Ventilatory Efficiency Research Articles

Automatic ventilation and cooling of the building using the combination of wind deflector and solar chimney (state 3D with differential perspective)

Using new sources of energy and inventing new methods for energy consumption has always been the focus of researchers. The building sector is known to contribute largely in total energy consumption and CO2. Expanding the availability of energy storage technology and materials is considered as crucial as discovering new energy sources. The International Energy Outlook by the EIA (Energy Information Administration of the outlook) examines and predicts future trends in building energy usage. It anticipates a 34% growth in energy consumption within the built environment over the next two decades, with an average annual increase of 1.5%. By 2030, it is projected that approximately 67% of this consumption will be attributed to dwellings, while the non-domestic sectors will account for about 33%. This study endeavors to combine one of these ventilation techniques from ancient Persian architecture, known as the windcatcher in the form of an innovative roof radiative cooling (Windcatcher) with a solar chimney. In order to save energy consumption and reduce environmental problems by presenting the idea of using solar energy to exhaust the air inside the building through the chimney and using the latent heat of water evaporation to create cooling that is carried out in the direction of the wind by the windcatcher. Hence, fuel consumption can be created in hot and dry areas, in a comfortable environment with suitable humidity conditions. The purpose of this research is to introduce computational areas (3D) and determine the governing values and methods calculated by Ansys Fluent software, which has enabled the use of suction and the creation of moisture balance and heat reduction without fuel consumption, which plays an important role in It implements energy efficiency in the building. This system is also able to save 60% cooling energy and 80% of the ventilation energy during peak hours in a warm and arid climate. Furthermore, the effects of a wall opening on ventilation and thermal efficiency were examined.

Application of Mixed-Mode Ventilation to Enhance Indoor Air Quality and Energy Efficiency in School Buildings

Indoor air quality and energy efficiency are instrumental aspects of school facility design and construction, as they directly affect the physical well-being, comfort, and academic output of both pupils and staff. The challenge of balancing the need for adequate ventilation to enhance indoor air quality with the goal of reducing energy consumption has long been a topic of debate. The implementation of mixed-mode ventilation systems with automated controls presents a promising solution to address this issue. However, a comprehensive literature review on this subject is still missing. To address this gap, this review examines the potential application of mixed-mode ventilation systems as a solution to attaining improved energy savings without compromising indoor air quality and thermal comfort in educational environments. Mixed-mode ventilation systems, which combine natural ventilation and mechanical ventilation, provide the versatility to alternate between or merge both methods based on real-time indoor and outdoor environmental conditions. By analyzing empirical studies, case studies, and theoretical models, this review investigates the efficacy of mixed-mode ventilation systems in minimizing energy use and enhancing indoor air quality. Essential elements such as operable windows, sensors, and sophisticated control technologies are evaluated to illustrate how mixed-mode ventilation systems dynamically optimize ventilation to sustain comfortable and healthy indoor climates. This paper further addresses the challenges linked to the design and implementation of mixed-mode ventilation systems, including complexities in control and the necessity for climate-adaptive strategies. The findings suggest that mixed-mode ventilation systems can considerably lower heating, ventilation, and air conditioning energy usage, with energy savings ranging from 20% to 60% across various climate zones, while also enhancing indoor air quality with advanced control systems and data-driven control strategies. In conclusion, mixed-mode ventilation systems offer a promising approach for school buildings to achieve energy efficiency and effective ventilation without sacrificing indoor environment quality.

Optimizing ventilation systems considering operational and embodied emissions with life cycle based method

Efforts to enhance the energy efficiency of Heating, Ventilation, and Air Conditioning (HVAC) systems have been bolstered by technical advancements and stringent regulations. However, HVAC systems not only emit during operation due to energy consumption but also have significant embodied emissions, which recent studies show can exceed those of the operational phase. This study introduces an optimization framework aimed at minimizing lifetime emissions—both operational and embodied—for ventilation systems, an area previously underexplored. The optimization framework incorporates detailed calculations of pressure drop, fan power and newly developed life cycle ventilation inventory data with a life cycle assessment perspectiveA case study of ventilation ductwork in a “BREEAM Excellent” certified energy-efficient building in Norway applies this optimization framework. Findings indicate that for this case, optimizing ductwork dimensions can reduce lifetime emissions of the ventilation system by 15 %, compared to the existing designs with an emission intensity of 0.3 kg CO2/kWh. Further, the study examines how the emission intensity of electricity generation and service lifetime influence total emissions, highlighting the growing importance of embodied emissions as electricity generation becomes cleaner. This underscores the necessity of considering both operational and embodied emissions in design decisions. This study presents an optimization tool for low-emissions ventilation design, capable of processing diverse layouts and aiding in decarbonizing ventilation systems towards achieving zero-emission buildings. Future integration with building information modeling (BIM) and artificial intelligence (AI) could further enhance autonomous low-carbon design and decision-making.

Experimental study of ventilation performance of three ventilation strategies using aerosols and tracer gas

Effective ventilation plays a crucial role in reducing the risk of infection by airborne contaminants. This study was conducted in a hospital ward of specific dimensions (41.58 m3) equipped with two respiratory thermal manikins: a healthcare worker and an infected patient. Three ventilation strategies were employed in the ventilation system: supply and exhaust air through upper grilles, upper and lower grilles, and swirl diffusers with lower grilles. The air flow rate of the ventilation system was maintained constant at 200 m3/h. The airflow was distributed 50-50% by a combination of a personalised ventilation system and personalised exhaust system. The effectiveness of a ventilation system and its combination with a personalised exhaust system was investigated using aerosol and tracer gas techniques. The efficacy of contaminant removal was evaluated in both the patient and healthcare inhaled volume. Determination of the clean air flow rate of the three ventilation system strategies at inhaled volume was carried out. Also, the exposure of healthcare worker to the contaminants exhaled by infected patient in the microenvironment formed by both was analysed. Experimental findings revealed that CO2 showed a higher ventilation efficiency compared to particles, independently of the ventilation strategy used. The highest clean air flow rate values were detected in the inhaled volume of patient infected. On the other hand, the highest particle removal efficiency was observed in swirl diffusers with lower grilles, which combined the ventilation system with the PES. This strategy also showed the lowest exposure values in the microenvironment.

Characteristics of radon transport and optimization of ventilation parameters in large-scale underground cavern

Radon penetrates into the underground caverns through the pores/fissures of the surrounding rock, resulting in high radon concentration area and endangering the health of construction personnel. The on-site monitoring of radon concentration in the underground powerhouse of Tuoba Hydropower Station is conducted in order to study the radon concentration level. The radon transport during the construction period of underground powerhouse under forced ventilation is established by Computational Fluid Dynamics (CFD) numerical simulation method. Furthermore, the distribution characteristics and long-term evolution law of radon concentration in underground powerhouse are revealed, and reasonable ventilation optimization measures are put forward and the results show that: (1) Blasting promotes the increase of radon concentration, while forced ventilation accelerates radon transport. (2) The airflow field along the axis is divided into a vortex distribution zone, a vortex influence zone and stable regions. (3) The radon transport includes both migration and diffusion processes based on forced ventilation. (4) The radon concentration decreases with the increase of height, while exhibits low concentration in the middle and high concentration on both sides at the same height. (5) Compared with forced ventilation, the combined ventilation can improve the ventilation efficiency and shorten the radon transport time. The research results can provide a scientific basis for the safety analysis and evaluation of deep engineering environment.

Characterisation of patients who develop atrial fibrillation-induced cardiomyopathy

IntroductionAtrial fibrillation (AF)-induced cardiomyopathy (AIC) is retrospectively defined after normalisation of left ventricular ejection fraction (LVEF) in sinus rhythm. It is unclear why some patients develop AIC.HypothesisPatients with AIC have...

Design and verifications of three building acoustic metamaterials for simultaneous noise insulation and ventilation

Ventilated acoustic metamaterials with simultaneous high noise insulation performance and sufficient ventilation aera are eagerly needed nowadays. Many acoustic metamaterials with high insulation capabilities are achieved at the expense of ventilation area of proposed configurations. Thus, there is a tradeoff between noise insulation capability and ventilation efficiency in metamaterial designing. Besides, most of the ventilated acoustic metamaterials are generally tested in impedance tubes, and they are seldom verified via building acoustic sound insulation laboratory testing. In this study, the traffic noise characteristics of two typical residential building away and nearby the main traffic road are measured, which both reveal that the traffic noises cover a broad frequency range of 200 Hz∼4000 Hz. Then, three ventilated acoustic metamaterials with the same out diameter (152.4 mm) but different ventilation areas (interior diameters of 29 mm, 60 mm, 100 mm) are investigated in detail via numerical simulations and experiments. The three metamaterials are fabricated with additive manufacturing techniques and their transmission loss performances are tested in impedance tubes firstly. Finally, their noise insulation performances are verified in the building acoustic sound insulation laboratory, where the acoustic excitation is white noise generated by a diffuse sound source and the sound transmitted into the receiving room is investigated. This study will pave a solid foundation for the applications of ventilated acoustic metamaterials.

A dynamic maintenance planning methodology for HVAC systems based on Fuzzy-TOPSIS and failure mode and Effect Analysis

Maintenance is critical to the efficiency of Heating, Ventilation, and Air Conditioning (HVAC) systems in buildings. The conventional maintenance methods are planned for ideal situations and cannot easily be adapted to prevailing management/operational conditions, resulting in increased use of resources and energy. This study developed a dynamic maintenance planning framework for HVAC systems employing Fuzzy-TOPSIS and FMEA and aimed at reducing and stabilising maintenance costs while enhancing system reliability. Fuzzy-TOPSIS technique was used to establish maintenance priorities based on a carefully identified set of criteria, including the risk priority number (RPN), which is adaptable to changing conditions and ensures continuous monitoring. This is a novel application to HVAC systems. A real-world implementation in an HVAC company involving data collection, fuzzification of expert evaluations, priority ranking of components, and development of maintenance ranking validated the framework's efficiency. The running conditions of the HVAC system under the new approach, expressed by the air quality and air leakages (by extension energy saving), showed a significant improvement at the various test points in the 600-h running. The results demonstrated significant cost savings, enhanced system reliability, improved energy efficiency, and better indoor air quality. This dynamic maintenance planning framework offers a concise and adaptable solution for optimising HVAC maintenance operations.

Analyzing convective heat transfer in combined solar chimneys: A theoretical and numerical study of key influencing parameters

Combined solar chimneys represent a potent mechanism for harnessing solar energy to bolster natural ventilation in green building designs. This study focuses on the impact of structural parameters and external conditions on the ventilation and heat transfer performance of such systems. Through scaling analysis and numerical simulations, this study investigate the flow dynamics and heat transfer mechanisms. The mechanism and the influence of three critical control parameters: inlet size ratio (h/H), ratio of inclined to vertical section lengths (L/H), and Rayleigh number (Ra) is examined. The results indicate that ventilation and heat exchange performance exhibit an initial increase followed by a decline as the inlet size ratio expands from 0.10 to 0.40. Optimal ventilation efficiency is observed at a Rayleigh number of 1.98 × 1014 with an inlet size ratio of 0.15. Conversely, a low ratio of inclined to vertical section lengths (L/H = 0.20) correlates with suboptimal ventilation performance. Both ventilation intensity and efficiency are positively correlated with increases in Ra. This research quantitatively delineates these relationships, providing a theoretical foundation for the design of natural ventilation systems in sustainable buildings using combined solar chimneys.

Exercise limitations in amyloid cardiomyopathy assessed by cardiopulmonary exercise testing-A multicentre study.

Amyloid cardiomyopathy is caused by the deposition of light chain (AL) or transthyretin amyloid (ATTR) fibrils, that leads to a restrictive cardiomyopathy, often resulting in heart failure (HF) with preserved or reduced ejection fraction. This study aimed to determine whether cardiac output reduction or ventilation inefficiency plays a predominant role in limiting exercise in patients with amyloid cardiomyopathy. We conducted a multicentre prospective study in patients with AL or ATTR cardiomyopathy who underwent cardiopulmonary exercise testing across four centres. Patients were compared with a propensity-score matched HF cohort based on age, gender, left ventricular ejection fraction (LVEF), and peak oxygen consumption (VO2). Data from 267 amyloid patients aged 77 (72, 81) years, 86% male, with a median N-terminal pro B-type natriuretic peptide (NT-proBNP) of 2187 (1140, 4383) ng/L, exercise parameters of peak VO2 of 14.1 (11.6;16.9) mL/min/kg, a minute ventilation to carbon dioxide production (VE/VCO2) slope of 37.4 (32.5, 42.6) and a LVEF of 50% (44%, 59%) were analysed. We identified 251 amyloid cardiomyopathy-HF matches. Amyloid patients had a signifnicantly higher VE/VCO2 slope [37.4, inter quartile range (IQR): 32.7, 43.1 vs. 32.1, IQR: 28.7, 37.0, P<0.0001], NT-proBNP (2249, IQR: 1187, 4420 vs. 718, IQR: 405, 2161ng/L, P<0.001), peak heart rate (121±28 vs. 115±27 beats/min, P=0.007) and peak ventilation (51, IQR: 42, 62 vs. 43, IQR: 33, 53L/min, P<0.0001) with earlier anaerobic threshold (VO2 at AT: 8.9, IQR: 6.8, 10.8 vs. 10.8, IQR: 8.9, 12.7mL/min/kg, P<0.0001) compared with HF. Between amyloid patients, AL patients (n=27) were younger (63, IQR: 58, 70 vs. 78, IQR: 72, 81years, P<0.0001), had lower VE/VCO2 slope (35.0, IQR: 30.0, 38.7 vs. 38.0, IQR: 32.8, 43.1, P=0.019), higher end-tidal carbon dioxide partial pressure both at AT (35.1±4.8 vs. 31.4±4.7mmHg, P<0.001) and peak exercise (32, IQR: 28, 35 vs. 30, IQR: 26, 33mmHg, P=0.039) as compared with ATTR (n=233). A higher VE/VCO2 slope and an earlier AT, determining functional capacity impairment, was assessed in patients with amyloid cardiomyopathy compared with the matched HF cohort. Additionally, patients with ATTR might display more severe exercise limitations as compared with AL.

Abstract 4134947: Explainable Machine Learning to Predict Heart Failure Outcomes Using Exercise and Clinical Data

Background: Heart failure (HF) hospitalizations are associated with disease burden and cardiovascular mortality. International guidelines highlight cardiopulmonary testing (CPET) for risk stratification and prognosis in HF. Identifying individuals at risk could direct interventions to prevent admissions. This study uses explainable machine learning (XML) tools to identify CPET and clinical variables predictive of HF hospitalizations. Hypothesis: XML analysis of CPET parameters and clinical factors can yield accurate, patient-specific prediction of HF admission within one year. Methods: A retrospective single center review of 178 CPETs in patients referred for HF was completed. Clinical data within one year of CPET trained a boosted machine learning model (XGBoost). SHAP (Shapley Additive Explanations) explainability analysis emphasized key features for model predictions. Results: 44 (24.7%) patients with CPET were admitted for HF within one year. The model predicted this outcome with an area under the receiver operating characteristic curve (AUC) of 0.772. SHAP analysis (Figure 1) selected factors for decision making: pulmonary artery systolic pressure (PASP) via cardiac catheterization or echocardiogram; oxygen consumption at the ventilatory threshold (VO 2 at VT); O 2 pulse at rest; ventilatory efficiency (VE/VCO 2 slope); minute ventilation per oxygen consumption at maximal exercise (VE/VO 2 max) during CPET; left ventricle end diastolic volume by echocardiogram; and sodium-glucose cotransporter-2 inhibitor usage. Peak VO2, predicted VO2, predicted O2 pulse, and VE/VCO2 slope were significant, consistent with past studies (Table 1). Conclusion: Our XML analysis emphasizes PASP (partially related to high left ventricular filling pressures) and VO 2 (at ventilatory threshold) as predictive for HF hospitalization within one year of CPET testing. Studies to prospectively evaluate these highlighted factors are needed to continue exploring predictive capabilities to tailor interventions.

Exercise Training in Patients With Hypertrophic Cardiomyopathy Without Left Ventricular Outflow Tract Obstruction: A Randomized Clinical Trial.

Patients with hypertrophic cardiomyopathy without left ventricular outflow tract obstruction commonly experience reduced exercise capacity. Physical training improves exercise capacity in these patients, but whether the underlying effects of exercise are a result of central hemodynamic or peripheral improvement is unclear. This study assessed whether exercise training reduces left ventricular filling pressure measured during exercise in patients with hypertrophic cardiomyopathy without left ventricular outflow tract obstruction. Between March 2019 and June 2022, patients with hypertrophic cardiomyopathy without left ventricular outflow tract obstruction were randomly assigned (1:1) to a 12-week (3 h/wk) supervised, moderate-intensity exercise training program or continued usual activity. The primary outcome was the change in invasively measured pulmonary capillary wedge pressure during mild exercise (25 W) from baseline to week 12. Pressure tracings were analyzed offline by a blinded investigator. Secondary outcomes included changes in peak oxygen consumption, cardiac index, quality of life, echocardiographic indices of diastolic function, and natriuretic peptides. Of 59 patients randomized (mean age, 58.1±12.2 years; 27% women), 51 (86%) completed all follow-up assessments. At week 12, the change in 25-W pulmonary capillary wedge pressure was -2.8±6.8 mm Hg in the exercise group, compared with +1.2±4.9 mm Hg in the usual-activity group (between-group difference, 4.0 mm Hg [95% CI, 0.7-7.3]; P=0.018). Peak oxygen consumption improved by +1.8±2.0 mL/kg/min in the exercise group versus -0.3±3.1 mL/kg/min in the usual-activity group (P=0.005). Exercise training improved the ventilatory efficiency (VE/VCO2) slope compared with usual activity (between-group difference, 2.0 [95% CI, 0.6-3.5]; P=0.006). Peak cardiac index improved by +0.38±1.38 L/min/m2 in exercise versus -0.85±1.20 L/min/m2 in the usual-activity group (P=0.002). Change in overall Kansas City Cardiomyopathy Questionnaire score was similar between groups. However, the change in physical limitation scores (+8.4±12.0 points in exercise versus +0.7±6.8 points in usual-activity group; P=0.034) and quality-of-life scores (+8.7±18.0 points in exercise versus 0.7±4.0 points in usual-activity group; P=0.01) differed significantly. There were no significant changes in diastolic function assessed by echocardiography or in natriuretic peptides. In patients with hypertrophic cardiomyopathy without left ventricular outflow tract obstruction, a 12-week moderate-intensity exercise training program resulted in reduced left ventricular filling pressures at mild exertion and improved exercise performance. URL: https://www.clinicaltrials.gov; Unique identifier: NCT03537183.

Pulmonary gas exchange in relation to exercise pulmonary hypertension in patients with heart failure with preserved ejection fraction.

Exercise pulmonary hypertension (ePH), defined as a mean pulmonary artery pressure (mPAP)/cardiac output (Qc) slope >3 WU during exercise, is common in patients with heart failure with preserved ejection fraction (HFpEF). However, the pulmonary gas exchange-related effects of an exaggerated ePH (EePH) response are not well-defined, especially in relation to dyspnea on exertion (DOE) and exercise intolerance. 48 HFpEF patients underwent invasive (pulmonary and radial artery catheters) constant-load (20W) and maximal incremental cycle testing. Hemodynamic measurements (mPAP and Qc), arterial blood and expired gases, and ratings of breathlessness (RPB, Borg 0-10) were obtained. The mPAP/Qc slope was calculated from rest-to-20W. Those with a mPAP/Qc slope >4.2 (median) were classified as HFpEF+EePH (n=24) and those with a mPAP/Qc slope <4.2 were classified as HFpEF (without EePH) (n=24). The A-aDO2, VD/VT (Bohr equation), and the VE/VCO2 slope (from rest-to-20W) were calculated. PaO2 was lower (p=0.03), and VD/VT was higher (p=0.03) at peak exercise in HFpEF+EePH compared with HFpEF. A-aDO2 was similar at peak exercise between groups (p=0.14); however, HFpEF+EePH achieved the peak A-aDO2 at a lower peak work rate (p<0.01). The VE/VCO2 slope was higher in HFpEF+EePH compared with HFpEF (p=0.01). RPB was ≥1-unit higher at 20W and VO2peak was lower (p<0.01) in HFpEF+EePH compared with HFpEF. These data suggest that EePH contributes to pulmonary gas exchange impairments during exercise by causing a V/Q mismatch that provokes both ventilatory inefficiency and hypoxemia, both of which seem to contribute to DOE and exercise intolerance in patients with HFpEF.

Causes of ventilatory inefficiency in lung resection candidates

Causes of ventilatory inefficiency in lung resection candidates

Enhancing Airflow in Row Houses: The Impact of Stilt Floors on Ventilation Efficiency in Humid Tropical Climates

Enhancing Airflow in Row Houses: The Impact of Stilt Floors on Ventilation Efficiency in Humid Tropical Climates

An Analysis of the Ventilation Efficiency of Various Configurations of Inlet and Outlet Vents in a Residential Building by CFD Simulation

Residential buildings in South Korea have equipped an energy recovery ventilation (ERV) system to improve energy efficiency as well as dilute indoor air pollution. While most studies have focused on the efficiency of energy exchange or the ventilation performance of the ERV itself, the ventilation performance can be improved by the proper location of inlet and outlet vents. For the present study, the ventilation performance of the inlet and outlet vents of the ERV was investigated by using CFD simulation. By varying the locations of inlet and outlet vents, the airflow distributions and the age of air were assessed. In addition, the air exchange effectiveness was analyzed by using the mean age of air quantitatively. As a result, a higher age of air was observed when inlet vents were moved to the center of the plan along the wall and an additional inlet or outlet vent was installed in the kitchen. In addition, the highest air exchange effectiveness was obtained when the inlet vents were located in the center of the plan along the wall. Considering the economic perspective, it is recommended to locate the inlet vents in the center to at least improve the ventilation performance.

Exploring physiological determinants of ventilatory inefficiency in hypertrophic cardiomyopathy patients

Abstract Background The role of cardiopulmonary exercise test (CPET) in hypertrophic cardiomyopathy (HCM) has been previously examined, revealing two prognostic parameters: peak Vo2 and the VE/VCO2 slope. Specifically, individuals with a VE/VCO2 value above 31 (ventilator inefficiency) demonstrate a poorer prognosis. Purpose This study aims to analyze the physiological factors contributing to ventilatory inefficiency in individuals with HCM. Methods In this retrospective study, 43 patients HCM patients underwent resting transthoracic echocardiography, CPET combined with echocardiography during physical exertion, and cardiac magnetic resonance imaging. Ventilatory inefficiency was defined as a VE/VCO2 slope exceeding 31, leading to the identification of two groups: Group A (those with ventilatory inefficiency) and Group B (those without ventilatory inefficiency). Results Nine patients exhibited ventilatory inefficiency, while 34 had a normal VE/VCO2 slope. No statistically significant differences were found between the two groups concerning clinical and therapeutic characteristics. Subjects with ventilatory inefficiency showed reduced oxygen pulse (8.3 ± 2.6 vs 11.7 ± 4, p 0.013) and peak VO2 values (13 ± 5 vs 19 ± 5, p 0.005), lower left ventricle global longitudinal strain (-15±3 vs -17± 2, p 0,012), the exertional TAPSE/SPAP ratio (0.46 [0.32-0.48] vs 0.58 [0.47-0.80], p 0.001), exertional TAPSE (23 ± 3 vs 28 ± 4, p 0.001), and indexed stroke volume of the left ventricle assessed by cardiac magnetic resonance imaging (38±8 vs 48±10, p 0.011) (Table 1). The right ventricular function under physical exertion (peak TAPSE and TAPSE/sPAP) and left ventricular functional parameters (index stroke volume and global longitudinal strain) predicted the presence of ventilatory inefficiency. Conclusions This study highlights the role of exertional parameters in the origin of ventilatory inefficiency.Correlation tableFigure with scatter plot

The impact of left venticular filling pressure indexed to cardiac output on exercise capacity in heart failure subjects

Abstract Background/Introduction Exercise intolerance is the most common symptom of patients with heart failure (HF), regardless of the phenotypes. We aim to investigate the determinants of exercise capacity in chronic stable HF with reduced, mildly reduced, preserved, and recovered ejection fraction (EF). Methods Ambulatory HF subjects were recruited for a combined cardiopulmonary exercise test and exercise stress echocardiography. Peak oxygen consumption (peak VO2) and minute ventilation-carbon dioxide production relationship (VE/VCO2 slope) were obtained. Impaired exercise capacity was referred to a peak VO2 of &amp;lt;14 ml/kg/min, and a VE/VCO2 slope of &amp;gt;34 was defined as ventilatory inefficiency. Results Among a total of 66 participants, there were 16 HF with reduced EF, 18 HF with mildly reduced EF, 12 HF preserved EF, and 20 HF recovered EF. While both LVEF, global longitudinal strain (GLS), E/e’ ratio and diastolic dysfunction indices were crudely associated with peak VO2 and VE/VCO2 slope, only diastolic dysfunction indices were independently predictive of impaired exercise capacity (odds ratio and 95% confidence intervals: 3.847, 1.369-10.810). GLS at rest was independently correlated with ventilatory inefficiency (1.404, 1.050-1.877). Among the exercise indices, the peak medial E/e' to cardiac output ratio was independently associated with impaired exercise capacity (3.478, 1.313-9.214) and peak GLS was best related to ventilatory inefficiency (1.403, 1.076-1.828). Conclusions Among resting and exertional echocardiographic variables, the peak medial E/e' to cardiac output ratio, a non-invasive assessment of exertional left ventricular filling pressure indexed to cardiac output, was the major determinant of exercise capacity in patients with different HF phenotypes.

Prognostic value of peak heart rate on cardiopulmonary exercise testing in patients with chronic heart failure

Abstract Backgrounds Many factors are known to be related to impaired exercise capacity or worse clinical outcomes in patients with chronic heart failure (CHF). Peak heart rate achievement by cardiopulmonary exercise testing (CPET) can be easily obtained on CPET. However, less data is available regarding the impact of peak heart rate on exercise capacity or long-term clinical outcomes in patients with CHF. Purpose We sought to investigate whether lower heart rate during peak exercise displayed poorer exercise capacity and worse clinical outcomes in patients with CHF. Methods We examined consecutive 435 patients with CHF referred for CPET in our university hospital between 2013 and 2018. The primary outcome was a composite of all-cause death or hospitalization due to worsening heart failure. Patients were divided into two groups according to the optimal cut-off value of peak heart rate based on receiver operating characteristic curve analysis. Results Patients with lower peak heart rate (≤112/min, n=164) were older and, higher brain natriuretic peptide level compared to those with higher peak heart rate (&amp;gt;112/min, n=271). Heart rate during peak exercise was significantly correlated with peak oxygen consumption (peak V̇O2) (Figure 1A), peak workload achievement (Figure 1B), and ventilatory efficiency (V̇E/V̇CO2 slope) (Figure 1C). There were 80 patients with events over a median follow-up period of 3.4 (Interquartile range 0.7–5.6) years. Patients with lower peak heart rate had about 3.0-fold higher risk of events compared to those with high peak heart rate (hazard ratio [HR] 3.17; 95% confidence interval [CI], 2.01–4.98) (Figure 2). In a multivariable Cox regression, 10 bpm-decreased in peak heart rate was associated with 12% increased adverse events (HR 0.88; 95%CI, 0.78–0.98). Conclusions Peak heart rate achievement on CPET was associated with reduced exercise capacity and worse clinical outcomes, suggesting that peak heart rate is useful for risk stratification in patients with CHF. Further study is required to identify therapies targeting peak heart rate to improve the exercise capacity or clinical outcomes in patients with CHF.Figure1Figure2

Cardiopulmonary exercise testing in long-term calcium channel blockers responders, does it normalize in the same way as pulmonary vascular resistance?

Abstract Background and aims Long-term calcium channel blockers (CCB) responders represent &amp;lt;10% of pulmonary arterial hypertension (PAH) patients and are known to have an excellent prognosis on high dose CCB. The few reports of lung histology of these patients suggest a predominant muscular thickening of the precapillary arterioles. Nevertheless, the classic intimal proliferation characteristic of PAH has also been reported, although to a lesser extent. Hence, we hypothesized that long-term CCB responders are likely to exhibit some degree of ventilatory inefficiency as a result of their impaired alveolo-capillary membrane. In this study, we aimed to evaluate the exercise performance of a contemporary cohort of long-term responders to CCB in terms of both exercise capacity and ventilatory efficiency, and whether there are differences depending on the haemodynamic severity. Methods We evaluated all long-term CCB responders with regular follow-up at our institution between 1996 to 2024 with at least one cardiopulmonary exercise test (CPET) and a right heart catheterization (RHC) within a three-year period, provided they had remained clinically stable without changes in pulmonary vasodilator treatment. Patients with additional PAH specific treatment were excluded. For data analysis purposes, the population was divided into 2 groups according to pulmonary vascular resistance (PVR). The cut-off point for PVR was set at ≥3. Results Twenty-four patients (91,6% female) with complete data were retrospectively enrolled. Baseline characteristics were as follows: median age 45.5 years (59-33) median mean pulmonary artery pressure of 26 mmHg (29-24) and median PVR of 3 WU (3-2.6). Regarding the whole cohort, peak oxygen consumption (pVO2) revealed mild impairment of functional capacity (mean pVO2: 1281 ± 245 ml/kg – 75 ± 15% of predicted). Ventilatory efficiency parameters were also mildy affected with low end-tidal carbon dioxide pressure at the anaerobic threshold (PETCO2@AT) (33.7±3.6mmHg), and increased minute ventilation (VE)/carbon dioxide output (VCO2) slope (33.5±4.5). The subgroup analysis depending on PVR showed no significant differences between groups in terms of pVO2 (1291.9 ±240 Vs. 1150 ±350 ml/kg, p:0.29 / 79%±16 vs 67%±12, p:0.8), VE/VCO2 slope (33 Vs. 34, p:0.21), or PETC02@AT (35 Vs. 33 mmHg, p:0.25). All CPET parameters by subgroups are displayed in Table 1. Conclusions Long-term CCB responders exhibit mildly reduced functional capacity. Moreover, they often fail to normalize the ventilatory efficiency parameters in most of the cases, even when PVR reaches close to normal values, suggesting persistent endothelial impairment.Results according to PVR