A respirometer for organ cultures

Uptake of volatile agents.

Beyond the lung: oxygen delivery and tissue oxygenation.

Commercial respirometers are capable of continuously and automatically measuring oxygen uptake in bioreactors. A method for continuously and automatically measuring carbon dioxide evolution can be retrofitted to commercial respirometers. Continuous and automatic measurements of carbon dioxide evolution are achieved by measuring the change in electrical conductivity of barium hydroxide solution. Continuous stirring of the barium hydroxide solution was necessary to prevent the carbon dioxide absorption from controlling the oxygen uptake rate. Three separate experiments (aqueous biodegradation of phenol, soil slurry biotreatment of soil contaminated with phenol, and aqueous biodegradation of crude oil) were conducted to test the oxygen uptake and carbon dioxide evolution measurement system. The respiratory quotient, defined as the ratio of carbon dioxide evolution to oxygen uptake, is close to one until a plateau of oxygen uptake is reached, after which it is greater than one due to degradation of biomass and metabolite products. Unsteady‐state simulation of CO2 evolution in batch reactors, based on the experimental data, showed that carbon dioxide exists primarily as bicarbonate in the liquid phase. The concentration of carbon dioxide in the gas phase is small mainly due to fast reaction with the stirred barium hydroxide solution.

Shelf sediments play a vital role in global biogeochemical cycling and are particularly important areas of oxygen consumption and carbon mineralisation. Total benthic oxygen uptake, the sum of diffusive and faunal mediated uptake, is a robust proxy to quantify carbon mineralisation. However, oxygen uptake rates are dynamic, due to the diagenetic processes within the sediment, and can be spatially and temporally variable. Four benthic sites in the Celtic Sea, encompassing gradients of cohesive to permeable sediments, were sampled over four cruises to capture seasonal and spatial changes in oxygen dynamics. Total oxygen uptake (TOU) rates were measured through a suite of incubation experiments and oxygen microelectrode profiles were taken across all four benthic sites to provide the oxygen penetration depth and diffusive oxygen uptake (DOU) rates. The difference between TOU and DOU allowed for quantification of the fauna mediated oxygen uptake and diffusive uptake. High resolution measurements showed clear seasonal and spatial trends, with higher oxygen uptake rates measured in cohesive sediments compared to the permeable sediment. The significant differences in oxygen dynamics between the sediment types were consistent between seasons, with increasing oxygen consumption during and after the phytoplankton bloom. Carbon mineralisation in shelf sediments is strongly influenced by sediment type and seasonality.

1. Standard conditions are described for preparing suspensions of washedTrypanosoma lewisiandT. equiperdumin modified Ringer–phosphate solution.2. Oxygen consumption was measured with differential manometers, using microflasks containing 2–5 × 107trypanosomes in 0·9 ml. of reaction mixture. Measurements of oxygen uptake were carried out at 37° C.3.T. lewisirespired slowly in the absence of substrate for up to 2 hr. The trypanosomes suffered little damage when stored at 5° C. for 24 hr. without substrate. No oxygen uptake was observed withT. equiperdumin the absence of substrate. The trypanosomes were viable after 24 hr. at 5° C. with glucose or glycerol as substrate, but not in the absence of substrate.4. With glucose as substrate, the rate of oxygen consumption byT. lewisiincreased with the age of infection. This change was more marked with glutamine as substrate.5. With glucosamine as substrate, the oxygen uptake ofT. lewisiwas at a slightly lower rate than with glucose. The rate of oxygen uptake was still lower with Nal-glutamic acid, asparagine, aspartic acid, casein hydrolysate, yeast extract and Difco Bacto-peptone. Thirteen other amino-acids had no effect on the motility of the trypanosomes.6. With glycerol as substrate, the oxygen uptake ofT. equiperdumwas at a slightly lower rate than with glucose. The rate of oxygen uptake was very low with yeast extract, casein hydrolysate and Difco Bacto-peptone. No oxygen uptake or motility was recorded with glutamine, Nal-glutamic acid, glucosamine, asparagine, aspartic acid,dl-alanine, or Na acetate. Thirteen other amino-acids had no effect on the motility of the trypanosomes.7. Ammonia was liberated from glutamine by adult and reproductive phaseT. lewisi.

STOICHIOMETRY OF OXYGEN UPTAKE, NADPH OXIDATION AND ETHYLMORPHINE N-DEMETHYLATION BY HEPATIC MICROSOMES

1. In the laboratory Eucidaris tribuloides showed a food preference for rock infested with the boring sponge Cliona lampa over turtle grass (Thalassia testudinum), several algae, and fish strips. 2. In the laboratory, urchins consumed wet rock infested with Cliona lampa at rates ranging from less than one to over three gm. per day depending on the size of the urchin. 3. Oxygen consumption of urchins was measured in the laboratory with a modified Scholander volumetric respirometer. 4. Oxygen uptake decreased significantly during the first day of starvation, but then remained relatively stable during several successive days of starvation. 5. There was not a significant correlation between gonad index or sex of the urchin and relative oxygen uptake. 6. Relative oxygen consumption decreased with increasing size of the urchin. Values for "b" indicated an oxygen uptake which was almost proportional to surface area at 20° and 30 ° C. 7. Oxygen uptake fluctuated during the first hour when urchins were placed in water several degrees colder than their ambient water. At the end of this hour, however, the rate of oxygen uptake had become relatively stable. Well-fed urchins manifested greater changes in their stabilized rates of oxygen uptake (Q10) at different temperatures than did starved urchins. 8. Urchins manifested partial seasonal acclimation of oxygen uptake as indicated by the fact that winter oxygen consumption curves were well above summer curves at the corresponding temperatures. The acclimation was probably not complete since mean summer oxygen uptake was higher at the summer ambient than the mean winter oxygen uptake at the winter ambient.

Measurement of lung oxygen consumption in a patient after double-lung transplant

In order to identify a critical or an optimal therapeutic value for oxygen delivery and oxygen uptake, we analysed data from 40 publications concerning the relationship between oxygen delivery and consumption in patients with adult respiratory distress syndrome, trauma or during sepsis, and in nonseptic controls. According to the outcome, the patients were allocated to either group 1 (survivors) or group 2 (nonsurvivors). While oxygen delivery and uptake (mean, SEM) were significantly higher in patients with adult respiratory distress syndrome (636, SEM 31 ml.min-1.m-2 and 155, SEM 5 ml.min-1.m-2), trauma (782, SEM 77 ml.min-1.m-2 and 167, SEM 10 ml.min-1.m-2) and sepsis (654, SEM 28 ml.min-1.m-2 and 163, SEM 5 ml.min-1.m-2) than in nonseptic controls (452, SEM 18 ml.min-1.m-2 and 126, SEM 3 ml.min-1.m-2, p < 0.05), there were no significant differences in these parameters between survivors and nonsurvivors. Although therapeutic manoeuvres were effective in increasing both oxygen delivery and consumption, these improvements were not paralleled by an increase in survival rate. The correlation between oxygen delivery and uptake is generally a result of the use of pooled data and therefore prone to mathematical coupling. This is true particularly for patients with adult respiratory distress syndrome and sepsis. Thus, our study failed to identify either an optimal or a critical value of oxygen delivery or oxygen consumption in critically ill patients.

Bolus doses of ephedrine are often used by anaesthesiologists for intraoperative hypotension. This randomized single-blind cross-over study was designed to simultaneously evaluate circulatory, respiratory and metabolic effects of intravenously given ephedrine in 12 healthy male volunteers. Oxygen uptake and carbon dioxide excretion were measured with indirect calorimetry and non-invasive transthoracic electrical bioimpedance was used for cardiac output measurements. The maximum effect on most variables was reached at 4-5 min. At 5 min after the administration of ephedrine 0.1 mg per kilogram body weight, there were significant increases in cardiac index, systolic and mean arterial blood pressure, expired minute volume, oxygen uptake and carbon dioxide excretion rates. There were no significant changes in the quotient between oxygen uptake rate and cardiac index, VO2/CI during the 30 min study period. The O2 saturation was not altered. The present study indicates that ephedrine increases oxygen demand and supply in a similar magnitude.

A pocket calculator program for noninvasive assessment of cardiorespiratory function

Objectives. The work set out to develop a bioreactor that incorporates a carbon dioxide removal unit within the apparatus gas phase, which is capable of operating without the need for supplementary compression apparatus. As part of testing the developed equipment in order to ascertain its capacity for enhanced biomass production, the principal fermentation system parameters that facilitate the optimal bioreactor productivity in conditions of carbon dioxide removal from the apparatus gas phase were identified.Methods. A series of tests were conducted on the fermentation unit with the objective of controlling the oxygen and carbon dioxide content in the gas phase of the bioreactor. This was achieved using an in-line gas analyzer fitted with electrochemical sensors. The oxygen and carbon dioxide content in the gas phase was determined by means of gas chromatography. The oxygen and natural gas flow rates were determined using a thermal electronic flow controller equipped with thermoresistive elements. The oxygen content of the cultural liquid was determined by means of an optical oxygen sensor with integrated transducer. The pH level in the bioreactor was monitored and maintained using an electrochemical pH sensor.Results. The efficacy of the newly devised jet-type bioreactor design, which permits the incorporation of a carbon dioxide removal unit into the fermentation system without requiring supplementary compression apparatus, was evaluated through experimentation. The system was tested with the carbon dioxide removal unit included in the design, resulting in a 64% increase in bioreactor productivity and a 18% reduction in oxygen consumption as a component of the gas supply.Conclusions. The operational parameters of a technological bioreactor that facilitate a stable continuous process of bacterial cultivation were identified.

Oxygen transfer and uptake rates during xanthan gum production.

To the Editor: Routine activities of daily living in young and adult individuals only induce a minimal challenge on maximal capacity, but with increasing age, less physically demanding tasks require increasingly more of the maximal physical capacity. The latter may make it almost impossible for a significant proportion of old subjects to perform even light activities of daily living (ADLs). A minimum aerobic threshold for independent living appears to fluctuate between 13 and 15 mL oxygen/min per kg, which has been suggested as a minimum requirement for successfully coping with everyday tasks.1,2 Interestingly, men have higher muscle mass and aerobic capacity than women, which may explain why men perform better in ADLs than women and why women in general are functionally dependent for about 4 years longer than men.3 This difference between the sexes may render old women more vulnerable because their maximal functional capacity may fall below the threshold of successful independent living. This study determined maximal oxygen uptake and the relative effort assessed as oxygen consumption necessary to perform selected everyday activities such as stair climbing, dressing, walking, and vacuuming in different age cohorts of women. Nine young (aged 32.2±1.7), eight middle-aged (54.1±1.3), and eight old (77.4±1.8) Danish women participated in the study. They all reported normal level of physical activity for Danish women such as daily walking, bicycling, or gardening. Maximal aerobic capacity was measured as maximal oxygen uptake (VO2max) using a progressive, maximal test on a Cybex cycle ergometer. Oxygen, carbon dioxide, ventilation, and respiratory exchange ratio were continuously analyzed using an on-line system (Innovision AMIS 2001, INNOVISION, Odense, Denmark).4 Oxygen consumption during everyday activities was performed during walking at a self-selected speed, dressing, stair climbing, and vacuuming (Figure 1). After 6 minutes of repetitive movements, expired air was collected in Douglas bags and analyzed for oxygen and carbon dioxide on a Beckmann analyzer. Maximal oxygen uptake and oxygen consumption during stair climbing, walking, dressing, and vacuuming in the three age groups of healthy community-dwelling women. Significant differences were observed between all three groups in VO2max and VO2max relative to body weight. Relative effort expressed as the percentage of oxygen consumption (l/min) during an everyday activity in relation to VO2max (l/min) increased with age in all everyday activities. Significant differences were observed between all groups. Absolute values of oxygen (l/min) used in the different everyday activities revealed no significant differences between the groups. Elderly women experience oxygen consumption during everyday activities near their VO2max, whereas middle-aged and young subjects possess a more significant margin between these two parameters. VO2max is reported to decrease 5% to 15% after age 25.5 The present study revealed an even more significant decrease of 29% between the young and the middle-aged groups (∼14.5%/decade) and 27% between the middle-aged and the old groups (∼10.8%/decade) in this parameter. Furthermore, the old women in this study were active and lived independently, in spite of this, the VO2max per kg of body weight was perilously close to the critical threshold claimed to be between 13 and 15 mL or O2/min per kg.1,2 It is important to notice that these data are cross-sectional and may not only reflect a biological change in VO2max, but also cultural and lifestyle differences. In the present study, all women were able to perform the four different everyday activities, but the elderly women had to make significantly higher efforts. During performance of the different everyday activities, no significant changes were observed in oxygen uptake between any of the groups, indicating that the same amount of oxygen is demanded for the same everyday activity independent of age, and significant changes were found in all activities between all groups in the relative effort of performance, demonstrating that older women perform these four everyday activities closer to their maximal capacity than younger subjects. Even very old subjects are able to increase their VO2max through regular training, which will optimize physical function and independence.4,6,7 Furthermore, a high VO2max demonstrates decrease in the risk of developing lifestyle diseases such as diabetes mellitus, osteoporosis, hypertension, cardiovascular diseases, and depression and even increase psychological well-being.8 In conclusion, oxygen consumption during performance of everyday activities was similar in the different age groups of women. In contrast, a significant age-related decline in VO2max was noticed. This narrows the window during aging between demand and capacity of oxygen consumption that makes everyday tasks such as stair climbing, walking, dressing, and vacuuming difficult—and finally impossible—to perform.

Simultaneous measurement of oxygen uptake and carbon dioxide emission during discontinuous ventilation in the tok-tok beetle, Psammodes striatus