Разработка конструкции стенда для испытаний системы выгрузки зерна комбайна КЗС-10К

Материалы VIII Междунар. науч.-техн. конф. студентов, магистрантов и молодых ученых, Гомель, 28–29 апр. 2008

Respiratory gas kinetics in patients with congestive heart failure during recovery from peak exercise

Background: Cardiopulmonary Exercise Testing (CPX) is essential for the assessment of exercise capacity for patients with Chronic Heart Failure (CHF). Respiratory gas and hemodynamic parameters such as Ventilatory Efficiency (VE/VCO2 slope), peak oxygen uptake (peak VO2), and heart rate recovery are established diagnostic and prognostic markers for clinical populations. Previous studies have suggested the clinical value of metrics related to respiratory gas collected during recovery from peak exercise, particularly recovery time to 50% (T1/2) of peak VO2. The current study explores these metrics in detail during recovery from peak exercise in CHF. Methods: Patients with CHF who were referred for CPX and healthy individuals without formal diagnoses were assessed for inclusion. All subjects performed CPX on cycle ergometers to volitional exhaustion and were monitored for at least five minutes of recovery. CPX data were analyzed for overshoot of respiratory exchange ratio (RER=VCO2/VO2), ventilatory equivalent for oxygen (VE/VO2), end-tidal partial pressure of oxygen (PETO2), and T1/2 of peak VO2 and VCO2. Results: Thirty-two patients with CHF and 30 controls were included. Peak VO2 differed significantly between patients and controls (13.5 ± 3.8 vs. 32.5 ± 9.8 mL/Kg*min−1, p < 0.001). Mean Left Ventricular Ejection Fraction (LVEF) was 35.9 ± 9.8% for patients with CHF compared to 61.1 ± 8.2% in the control group. The T1/2 of VO2, VCO2 and VE was significantly higher in patients (111.3 ± 51.0, 132.0 ± 38.8 and 155.6 ± 45.5s) than in controls (58.08 ± 13.2, 74.3 ± 21.1, 96.7 ± 36.8s; p < 0.001) while the overshoot of PETO2, VE/VO2 and RER was significantly lower in patients (7.2 ± 3.3, 41.9 ± 29.1 and 25.0 ± 13.6%) than in controls (10.1 ± 4.6, 62.1 ± 17.7 and 38.7 ± 15.1%; all p < 0.01). Most of the recovery metrics were significantly correlated with peak VO2 in CHF patients, but not with LVEF. Conclusions: Patients with CHF have a significantly blunted recovery from peak exercise. This is reflected in delays of VO2, VCO2, VE, PETO2, RER and VE/VO2, reflecting a greater energy required to return to baseline. Abnormal respiratory gas kinetics in CHF was negatively correlated with peak VO2 but not baseline LVEF

Cardiac function and long-term volume load : Physiological investigations in endurance athletes and in patients operated on for aortic regurgitation

Background and aims. The heart is a remarkably adaptable organ, continuously changing its output to match metabolic demands and haemodynamic load. But also in long-term settings, such as in chronic or repeated volume load, there are changes in cardiac dimensions and mass termed cardiac hypertrophy. Depending on the stimulus imposing the volume load this hypertrophy differs in extent and phenotype. We aimed to study cardiac function in two settings with long-term volume load, including patients previously operated for aortic regurgitation and healthy females performing endurance training. Methods. In paper I, 21 patients (age 52±12 years, all male) operated on with aortic valve replacement for aortic regurgitation (AR) underwent a cardiopulmonary exercise test (CPET) and an echocardiographic evaluation in average 49±15 months following surgery. The peak oxygen uptake (peakVO2) was compared to results from a pre-operative and a six months follow-up, and relations to echocardiographic measures were determined. In papers II–IV, 48 endurance trained female athletes (ATH, age 21±2 years) were compared to 46 untrained females (CON, age 21±2 years) regarding echocardiographic measures of cardiac dimensions, global and regional cardiac function and maximal aerobic capacity (VO2max) determined with CPET. Relations between VO2max and cardiac variables were explored. Results. In paper I, peakVO2 had decreased from 26±6 to 23±5 mL/kg/min in patients from the first to second, late follow-up. This decrease was larger than expected by their increased age alone, and a majority of patients had a cardiorespiratory fitness below average according to reference values from healthy subjects of the same age, sex and weight. In papers II–IV, we found that ATH (VO2max 52±5 mL/kg/min) had larger atrial, ventricular and inferior vena cava dimensions compared to CON (VO2max 39±5 mL/kg/min). ATH had increased measures of right ventricular (RV) systolic function (RV atrioventricular plane displacement indexed by cardiac length 2.5±0.3 vs. 2.3±0.3, p=0.001) and left ventricular (LV) diastolic function (mitral E-wave velocity 0.92±0.17 vs. 0.86±0.11 m/s, p=0.029). In addition, systolic synchrony was similar between groups while there were heterogeneous differences in diastolic and systolic function across different myocardial segments. VO2max was most strongly related to LV end-diastolic volume (r=0.709, p<0.001). Conclusions. Decreasing peakVO2 following surgery for AR, despite a normalisation in cardiac dimension could either be a result of a remaining, slight myocardial dysfunction or post-operative negative influence on cardiac performance by filling disturbances or the prosthetic valve itself, or, a sign of an inadequate post-operative level of physical activity and lack of exercise training. This stresses the importance of post-operative management and methods for increasing aerobic capacity, where exercise testing could be valuable for guiding patients and tailoring exercise protocols. The eccentric cardiac hypertrophy in ATH, symmetrically distributed across the heart, depicts the physiological hypertrophy in response to volume load in endurance training. Cardiac function was similar, or for some measures slightly improved in ATH compared to CON and LV dimensions, rather than cardiac function, were predictors of VO2max. As the heart of female athletes has been far less studied than that in males, our results add knowledge regarding the female athlete’s heart, and our results of differences in segmental cardiac function merits further research

Summary

Decreased aerobic capacity 4 years after aorti

Vascular Adaptation to Indoor Cycling Exercise in Premenopausal Women

The early vascular adaptation to indoor cycling, a popular activity at many fitness centres, is incompletely evaluated. Forty two healthy women (21-45 years) underwent measurements of arterial wall properties and geometry as well as a maximal bicycle exercise test before and after a 3 months period during which 21 of the women joined indoor cycling classes at a gym 2-3 times per week, while 21 women served as time controls. Peak work load increased by in average 16% (pamp;lt;0.001) and ascending aortic diameter by 4% (pamp;lt;0.01) in the exercise group, while unchanged in control group. The exercise intervention had no significant influence on the local intima-media thickness, blood pressure or the pulse pressure wave configuration while the carotid artery distensibility (pamp;lt;0.05) was higher after the intervention. There was a positive correlation between change in () peak work load and -diameter of tubular ascending aorta (r=0.42, pamp;lt;0.01) in the exercise group. In conclusion, after only 3 months of bicycle exercise training, signs of central arterial remodelling were seen in premenopausal women, which was associated to improvement in exercise capacity.Funding Agencies|Futurum-academy for Health and Care Region Jonkoping County, Sweden; FORSS-the Research Council of South-East Sweden; Linkoping University Hospital; Swedish Research Council [12161]; Swedish Heart-Lung Foundation</p

Decreased aerobic capacity 4 years after aortic valve replacement in male patients operated upon for chronic aortic regurgitation

Exercise testing is underutilized in patients with valve disease. We have previously found a low physical work capacity in patients with aortic regurgitation 6 months after aortic valve replacement (AVR). The aim of this study was to evaluate aerobic capacity in patients 4 years after AVR, to study how their peak oxygen uptake (peakVO2) had changed postoperatively over a longer period of time. Twenty-one patients (all men, 52 +/- 13 years) who had previously undergone cardiopulmonary exercise testing (CPET) pre- and 6 months postoperatively underwent maximal exercise testing 49 +/- 15 months postoperatively using an electrically braked bicycle ergometer. Breathing gases were analysed and the patients physical fitness levels categorized according to angstrom strands and Wassermans classifications. Mean peakVO2 was 22.8 +/- 5.1 ml x kg-1 x min-1 at the 49-month follow-up, which was lower than at the 6-month follow-up (25.6 +/- 5.8 ml x kg-1 x min-1, P = 0.001). All but one patient presented with a physical fitness level below average using angstrom strands classification, while 13 patients had a low physical capacity according to Wassermans classification. A significant decrease in peakVO2 was observed from six to 49 months postoperatively, and the decrease was larger than expected from the increased age of the patients. CPET could be helpful in timing aortic valve surgery and for the evaluation of need of physical activity as part of a rehabilitation programme.Funding Agencies|Swedish Heart and Lung foundation||County Council of Ostergotland, Sweden||</p

Decreased aerobic capacity 4 years after aortic valve replacement in male patients operated upon for chronic aortic regurgitation

Exercise testing is underutilized in patients with valve disease. We have previously found a low physical work capacity in patients with aortic regurgitation 6 months after aortic valve replacement (AVR). The aim of this study was to evaluate aerobic capacity in patients 4 years after AVR, to study how their peak oxygen uptake (peakVO2) had changed postoperatively over a longer period of time. Twenty-one patients (all men, 52 +/- 13 years) who had previously undergone cardiopulmonary exercise testing (CPET) pre- and 6 months postoperatively underwent maximal exercise testing 49 +/- 15 months postoperatively using an electrically braked bicycle ergometer. Breathing gases were analysed and the patients physical fitness levels categorized according to angstrom strands and Wassermans classifications. Mean peakVO2 was 22.8 +/- 5.1 ml x kg-1 x min-1 at the 49-month follow-up, which was lower than at the 6-month follow-up (25.6 +/- 5.8 ml x kg-1 x min-1, P = 0.001). All but one patient presented with a physical fitness level below average using angstrom strands classification, while 13 patients had a low physical capacity according to Wassermans classification. A significant decrease in peakVO2 was observed from six to 49 months postoperatively, and the decrease was larger than expected from the increased age of the patients. CPET could be helpful in timing aortic valve surgery and for the evaluation of need of physical activity as part of a rehabilitation programme.Funding Agencies|Swedish Heart and Lung foundation||County Council of Ostergotland, Sweden||</p

Classification and occurrence of an abnormal breathing pattern during cardiopulmonary exercise testing in subjects with persistent symptoms following COVID-19 disease

Reduced exercise capacity and several limiting symptoms during exercise have been reported following severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. From clinical observations, we hypothesized that an abnormal breathing pattern (BrP) during exercise may be common in these patients and related to reduced exercise capacity. We aimed to (a) evaluate a method to classify the BrP as normal/abnormal or borderline in terms of inter-rater agreement; (b) determine the occurrence of an abnormal BrP in patients with post-COVID; and (c) compare characteristics of post-COVID patients with normal and abnormal BrP. In a retrospective, cross-sectional study of patients referred for CPET due to post-COVID April 2020-April 2021, we selected subjects without a history of intensive care and with available medical records. Three raters independently categorized patients BrP as normal, abnormal, or borderline, using four traditional CPET plots (respiratory exchange ratio, tidal volume over ventilation, ventilatory equivalent for oxygen, and ventilation over time). Out of 20 patients (11 male), 10 were categorized as having a normal, 7 an abnormal, and three a borderline BrP. Inter-rater agreement was good (Fleiss kappa: 0.66 [0.66-0.67]). Subjects with an abnormal BrP had lower peak ventilation, lower exercise capacity, similar ventilatory efficiency and a similar level of dyspnea at peak exercise, as did subjects with a normal BrP. Patients BrP was possible to classify with good agreement between observers. A third of patients had an abnormal BrP, associated with lower exercise capacity. which could possibly explain exercise related symptoms in some patients with post-COVID syndrome

Authors reply to Reference values for systolic blood pressure at upright bicycle exercise tests by Alfred Hager

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Cardiac systolic regional function and synchrony in endurance trained and untrained females

Background Most studies on cardiac function in athletes describe overall heart function in predominately male participants. We aimed to compare segmental, regional and overall myocardial function and synchrony in female endurance athletes (ATH) and in age-matched sedentary females (CON). Methods In 46 ATH and 48 CON, echocardiography was used to measure peak longitudinal systolic strain and myocardial velocities in 12 left ventricular (LV) and 2 right ventricular (RV) segments. Regional and overall systolic function were calculated together with four indices of dyssynchrony. Results There were no differences in regional or overall LV systolic function between groups, or in any of the four dyssynchrony indices. Peak systolic velocity (s′) was higher in the RV of ATH than in CON (9.7±1.5 vs 8.7±1.5 cm/s, p=0.004), but not after indexing by cardiac length (p=0.331). Strain was similar in ATH and CON in 8 of 12 LV myocardial segments. In septum and anteroseptum, basal and mid-ventricular s′ was 6–7% and 17–19% higher in ATH than in CON (p&lt;0.05), respectively, while s′ was 12% higher in CON in the basal LV lateral wall (p=0.013). After indexing by cardiac length, s′ was only higher in ATH in the mid-ventricular septum (p=0.041). Conclusions We found differences between trained and untrained females in segmental systolic myocardial function, but not in global measures of systolic function, including cardiac synchrony. These findings give new insights into cardiac adaptation to endurance training and could also be of use for sports cardiologists evaluating female athletes