Prediction Of Oxygen Consumption Research Articles

Pulmonary responses following cardiac rehabilitation and the relationship with functional outcomes in children and young adults with heart disease.

Patients with congenital heart disease (CHD) often have pulmonary abnormalities and exercise intolerance following cardiac surgery. Cardiac rehabilitation (CR) improves exercise capacity in patients with CHD, but minimal study has been performed to see if resting and dynamic pulmonary performance improves following CR in those with prior cardiac surgery. This was a retrospective cohort study of all patients who completed ≥12 weeks of CR from 2018 through 2022. Demographic, cardiopulmonary exercise test (CPET), spirometry, 6-minute walk, functional strength measures, and outcomes data were collected. Data are presented as median[IQR]. A Student's t-test was used for comparisons between groups and serial measurements were measured with a paired t-test. A p < 0.05 was considered significant. There were a total of 37 patients [age 16.7 (14.2-20.1) years; 46% male] included. Patients with prior surgery (n = 26) were more likely to have abnormal spirometry data than those without heart disease (n = 11) (forced vital capacity [FVC] 76.7 [69.1-84.3]% vs. 96.4 [88.1-104.7]%, p = 0.002), but neither group experienced a significant change in spirometry. On CPET, peak oxygen consumption increased but there was no change in other pulmonary measures during exercise. Percent predicted FVC correlated with hand grip strength (r = 0.57, p = 0.0003) and percent predicted oxygen consumption (r = 0.43, p = 0.009). The number of prior sternotomies showed negative associations with both percent predicted FVC (r = -0.43, p = 0.04) and FEV1 (r = -0.47, p = 0.02). Youth and young adults with a prior history of cardiac surgery have resting and dynamic pulmonary abnormalities that do not improve following CR. Multiple sternotomies are associated with worse pulmonary function.

Net Heart Rate for Estimating Oxygen Consumption in Active Adults.

The aim of this study was to verify the accuracy of predicting oxygen consumption (O2) in predominantly aerobic activities based on net heart rate (netHR), sex, and body mass index (BMI) in active adults. NetHR is the value of the difference between the resting HR (HRrest) and the average HR value obtained during a given session or period of physical activity. These activities must be continuous, submaximal, and of a stabilized intensity. The magnitude of the netHR depends mainly on the intensity of the exercise. The HR is measured in beats per minute (bpm). A total of 156 participants, 52 women and 104 men, between the ages of 18 and 81, had their netHR and net oxygen intake (netVO2) assessed. There were 79 participants in group 1 (prediction sample) (52 males and 27 females). There were 77 people in group 2 (validation sample) (52 males and 25 females). The results of the multiple linear regression showed that netVO2 (R2 = 85.2%, SEE = 3.38) could be significantly predicted by sex (p < 0.001), netHR (p < 0.001), and BMI (p < 0.001). The Bland-Altman plots satisfied the agreement requirements, and the comparison of the measured and estimated netVO2 revealed non-significant differences with a trivial effect size. We calculated the formula NetVO2 (mL/(kg·min)) = 16 + 3.67 (sex) + 0.27 (netHR) - 0.57 (BMI) to predict netVO2, where netVO2 is the amount of oxygen uptake (mL/(kg·min)) above the resting value, netHR is the heart rate (beats per minute) above the resting value measured during exercise, sex is equal to zero for women and one for men, and BMI is the body mass index. In addition, based on the knowledge of VO2, it was possible to estimate the energy expenditure from a particular training session, and to determine or prescribe the exercise intensity in MET (metabolic equivalent of task).

Unsupervised Cluster Analysis Reveals Distinct Subtypes of ME/CFS Patients Based on Peak Oxygen Consumption and SF-36 Scores

PurposeMyalgic encephalomyelitis, commonly referred to as chronic fatigue syndrome (ME/CFS), is a severe, disabling chronic disease and an objective assessment of prognosis is crucial to evaluate the efficacy of future drugs. Attempts are ongoing to find a biomarker to objectively assess the health status of (ME/CFS), patients. This study therefore aims to demonstrate that oxygen consumption is a biomarker of ME/CFS provides a method to classify patients diagnosed with ME/CFS based on their responses to the Short Form-36 (SF-36) questionnaire, which can predict oxygen consumption using cardiopulmonary exercise testing (CPET). MethodsTwo datasets were used in the study. The first contained SF-36 responses from 2,347 validated records of ME/CFS diagnosed participants, and an unsupervised machine learning model was developed to cluster the data. The second dataset was used as a validation set and included the cardiopulmonary exercise test (CPET) results of 239 participants diagnosed with ME/CFS. Participants from this dataset were grouped by peak oxygen consumption according to Weber's classification. The SF-36 questionnaire was correctly completed by only 92 patients, who were clustered using the machine learning model. Two categorical variables were then entered into a contingency table: the cluster with values {0,1} and Weber classification {A, B, C, D} were assigned. Finally, the Chi-square test of independence was used to assess the statistical significance of the relationship between the two parameters. FindingsThe results indicate that the Weber classification is directly linked to the score on the SF-36 questionnaire. Furthermore, the 36-response matrix in the machine learning model was shown to give more reliable results than the subscale matrix (p − value < 0.05) for classifying patients with ME/CFS. ImplicationsLow oxygen consumption on CPET can be considered a biomarker in patients with ME/CFS. Our analysis showed a close relationship between the cluster based on their SF-36 questionnaire score and the Weber classification, which was based on peak oxygen consumption during CPET. The dataset for the training model comprised raw responses from the SF-36 questionnaire, which is proven to better preserve the original information, thus improving the quality of the model.

Surrogate Modelling for Oxygen Uptake Prediction Using LSTM Neural Network.

Oxygen uptake (V˙O2) is an important metric in any exercise test including walking and running. It can be measured using portable spirometers or metabolic analyzers. Those devices are, however, not suitable for constant use by consumers due to their costs, difficulty of operation and their intervening in the physical integrity of their users. Therefore, it is important to develop approaches for the indirect estimation of V˙O2-based measurements of motion parameters, heart rate data and application-specific measurements from consumer-grade sensors. Typically, these approaches are based on linear regression models or neural networks. This study investigates how motion data contribute to V˙O2 estimation accuracy during unconstrained running and walking. The results suggest that a long short term memory (LSTM) neural network can predict oxygen consumption with an accuracy of 2.49 mL/min/kg (95% limits of agreement) based only on speed, speed change, cadence and vertical oscillation measurements from an inertial navigation system combined with a Global Positioning System (INS/GPS) device developed by our group, worn on the torso. Combining motion data and heart rate data can significantly improve the V˙O2 estimation resulting in approximately 1.7-1.9 times smaller prediction errors than using only motion or heart rate data.

Peak Work Rate Increases With Lower Extremity-Focused Exercise Training in Adolescents With Fontan Circulation.

Background Skeletal muscle deficits are associated with worse exercise performance in the Fontan circulation and may be improved by exercise training. We aimed to assess the change in leg lean mass (a marker of skeletal muscle), exercise performance, and functional health status after a lower extremity-focused exercise intervention in adolescents with Fontan circulation. Methods and Results Densitometry for measurement of leg lean mass, cardiopulmonary exercise test, exercise cardiac magnetic resonance, peripheral vascular testing, physical activity questionnaire, and quality of life assessment were performed at baseline and after a 24-week, hybrid center- and home-based training program. Leg lean mass Z-scores were generated, and exercise parameters were expressed as percentage expected based on reference data. The effect of training was assessed by paired t-tests and simple linear regression. Twenty participants (15.6±1.7 years, 50% male) demonstrated low baseline leg lean mass Z-scores with no significant improvement with training (-1.38±1.02 pre versus -1.31±1.06 post, P=0.33). Maximum and percent predicted work increased from 121.9±29.8 (0.66±0.12) to 131.3±35.1 (0.70±0.15) watts (P=0.02). Peak respiratory exchange ratio increased (1.19±0.02 versus 1.25±0.01, P=0.02) but percent predicted oxygen consumption was unchanged, suggesting higher anaerobic activity after training. Physical activity questionnaire score positively associated with peak work at baseline (ß=18.13 [95% CI, 0.83-35.44], R2=0.21; P=0.04) but physical activity questionnaire, quality of life scores, exercise cardiac magnetic resonance performance, and peripheral vascular function were unchanged with training. Conclusions Peak work rate and anaerobic activity increased with lower extremity-focused training in adolescents with Fontan circulation. Larger studies should test the impact of these changes on functional status and quality of life.

Hybrid Model for Predicting Oxygen Consumption in BOF Steelmaking Process Based on Cluster Analysis

The amount of oxygen blown into the converter directly affects the productivity of the converter and the quality of the molten steel, so it is crucial to accurately predict oxygen consumption. Herein, a hybrid model for predicting oxygen consumption in basic oxygen furnace steelmaking process is established. The oxygen consumption of converter is divided into two types: the determined oxygen consumption and the estimated oxygen consumption. The determined oxygen consumption is calculated by mechanism model. And the estimated oxygen consumption is calculated by statistical model. The method of cluster analysis is also introduced into the model. After clustering the data, a statistical model for predicting the estimated oxygen consumption in each subcategory is established, which further improves the prediction accuracy of the model. After dividing the original data into three categories, the hit rate of the hybrid model is 93.3%, when the relative errors of the model are restricted within 5%. As a result, the hybrid model is fully capable of predicting oxygen consumption in converters.

MRI Phase-Contrast Blood Flow in Fasting Pediatric Patients with Fontan Circulation Correlates with Exercise Capacity.

To assess regional blood flow in fasting pediatric patients with Fontan circulation by using MRI and to explore associations with clinical parameters. In this retrospective study, pediatric patients who had undergone the Fontan procedure (<18 years of age) and had undergone clinical cardiac MRI, performed after at least 4 hours of fasting, between 2018 and 2021 were included. Regional blood flow was compared with published healthy volunteer data (n = 19) and assessed in relation to hemodynamic parameters and clinical status. Data are presented as medians, with first to third quartiles in parentheses. Mann-Whitney U, Kruskal-Wallis, χ2, and Spearman rank correlation tests were used. Fifty-five patients (38 boys) with median age at MRI of 14 years (IQR, 11-16 years) and median time from Fontan procedure to MRI of 10 years (IQR, 8-12 years) were included. Patients after Fontan procedure had lower ascending aortic, inferior vena cava, and total systemic blood flow compared with healthy volunteers (3.00 L/min/m2 [IQR, 2.75-3.30 L/min/m2] vs 3.61 L/min/m2 [IQR, 3.29-4.07 L/min/m2]; 1.73 L/min/m2 [IQR, 1.40-1.94 L/min/m2] vs 2.24 L/min/m2 [IQR, 2.06-2.75 L/min/m2]; 2.78 L/min/m2 [IQR, 2.45-3.10 L/min/m2] vs 3.95 L/min/m2 [IQR, 3.20-4.30 L/min/m2], respectively; P < .001). Portal vein flow was greater than hepatic vein flow in 25% of patients. Fontan blood flow was inversely correlated with pre-Fontan mean pulmonary artery pressure (Spearman rank correlation coefficient [rs ]= -0.42, P = .005) and ventricular end diastolic pressure (rs = -0.33, P = .04) and positively correlated with post-Fontan percent predicted oxygen consumption at peak workload (rs = 0.34, P = .02). Reference ranges are provided for regional systemic blood flow derived by using MRI in fasting pediatric patients with Fontan circulation, who had lower systemic blood flow compared with healthy volunteers. Lower fasting Fontan blood flow correlated with lower exercise capacity.Keywords: Pediatrics, Heart, Congenital, MR Imaging, Hemodynamics/Flow Dynamics, Cardiac Supplemental material is available for this article. © RSNA, 2022.

Markers of Right Ventricle Dysfunction Predict Exercise Capacity on Left Ventricular Assist Device (LVAD) Patients

<h3>Purpose</h3> Although Left Ventricular Assist Device (LVAD) improves functional capacity, on average LVAD patients are unable to achieve the aerobic capacity of normal healthy subjects or mild heart failure patients. The aim of this study was to examine if markers of right ventricular (RV) function influence maximal exercise capacity. <h3>Methods</h3> This was a single-centre prospective study that enrolled 20 consecutive HeartWare ventricular assist device (HVAD) patients who were admitted at the Freeman Hospital (Newcastle upon Tyne, United Kingdom) for a heart transplant assessment from August 2017 to October 2018. <h3>Results</h3> Mean peak oxygen consumption (Peak VO₂) was 14.0 ± 5.0 ml/kg/min, and mean peak age and gender-adjusted percent predicted oxygen consumption (%VO₂) was 40.0 ± 11.5 %. Patients were subdivided into 2 groups based on the median peak VO₂, so each group consisted of 10 patients (50%). Right-sided and pulmonary pressures were consistently higher in the group with poorer exercise tolerance. Patients with poor exercise tolerance (peak VO₂ below the median) had higher right atrial pressures at rest (10.6mmHg ± 6.4 versus 4.3mmHg ± 3.2, p=0.02) and the increase with passive leg raising was significantly greater than those with preserved exercise tolerance (peak VO₂ above the median). Patients with poor functional capacity also had greater RV dimensions (4.4 cm ± 0.5 versus 3.7 cm ± 0.5, p=0.02) and a higher incidence of significant tricuspid regurgitation (TR) (moderate or severe TR in 5 patients in the poor exercise capacity group versus none in the preserved exercise capacity group, p=0.03). <h3>Conclusion</h3> Echocardiographic and hemodynamic markers of RV dysfunction discriminate between preserved and non-preserved exercise capacity in HVAD patients.

Progression in Fontan conduit stenosis and hemodynamic impact during childhood and adolescence

ObjectiveTo characterize changes in Fontan conduit size over time and determine if cross-sectional area (CSA) affects cardiac output, pulmonary artery growth, and exercise capacity. MethodsWe conducted a retrospective cross-sectional study of patients with Fontan physiology who underwent cardiac magnetic resonance imaging or cardiac catheterization between January 2013 and October 2019. We collected Fontan and pulmonary artery measurements, hemodynamic data, and cardiopulmonary exercise test data. We identified 158 patients with an extracardiac Fontan. We measured minimum and mean Fontan conduit CSA and assessed whether these correlated with Nakata index, cardiac index, or exercise capacity. ResultsMinimum Fontan CSA decreased by a median of 33% (24%, 40%) during a mean follow-up of 9.6 years. Median percentage decrease in Fontan CSA did not differ among 16-, 18-, and 20-mm conduits (P = .29). There was a significant decrease in the minimum Fontan CSA (33% [25%, 41%]) starting less than 1-year post-Fontan. Median Nakata index was 177.6 mm2/m2 (149.1, 210.8) and was not associated with Fontan CSA/BSA (ρ = 0.09, P = .29). Fontan CSA/BSA was not associated with cardiac index (ρ = –0.003, P = .97). A larger Fontan CSA/BSA had a modest correlation with % predicted oxygen consumption (ρ = 0.31, P = .013). ConclusionsFontan conduit CSA decreases as early as 6 months post-Fontan. The minimum Fontan CSA/BSA was not associated with cardiac index or pulmonary artery size but did correlate with % predicted peak oxygen consumption.

Maximal versus sub-maximal effort during cardiopulmonary exercise testing in adults with congenital heart disease: outcome analysis of short-term cardiac-related events.

Peak respiratory exchange ratio is an objective marker of patient effort during cardiopulmonary exercise testing. We evaluated exercise variables in 175 adult congenital heart disease patients and the impact of respiratory exchange ratio on the prognostic value of exercise variables for short-term cardiac-related events. Of 175 patients, 110 completed the exercise test with a peak respiratory exchange ratio of ≥1.10 and the remaining 65 had a peak respiratory exchange ratio of <1.10. Peak oxygen consumption, the percentage of oxygen consumption at the ventilatory threshold, peak heart rate, percentage predicted peak heart rate, double product, oxygen uptake efficiency slope, and the number of patients with exercise oscillatory ventilation were reduced significantly in patients with a respiratory exchange ratio of <1.10 compared to those with a respiratory exchange ratio of ≥1.10. After a median follow-up of 21 months, total cardiac-related events occurred in 37 (21%) patients. Multivariate Cox proportional hazard analysis showed that the percentage predicted peak oxygen consumption, and oxygen uptake efficiency slope were independent predictors of cardiac-related events only in patients with a peak respiratory exchange ratio of ≥1.10. Sub-maximal exercise performance can be preserved in adult congenital heart disease patients. The percentage predicted oxygen consumption and the oxygen uptake efficiency slope are two independent predictors for short-term cardiac-related events in adult congenital heart disease patients.

Markers of Right Ventricular Dysfunction Predict Maximal Exercise Capacity After Left Ventricular Assist Device Implantation.

Although left ventricular assist device (LVAD) improves functional capacity, on average LVAD patients are unable to achieve the aerobic capacity of normal healthy subjects or mild heart failure patients. The aim of this study was to examine if markers of right ventricular (RV) function influence maximal exercise capacity. This was a single-center prospective study that enrolled 20 consecutive HeartWare ventricular assist device patients who were admitted at the Freeman Hospital (Newcastle upon Tyne, United Kingdom) for a heart transplant assessment from August 2017 to October 2018. Mean peak oxygen consumption (Peak VO2) was 14.0 ± 5.0 ml/kg/min, and mean peak age and gender-adjusted percent predicted oxygen consumption (%VO2) was 40.0% ± 11.5%. Patients were subdivided into two groups based on the median peak VO2, so each group consisted of 10 patients (50%). Right-sided and pulmonary pressures were consistently higher in the group with poorer exercise tolerance. Patients with poor exercise tolerance (peak VO2 below the median) had higher right atrial pressures at rest (10.6 ± 6.4 vs. 4.3 mmHg ± 3.2; p = 0.02) and the increase with passive leg raising was significantly greater than those with preserved exercise tolerance (peak VO2 above the median). Patients with poor functional capacity also had greater RV dimensions (4.4 cm ± 0.5 vs. 3.7 cm ± 0.5; p = 0.02) and a higher incidence of significant tricuspid regurgitation (moderate or severe tricuspid regurgitation in five patients in the poor exercise capacity group vs. none in the preserved exercise capacity group; p = 0.03). In conclusion, echocardiographic and hemodynamic markers of RV dysfunction discriminate between preserved and nonpreserved exercise capacity in HeartWare ventricular assist device patients.

Validation of the Severity of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome by Other Measures than History: Activity Bracelet, Cardiopulmonary Exercise Testing and a Validated Activity Questionnaire: SF-36.

Introduction: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a severe and disabling chronic disease. Grading patient’s symptom and disease severity for comparison and therapeutic decision-making is necessary. Clinical grading that depends on patient self-report is subject to inter-individual variability. Having more objective measures to grade and confirm clinical grading would be desirable. Therefore, the aim of this study was to validate the clinical severity grading that has been proposed by the authors of the ME International Consensus Criteria (ICC) using more standardized measures like questionnaires, and objective measures such as physical activity tracking and cardiopulmonary exercise testing. Methods and results: The clinical database of a subspecialty ME/CFS clinic was searched for patients who had completed the SF 36 questionnaire, worn a SensewearTM armband for five days, and undergone a cardiopulmonary exercise test. Only patients who completed all three investigations within 3 months from each other—to improve the likelihood of stable disease—were included in the analysis. Two-hundred-eighty-nine patients were analyzed: 121 were graded as mild, 98 as moderate and 70 as having severe disease. The mean (SD) physical activity subscale of the SF-36 was 70 (11) for mild, 43 (8) for moderate and 15 (10) for severe ME/CFS patients. The mean (SD) number of steps per day was 8235 (1004) for mild, 5195 (1231) for moderate and 2031 (824) for severe disease. The mean (SD) percent predicted oxygen consumption at the ventilatory threshold was 47 (11)% for mild, 38 (7)% for moderate and 30 (7)% for severe disease. The percent peak oxygen consumption was 90 (14)% for mild, 64 (8)% for moderate and 48 (9)% for severe disease. All comparisons were p < 0.0001. Conclusion: This study confirms the validity of the ICC severity grading. Grading assigned by clinicians on the basis of patient self-report created groups that differed significantly on measures of activity using the SF-36 physical function subscale and objective measures of steps per day and exercise capacity. There was variability in function within severity grading groups, so grading based on self-report can be strengthened by the use of these supplementary measures.

Gaussian Process-Based Hybrid Model for Predicting Oxygen Consumption in the Converter Steelmaking Process

Oxygen is one of the most important energies used in converter steelmaking processes of integrated iron and steel works. Precisely forecasting oxygen consumption before processing can benefit process control and energy optimization. This paper assumes there is a linear relationship between the oxygen consumption and input materials, and random noises are caused by other unmeasurable materials and unobserved reactions. Then, a novel hybrid prediction model integrating multiple linear regression (MLR) and Gaussian process regression (GPR) is introduced. In the hybrid model, the MLR method is developed to figure the global trend of the oxygen consumption, and the GPR method is applied to explore the local fluctuation caused by noise. Additionally, to accelerate the computational speed on the practical data set, a K-means clustering method is devised to respectively train a number of GPR models. The proposed hybrid model is validated with the actual data collected from an integrated iron and steel work in China, and compared with benchmark prediction models including MLR, artificial neural network, support vector machine and standard GPR. The forecasting results indicate that the suggested model is able to not only produce satisfactory point forecasts, but also estimate accurate probabilistic intervals.

Pulmonary effects on exercise testing in tetralogy of Fallot patients repaired with a transannular patch.

A transannular patch is often used in the contemporary surgical repair of tetralogy of Fallot. This can lead to significant pulmonary insufficiency and increased right ventricular volumes and ultimately pulmonary valve replacement. Cardiopulmonary exercise testing is used to assess exercise capacity in tetralogy of Fallot patients before pulmonary valve replacement. There is only few published literatures on how lung function affects functional capacity in tetralogy of Fallot patients repaired with a transannular patch. A retrospective chart review was done from 2015 to 2017 on patients with tetralogy of Fallot who underwent maximal effort cardiopulmonary exercise testing with cycle ergometry and with concurrent pulmonary function testing. Tetralogy of Fallot patients repaired with a transannular patch without pulmonary valve replacement were compared with age, gender, and size-matched normal controls. In the tetralogy of Fallot group, 24 out of 57 patients underwent primary repair with a transannular patch. When compared to the normal controls, they demonstrated abnormal predicted forced expiratory volume in one second (79 ± 23.1% versus 90.7 ± 14.1%, p&lt;0.05), predicted maximal voluntary ventilation (74 ± 18% versus 90.5 ± 16.2%, p&lt;0.05) while having low-normal predicted forced vital capacity (80.5 ± 17.2% versus 90.2 ± 12.4%, p&lt;0.05) and normal breathing reserve percentage (50.3 ± 11.3% versus 47.5 ± 17.3%, p = 0.52). Cardiopulmonary exercise testing abnormalities included significantly lower percent predicted oxygen consumption (63.2 ± 12.2% versus 87 ± 12.1%, p&lt;0.05), maximal heart rate (171.8 ± 18.9 versus 184.6 ± 13.6, p&lt;0.05), and percent predicted maximum workload (61.7 ± 15.9% versus 88.3 ± 21.5%, p&lt;0.05). Tetralogy of Fallot patients repaired with a transannular patch can have abnormal pulmonary function testing with poor exercise capacity in addition to chronotropic incompetence and impaired muscular power.

P6521Comparison of peak oxygen consumption and percent of predicted oxygen consumption for predicting prognosis in young and female heart failure patients

P6521Comparison of peak oxygen consumption and percent of predicted oxygen consumption for predicting prognosis in young and female heart failure patients

Accelerometry-Derived Relative Exercise Intensities in Elite Women's Basketball.

This study assessed accelerometry-derived relative exercise intensity during elite women's basketball match play. The influence of player position/role and match period on relative exercise intensities was evaluated. Ten basketballers wore accelerometers during a Yo-Yo intermittent recovery test (Yo-Yo-IR1) and 18 competitive matches. Relative exercise intensity was quantified using predicted oxygen consumption reserve determined using correlations from Yo-Yo-IR1. Total time, bout frequency and bout duration were calculated in seven intensity zones and compared between quarters, positions (back-court vs. front-court) and roles (starters vs. bench). Back-court players spent 6.0±1.9% more match time performing supramaximal activity when compared to front-court players (p<0.045). Back-court players experienced more supramaximal bouts (125±37 vs. 52±36; p=0.031) of greater average duration (2.1±0.4 vs. 1.4±0.2 s; p=0.021) and maximum duration (7±2 vs. 3±1 s; p=0.020). More sedentary to very light activity was observed in the 2nd and 4th quarters compared to the 1st and 3rd quarters (p<0.05). Despite reduced playing time, bench players performed similar amounts of maximal and supramaximal exercise when compared to starters (p≥0.279). Player position, role and match periods influence the demands of women's basketball; these factors should be considered when designing match-specific conditioning programs.

Influence of Stream‐Subsurface Exchange Flux and Bacterial Biofilms on Oxygen Consumption Under Nutrient‐Rich Conditions

AbstractThe lack of a complete understanding of the complex reciprocal interactions between hydrological processes and the structure and function of microbial communities limits our ability to improve the predictions of microbial metabolism in streams. We report here on how overlying water velocity and losing and gaining flux interact with bacterial community structure and its activity to control oxygen consumption in a sandy streambed under high nutrient levels. We used an experimental flume packed with natural sediment and measured the bacterial biomass distribution and oxygen profiles in the streambed and across bed forms. Local oxygen consumption rates were calculated with a 1‐D numerical model (GRADIENT). Bacterial abundance and production rates varied across the bed form within 1 order of magnitude, while their taxonomic classes were similar across bed forms despite variations in flow conditions and sediment disturbance events. However, bacterial production rates were not directly correlated with bacterial abundance. On the other hand, oxygen consumption rates ranged over 4 orders of magnitude across the bed forms and were highly correlated with the vertical exchange flux between the water and the streambed. The results strongly suggest that under high nutrient levels, the system is, in general, transport limited and that predicting oxygen consumption rates depends on local vertical exchange fluxes.

Revisiting The ACSM Metabolic Equation For Walking

The ACSM has long published a metabolic equation using walking speed and grade to predict oxygen consumption. The small homogeneous sample (n=3, trained men) used to derive the speed component of this equation calls into question its generalizability. Further, the equation’s free-living application is limited by the difficulty of measuring speed. Conversely, walking cadence (steps/min) is a practical and measurable metric that has been shown to be a reasonable proxy for walking intensity. PURPOSE: To develop a metabolic equation using cadence to predict oxygen consumption (VO2; mL/kg/min) during level walking (and compare its predictive accuracy to that of the ACSM metabolic equation) in a large sample of men and women aged 21-40 years. METHODS: Sixty-nine adults (52% women, mean±SD age=30.0±5.6 years, BMI=24.6±3.3 kg/m2) completed 5-min treadmill bouts separated by 2-min rest at four speeds: 53.6, 67.1, 80.5, and 93.9 m/min (2.0, 2.5, 3.0, 3.5 mph). The cadence-VO2 relationship was quantified with a quadratic model of best fit, producing the cadence metabolic equation. For an unbiased evaluation of this equation, leave one out cross-validation (LOOCV) was then performed and the root mean square error (RMSE) was calculated. The ACSM metabolic equation for walking was then applied to these data for comparison, and its predictive accuracy was evaluated by determining its RMSE. The bias of both metabolic equations was also calculated. RESULTS: The cadence metabolic equation was [VO (mL/kg/min) = 0.0021*C2 – 0.24*C + 15.4, where C2 = cadence]. The RMSE [±95% CI] from the LOOCV of the cadence metabolic equation was 2.5 [±1.0] mL/kg/min and its bias [±95% CI] was 0.6 [±0.3] mL/kg/min. The RMSE from applying the ACSM walking metabolic equation to this data was 3.1 [±1.2] mL/kg/min, with a bias of -2.5 [±0.2] mL/kg/min. CONCLUSION: In the same way that speed is used in the ACSM metabolic equation, cadence may also be used in a walking metabolic equation with similar error and reduced bias. The greater sample size and sex distribution used herein to develop this cadence-based metabolic equation suggests greater potential to produce accurate and generalizable estimations. Future research should test this equation during overground walking and incorporate grade as an additional variable.

Proportionality of Anthropometric and Physical Fitness Performance on Youth Aerobic Capacity Model

Oxygen consumption is linked to the overall fitness performance and all the causes of the mortality and cardio-respiratory fitness is determined by the oxygen consumption. The purpose of the current study was to determine the relationship between predicted oxygen consumption towards physical fitness and anthropometric components on Malaysian youth. A total of 219 male student-athletes randomly were recruited to participate in this study with aged between 13-15 years old groups from entire state in Malaysia. Anthropometric and physical fitness battery test were conducted to the student-athletes and recorded for further analysis. To achieve an objective, Multiple Linear Regression were computed whereas VO2max denoted as a determiner meanwhile others physical fitness components and anthropometrics were selected for the predictors. Even though aerobic capacity model shows weak association on anthropometrics and physical performances (R2= 0.275, ? 27.5%), still it proved to be a significant effect, p

Maldistribution of pulmonary blood flow in patients after the Fontan operation is associated with worse exercise capacity

BackgroundMaldistribution of pulmonary artery blood flow (MPBF) is a potential complication in patients who have undergone single ventricle palliation culminating in the Fontan procedure. Cardiovascular magnetic resonance (CMR) is the best modality that can evaluate MPBF in this population. The purpose of this study is to identify the prevalence and associations of MPBF and to determine the impact of MPBF on exercise capacity after the Fontan operation.MethodsThis retrospective single-center study included all patients after Fontan operation who had maximal cardiopulmonary exercise test (CPET) and CMR with flow measurements of the branch pulmonary arteries. MPBF was defined as > 20% difference in branch pulmonary artery flow. Exercise capacity was measured as percent of predicted oxygen consumption at peak exercise (% predicted VO2). Linear and logistic regression models were used to determine univariate and multivariable predictors of exercise capacity and correlates of MPBF, respectively.ResultsA total of 147 patients who had CMR between 1999 and 2017 were included (median age at CMR 21.8 years [interquartile range (IQR) 16.5–30.6]) and the median time between CMR and CPET was 2.8 months [IQR 0–13.8]. Fifty-three patients (36%) had MPBF (95% CI 29–45%). The mean % predicted VO2 was 63 ± 16%. Patients with MPBF had lower mean % predicted VO2 compared to patients without MPBF (60 ± 14% versus 65 ± 16%, p = 0.04). On multivariable analysis, a lower % predicted VO2 was independently associated with longer time since Fontan, higher ventricular mass-to-volume ratio, and MPBF. On multivariable analysis, only compression of the branch pulmonary arteries by the ascending aorta or aortic root was associated with MPBF (OR 6.5, 95% CI 5.6–7.4, p < 0.001).ConclusionIn patients after the Fontan operation, MPBF is common and is independently associated with lower exercise capacity. MPBF was most likely to be caused by pulmonary artery compression by the aortic root or the ascending aorta. This study identifies MPBF as an important risk factor and as a potential target for therapeutic interventions in this fragile patient population.