Oxygen Utilization Coefficient Research Articles

Conjunctival oxygen tension monitoring in experimental septic shock.

Continuous non-invasive monitoring of conjunctival oxygen tension (PcjO2) versus 'conventional' invasive hemodynamic and oxygen transport variables was evaluated in a porcine model of septic shock induced by a continuous i.v. infusion of E. coli endotoxin over 2 hours. Seventeen pigs under ketamine anesthesia and breathing air spontaneously were investigated. PcjO2, which reflects local oxygen tension at tissue level, correlated significantly at baseline and throughout the septic course with mixed venous oxygen saturation and oxygen utilization coefficient. All these correlations were significant at the 1% level. The corresponding correlations between PcjO2 and cardiac output were significant at the 5% level. A finding of great importance was that changes in PcjO2 preceded major changes in the intermittently measured physiological variables such as SvO2 and cardiac output. We conclude that PcjO2 monitoring is a valuable non-invasive method and which can provide a continuous assessment of the hemodynamic and oxygenation status in experimental septic shock.

Effect of booster blood transfusions on oxygen utilization in infants with bronchopulmonary dysplasia

To assess the impact of booster transfusions on oxygen utilization in infants with bronchopulmonary dysplasia, we noninvasively measured oxygen consumption (VO2) and the variables of systemic oxygen transport (SOT) before and 24 hours after transfusion therapy in 10 oxygen-dependent infants with bronchopulmonary dysplasia. The infants had been born with a mean gestational age of 27.6 weeks and a mean birth weight of 0.88 kg. Study weight averaged 1.24 +/- 0.35 kg, and study age averaged 5.5 +/- 2.4 weeks. Requirements for fractional concentration of inspired oxygen averaged 0.41 +/- 0.15 to maintain an oxygen saturation of 0.93 +/- 0.02. The VO2 was measured by means of a commercially available analyzer through a flow-through circuit and pump connected to a hood or in line with the ventilator. Cardiac output was calculated by means of pulsed Doppler ultrasonography. Oxygen saturation was measured by means of transcutaneous pulse oximetry. The coefficient of oxygen utilization was calculated as VO2/SOT. Transfusion consisted of packed erythrocytes (10 ml/kg). Oxygen utilization fell in all subjects after transfusion (p less than 0.01), but it fell more substantially in subjects with higher coefficients of oxygen utilization (r = -0.80, p less than 0.01), suggesting a physiologic benefit in selected patients, particularly those with higher levels of oxygen utilization. There was also a significant increase in overall systemic oxygen transport (p less than 0.01) and decrease in VO2 (p less than 0.02). Hemoglobin levels alone did not correlate with overall systemic oxygen transport, VO2, or level of oxygen use before transfusion, and thus did not predict which subjects would have a physiologic benefit from transfusion as reflected by falls in oxygen utilization.

Continuous monitoring of gas exchange and oxygen use with dual oximetry

The utility of integrated pulse and pulmonary artery oximetry, known as dual oximetry, was evaluated by monitoring 10 critically ill surgical patients for a total of 208 patient hours. The ventilation-perfusion index (VQI), an estimate of venous admixture, and the oxygen extraction index (O 2EI), an estimate of tissue oxygen utilization coefficient, previously described, were calculated on-line from arterial and mixed venous oxyhemoglobin saturations using a computer. Effective monitoring was accomplished 85% of the total time. The dual oximetry device was nonfunctional owing to equipment failure only 15% of the time, even though no undue attention was given to instructing the staff on operation of the oximeters. Accuracy of VQI and O 2EI was reconfirmed by this study. Drift in the saturations, VQI, and O 2EI during the 6-h period between calibrations was negligible. The 95% range of random variability was ± 2% for SaO 2 ± 3% for SvO 2, ± 5% for VQI, and ± 0.04 for O 2EI. Thirty-six episodes of arterial blood desaturation below 90% were detected by continuous oximetry. In contrast, 74 routine arterial blood samples revealed only four such episodes. Dual oximetry appears to be a technically reliable and accurate method of monitoring pulmonary gas exchange and tissue oxygen utilization. The equipment provided stable readings for at least six hours without recalibration. Random variability is sufficiently small to allow early detection of alterations in pulmonary and circulatory function without blood sampling.

Estimation of oxygen utilization by dual oximetry.

Total body oxygen utilization coefficient was estimated using continuous pulse and pulmonary artery oximetry (dual oximetry) in 17 patients with respiratory failure. Change in arterial and mixed venous oxygen saturations was induced by altering airway pressure. Continuous measurement of mixed venous oxygen saturation provided an accurate and linear estimate of oxygen utilization coefficient (r = -0.92), the true values being overestimated by 0.05 +/- 0.06 (mean +/- SD). Addition of pulse oximetry improved the correlation (r = 0.93) and decreased the difference between absolute values (0.02 +/- 0.06). Oxygen utilization coefficient can be estimated reliably in an online fashion using pulmonary artery oximetry. However, the use of dual oximetry will further improve the estimate.

Polycythemia in Chronic Obstructive Pulmonary Disease: A Study of Serum and Urine Erythropoietin and Medullary Erythroid Progenitors

In order to investigate the mechanism of polycythemia in chronic obstructive pulmonary disease (COPD), serum and urinary levels of erythropoietin and medullary erythroid progenitors were studied in 21 patients; nine were nonpolycythemic (hematocrit, 39 +/- 4 percent; red blood cell [RBC] mass, 28 +/- 5 ml/kg; forced expiratory volume in one second [FEV1], 0.6 +/- 0.1 L), and 12 patients were polycythemic (hematocrit, 52 +/- 7 percent; RBC mass, 46 +/- 7 ml/kg; FEV1, 0.9 +/- 0.3 L). Hypoxia was severe in both groups, with mean arterial oxygen pressure of 47 mm Hg. The following parameters of tissue oxygenation were not significantly different between the two groups: arterial and mixed-venous oxygen saturations; cardiac output; oxygen utilization coefficient; 2, 3-diphosphoglycerate, and carboxyhemoglobin level. The level of erythropoietin was measured by bioassay in vitro. The level was increased in the serum of 85 percent (18) and in the urine of 38 percent (8) of the patients. There was no significant difference between the nonpolycythemic and polycythemic groups. Without exogenous erythropoietin, none of the subjects showed spontaneous colonies of erythroid progenitors. The addition of one unit of erythropoietin induced a similar normal proliferation of erythroid progenitors in both groups. The absence of adaptative polycythemia in the nonpolycythemic group with severe hypoxia was seemingly related neither to a quantitative deficit of erythropoietin nor to a lack of sensitivity of erythroid progenitors to its action.

Titration of Continuous Positive Airway Pressure by Real-Time Dual Oximetry

The clinical utility of combined pulse and pulmonary artery oximetry (dual oximetry) in titrating continuous positive airway pressure (CPAP) therapy was tested in 17 patients with acute respiratory failure. The level of CPAP was altered in 2.5 cmH2O increments and decrements, while conventional measurements of cardiopulmonary function and continuous dual oximetry were performed. Then, optimum CPAP levels were selected using both techniques independently. The difference in optimum CPAP determined by the two methods was 0 cmH2O in ten of 17 patients, less than or equal to 2.5 cmH2O in 14 of 17 patients, and 5.0 to 7.5 cmH2O in the remaining three patients. When a difference existed, CPAP level determined with dual oximetry was consistently lower than the level selected by conventional means. The results indicate that the estimates of venous admixture and oxygen utilization coefficient obtained using dual oximetry provide sufficient information for rapid and accurate titration of CPAP in the majority of patients with acute respiratory failure.

TITRATION OF CONTINUOUS POSITIVE AIRWAY PRESSURE BY REAL-TIME DUAL OXIMETRY

The clinical utility of combined pulse and pulmonary artery oximetry (dual oximetry) in titrating continuous positive airway pressure (CPAP) therapy was tested in 17 patients with acute respiratory failure. The level of CPAP was altered in 2.5 cmH2O increments and decrements, while conventional measurements of cardiopulmonary function and continuous dual oximetry were performed. Then, optimum CPAP levels were selected using both techniques independently. The difference in optimum CPAP determined by the two methods was 0 cmH2O in ten of 17 patients, less than or equal to 2.5 cmH2O in 14 of 17 patients, and 5.0 to 7.5 cmH2O in the remaining three patients. When a difference existed, CPAP level determined with dual oximetry was consistently lower than the level selected by conventional means. The results indicate that the estimates of venous admixture and oxygen utilization coefficient obtained using dual oximetry provide sufficient information for rapid and accurate titration of CPAP in the majority of patients with acute respiratory failure.

Effect of arm position on cardiovascular responses during isometric handgrips.

Sixteen subjects (eight women and eight men, age 20-25 years) carried out in the seated position, isometric contractions sustained until exhaustion of the digital flexors. The subject's arm was placed in two positions, high and low. The muscle tensions used were 30, 40 and 50% of maximum voluntary contraction (MVC). Under these conditions, for a given relative force, the duration of contraction (limit-time) was not modified by the arm position. In the male subjects, increases in heart rate (HR) and systolic blood pressure (SBP) were slightly more pronounced in the low than the high position, but the differences were not significant. Limit times in the high position were similar to those in the low position, and, in the absence of an increase in HR and SBP, this seemed to be due to an increase in cardiac output consequent upon a transient improvement in venous return together with an increase in the coefficient of oxygen utilization.

Continuous venous oximetry in surgical patients.

A prospective study was performed to evaluate the efficacy of continuous venous oximetry to supplement traditional hemodynamic monitoring in 39 critically ill surgical patients. There was no statistically significant difference in SvO2 between the continuous in vivo values and in vitro values (0.694 +/- 0.095 vs. 0.698 +/- 0.108). There was no statistically significant correlation between continuously measured SvO2 and PaO2 (r = 0.09, p greater than 0.5), SaO2 (r = 0.08, p greater than 0.5), or oxygen consumption (r = 0.46, p greater than 0.5). There was a slight but statistically significant correlation between continuously measured SvO2 and cardiac output (r = 0.40, p less than 0.025) and oxygen delivery (r = 0.49, p less than 0.005). There was a highly significant correlation between continuously measured SvO2 and oxygen utilization coefficient (r = -0.96, p less than 0.001). Continuously measured SvO2 is a reliable predictor of SvO2 measured intermittently by in vitro methods. In critically ill surgical patients, SvO2 does not correlate highly with the individual determinants of oxygen transport but rather correlates with the oxygen utilization coefficient and therefore reflects the overall balance between oxygen consumption and delivery.

The influence of thoracic epidural analgesia on the circulation at rest and during physical exercise in man.

The effects of thoracic epidural analgesia (TEA) on the circulation at rest, during, and after physical exercise were investigated in 10 volunteers. At rest, TEA did not affect oxygen consumption (VO2) or cardiac output (Q), but heart rate (HR) was, increased by 7 beats/min, and stroke volume decreased correspondingly by 13 ml. Systolic arterial blood pressure was slightly reduced, but no other changes in systemic or pulmonary circulatory parameters were produced. TEA did not change VO2 during exercise, a 2.11/min reduction of Q being accompanied by a 4.2% increase of oxygen utilization coefficient. HR showed a relative reduction of about 10%. At moderate work loads during TEA, systemic arterial blood pressures were significantly lower than during control exercise. The resulting rate pressure product (RPP) was markedly reduced, while total peripheral resistance (TPR) remained unchanged. During recovery after the termination of exercise during TEA, VO2, Q, HR, RPP and TPR fell more rapidly towards values obtained at rest. From a clinical point of view the results support the safeness of TEA and also support its use in surgical patients with heart disease.

Diurnal rhythm of parameters of external respiratory function in clinically healthy persons

The diurnal rhythm of parameters of external respiratory function was studied in 67 clinically healthy persons aged from 20 to 62 years by spirography and pneumotachometry. Tests were carried out 4 times a day: at 2 and 7 a.m., 12 noon, and 9 p.m. In the younger and middle-aged subjects a statistically significant decrease was found in the minute respiratory volume at night and an increase in the power of inspiration in the evening. The respiration rate, the O2 consumption per minute, the maximal ventilation of the lungs and their vital capacity, the coefficient of oxygen utilization, and the power of expiration did not vary significantly during the 24-h period. In healthy subjects of the older group a significant decrease was found in the respiration rate, the maximal ventilation of the lungs, and the index of the rate of air movement at night; the minute volume of respiration was increased in the afternoon and evening and reduced at night, the values of Tiffeneau's test and the power of expiration were increased at midday, while the respiratory reserve was reduced in the afternoon and evening.

The effect of exogenous progesterone on the rate of blood flow of the uterus of ovariectomized sheep.

Progesterone was administered to fifteen ovariectomized non‐pregnant sheep in order to observe its effect on the rate of uterine blood flow (ml./kg/min), and on the relationship between these rates of flow and metabolism, as reflected in estimates of the arteriovenous oxygen difference and the uterine cavity‐aortic blood temperature difference. No effects were observed when only progesterone was administered, but when progesterone was given to ewes already receiving oestrogens, the rate of uterine blood flow fell and coefficient of oxygen utilization and temperature difference increased. The possible significance of these observations to cyclical changes observed during the oestrous cycle is discussed.

Blood flow and gaseous metabolism of the rabbit uterus during pregnancy

Using indwelling plastic catheters, blood samples were drawn from an artery and a uterine vein of anesthetized and unanesthetized rabbits at selected stages in gestation. Oxygen content and oxygen capacity were determined on the samples. The coefficient of oxygen utilization by the uterus increased from an average value of 15 per cent early in gestation to 63 per cent in the last few days of the gestation period. The antipyrine method was employed for measuring the rate of blood flow per kilogram of tissue. Uterine blood flow was high in early pregnancy and decreased as gestation advanced. The rate of O2 consumption per kilogram remained unchanged from the eleventh week onward; the average value was 7.42 c.c. per kilogram per minute.

Uterine blood flow and oxygen consumption of the pregnant uterus of the Macaca mulatta

The antipyrine method was employed for measuring the rate of blood flow per kilogram of tissue in the pregnant uterus of unanesthetized and recently stressed Macaca mulatta. There is a trend toward a decreased flow with advancing pregnancy of approximately 250 c.c. per kilogram per minute at 80 days to about 140 c.c. per kilogram per minute near term. The oxygen consumption of the uterus and its contents shows no trend to change from 75 days onward. These findings are associated with a decrease in uterine venous percentage oxygen saturation and an increase in the coefficient of oxygen utilization by the uterus.

Oxygen, carbon dioxide, and hydrogen ion concentration in arterial and uterine venous blood of pregnant goats

Using indwelling plastic catheters, blood samples were drawn from an artery and a uterine vein of unanesthetized pregnant goats at selected stages in gestation. Oxygen and carbon dioxide contents, pH, and oxygen capacity were determined on the samples. The coefficient of oxygen utilization by the uterus increased from 9 per cent early in gestation to 25 per cent in the last third of the gestation period of 145 to 147 days. The CO2 tension of the arterial blood ranged between 25.1 and 31.9 mm. Hg (average, 28.6) and the pH was 7.32 to 7.49 (average, 7.41).

吹込み気泡の溶融金属への吸収速度

The absorption of bubbles into a liquid metal was conducted in a 40mm ∅; sinter mullite crucible at 1000°C. Oxygen was blown through the 1.2mm ∅; nozzle of a silica tube into 150-700g silver.The depth of the immersed nozzle H was 9-64mm. The oxygen flow rate Vg was 0.88-3.23 Ncc/sec. The absorption rates of blown oxygen into molten silver were measured by the ZrO2·CaO solid electrolyte galvanic cell. By estimating the diameters and rising velocities of bubbles, the metal phase mass transfer coefficients were obtained. At the smaller depth, the observed values were higher than the theoretical ones by Higbie's model. As the depth became larger, the observed values approached to the theoretical ones. At the lower oxygen concentration, the absorption efficiency of oxygen was very high, but towards the saturated content of oxygen, it dropped rapidly. These phenomena were explained theoretically. In conclusion, the connection with the practical problems was discussed, especially with the oxygen utilization coefficient in open-hearth furnace and converter.

Blood flow and oxygen consumption of the uterus of the non-pregnant ewe.

Observations on the coefficient of oxygen utilization of the uterus have been made for periods of days and weeks in a series of ‘unstressed’ non‐pregnant ewes by means of indwelling catheters in an artery and the uterine vein. They indicate that the rate of oxygen transport to the uterus with respect to its oxygen consumption varies over a wide range. The two rates (ml./kg./min.) were estimated in twenty ‘unstressed’ ewes that had been divided into three groups on the basis of the appearance of the ovaries and uterus at laparotomy 2 or 3 days earlier. In ten ewes, at least one ovary contained a large protruding corpus luteum (Group I); in three, one ovary contained one or more large follicles (Group II) whereas in seven the ovaries lacked either of these distinguishing features (Group III). The average rates of uterine blood flow and oxygen consumption in these three groups were 119 and 5·26; 540·6 and 5·0 and 267·4 and 5·4 respectively.

A study of the oxygenation of the fetus and newborn and its relation to that of the mother

This report deals with oxygen concentrations in maternal (artery and uterine vein), fetal (umbilical vein and artery), and newborn (umbilical artery) blood samples. Studies were made in 63 pregnant women at term, not in labor, and delivered by cesarean section. The results indicate a wide range of variation in the various samples. Data are also included for calculation of respiratory quotient and coefficient of oxygen utilization across the intact uterus. No relationship was found between Apgar scoring and percentage oxygen saturation in fetal vessels and blood in newborn infants.

Gestational changes in arteriovenous differences of oxygen across the uterus of the rhesus monkey

Data on arteriovenous differences of oxygen and pH across the placenta of the rhesus monkey, Macula mulatta, throughout pregnancy are presented. The coefficient of oxygen utilization increased with gestation. The oxygen saturation, oxygen tension, and pH of the uterine venous drainage decreased with increasing gestation.

EFFECT OF HYPOTHERMIA ON MYOCARDIAL METABOLISM.

Effect of hypothermia of 25 C for 24 hr was determined on myocardial metabolism and efficiency in dogs fasted for approximately 15 hr and anesthetized with sodium pentobarbital. Coronary blood flow, cardiac output, myocardial oxygen and substrate utilization, and mechanical efficiency of the heart were determined at normal and reduced body temperatures. Prolonged reduction of myocardial temperature with concomitant reduction in coronary blood flow led to diminished oxygen and substrate utilization. Myocardial glycolysis began after 12 hr of cooling when pyruvate utilization stopped in negative balance. After 24 hr the heart stopped utilizing carbohydrates with negative arteriovenous differences for these substrates (in the presence of normal arterial carbohydrate levels), but continued to utilize nonesterified fatty acid. The coefficient of oxygen utilization for the heart increased following 24 hr of cooling, suggesting a relative state of myocardial hypoxia. The appearance of hypoxia and glycolysis during the late hours of cooling suggests that the limit of tolerance of the heart to cooling was near.