent a CPET. Linear, quadratic, and polynomial mathematical regression equations were applied to identify the best CPET parameters Z-scores, according to anthropometric parameters (sex, age, height, weight, and BMI). This study provided Z-scores for maximal CPET parameters (heart rate, respiratory exchange ratio, workload, and oxygen pulse), submaximal CPET parameters (ventilatory anaerobic threshold, VE/VCO₂ slope, and oxygen uptake efficiency slope), and maximum ventilatory CPET parameters (tidal volume, respiratory rate, breathing reserve, and ventilatory equivalent for CO₂ and O₂).

CONCLUSIONS

This study defined paediatric reference Z-score values for the main cycle ergometer CPET parameters, in addition to the existing reference values for VO_2max, applicable to children of normal and extreme weights. Providing Z-scores for CPET parameters in the paediatric population should be useful in the follow-up of children with various chronic diseases. Thus, new paediatric research fields are opening up, such as prognostic studies and clinical trials using cardiopulmonary fitness outcomes. Trial registration NCT04876209-Registered 6 May 2021-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04876209 .

How Does the Method Used to Measure the VE/VCO2 Slope Affect Its Value? A Cross-Sectional and Retrospective Cohort Study

Cardiopulmonary exercise testing (CPET) was limited to peak oxygen consumption analysis (VO₂peak), and now the ventilation/carbon dioxide production (VE/VCO₂) slope is recognized as having independent prognostic value. Unlike VO₂peak, the VE/VCO₂ slope does not require maximal effort, making it more feasible. There is no consensus on how to measure the VE/VCO₂ slope; therefore, we assessed whether different methods affect its value. This is a retrospective study assessing sociodemographic data, left ventricular ejection fraction, CPET parameters, and indications of patients referred for CPET. The VE/VCO₂ slope was measured to the first ventilatory threshold (VT1-slope), secondary threshold (VT2-slope), and included all test data (full-slope). Of the 697 CPETs analyzed, 308 reached VT2. All VE/VCO₂ slopes increased with age, regardless of test indications. In patients not reaching VT2, the VT1-slope was 32 vs. 36 (p < 0.001) for the full-slope; in those surpassing VT2, the VT1-slope was 29 vs. 33 (p < 0.001) for the VT2-slope and 37 (all p < 0.001) for the full-slope. The mean difference between the submaximal and full-slopes was ±4 units, sufficient to reclassify patients from low to high risk for heart failure or pulmonary hypertension. We conclude that the method used for determining the VE/VCO₂ slope greatly influences the result, the significant variations limiting its prognostic value. The calculation method must be standardized to improve its prognostic value.

A Systematic Approach for the Interpretation of Cardiopulmonary Exercise Testing in Children with Focus on Cardiovascular Diseases

Cardiopulmonary exercise testing (CPET) is the clinical standard for children with congenital heart disease (CHD), heart failure (HF) being assessed for transplantation candidacy, and subjects with unexplained dyspnea on exertion. Heart, lung, skeletal muscle, peripheral vasculature, and cellular metabolism impairment frequently lead to circulatory, ventilatory, and gas exchange abnormalities during exercise. An integrated analysis of the multi-system response to exercise can be beneficial for differential diagnosis of exercise intolerance. The CPET combines standard graded cardiovascular stress testing with simultaneous ventilatory respired gas analysis. This review addresses the interpretation and clinical significance of CPET results with specific reference to cardiovascular diseases. The diagnostic values of commonly obtained CPET variables are discussed using an easy-to-use algorithm for physicians and trained nonphysician personnel in clinical practice.

Nutritional State and COPD: Effects on Dyspnoea and Exercise Tolerance

Chronic Obstructive Pulmonary Disease (COPD) is a disease that is spreading worldwide and is responsible for a huge number of deaths annually. It is characterized by progressive and often irreversible airflow obstruction, with a heterogeneous clinical manifestation based on disease severity. Along with pulmonary impairment, COPD patients display different grades of malnutrition that can be linked to a worsening of respiratory function and to a negative prognosis. Nutritional impairment seems to be related to a reduced exercise tolerance and to dyspnoea becoming a major determinant in patient-perceived quality of life. Many strategies have been proposed to limit the effects of malnutrition on disease progression, but there are still limited data available to determine which of them is the best option to manage COPD patients. The purpose of this review is to highlight the main aspects of COPD-related malnutrition and to underline the importance of poor nutritional state on muscle energetics, exercise tolerance and dyspnoea.

Correlation between three-dimensional echocardiography and cardiopulmonary fitness in patients with univentricular heart: A cross-sectional multicentre prospective study

BACKGROUND

The prognosis of patients with a functional single ventricle has improved, with better cardiopulmonary fitness, health-related quality of life and survival. Conventional echocardiography remains the first-line technique in single ventricle follow-up. Three-dimensional (3D) echocardiography has shown recent value in congenital cardiology, but its ability to predict functional status in patients with a single ventricle remains unknown.

AIM

To evaluate, in patients with a single ventricle, the association between 3D echocardiography variables and functional status determined by cardiopulmonary fitness.

METHODS

Children and adults with a functional single ventricle were prospectively enrolled in this multicentre study. Cardiopulmonary fitness was assessed by cardiopulmonary exercise test, with measures of maximum oxygen uptake (VO_2max) and ventilatory efficiency (VE/VCO₂ slope). 3D echocardiography was performed with off-line reproducibility analyses, using TomTec Arena™ software. Health-related quality of life was assessed using the SF-36 questionnaire.

RESULTS

A total of 33 patients were screened, and 3D echocardiography analyses were feasible in 22 subjects (mean age 28±9years). 3D echocardiography ejection fraction correlated with percent-predicted VO_2max (r=0.64, P<0.01), VE/VCO₂ slope (r=-0.41, P=0.05), two-dimensional echocardiography ejection fraction (r=0.55, P<0.01) and health-related quality of life physical functioning dimension (r=0.56, P=0.04). 3D echocardiography indexed end-systolic volume correlated with percent-predicted VO_2max (r=-0.45, P=0.03) and VE/VCO₂ slope (r=0.65, P<0.01). 3D echocardiography reproducibility was good.

CONCLUSIONS

Single ventricle ejection fraction and volumes measured by 3D echocardiography correlated with cardiopulmonary fitness, as determined by two main prognostic cardiopulmonary exercise test variables: VO_2max and VE/VCO₂ slope. Despite good reproducibility, 3D echocardiography feasibility remained limited. 3D echocardiography may be of value in single ventricle follow-up, provided that the technique and analysis software are improved.

Cardiopulmonary exercise testing for heart failure: pathophysiology and predictive markers

Despite the numerous recent advancements in therapy, heart failure (HF) remains a principle cause of both morbidity and mortality. HF with preserved ejection fraction (HFpEF), a condition that shares the prevalence and adverse outcomes of HF with reduced ejection fraction, remains poorly recognised in its initial manifestations. Cardiopulmonary exercise testing (CPET), defined as a progressive work exercise test that includes non-invasive continuous measurement of cardiovascular and respiratory parameters, provides a reliable mode to evaluate for early features and for the assessment of prognostic features of both forms of HF. While CPET measurements are standard of care for advanced HF and transplant programmes, they merit a broader clinical application in the early diagnosis and assessment of patients with HFpEF. In this review, we provide an overview of the pathophysiology of exercise intolerance in HF and discuss key findings in CPETs used to evaluate both severity of impairment and the prognostic implications.

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.

Determinants of ventilatory inefficiency in transthyretin cardiac amyloidosis: The role of excessive ventilatory drive

Background and objective: Along with impaired aerobic capacity, increased slope of the relationship between ventilation (VE) and pulmonary CO2 output (VCO2), i.e., VE-VCO2 slope is a common finding in patients with cardiac amyloidosis (CA), which suggests ventilatory inefficiency. Little is known about mechanisms leading to ventilatory inefficiency in CA patients. The purpose of this investigation was to examine the factors that underlie the abnormal ventilatory efficiency in transthyretin hereditary CA patients, such as excessive ventilatory drive, inability of pulmonary blood flow to increase adequately during exercise and excessive sympathetic stimulation, which are known mechanisms of VE-VCO2 slope increase.

Methods: In this single-center retrospective observational study, consecutive patients (n = 41) with known familial transthyretin amyloidosis p.Val142Ile mutation carriers with confirmed cardiac phenotype were included.

Results: Compared with CA patients without ventilatory inefficiency (VE-VCO2 slope &lt; 36), patients with ventilatory inefficiency (VE-VCO2 slope ≥ 36) had increased inter-ventricular septum thickness, lower VO2 peak along with hyperventilation, and prolonged post-exercise heart rate recovery. By multivariate analysis, only excess of minute-ventilation at anaerobic threshold (β = 0.127; p = 0.011) remained an independent predictor of ventilatory inefficiency.

Conclusion: Our data suggest that high ventilatory stimulation during exercise leading to hyperventilation is the main determinant of ventilatory inefficiency in hereditary transthyretin cardiac amyloidosis patients. This novel finding helps to better understand the mechanism of exercise intolerance in these patients where physiological limitation may be related to both heart dysfunction and abnormal pulmonary response.

Diagnostic and Prognostic Values of Cardiopulmonary Exercise Testing in Cardiac Amyloidosis

Cardiac amyloidosis (CA) is a myocardial disease characterized by extracellular amyloid infiltration throughout the heart, resulting in increased myocardial stiffness, and restrictive heart wall chamber behavior. Its diagnosis among patients hospitalized for cardiovascular diseases is becoming increasingly frequent, suggesting improved disease awareness, and higher diagnostic capacities. One predominant functional manifestation of patients with CA is exercise intolerance, objectified by reduced peak oxygen uptake (VO₂ peak), and assessed by metabolic cart during cardiopulmonary exercise testing (CPET). Hemodynamic adaptation to exercise in patients with CA is characterized by low myocardial contractile reserve and impaired myocardial efficiency. Rapid shallow breathing and hyperventilation, in the absence of ventilatory limitation, are also typically observed in response to exercise. Ventilatory inefficiency is further suggested by an increased VE-VCO2 slope, which has been attributed to excessive sympathoexcitation and a high physiological dead space (VD/VT) ratio during exercise. Growing evidence now suggests that, in addition to well-established biomarker risk models, a reduced VO₂ peak is potentially a strong and independent predictive factor of adverse patient outcomes, both for monoclonal immunoglobulin light chain (AL) or transthyretin (ATTR) CA. Besides generating prognostic information, CPET can be used for the evaluation of the impact of therapeutic interventions in patients with CA.

Double gas transfer factors (DLCO-DLNO) at rest in patients with congenital heart diseases correlates with their ventilatory response during maximal exercise

Aim

Exercise capacity is altered in congenital heart diseases (CHD) with potentially impaired pulmonary perfusion adaptation during exercise, such as in single ventricle or in significant pulmonary regurgitation. This study aimed to evaluate the value of double gas transfer factor analysis, at rest in conjunction with postural manoeuvres, to explore the various components of pulmonary gas transfer and its association with exercise capacity.

Methods

A total of 40 subjects (24 CHD, 16 controls) underwent a combined measurement of lung diffusing capacity for carbon monoxide and nitric oxide (DLCO-DLNO) to determine pulmonary membrane diffusion (Dm) and Vcap, in sitting then supine position. CHD patients performed a maximal cardiopulmonary exercise test.

Results

Compared to normal controls, the CHD group's DLNO, DLCO, Vcap, and alveolar volume (AV) at rest, in the sitting position were depressed, whereas the DLCO/AV and DLNO/AV were similar. The magnitude of Dm and Vcap adaptation induced by postural change was similar in both groups, indicating a preserved pulmonary capillary recruitment capacity in CHD. In the CHD group, at rest, for each ml of postural-induced increase in Vcap we observed during exercise a VE/VCO2 slope decrease of 0.46 (95% CI[0.83; 0.098]), indicating a better ventilatory response to exercise.

Conclusion

CHD patients with impaired pulmonary circulation have a reduced Dm and Vcap mainly due to decreased pulmonary volume but maintain a normal capacity to adapt these parameters through a simple recruitment manoeuver. Vcap adaptation evaluated at rest predicts the level of ventilatory efficiency during exercise, which represents a main limiting factor in these CHD patients.

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

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

The Impact of Mavacamten on the Pathophysiology of Hypertrophic Cardiomyopathy: A Narrative Review

Hypertrophic cardiomyopathy (HCM) is a chronic, progressive disease of the cardiomyocyte with a diverse and heterogeneous clinical presentation and course. This diversity and heterogeneity have added to the complexity of modeling the pathophysiological pathways that contribute to the disease burden. The development of novel therapeutic approaches targeting precise mechanisms within the underlying biology of HCM provides a tool to model and test these pathways. Here, we integrate the results of clinical observations with mavacamten, an allosteric, selective, and reversible inhibitor of cardiac myosin, the motor unit of the sarcomere, to develop an integrated pathophysiological pathway model of HCM, confirming the key role of excess sarcomeric activity. This model may serve as a foundation to understand the role of HCM pathophysiological pathways in the clinical presentation of the disease, and how a targeted therapeutic intervention capable of normalizing sarcomeric activity and repopulating low-energy utilization states may reduce the impact of these pathways in HCM and potentially related disease states.

Increased Oxygen Extraction by Pulmonary Rehabilitation Improves Exercise Tolerance and Ventilatory Efficiency in Advanced Chronic Obstructive Pulmonary Disease

Background: In cardiopulmonary exercise testing (CPET), oxygen uptake (V’_O2) is calculated using the product of minute ventilation (V’_E) and the difference between inspiratory and expiratory O₂ concentrations (ΔFO₂). However, little is known about the response of ΔFO₂ to pulmonary rehabilitation (PR). The aim of the present study was (1) to investigate whether PR increases peak V’_O2, based on whether ΔFO₂ or V’_E at peak exercise increase after PR, and (2) to investigate whether an improvement in ΔFO₂ correlates with an improvement in ventilatory efficiency. Methods: A total of 38 patients with severe and very severe COPD, whose PR responses were evaluated by CPET, were retrospectively analyzed. Results: After PR, peak V’_O2 was increased in 14 patients. The difference in ΔFO₂ at peak exercise following PR correlated with the difference in peak V’_O2 (r = 0.4884, p = 0.0019), the difference in V’_E/V’_CO2-nadir (r = −0.7057, p < 0.0001), and the difference in V’_E–V’_CO2 slope (r = −0.4578, p = 0.0039), but it did not correlate with the difference in peak V’_E. Conclusions: The increased O₂ extraction following PR correlated with improved exercise tolerance and ventilatory efficiency. In advanced COPD patients, a new strategy for improving O₂ extraction ability might be effective in those in whom ventilatory ability can be only minimally increased.

Neural respiratory drive in chronic thromboembolic pulmonary hypertension: Effect of balloon pulmonary angioplasty

Excessive ventilation (V̇E) during exercise, ascribed to heightened neural ventilatory drive and/or to increased "wasted" ventilation, is a feature of chronic thromboembolic pulmonary hypertension (CTEPH). In selected CTEPH patients, balloon pulmonary angioplasty (BPA) allows near-normalization of resting haemodynamic parameters but does not allow excess exercise hyperventilation to normalize. Neural ventilatory drive can be estimated by studying how arterial PCO₂ (PaCO₂), end-tidal PCO₂ (PETCO₂), V̇E and CO₂ output (V̇CO₂) change across the exercise-to-recovery transition during a cardiopulmonary exercise test. Increased "wasted" ventilation can be quantified by the physiological dead space fraction of tidal volume (VD/VT) calculated with the Enghoff simplification of the Bohr equation. These measurements were made before and after BPA in 22 CTEPH patients without significant cardiac and/or pulmonary comorbidities. Our observations suggest that before BPA, excessive hyperventilation was secondary to both heightened neural ventilatory drive and increased "wasted" ventilation; after BPA, measurements made across the exercise-to-recovery transition suggest that heightened neural ventilatory drive was no longer present.

Cardiopulmonary exercise testing in interstitial lung diseases and the value of ventilatory efficiency

Interstitial lung diseases (ILDs) are diverse parenchymal pulmonary disorders, primarily characterised by alveolar and interstitial inflammation and/or fibrosis, and sharing pathophysiological similarities. Thus, patients generally harbour common respiratory symptoms, lung function abnormalities and modified exercise adaptation. The most usual and disabling complaint is exertional dyspnoea, frequently responsible for premature exercise interruption. Cardiopulmonary exercise testing (CPET) is increasingly used for the clinical assessment of patients with ILD. This is because exercise performance or dyspnoea on exertion cannot reliably be predicted by resting pulmonary function tests. CPET, therefore, provides an accurate evaluation of functional capacity on an individual basis. CPET can unmask anomalies in the integrated functions of the respiratory, cardiovascular, metabolic, peripheral muscle and neurosensory systems in ILDs. CPET uniquely provides an evaluation of all above aspects and can help clinicians shape ILD patient management. Preliminary evidence suggests that CPET may also generate valuable prognostic information in ILDs and can be used to shed light on the presence of associated pulmonary hypertension. This review aims to provide comprehensive and updated evidence concerning the clinical utility of CPET in ILD patients, with particular focus on the physiological and clinical value of ventilatory efficiency (V˙_E/V˙_CO2 ).

Ventilatory efficiency and its clinical and prognostic value in adults with cystic fibrosis

Cystic fibrosis, due to the absence or abnormal function of the cystic fibrosis transmembrane conductance regulator, is the most common life-limiting autosomal recessive genetic disorder among the Caucasian population. The lungs are particularly affected due to thick and tenacious mucus causing parenchymal anomalies ranging from bronchiectasis, progressive airflow limitation, respiratory infections, lung destruction and ultimately respiratory failure. Despite the remarkable advances in treatment that have greatly improved survival, most patients experience progressive exercise curtailment, with the consequence that a growing number of patients with cystic fibrosis will be referred for exercise-based evaluations in the forthcoming years. Cardiopulmonary exercise testing, in particular, is a useful tool to assess the mechanisms of exercise intolerance in individual patients that may have treatment and prognostic implications. In this review, we will focus on ventilatory efficiency and its clinical and prognostic value in adults with cystic fibrosis.

ACUTE TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) IMPROVES VENTILATORY VARIABILITY AND AUTONOMIC MODULATION IN RESISTANT HYPERTENSIVE PATIENTS

Here, we assessed the impact of one session of transcranial direct current stimulation (tDCS) or SHAM (20 min, each) on ventilatory responses to cardiopulmonary exercise test, central and peripheral blood pressure (BP), and autonomic modulation in resistant hypertensive (RHT) patients. RHT subjects (n = 13) were randomly submitted to SHAM and tDCS crossing sessions (1 week of "washout"). Patients and a technician who set the tDCS/Sham room up were both blind. After brain stimulation, patients were submitted to a cardiopulmonary exercise test to evaluate ventilatory and cardiovascular response to exercise. Hemodynamic (Finometer®, Beatscope), and autonomic variables were measured at baseline (before tDCS/Sham) and after incremental exercise. RESULTS: Our study shows that tDCS condition improved heart rate recovery, VO2 peak, and vagal modulation (after cardiopulmonary exercise test); attenuated the ventilatory variability response, central and peripheral blood pressure well as sympathetic modulation (after cardiopulmonary exercise test) in comparison with SHAM. These data suggest that acute tDCS sessions prevented oscillatory ventilation behavior during the cardiopulmonary exercise test and mitigated the increase of systolic blood pressure in RHT patients. After the exercise test, tDCS promotes better vagal reentry and improved autonomic modulation, possibly reducing central blood pressure and aortic augmentation index compared to SHAM. Brazilian Registry of Clinical Trials (ReBEC): https://ensaiosclinicos.gov.br/rg/RBR-8n7c9p.

Physical activity and fitness in the community: the Framingham Heart Study

AIMS

While greater physical activity (PA) is associated with improved health outcomes, the direct links between distinct components of PA, their changes over time, and cardiorespiratory fitness are incompletely understood.

METHODS AND RESULTS

Maximum effort cardiopulmonary exercise testing (CPET) and objective PA measures [sedentary time (SED), steps/day, and moderate-vigorous PA (MVPA)] via accelerometers worn for 1 week concurrent with CPET and 7.8 years prior were obtained in 2070 Framingham Heart Study participants [age 54 ± 9 years, 51% women, SED 810 ± 83 min/day, steps/day 7737 ± 3520, MVPA 22.3 ± 20.3 min/day, peak oxygen uptake (VO2) 23.6 ± 6.9 mL/kg/min]. Adjusted for clinical risk factors, increases in steps/day and MVPA and reduced SED between the two assessments were associated with distinct aspects of cardiorespiratory fitness (measured by VO2) during initiation, early-moderate level, peak exercise, and recovery, with the highest effect estimates for MVPA (false discovery rate <5% for all). Findings were largely consistent across categories of age, sex, obesity, and cardiovascular risk. Increases of 17 min of MVPA/day [95% confidence interval (CI) 14-21] or 4312 steps/day (95% CI 3439-5781; ≈54 min at 80 steps/min), or reductions of 249 min of SED per day (95% CI 149-777) between the two exam cycles corresponded to a 5% (1.2 mL/kg/min) higher peak VO2. Individuals with high (above-mean) steps or MVPA demonstrated above average peak VO2 values regardless of whether they had high or low SED.

CONCLUSIONS

Our findings provide a detailed assessment of relations of different types of PA with multidimensional cardiorespiratory fitness measures and suggest favourable longitudinal changes in PA (and MVPA in particular) are associated with greater objective fitness.

Evidence for impaired chronotropic responses to and recovery from 6-minute walk test in women with post-acute COVID-19 syndrome

NEW FINDINGS

What is the central question of this study? Are chronotropic responses to a 6-minute walk test different in women with post-acute coronavirus disease 2019 (COVID-19) syndrome compared with control subjects? What is the main finding and its importance? Compared with control subjects, the increase in heart rate was attenuated and recovery delayed after a 6-minute walk test in participants after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Women reporting specific symptoms at time of testing had greater impairments compared with control subjects and SARS-CoV-2 participants not actively experiencing these symptoms. Such alterations have potential to constrain not only exercise tolerance but also participation in free-living physical activity in women during post-acute recovery from COVID-19.

ABSTRACT

The short-term cardiopulmonary manifestations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are well defined. However, the implications of cardiopulmonary sequelae, persisting beyond acute illness, on physical function are largely unknown. Herein, we characterized heart rate responses to and recovery from a 6-minute walk test (6MWT) in women ∼3 months after mild-to-moderate SARS-CoV-2 infection compared with non-infected control subjects. Forty-five women (n = 29 SARS-CoV-2; n = 16 controls; age = 56 ± 11 years; body mass index = 25.8 ± 6.0 kg/m² ) completed pulmonary function testing and a 6MWT. The SARS-CoV-2 participants demonstrated reduced total lung capacity (84 ± 8 vs. 93 ± 13%; P = 0.006), vital capacity (87 ± 10 vs. 93 ± 10%; P = 0.040), functional residual capacity (75 ± 16 vs. 88 ± 16%; P = 0.006) and residual volume (76 ± 18 vs. 93 ± 22%; P = 0.001) compared with control subjects. No between-group differences were observed in 6MWT distance (P = 0.194); however, the increase in heart rate with exertion was attenuated among SARS-CoV-2 participants compared with control subjects (+52 ± 20 vs. +65 ± 18 beats/min; P = 0.029). The decrease in heart rate was also delayed for minutes 1-5 of recovery among SARS-CoV-2 participants (all P < 0.05). Women reporting specific symptoms at the time of testing had greater impairments compared with control subjects and SARS-CoV-2 participants not actively experiencing these symptoms. Our findings provide evidence for marked differences in chronotropic responses to and recovery from a 6MWT in women several months after acute SARS-CoV-2 infection.

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Mechanisms of Exercise Capacity Improvement after Cardiac Rehabilitation Following Myocardial Infarction Assessed with Combined Stress Echocardiography and Cardiopulmonary Exercise Testing

Cardiac rehabilitation (CR) is indicated in all patients after acute myocardial infarction (AMI) to improve prognosis and exercise capacity (EC). Previous studies reported that up to a third of patients did not improve their EC after CR (non-responders). Our aim was to assess the cardiac and peripheral mechanisms of EC improvement after CR using combined exercise echocardiography and cardiopulmonary exercise testing (CPET-SE). The responders included patients with an improved EC assessed as a rise in peak oxygen uptake (VO₂) ≥ 1 mL/kg/min. Peripheral oxygen extraction was calculated as arteriovenous oxygen difference (A-VO₂Diff). Out of 41 patients (67% male, mean age 57.5 ± 10 years) after AMI with left ventricular ejection fraction (LVEF) ≥ 40%, 73% improved their EC. In responders, peak VO₂ improved by 27% from 17.9 ± 5.2 mL/kg/min to 22.7 ± 5.1 mL/kg/min, p < 0.001, while non-responders had a non-significant 5% decrease in peak VO₂. In the responder group, the peak exercise heart rate, early diastolic myocardial velocity at peak exercise, LVEF at rest and at peak exercise, and A-VO₂Diff at peak exercise increased, the minute ventilation to carbon dioxide production slope decreased, but the stroke volume and cardiac index were unchanged after CR. Non-responders had no changes in assessed parameters. EC improvement after CR of patients with preserved LVEF after AMI is associated with an increased heart rate response and better peripheral oxygen extraction during exercise.

Persistent Exertional Intolerance after COVID-19: Insights from Invasive Cardiopulmonary Exercise Testing

BACKGROUND

Some Coronavirus disease 2019 (COVID-19) patients who have recovered from their acute infection after experiencing only mild symptoms continue to exhibit persistent exertional limitation that is often unexplained by conventional investigative studies.

RESEARCH QUESTION

What is the patho-physiological mechanism of exercise intolerance that underlies the post-COVID-19 long haul syndrome following COVID-19 in patients without cardio-pulmonary disease?

STUDY DESIGN AND METHODS

This study examined the systemic and pulmonary hemodynamics, ventilation, and gas exchange in 10 post-COVID-19 patients without cardio-pulmonary disease during invasive cardiopulmonary exercise testing (iCPET) and compared the results to 10 age- and sex matched controls. These data were then used to define potential reasons for exertional limitation in the post-COVID-19 cohort.

RESULTS

Post-COVID-19 patients exhibited markedly reduced peak exercise aerobic capacity (VO₂) compared to controls (70±11%predicted vs. 131±45%predicted; p<0.0001). This reduction in peak VO₂ was associated with impaired systemic oxygen extraction (i.e., narrow CaVO₂/CaO₂) compared to controls (0.49±0.1 vs. 0.78±0.1, p<0.0001) despite a preserved peak cardiac index (7.8±3.1 vs. 8.4±2.3 L/min, p>0.05). Additionally, post-COVID-19 patients demonstrated greater ventilatory inefficiency (i.e., abnormal VE/VCO₂ slope: 35±5 vs. 27±5, p=0.01) compared to controls without an increase in dead space ventilation.

INTERPRETATION

Post-COVID-19 patients without cardiopulmonary disease demonstrate a marked reduction in peak VO₂ from a peripheral rather than a central cardiac limit along with an exaggerated hyper-ventilatory response during exercise.

Oxygen Extraction Based on Inspiratory and Expiratory Gas Analysis Identifies Ventilatory Inefficiency in Chronic Obstructive Pulmonary Disease

Aims: In contrast to cardiovascular disease, low rather than high ventilatory inefficiency, evaluated by the minute ventilation-carbon dioxide output (V'_E-V'_CO2)-slope, has been recognized as being related to greater disease severity in chronic obstructive pulmonary disease (COPD). To better care for patients with cardiopulmonary disease, understanding the physiological correlation between ventilatory inefficiency and exercise limitation is necessary, but remains inadequate. Given that oxygen uptake (V'_O2) evaluated by cardiopulmonary exercise testing (CPET) depends on both the ventilatory capability and oxygen extraction, i.e., the difference between inspiratory and expiratory oxygen concentration (ΔFO₂), the aim of this study was to investigate the correlations between V'_E-V'_CO2-slope and the ΔFO₂ during exercise and their physiological implications in patients with COPD.

Methods: A total of 156 COPD patients (mean age, 70.9 ± 7.2 years) with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages I–IV and 16 controls underwent CPET with blood gas analysis.

Results: With the progression of COPD, mechanical ventilatory constraints together with a slower respiratory frequency led to exertional respiratory acidosis. In GOLD IV cases, (1) decrease in the dependence of reduced peak V'_O2 on V'_E led to an increase in its dependence on peak ΔFO₂ during exercise; and (2) the ΔFO₂-V'_CO2-slope became steeper, correlating with the severity of exertional respiratory acidosis (r = 0.6359, p < 0.0001). No significant differences in peak exercise ΔFO₂ or V'_E-V'_CO2-slope were observed among the various GOLD stages. In all subjects, including controls, peak exercise ΔFO₂ had the strongest correlation with the V'_E-V'_CO2-slope (r = −0.8835, p < 0.0001) and correlated well with body mass index (r = 0.3871, p < 0.0001), although it did not correlate with the heart rate-V'_CO2-relationship and V'_E.

Conclusions: Ventilatory efficiency related to CO₂ clearance might depend on exertional oxygen extraction in the body. Measuring ΔFO₂ might be a key component for identifying ventilatory inefficiency and oxygen availability. Increasing ΔFO₂ would help to improve ventilatory inefficiency and exercise tolerance separately from cardiac and ventilatory capability in COPD patients.

Exercise Capacity, Ventilatory Response, and Gas Exchange in COPD Patients With Mild to Severe Obstruction Residing at High Altitude

Background

Exercise intolerance, desaturation, and dyspnea are common features in patients with chronic obstructive pulmonary disease (COPD). At altitude, the barometric pressure (BP) decreases, and therefore the inspired oxygen pressure and the partial pressure of arterial oxygen (PaO₂) also decrease in healthy subjects and even more in patients with COPD. Most of the studies evaluating ventilation and arterial blood gas (ABG) during exercise in COPD patients have been conducted at sea level and in small populations of people ascending to high altitudes. Our objective was to compare exercise capacity, gas exchange, ventilatory alterations, and symptoms in COPD patients at the altitude of Bogotá (2,640 m), of all degrees of severity.

Methods

Measurement during a cardiopulmonary exercise test of oxygen consumption (VO₂), minute ventilation (VE), tidal volume (VT), heart rate (HR), ventilatory equivalents of CO₂ (VE/VCO₂), inspiratory capacity (IC), end-tidal carbon dioxide tension (PETCO₂), and ABG. For the comparison of the variables between the control subjects and the patients according to the GOLD stages, the non-parametric Kruskal–Wallis test or the one-way analysis of variance test was used.

Results

Eighty-one controls and 525 patients with COPD aged 67.5 ± 9.1 years were included. Compared with controls, COPD patients had lower VO₂ and VE (p < 0.001) and higher VE/VCO₂ (p = 0.001), A-aPO₂, and V_D/V_T (p < 0.001). In COPD patients, PaO₂ and saturation decreased, and delta IC (p = 0.004) and VT/IC increased (p = 0.002). These alterations were also seen in mild COPD and progressed with increasing severity of the obstruction.

Conclusion

The main findings of this study in COPD patients residing at high altitude were a progressive decrease in exercise capacity, increased dyspnea, dynamic hyperinflation, restrictive mechanical constraints, and gas exchange abnormalities during exercise, across GOLD stages 1–4. In patients with mild COPD, there were also lower exercise capacity and gas exchange alterations, with significant differences from controls. Compared with studies at sea level, because of the lower inspired oxygen pressure and the compensatory increase in ventilation, hypoxemia at rest and during exercise was more severe; PaCO₂ and PETCO₂ were lower; and VE/VO₂ was higher.

Impact of COVID-19 on exercise pathophysiology: a combined cardiopulmonary and echocardiographic exercise study

Survivors from COVID-19 pneumonia can present with persisting multisystem involvement (lung, pulmonary vessels, heart, muscle, red blood cells) that may negatively affect exercise capacity. We sought to determine the extent and the determinants of exercise limitation in patients with COVID-19 at the time of hospital discharge. Eighteen consecutive patients with COVID-19 and 1:1 age-, sex-, and body mass index-matched controls underwent: spirometry, echocardiography, cardiopulmonary exercise test and exercise echocardiography for the study of pulmonary circulation. Arterial blood was sampled at rest and during exercise in patients with COVID-19. Patients with COVID-19 lie roughly on the same oxygen consumption isophlets than controls both at rest and during submaximal exercise, thanks to supernormal cardiac output (P < 0.05). Oxygen consumption at peak exercise was reduced by 30% in COVID-19 (P < 0.001), due to a peripheral extraction limit. In addition, within COVID-19 patients, hemoglobin content was associated with peak oxygen consumption (R² = 0.46, P = 0.002). Respiratory reserve was not exhausted (median [IRQ], 0.59 [0.15]) in spite of moderate reduction of forced vital capacity (79 ± 40%). Pulmonary artery pressure increase during exercise was not different between patients and controls. Ventilatory equivalents for carbon dioxide were higher in patients with COVID-19 than in controls (39.5 [8.5] vs. 29.5 [8.8], P < 0.001), and such an increase was mainly explained by increased chemosensitivity. When recovering from COVID-19, patients present with reduced exercise capacity and augmented exercise hyperventilation. Peripheral factors, including anemia and reduced oxygen extraction by peripheral muscles were the major determinants of deranged exercise physiology. Pulmonary vascular function seemed unaffected, despite restrictive lung changes.NEW & NOTEWORTHY At the time of hospital discharge, patients with COVID-19 present with reduced functional capacity and exercise hyperventilation. Peripheral factors, namely reduced oxygen extraction (myopathy) and anemia, which are not fully compensated by a supernormal cardiac output response, account for exercise limitation before exhaustion of the respiratory reserve. Enhanced chemoreflex sensitivity, rather increased dead space, mainly accounts for exercise hyperventilation. The pulmonary vascular response to exercise circulation of survived patients with COVID-19 does not present major pathological changes.

Transcutaneous PCO2 -based dead space ventilation at submaximal exercise accurately discriminates healthy controls from patients with chronic obstructive pulmonary disease

BACKGROUND

Increased physiological dead space ventilation (V_D /V_T ) at exercise reflects pulmonary gas exchange impairment and is a sensitive marker of cardio-respiratory disease. V_D /V_T is typically not measured during routine cardiopulmonary exercise testing (CPET) because its calculation requires arterial blood gas analysis for determination of PaCO₂ . Instead, dead space ventilation is indirectly evaluated as a determinant of the ventilation (VE)/VCO₂ relationship, which also depends on the PaCO₂ set point. We hypothesized that V_D /V_T calculations based on non-invasive transcutaneous PCO₂ (PtcCO₂ ) measurement had better diagnostic characteristics than the VE/VCO₂ slope for the discrimination of healthy subjects from patients with COPD, a common disease associated with impaired pulmonary gas exchange.

METHODS

Retrospective study of 19 healthy controls and 24 COPD patients who underwent CPET with continuous PtcCO₂ monitoring. Areas under receiver operating characteristics curves (AUC) were calculated to assess diagnostic accuracy of CPET measurement for the discrimination of COPD and Controls.

RESULTS

The AUC for PtcCO₂ -based V_D /V_T at VT1 (0.977) was significantly higher than for the VE/VCO₂ slope (0.660), SpO₂ at peak exercise (0.913), decrease in inspiratory capacity (0.719), and ventilatory reserve (0.708). At a threshold of 0.24, the sensitivity and specificity of PtcCO₂ -based V_D /V_T for the discrimination of COPD patients and healthy Controls were 100% and 84%, respectively. All Control subjects had PtcCO₂ -based V_D /V_T  ≤ 0.25.

CONCLUSIONS

PtcCO₂ -based V_D /V_T was the most accurate measurement to discriminate healthy controls from subjects with COPD, a chronic lung disease associated with altered pulmonary gas exchange. Non-invasive monitoring of PtcCO₂ may be useful for routine CPET.

Cardiopulmonary Exercise Testing in Combined Pulmonary Fibrosis and Emphysema

BACKGROUND

Combined pulmonary fibrosis and emphysema (CPFE) is a distinct entity among fibrosing lung diseases with a high risk for lung cancer and pulmonary hypertension (PH). Notably, concomitant PH was identified as a negative prognostic indicator that could help with early diagnosis to provide important information regarding prognosis.

OBJECTIVES

The current study aimed to determine whether cardiopulmonary exercise testing (CPET) can be helpful in differentiating patients having CPFE with and without PH.

METHODS

Patients diagnosed with CPFE in 2 German cities (Hemer and Greifswald) over a period of 10 years were included herein. CPET parameters, such as peak oxygen uptake (peak VO2), functional dead space ventilation (VDf/VT), alveolar-arterial oxygen difference (AaDO2), arterial-end-tidal CO2 difference [P(a-ET)CO2] at peak exercise, and the minute ventilation-carbon dioxide production relationship (VE/VCO2 slope), were compared between patients with and without PH.

RESULTS

A total of 41 patients with CPET (22 with PH, 19 without PH) were analyzed. Right heart catheterization was performed in 15 of 41 patients without clinically relevant complications. Significant differences in peak VO2 (861 ± 190 vs. 1,397 ± 439 mL), VO2/kg body weight/min (10.8 ± 2.6 vs. 17.4 ± 5.2 mL), peak AaDO2 (72.3 ± 7.3 vs. 46.3 ± 14.2 mm Hg), VE/VCO2 slope (70.1 ± 31.5 vs. 39.6 ± 9.6), and peak P(a-ET)tCO2 (13.9 ± 3.5 vs. 8.1 ± 3.6 mm Hg) were observed between patients with and without PH (p < 0.001). Patients with PH had significantly higher VDf/VT at rest, VT1, and at peak exercise (65.6 ± 16.8% vs. 47.2 ± 11.6%; p < 0.001) than those without PH. A cutoff value of 44 for VE/VCO2 slope had a sensitivity and specificity of 94.7 and 72.7%, while a cutoff value of 11 mm Hg for P(a-ET)CO2 in combination with peak AaDO2 >60 mm Hg had a specificity and sensitivity of 95.5 and 84.2%, respectively. Combining peak AaDO2 >60 mm Hg with peak VO2/body weight/min <16.5 mL/kg/min provided a sensitivity and specificity of 100 and 95.5%, respectively.

CONCLUSION

This study provided initial data on CPET among patients having CPFE with and without PH. CPET can help noninvasively detect PH and identify patients at risk. AaDO2 at peak exercise, VE/VCO2 slope, peak P(a-ET)CO2, and peak VO2 were parameters that had high sensitivity and, when combined, high specificity.

Motor Pathophysiology Related to Dyspnea in COPD Evaluated by Cardiopulmonary Exercise Testing

In chronic obstructive pulmonary disease (COPD), exertional dyspnea, which increases with the disease’s progression, reduces exercise tolerance and limits physical activity, leading to a worsening prognosis. It is necessary to understand the diverse mechanisms of dyspnea and take appropriate measures to reduce exertional dyspnea, as COPD is a systemic disease with various comorbidities. A treatment focusing on the motor pathophysiology related to dyspnea may lead to improvements such as reducing dynamic lung hyperinflation, respiratory and metabolic acidosis, and eventually exertional dyspnea. However, without cardiopulmonary exercise testing (CPET), it may be difficult to understand the pathophysiological conditions during exercise. CPET facilitates understanding of the gas exchange and transport associated with respiration-circulation and even crosstalk with muscles, which is sometimes challenging, and provides information on COPD treatment strategies. For respiratory medicine department staff, CPET can play a significant role when treating patients with diseases that cause exertional dyspnea. This article outlines the advantages of using CPET to evaluate exertional dyspnea in patients with COPD.