Estimation Of Oxygen Consumption Research Articles

The Estimated Fick Method Systematically Over-Estimates Cardiac Index Compared to Thermodilution in Children.

Cardiac index (CI) may be derived from the Fick method, using measured or estimated oxygen consumption (VO2), or from thermodilution. In children, LaFarge VO2 estimates correlate poorly with measured VO2 values. In a large adult cohort, there was only modest correlation between estimated Fick CI (eFick CI) and thermodilution CI (TDCI).We evaluated the extent of agreement between eFick CI using LaFarge estimates of VO2 and TDCI in a pediatric cohort. A retrospective, single-center chart review of patients 3-18years of age who underwent cardiac catheterization with documented eFick CI and TDCI from 2004 to 2020 included 201 catheterizations from 161 unique patients. The mean patient age at catheterization was 12.2y (SD 4.4y). The most frequent diagnosis was cardiomyopathy, followed by congenital heart disease and pulmonary hypertension. TDCI and eFick CI differed by > 20% in 49% of catheterizations. eFick CI systematically exceeded TDCI by a mean percentage difference of 24% (SD 31%). Higher mean CI ((eFick CI + TDCI)/2) and older age were predictive of greater percent difference between eFick CI and TDCI. For each increase in mean CI by 1.0 L/min/m2, the expected percent difference in CI increased by 9.9% (p < 0.001). In pediatric patients undergoing cardiac catheterization, eFick CI with LaFarge VO2 systematically exceeds TDCI. The difference between methods is frequently > 20%, which may have clinically significant implications. Discrepancies between eFick CI and TDCI increase at higher mean CI.

Killer whale respiration rates.

Measuring breathing rates is a means by which oxygen intake and metabolic rates can be estimated to determine food requirements and energy expenditure of killer whales (Orcinus orca) and other cetaceans. This relatively simple measure also allows the energetic consequences of environmental stressors to cetaceans to be understood but requires knowing respiration rates while they are engaged in different behaviours such as resting, travelling and foraging. We calculated respiration rates for different behavioural states of southern and northern resident killer whales using video from UAV drones and concurrent biologging data from animal-borne tags. Behavioural states of dive tracks were predicted using hierarchical hidden Markov models (HHMM) parameterized with time-depth data and with labeled tracks of drone-identified behavioural states (from drone footage that overlapped with the time-depth data). Dive tracks were sequences of dives and surface intervals lasting ≥ 10 minutes cumulative duration. We calculated respiration rates and estimated oxygen consumption rates for the predicted behavioural states of the tracks. We found that juvenile killer whales breathed at a higher rate when travelling (1.6 breaths min-1) compared to resting (1.2) and foraging (1.5)-and that adult males breathed at a higher rate when travelling (1.8) compared to both foraging (1.7) and resting (1.3). The juveniles in our study were estimated to consume 2.5-18.3 L O2 min-1 compared with 14.3-59.8 L O2 min-1 for adult males across all behaviours based on estimates of mass-specific tidal volume and oxygen extraction. Our findings confirm that killer whales take single breaths between dives and indicate that energy expenditure derived from respirations requires using sex, age, and behavioural-specific respiration rates. These findings can be applied to bioenergetics models on a behavioural-specific basis, and contribute towards obtaining better predictions of dive behaviours, energy expenditure and the food requirements of apex predators.

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).

Application and performance of heart-rate-based methods to estimate oxygen consumption at different exercise intensities in postmenopausal women.

Heart rate (HR) is a widespread method to estimate oxygen consumption ( O2), exercise intensity, volume, and energy expenditure. Still, accuracy depends on lab tests or using indexes like HRnet and HRindex. This study addresses HR indexes' applicability in postmenopausal women (PMW), who constitute over 50% of the aging population and may have unique characteristics (e.g., heart size) affecting HR use. Fourteen PMW underwent a cycling ramp incremental test to establish the relationships between O2 (in MET) and absolute HR, HRnet, and HRindex. In a second group of ten PMW, population-specific and general equations were tested to predict MET and energy expenditure during six constant work exercises at various intensities. Pulmonary gas exchange and HR were continuously measured using a metabolic cart. Correlations, Bland-Altman analysis, and two-way RM-ANOVA were used to compare estimated and measured values. Strong linear relationships between the three HR indexes and MET were found in Group 1. In Group 2, population-specific equations showed medium-to-high correlations, precision, and no significant biases when estimating MET and energy expenditure. HRnet and HRindex outperformed absolute HR in accuracy. General HR equations had similar correlations but exhibited larger biases and imprecision. Statistical differences between measured and estimated values were observed at all intensities with general equations. This investigation confirms the suitability of HR for estimating aerobic metabolism in one of the most significant aging populations. However, it emphasizes the importance of considering individual variability and developing population-specific models when utilizing HR to infer metabolism.

An Approach for Estimating Oxygen Consumption in Tissues Based on TOLD MRI Signal

An Approach for Estimating Oxygen Consumption in Tissues Based on TOLD MRI Signal

Diving behaviour of southern elephant seals: new models of behavioural and ecophysiological adjustments of oxygen store management.

Among pinnipeds, southern elephant seals (SESs, Mirounga leonina) are extreme divers that dive deeply and continuously along foraging trips to restore their body stores after fasting on land during breeding or moulting. Their replenishment of body stores influences their energy expenditure during dives and their oxygen (O2) reserves (via muscular mass), yet how they manage their O2 stores during their dives is not fully understood. In this study, 63 female SESs from Kerguelen Island were equipped with accelerometers and time-depth recorders to investigate changes in diving parameters through their foraging trips. Two categories of dive behaviour were identified and related to the body size of individuals, with smaller SESs performing shallower and shorter dives requiring greater mean stroke amplitude compared with larger individuals. In relation to body size, the larger seals had lower estimated oxygen consumption levels for a given buoyancy (i.e. body density) compared with smaller individuals. However, both groups were estimated to have the same oxygen consumption of 0.079±0.001 ml O2 stroke-1 kg-1 for a given dive duration and at neutral buoyancy when the cost of transport was minimal. Based on these relationships, we built two models that estimate changes in oxygen consumption according to dive duration and body density. The study highlights that replenishing body stores improves SES foraging efficiency, as indicated by increased time spent at the bottom of the ocean. Thus, prey-capture attempts increase as SES buoyancy approaches the neutral buoyancy point.

QUALITY OF EMERGENCY STAIR TRAVEL DEVICES

Emergency stair travel devices are designed to evacuate people from buildings and used duringinitial unguided spontaneous evacuations as well as by professional emergency services. Therequirements for evacuation chairs are varied: they are determined by the technical conditions ofthe building, by the specific way of operation of non-professional and professional operators, andon the other hand, they must take into account the specificity of evacuated people. The problemis to indicate the quality parameters of the evacuation chairs so that these chairs can be adaptedto the organization and equipment system. The article aims to indicate and justify such qualityparameters. The starting point was a quantitative analysis of scientific documents. It was foundthat there are only 33 scientific documents directly related to research on the evacuation of peoplewith physical disabilities. Based on the literature, the tested evacuated devices were classified intothree main types: hand-carried, tracked, and sled. Three groups of potential users of emergencystair travel devices have been identified: 1) non-professional rescuer, i.e., a person assisting inthe first spontaneous phase of evacuation; (2) professional rescuer, meaning a firefighter or otherprofessional who is physically fit and well versed in the operation of equipment and evacuationprocedures; this type of user usually appears in the second phase of the evacuation; (3) evacuee. Eachof these groups has specific needs and evaluates the quality of the device in different ways. Basedon the analysis of scientific literature, the following predictors of the quality of emergency stairtravel devices have been identified: average evacuation time(s), evacuation speed (m/s), numberof rescuers (pcs.), effort of rescuers (estimated oxygen consumption or pulse rate) and comfort ofthe person being rescued (estimated by pulse frequency or based on surveys). The expert analysispoints out that essential requirements for evacuation devices vary for different people and do notoverlap. For a person being evacuated, for example, the position of the body during evacuation isimportant, and from the point of view of rescuers, the ease of use, mobility and tolerance for errorsin use are important in case of evacuation. Both groups of rescuers have similar requirements, butthey have different priorities.

Performance of Different Accelerometry-Based Metrics to Estimate Oxygen Consumption during Track and Treadmill Locomotion over a Wide Intensity Range.

Accelerometer data can be used to estimate incident oxygen consumption (VO2) during physical activity. Relationships between the accelerometer metrics and VO2 are typically determined using specific walking or running protocols on a track or treadmill. In this study, we compared the predictive performance of three different metrics based on the mean amplitude deviation (MAD) of the raw three-dimensional acceleration signal during maximal tests performed on a track or treadmill. A total of 53 healthy adult volunteers participated in the study, 29 performed the track test and 24 the treadmill test. During the tests, the data were collected using hip-worn triaxial accelerometers and metabolic gas analyzers. Data from both tests were pooled for primary statistical analysis. For typical walking speeds at VO2 less than 25 mL/kg/min, accelerometer metrics accounted for 71-86% of the variation in VO2. For typical running speeds starting from VO2 of 25 mL/kg/min up to over 60 mL/kg/min, 32-69% of the variation in VO2 could be explained, while the test type had an independent effect on the results, except for the conventional MAD metrics. The MAD metric is the best predictor of VO2 during walking, but the poorest during running. Depending on the intensity of locomotion, the choice of proper accelerometer metrics and test type may affect the validity of the prediction of incident VO2.

Do we need to rethink the determination of exercise-related energy expenditure in cardiac telerehabilitation interventions?

The American College of Sports Medicine determined the energy consumption of daily activities and sports. Cardiac telerehabilitation (CTR) requires knowing how much energy people consume in daily life outside of cardiac rehabilitation activities. Therefore, we have investigated if the estimated values are valid in CTR. Data from two studies were incorporated. The first study measured ventilatory threshold (VT)1, VT2, and peak exercise on cardiopulmonary exercise testing (CPET) collected from 272 cardiac (risk) patients and compared them to the estimated oxygen consumption (VO2) at low-to-moderate-intense exercise (3–6 metabolic equivalents [METs]). Next, a patient-tailored application was developed to support CTR using these estimated values, and the intervention (the second study) was conducted with 24 coronary artery disease patients using this application during a CTR intervention. In the first study, VO2 at VT1, VT2 and peak exercise corresponded to 3.2 [2.8, 3.8], 4.3 [3.8, 5.3], and 5.4 [4.5, 6.2] METs, which are significantly different from the estimated VO2 at low-to-moderate-intense exercise, especially lower in older, obese, female, and post-myocardial infarction/heart failure patients. These VO2 varied considerably between patients. The telerehabilitation study did not show significant progress in peak VO2, but using the application's estimated target, 97.2% of the patients achieved their weekly target, which is a significant overestimate. The estimated and observed exercise-related energy expenditures by CPET were significantly different, resulting in an overestimation of the exercise done by the patients at home. The results can have a significant impact on the quantification of exercise dose during (tele)rehabilitation programs.

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.

Physiological Response to the 6-Minute Frame Running Test in Children and Adults With Cerebral Palsy.

To determine the physiological response and association to peak oxygen uptake of the 6-minute Frame Running test (6-MFRT) in persons with cerebral palsy (CP). Twenty-four participants with CP, Gross Motor Function Classification System II/III/IV, performed the 6-MFRT. Distance, peak heart rate (HR peak ), peak respiratory exchange ratio (RER peak ), and peak oxygen uptake ( O 2peak ) were measured. HR peak ranged from 146 to 201 beats per minute, RER peak from 0.94 to 1.49, 6-MFRT distance from 179 to 1220 m and O 2peak from 0.62 to 2.18 L/min. HR peak was achieved in 63%, RER peak in 71%. A strong correlation was observed between 6-MFRT and O 2peak . The 6-MFRT represented a (near) maximum effort for 75% of the participants and the 6-MFRT can be used to estimate oxygen consumption on an individual basis.

Causes of the extensive hypoxia in the Gulf of Riga in 2018

Abstract. The Gulf of Riga is a relatively shallow bay connected to the deeper central Baltic Sea (Baltic Proper) via straits with sills. The decrease in the near-bottom oxygen levels from spring to autumn is a common feature in the gulf, but in 2018, extensive hypoxia was observed. We analyzed temperature, salinity, oxygen, and nutrient data collected in 2018, along with historical data available from environmental databases. Meteorological and hydrological data from the study year were compared with their long-term means and variability. We suggest that pronounced oxygen depletion occurred in 2018 due to a distinct development of vertical stratification. Seasonal stratification developed early and was stronger in spring–summer 2018 than on average due to high heat flux and weak winds. Dominating northeasterly winds in early spring and summer supported the inflow of saltier waters from the Baltic Proper that created an additional deep pycnocline restricting vertical transport between the near-bottom layer (NBL) and the water column above. The estimated oxygen consumption rate in the NBL in spring–summer 2018 was about 1.7 mmolO2m-2h-1, which exceeded the oxygen input to the NBL due to advection and vertical mixing. Such a consumption rate leads to near-bottom hypoxia in all years when vertical mixing in autumn reaches the seabed later than on average according to the long-term (1979–2018) meteorological conditions. The observed increase in phosphate concentrations in the NBL in summer 2018 suggests a significant sediment phosphorus release in hypoxic conditions counteracting the mitigation measures to combat eutrophication. Since climate change projections predict that meteorological conditions comparable to those in 2018 will occur more frequently, extensive hypoxia would be more common in the Gulf of Riga and other coastal basins with similar morphology and human-induced elevated input of nutrients.

Estimated Oxygen Consumption with the Abbreviated Method and Its Association with Vaccination and PCR Tests for COVID-19 from Socio-Demographic, Anthropometric, Lifestyle, and Morbidity Outcomes in Chilean Adults.

COVID-19 causes cardiovascular and lung problems that can be aggravated by confinement, but the practice of physical activity (PA) could lessen these effects. The objective of this study was to evaluate the association of maximum oxygen consumption (O2max) with vaccination and PCR tests in apparently healthy Chilean adults. An observational and cross-sectional study was performed, in which 557 people from south-central Chile participated, who answered an online questionnaire on the control of COVID-19, demographic data, lifestyles, and diagnosis of non-communicable diseases. O2max was estimated with an abbreviated method. With respect to the unvaccinated, those who received the first (OR:0.52 [CI:0.29;0.95], p = 0.019) and second vaccine (OR:0.33 [CI:0.18;0.59], p = 0.0001) were less likely to have an increased O2max. The first vaccine was inversely associated with O2max (mL/kg/min) (β:−1.68 [CI:−3.06; −0.3], p = 0.017), adjusted for BMI (β:−1.37 [CI:−2.71; −0.03], p = 0.044) and by demographic variables (β:−1.82 [CI:−3.18; −0.46], p = 0.009); similarly occur for the second vaccine (β: between −2.54 and −3.44, p < 0.001) on models with and without adjustment. Having taken a PCR test was not significantly associated with O2max (mL/kg/min). It is concluded that vaccination significantly decreased O2max, although it did not indicate cause and effect. There is little evidence of this interaction, although the results suggest an association, since O2max could prevent and attenuate the contagion symptoms and effects.

Heart rate as a proxy for estimating oxygen consumption rates in loggerhead turtles (Caretta caretta).

ABSTRACTHeart rates of air-breathing diving animals can change on a short time scale due to the diving response during submergence. Heart rate is used frequently as a proxy for indirectly estimating metabolic rates on a fine time scale. However, most studies to date have been conducted on endothermic diving animals, and the relationships between metabolic rates and heart rates in ectothermic diving animals have not been well studied. Sea turtles are unique model organisms of diving ectotherms because they spend most of their life in the ocean and perform deep and/or long dives. In this study, we examined the relationship between heart rates and metabolic rates in captive loggerhead turtles, Caretta caretta, to estimate oxygen consumption rates during each dive based on heart rates. The oxygen consumption rates (V̇O2: mlO2 min−1 kg−1) and average heart rates (fH: beats min−1) were measured simultaneously in indoor tanks at water temperatures of 15–25°C. Our results showed that oxygen consumption rate was affected by heart rate and water temperature in loggerhead turtles. Based on the collected data, we formulated the model equation as V̇O2=0.0124fH+0.0047Tw - 0.0791. The equation can be used for estimating fine-scaled field metabolic rates in free-ranging loggerhead turtles. The results of this study will contribute to future comparative studies of the physiological states of ectothermic diving animals.

Impacto de la rehabilitación pulmonar en pacientes con enfermedad pulmonar restrictiva

IntroductionRestrictive lung diseases present alterations in thoracic-pulmonary mechanics, reduced functional capacity and lung function. Intrinsic and extrinsic alterations can be found where the interstitium, thoracic expandability and even lung parenchymal conditions are altered. Pulmonary rehabilitation could benefit patients with the restrictive condition and improve their functional condition. ObjectiveEstablish the impact of pulmonary rehabilitation in patients with intrinsic and extrinsic restrictive respiratory compromise on dyspnea, functional capacity, anxiety/depression and health-related quality of life. MethodsLongitudinal descriptive study with 50 patients with restrictive lung disease who performed pulmonary rehabilitation in a clinic in the city of Cali, Colombia. The participants linked to the study were separated into two groups, the first with intrapulmonary restrictive disease (IRD) and the second group with extrapulmonary restrictive disease (ERD). ResultsThe mean age of the patients was 53.3years. Among the restrictive intrapulmonary diseases there were: diffuse interstitial lung disease (ILD), post-condition pneumonia and/or acute respiratory distress syndrome (ARDS) and sequelae of pulmonary tuberculosis. Extrapulmonary respiratory diseases: lung resection, pulmonary lobe resection, and wedge resection. At the end of pulmonary rehabilitation, the IRD group presented statistically significant improvements in distance covered, estimated oxygen consumption (VO2e), dyspnea, anxiety, and quality of life. The ERD group presented a significant increase in the distance traveled and VO2e. ConclusionPatients with restrictive lung disease improve the distance traveled, VO2e, dyspnea, anxiety and quality of life; patients with extrapulmonary respiratory disease show improvements in functional capacity.

Relationship Between Estimated VO2max and Handgrip Strength in Healthy Young Nigerian Adults

Purpose: This study investigated the relationship between estimated oxygen consumption (VO2max) and handgrip strength (HGS) among healthy young Nigerian adults. Methods: This was a cross sectional study, which involved 400 volunteers (171 males; 229 females) aged between 18–40years. Participants’ HGS was assessed using a CAMRY EH-101 hand dynamometer while VO2max was estimated using a standard formula that includes measurement of resting heart rate. Demographic data was summarized using percentages, mean and standard deviation. Physical activity level of the participants was assessed using long form of the International Physical Activity Questionnaire. Independent t-test was used to compare the mean values of the variables between male and female participants. Pearson’s correlation was used to determine the strength of relationship between estimated VO2max and HGS, while multiple regression analysis was conducted to determine the predictors of estimated VO2max using HGS as well as body mass index (BMI), physical activity (PA) level, age and sex as co‐variates. Level of significance was set at p&lt;0.05. Results: HGS, VO2max and PA level were significantly (p= 0.001) different between male and female participants. There was a significant moderate correlation between HGS and VO2max (r= 0.40, p= 0.001). The results of the regression analysis showed that HGS is not significant predictor of estimated VO2max; whereas, sex, BMI and PA level were significant predictors of estimated VO2max. Conclusion: Although HGS is moderately correlated with estimated VO2max, HGS may not be a relevant tool for predicting estimated VO2max in healthy young adults.

50 Years Ago in TheJournalofPediatrics: Measured versus Estimated Oxygen Consumption Values in Infants with Congenital Heart Disease

50 Years Ago in TheJournalofPediatrics: Measured versus Estimated Oxygen Consumption Values in Infants with Congenital Heart Disease

Respuesta a rehabilitación pulmonar en mujeres con EPOC: comparación entre enfermedad asociada a humo de leña y cigarrillo

IntroductionChronic obstructive pulmonary disease is an entity with high morbidity and mortality that is mainly generated by exposure to cigarette smoking and exposure to wood smoke; previous studies have shown increasing interest between the 2 types of exposure. ObjectiveTo compare the effect of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease who have had exposure to cigarettes versus patients exposed to biomass wood smoke in a fourth level clinic in Santiago de Cali (Colombia). Materials and methodsProspective and longitudinal study, all patients who attended from January 2016 to December 2017 were recruited and met the inclusion criteria, later they were divided into 2 groups: Wood Smoke and Cigarette. Pulmonary function tests, health-related quality of life assessment, symptom assessment and comparison of functional aerobic capacity were recorded with the six-minute walk test and estimated oxygen consumption before and after rehabilitation. ResultsFifteen patients with exposure to wood smoke and 17 to cigarettes completed the rehabilitation. In the intragroup comparison, significant differences (P<.05) were found in the distance traveled, in modified Medical Research Council dyspnea scale (mMRC) the estimated oxygen consumption, also in the Saint George Respiratory Questionnaire. In the comparison between groups, no differences were found in the variables studied. ConclusionPulmonary rehabilitation generated clinics changes significant in the variables studied in the 2 types of exposure; these changes being similar in the 2 groups studied in the present investigation.

Relationship Between Heart Rate, Oxygen Consumption, and Energy Expenditure in Futsal.

The primary aim of this study was to compare the measured oxygen consumption (Measured-VO2) in a simulated futsal game (S-Game) with the estimated oxygen consumption (Estimated-VO2) through a regression equation between heart rate (HR) and oxygen consumption (VO2) (HR-VO2) in treadmill running, and a secondary aim was to calculate the total energy expenditure (EE) in S-Game. Ten professional players (22.20 ± 3.22 years) were evaluated. HR-VO2 was determined individually in the continuous test on the treadmill (ContTest). The Measured-VO2 in S-Game was compared with the Estimated-VO2 in the ContTest. Alactic and lactic pathways were estimated by VO2. The Estimated-VO2 presented no statistically significant difference with the Measured-VO2, using the paired t-test (p = 0.38). However, the correlation between Estimated- and Measured-VO2 was very weak (r = −0.05), and it presented poor agreement (concordance correlation coefficient = −0.04). In addition, a Bland–Altman plot presented bias of −2.8 ml/kg/min and individual difference as large as 19 ml/kg/min. The HR-VO2 determined by the ContTest was not a good individual predictor of VO2. The high intensity and intermittent nature of the futsal game possibly caused dissociation in the HR-VO2 relationship. ContTest is not recommended for estimating VO2 and calculating individual EE in the futsal game. This is recommended only for the group mean. The total EE in S-Game was 13.10 ± 1.25 kcal.min−1 (10.81 ± 1.57 metabolic equivalents). The contributions from the metabolic pathways were as follows: aerobic (93%), alactic (5%), and lactic (2%).

Rejuvenated RBCs Increase Oxygen Consumption in a Simulated Exchange Transfusion Model of Sickle Cell Disease Patients

Introduction: Exchange transfusion of red blood cells (RBCs) in patients with Sickle Cell Disease (SCD) may require 6 to 8 units to reduce sickle hemoglobin (Hb-S) to less than 30 percent of total hemoglobin (NIH No. 02-2117). Low oxygen affinity (high p50) in patients with SCD is manifested by impaired blood viscosities and reduced hemoglobin concentration. Well characterized RBC metabolic changes during liquid storage of donor RBC include an increase in the affinity of hemoglobin for oxygen (low p50) by depletion of 2,3-diphosphoglycerate (2,3-DPG). Transfusion of stored RBCs (Standard RBC) suggests inefficient and impaired O2 delivery to tissues compared to fresh circulating RBCs (Hasan 1994, Scott 2016) or after exchange transfusion in SCD (Uchida 1998). Extracorporeal manipulation of p50 through RBC rejuvenation increases the level of 2,3-DPG and increases the p50 of stored RBCs by right-shifting the Oxyhemoglobin Dissociation Curve (ODC) (Dennis 1979). Rejuvenation occurs by incubating RBCs at 37 °C for 60 minutes with a rejuvenation solution (Citra Labs). An exchange transfusion simulation model was developed to evaluate the changes in oxygen release capacity of rejuvenated RBCs and the potential impact on estimated oxygen consumption (VO2) compared to Standard RBCs.Methods: Oxyhemoglobin dissociation curves were generated from (5) RBC units (leukocyte-reduced), CPD/AS-1, on Day 0, after 21 days of storage (Standard RBC), and after rejuvenation on day 21 (REJ RBC) which were used to estimate p50 values of the donor/recipient mixtures after each exchange transfusion and to determine VO2 as previously described (Li 2016, Srinivasan 2017). An elevated p50 of 30.4 mm Hg, typical for SCD patients (Uchida 1998), was used to estimate the baseline VO2 (200 mL O2/min). VO2 was determined after each simulated RBC exchange with Standard or REJ RBCs assuming a constant blood volume of 5L, cardiac output of 5 L/min, total hemoglobin concentration of 10 g/dL. The model assumed an exchange rate of one apheresis unit of circulating RBCs to transfusion of one unit of Standard or REJ RBCs.Results: Donor RBC p50 was 26.9 ± 2.0 mm Hg on Day 0 and declined with storage to 17.6 ± 1.5 mm Hg at 21 days (p < 0.001, t-test). Rejuvenation restored p50 to 34.8 ± 2.7 mm Hg which was significantly higher than Day 0 (p < 0.001, t-test). The model predicted a reduction in Hb-S from 70 % to 22%, a decrease in p50 after the 8 unit exchange transfusion to 21.6 mm Hg with Standard RBC, but an increase in p50 to 33.3 mm Hg with REJ RBC (Figures 1a & 1b). Similarly, VO2 increased in the REJ RBC group but decreased sequentially with Standard RBC upon each additional exchange transfusion (Figure 1c). The model predicted a decrease in VO2 to 118 mL O2/min for the Standard RBC group and an increase to 233 mL O2/min with REJ RBC group after the exchange transfusion.Conclusions: The model predicted a baseline VO2 of 200 mL O2/min; however, in fresh whole blood from healthy volunteers with Hb-A, normal VO2 was estimated at 244 mL O2/min (Srinivasan 2017). This simulation suggested that performing an exchange transfusion with REJ RBCs could achieve 95% of normal oxygen consumption assuming a constant cardiac output even though the hemoglobin was maintained at 10 g/dL. While exchange transfusion has been a successful therapy to reduce the Hb-S percentage in chronically transfused SCD patients, improving tissue oxygen exchange may not yet be optimized as evidenced by post transfusion declines in p50 (Miller 1980, Uchida 1998). The model is limited because it does not account for improved rheological properties and blood viscosity following exchange transfusion, which was previously reported to improve exercise capacity even though p50 declined (Miller 1980). The model also did not account for any influence from irreversibly sickled cells. Transfusion practices to correct anemia and improve tissue oxygenation may be less effective than intended due to the diminished oxygen release capacity of standard stored RBC units. Transfusion strategies should consider whether the use of RBCs with increased p50 may be physiologically advantageous.Figure 1: Predicted ODC (a) before and after the simulated exchange transfusion with Standard or REJ RBCs and predicted Hb-A vs Hb-S ratios (b) and VO2 (c) after each unit of the exchange transfusion with Standard or rejuvenated RBCs. [Display omitted] DisclosuresKausch:Zimmer Biomet: Employment, Research Funding. Gray:Zimmer Biomet: Employment, Research Funding. Landrigan:Zimmer Biomet: Employment, Research Funding.