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At least 19 recordsLinked to original sources
PubMed1999

Cardiopulmonary bypass and oxygen consumption: oxygen delivery and hemodynamics.

BACKGROUND: This study was undertaken to investigate the relations between whole body oxygen consumption (VO2), oxygen delivery (DO2), and hemodynamic variables during cardiopulmonary bypass. METHODS: One hundred one patients were studied during cooling, hypothermia, and rewarming. Oxygen consumption, DO2, hemodynamics, and DO2crit were measured at these times. RESULTS: There was a direct linear relation between DO2 and VO2 during all three times. No relation between VO2 and hemodynamics was detected during cooling; during hypothermia, an inverse linear relation with peripheral arterial resistance was found. Finally, during rewarming, there was a direct relation with pump flow rate, and an inverse relation with arterial pressure and arterial resistance. The same relations among the variables were found at delivery levels above or below DO2crit. CONCLUSIONS: During cardiopulmonary bypass there is a direct linear relation between DO2 and VO2; the relations with hemodynamic variables depend on the phases of cardiopulmonary bypass. This suggests that increasing delivery levels may recruit and perfuse more vascular beds, and higher delivery levels are advisable during perfusion. During rewarming and hypothermia, lower arterial resistances are also desirable to optimize VO2.

Aged↗
PubMed2001

Photochemical oxygen consumption, oxygen evolution and spectral changes during UVA irradiation of EMT6 spheroids.

Remarkable rates of oxygen consumption are observed via microelectrode measurements immediately upon the onset of 325 nm irradiation of multicell tumor spheroids. Consumption is irradiance dependent over the range 20-200 mW cm-2, and its magnitude is comparable to that observed previously in the same system using exogenous photosensitizers. Oscillations in the oxygen concentrations suggest that oxygen is also being evolved during irradiation. Oxygen evolution is likely the result of enzymatic dissociation of hydrogen peroxide, which is formed through UV-induced photochemistry. Irradiation of spheroids at 442 and at 514 nm produces a much more modest but detectable oxygen consumption. The dynamics of oxygen concentration changes are quite different at these wavelengths, suggesting a different photochemical mechanism. In these cases, initial oxygen depletion is followed immediately by a more gradual, monotonic increase in the oxygen concentration, consistent with irreversible photobleaching. No oscillations in the oxygen concentration are detectable. At 662 nm, no oxygen consumption was observed over the range of irradiances studied. Fluorescence spectra of cells prior to irradiation include contributions from anthranilic acid and reduced nicotinamide adenine dinucleotide (NADH). During 325 nm irradiation, anthranilic acid is rapidly and irreversibly bleached, while NADH emission undergoes only modest reduction.

Animals↗
PubMed1988

Myocardial oxygen consumption, oxygen supply/demand heterogeneity, and microvascular patency in regionally stunned myocardium.

Although oxygen consumption closely parallels mechanical work in the normal heart, previous studies have found that stunned myocardium may have normal or even increased oxygen consumption despite depressed function. In this study we used microspectrophotometry to measure the oxygen saturations within arteries and veins of less than 100 micron diameter in quick-frozen biopsy samples from normal and regionally stunned myocardium of 10 open-chest anesthetized dogs. Regional myocardial blood flow, measured by radioactive microspheres, was similar in stunned and normal regions, as was mean arteriolar oxygen saturation. However, mean venous oxygen saturation was lower in the stunned region (epicardium 38.0% vs 43.8%, p less than .02; endocardium 36.2% vs 39.5%, p = .12), indicating increased oxygen extraction and consumption, despite a marked reduction in mean systolic segmental shortening from 14.4% to 0.5%. In addition, there was greater vein-to-vein heterogeneity of oxygen saturation in the stunned region, with an excess of veins having low saturations (statistically significant in epicardium, nonsignificant trend in endocardium). Microvascular injections studies with Microfil or drafting ink revealed filling of over 95% of arterioles and 85% of capillaries in the stunned region, similar to the findings in the normal region. Our results are consistent with an inefficient transfer of energy into myocyte contraction or an increased use of energy for noncontractile activities in stunned myocardium. In addition, the finding of increased heterogeneity of oxygen extraction suggests that the injury to stunned myocardium may not be uniform to all contractile elements, but instead may be focally and irregularly distributed.

Animals↗
PubMed1985

Assisted ventilation in patients with preexisting cardiopulmonary disease. The effect on systemic oxygen consumption, oxygen transport, and tissue perfusion variables.

We have evaluated systemic oxygen consumption (VO2), systemic oxygen transport, and tissue perfusion variables in 30 patients with preexisting cardiac and underlying pulmonary disease during continuous positive-pressure ventilation and positive end-expiratory pressure [PEEP], during intermittent mandatory ventilation (IMV and PEEP), and during spontaneous ventilation (continuous positive airway pressure [CPAP]), with end-expiratory pressure held constant during all ventilatory modes. Using radionuclide angiography together with invasive determinations of pressure and flow, we also measured left and right ventricular ejection fractions and calculated the end-systolic (ESVI) and end-diastolic (EDVI) volume indices of both ventricles. We found that oxygen transport was significantly greater during CPAP (583 +/- 172 ml/min/M2)(mean +/- SD) than during either IMV and PEEP (543 +/- 151 ml/min/sq; p less than 0.01) or CPPV and PEEP (526 +/- 159 ml/min/M2; p less than 0.01); however, we found no significant change in systemic VO2 with conversion from CPPV and PEEP to CPAP. The increase in oxygen transport was related to a greater cardiac index and, more specifically, to a higher heart rate during CPAP (CPAP, 106 +/- 16 beats per minute; CPPV and PEEP, 97 +/- 14 beats per minute) (p less than 0.01). Enhanced oxygen transport during CPAP was also associated with an increase in mixed venous oxygenation and a decrease in arterial lactate. Although neither the mean left ventricular EDVI nor ESVI changed from CPPV and PEEP to CPAP, the mean pulmonary capillary wedge pressure increased (CPPV and PEEP, 12 +/- 5 mm Hg; CPAP, 14 +/- 7 mm Hg) (p less than 0.01), suggesting the possibility of a decrease in left ventricular compliance with the spontaneous ventilatory mode. This study suggests that in the absence of ventilatory failure, spontaneous ventilation provides for better systemic oxygen transport and overall tissue perfusion than either controlled ventilation or IMV; however, this benefit of enhanced oxygen delivery with spontaneous ventilation may potentially be offset by a decrease in left ventricular compliance.

Aged↗
PubMed1998

[Recovery of the oxygen consumption, oxygen transport, and cardiac activity after hypothermia followed by respiration and cardiac arrest in rats].

After a 1 hr deep prolonged immersion hypothermia, warming up of experimental rats in water (the temperature increase 0.25 degree C/min) entailed a complete recovery of all the parameters of gas exchange, haemodynamics, external respiration, and the blood. After a 3 hr hypothermia, under the same conditions of warming up, oxygen consumption, CO2 production, and 1 min blood volume were obviously decreased, and the animals died within 0.5-1.0 hr.

Animals↗
PubMed2000

Correlated oscillations in glucose consumption, oxygen consumption, and intracellular free Ca(2+) in single islets of Langerhans.

Micron-sized sensors were used to monitor glucose and oxygen levels in the extracellular space of single islets of Langerhans in real-time. At 10 mM glucose, oscillations in intraislet glucose concentration were readily detected. Changes in glucose level correspond to changes in glucose consumption by glycolysis balanced by mass transport into the islet. Oscillations had a period of 3.1 +/- 0.2 min and amplitude of 0.8 +/- 0.1 mM glucose (n = 21). Superimposed on these oscillations were faster fluctuations in glucose level during the periods of low glucose consumption. Oxygen level oscillations that were out of phase with the glucose oscillations were also detected. Oscillations in both oxygen and glucose consumption were strongly dependent upon extracellular Ca(2+) and sensitive to nifedipine. Simultaneous measurements of glucose with intracellular Ca(2+) ([Ca(2+)](i)) revealed that decreases in [Ca(2+)](i) preceded increases in glucose consumption by 7.4 +/- 2.1 s during an oscillation (n = 9). Conversely, increases in [Ca(2+)](i) preceded increases in oxygen consumption by 1.5 +/- 0.2 s (n = 4). These results suggest that during oscillations, bursts of glycolysis begin after Ca(2+) has stopped entering the cell. Glycolysis stimulates further Ca(2+) entry, which in turn stimulates increases in respiration. The data during oscillation are in contrast to the time course of events during initial exposure to glucose. Under these conditions, a burst of oxygen consumption precedes the initial rise in [Ca(2+)](i). A model to explain these results is described.

Animals↗
PubMed1989

Independent measurement of oxygen consumption and oxygen delivery.

This experiment investigated the relationship between oxygen consumption and oxygen delivery (cardiac output X arterial oxygen content) in an acute canine model. Previous studies investigating this relationship have largely utilized methods in which oxygen consumption and oxygen delivery were each calculated using the same measured variables resulting in mathematical coupling of variables. In this study, oxygen consumption was measured directly by closed-circuit spirometry. Oxygen delivery was independently controlled using right atrial bypass. These techniques assured that the values for oxygen consumption and oxygen delivery were derived entirely independently. In our study using 11 dogs, we found that oxygen consumption was constant and independent of oxygen delivery at oxygen delivery levels greater than 8.0 cc/kg/min (normal canine oxygen delivery 20-25 cc/kg/min). Oxygen consumption was linearly related to oxygen delivery at oxygen delivery levels less than or equal to 8.0 cc/kg/min. Below this critical level of oxygen delivery, animals were more acidotic and hypotensive than at higher delivery levels.

Animals↗
PubMed1986

Effects of methyl mercury on sperm oxygen consumption.

Oxygen consumption and percent motile spermatozoa were determined for semen samples from healthy male monkeys Macaca fascicularis. Methyl mercury was added to the samples, in the oxygen measurement chamber, at a concentration of 9 p.p.m. for 15 min. and then increased to 15 p.p.m. for 15-30 min. Oxygen consumption and percent motility were determined during each period. Methyl mercury addition resulted in decreased sperm motility, but we did not detect any inhibition in the rate of oxygen consumption accompanying the decreased motility. On the contrary, the rate of oxygen consumption increased at 15 p.p.m. within 15 min., while the sperm motility was close to zero. Antimycin inhibited the increased rate of oxygen consumption demonstrating the mitochondrial source of this increased rate. Oligomycin also inhibited the increased rate of oxygen consumption due to methyl mercury, thus excluding the possibility of uncoupling of mitochondrial oxidative phosphorylation. Interference with mitochondrial energy production does not seem to be the primary mechanism of methyl mercury-induced decreased spermatozoal motility. Methyl mercury interference with the dynein/microtubule sliding assembly now seems to us to be a more tenable hypothesis.

Adenosine Triphosphate↗
PubMedDate not supplied

A comparison of three methods of analyzing post-exercise oxygen consumption.

Oxygen consumption after exercise is frequently plotted as a function of time and then the area under the curve (AUC) is calculated. Subsequently, this AUC is further manipulated and thus, differences between these manipulations may impact the interpretation of changes in oxygen consumption after exercise. The purpose of this study was to determine if the method of calculating AUC influences the interpretation of changes in post-exercise oxygen consumption in response to long-term aerobic exercise. Forty-three moderately obese, sedentary participants volunteered to participate in this study (26 women and 17 men). All participants performed verified supervised exercise during the study. Supervised treadmill exercise was initially conducted for 3 d/week at 60 % of heart rate reserve (HRR) for 30 min and progressed to 5 d/week at 75 % of HRR for 45 min across the first 4 months. Pre-exercise, exercise, and post-exercise oxygen consumption was measured at baseline and 9 months. AUC was calculated by three methods; total, incremental, and positive incremental. Descriptive statistics and dependent T-tests were calculated for each method of calculating the AUC. In addition, the intra-individual coefficient of variation was determined for each individual for each AUC method. A pearson product moment correlation was calculated for each method to determine the strength of the relationship between pre- and post-training values. The change in post-exercise oxygen AUC after nine months of training was 5.36+/-10.90 L, 2.17+/-7.61 L, and 1.74+/-9.10 L for the total, incremental, and positive incremental methods, respectively. There was significant change in post-exercise total AUC from baseline to 9-months (5.36 +/- 10.90 L), while there was no significant change in incremental or positive incremental AUC. There was a moderately high correlation (r=0.67, p <0.05) between baseline and 9-months for the total AUC method, while there was no significant correlation for incremental and positive incremental AUC methods. These results suggest that the method used to calculate AUC can lead to a different interpretation of the effects of training on post-exercise oxygen consumption. From this data, it appears that analyzing post exercise oxygen consumption with the total area under the curve method has a greater ability to detect a change from aerobic training, than either the positive or incremental area under the curve methods.

Adaptation, Physiological↗
PubMed1991

[Effect of peroperative analgesia on immediate postoperative oxygen consumption].

Oxygen consumption in the immediate postoperative period was assessed in a series of twelve patients undergoing maxillofacial surgery, randomly assigned to two groups (n = 6 for each). The anaesthetic protocol was the same in all patients: premedication with flunitrazepam 30 micrograms.kg-1, induction with flunitrazepam 20 micrograms.kg-1, fentanyl 5 micrograms.kg-1, thiopentone 5 mg.kg-1, pancuronium bromide 80 micrograms.kg-1, and maintenance during the first three hours with flunitrazepam 10 micrograms.kg-1.h-1 and pancuronium 0.03 micrograms.kg-1.h-1. All the patients were given a continuous infusion of fentanyl during the whole length of the surgery: in Group I (GI), 3 micrograms.kg-1.h-1 and in Group II (GII), 1 microgram.kg-1.h-1. The patients in Group II were also given enflurane 1.2 +/- 0.3 vol %. During the immediate postoperative period, the parameters studied were measured by means of an Engström Metabolism Calculator at the 15th, 30th, 45th, 60th, 120th and 240th minutes, and at the time of extubation. In GII, postoperative heart rate and lactic acid levels were higher than in GI (p less than 0.05). Both groups had oxygen consumption values greater than theoretical resting levels. However, postoperative oxygen consumption was greatly increased in GII with respect to GI during the first 4 hours (p less than 0.01). The respiratory quotient was greater in GI than in GII at the end of the study (p less than 0.05). These data indicate that the intraoperative analgesic technique influences postoperative oxygen consumption. A dose of fentanyl of 3 micrograms.kg-1.h-1 is more efficient than one of 1 microgram.kg-1.h-1 associated with enflurane.

Adult↗
PubMed1990

Pathologic dependence of oxygen consumption on oxygen delivery in acute respiratory failure secondary to AIDS-related Pneumocystis carinii pneumonia.

Oxygen consumption is pathologically dependent on oxygen delivery in ARDS and sepsis. We asked whether oxygen consumption is dependent on oxygen delivery in severe acute respiratory failure secondary to AIDS-related PCP. In five patients who had AIDS-related PCP, diffuse bilateral pulmonary infiltrates, no evidence of bacterial infection, and acute respiratory failure requiring mechanical ventilation with arterial oxygen tensions less than 75 mm Hg while breathing at least 50 percent oxygen, and PEEP greater than 10 cm H2O, we determined oxygen delivery and consumption by calculation from thermodilution cardiac output and arterial and mixed venous oxygen contents. Oxygen delivery was increased using transfusion of two units of packed red blood cells over one hour. Oxygen delivery increased 22 percent (638 +/- 204 to 778 +/- 201 ml/min.m2, p less than or equal to 0.006). Oxygen consumption increased 11 percent (134 +/- 34 to 149 +/- 29 ml/min.m2, p less than or equal to 0.02). The oxygen extraction ratio did not change. We conclude that similar to ARDS and sepsis, oxygen consumption may be pathologically dependent on oxygen delivery in patients who have severe acute respiratory failure secondary to AIDS-related PCP.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Biphasic oxygen kinetics of cellular respiration and linear oxygen dependence of antimycin A inhibited oxygen consumption.

Oxygen kinetics in fibroblasts was biphasic. This was quantitatively explained by a major mitochondrial hyperbolic component in the low-oxygen range and a linear increase of rotenone- and antimycin A-inhibited oxygen consumption in the high-oxygen range. This suggests an increased production of reactive oxygen species and oxidative stress at elevated, air-level oxygen concentrations. The high oxygen affinity of mitochondrial respiration provides the basis for the maintenance of a high aerobic scope at physiological low-oxygen levels, whereas further pronounced depression of oxygen pressure induces energetic stress under hypoxia.

Antimycin A↗
PubMed1992

The dependency of oxygen consumption on oxygen delivery in critically ill postoperative patients is mimicked by variations in sedation.

The finding of a dependence of oxygen consumption on oxygen delivery in critically ill patients has encouraged interventions to increase oxygen delivery index (DO2I) to overcome tissue hypoxia. In individuals other factors may influence oxygen consumption index (VO2I) and DO2I and may cause an apparently dependent relationship. We studied the effects of sedation and temperature on the VO2I/DO2I relationship in 13 perioperative patients. Pooled data showed significant correlations between VO2I and DO2I (r greater than 0.6, p less than 0.05) but also between VO2I and sedation score (r greater than 0.7, p less than 0.05), but not VO2I and temperature (r less than 0.5). When VO2I was standardized for the effects of sedation score (SS), the relationship between VO2I and DO2I was lost (r less than 0.5). Seven of 13 patients had significant (p less than 0.05) correlations between VO2I and SS and six of 13 between VO2I and DO2I; when standardized for the effect of varying sedation, no relationships were significant. When interpreting oxygen transport data from critically ill patients, the effects of sedation but not temperature must be taken into account; otherwise a false impression of a dependent relationship between VO2I and DO2I may cause unnecessary treatment.

Biological Transport↗
PubMed1990

[Relation between oxygen consumption and oxygen delivery in chronic obstructive pulmonary diseases and chronic cor pulmonale].

An investigation of 13 cases of COPD and 15 cases of chronic cor pulmonale caused by COPD revealed that oxygen consumption was not related to oxygen delivery in these patients. Tissue hypoxia was not so severe in stable state of COPD and remitting period of chronic cor pulmonale, although the oxygen delivery was decreased. The demand of oxygen consumption could still be met by means of compensatory mechanism in the body. Oxygen consumption was usually a little lower than normal (114.0 +/- 11.2 ml/min/M2) in COPD; while that in cor pulmonale a little higher than normal (145 +/- 32.4 ml/min/M2). There was significant difference (P less than 0.01). This could be used as one of the diagnostic criteria when combined with clinical data.

Female↗
PubMed1979

Effect of feeding on neonatal oxygen consumption.

Oxygen consumption was measured in 9 short-gestation infants before feeding and for an hour after, using a closed-circuit metabolism chamber. Using the same system, O2 consumption of 9 term infants was measured for varying periods, beginning one hour from the end of the last feed. In the short-gestation infants a rise was found in the 15--45 minutes after feeding; O2 consumption then fell, and after 60 minutes had reached prefeed levels. The term infants showed no decrease with time after the first hour, as would be expected if the effect of feeding on O2 consumption extended beyond this. It is concluded that increased O2 demand after appropriate feeding does not extend beyond one hour postprandially.

Eating↗