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Nature Metabolism Aug 2022Measurement of oxygen consumption is a powerful and uniquely informative experimental technique. It can help identify mitochondrial mechanisms of action following... (Review)
Review
Measurement of oxygen consumption is a powerful and uniquely informative experimental technique. It can help identify mitochondrial mechanisms of action following pharmacologic and genetic interventions, and characterize energy metabolism in physiology and disease. The conceptual and practical benefits of respirometry have made it a frontline technique to understand how mitochondrial function can interface with-and in some cases control-cell physiology. Nonetheless, an appreciation of the complexity and challenges involved with such measurements is required to avoid common experimental and analytical pitfalls. Here we provide a practical guide to oxygen consumption measurements covering the selection of experimental models and instrumentation, as well as recommendations for the collection, interpretation and normalization of data. These guidelines are provided with the intention of aiding experimental design and enhancing the overall reputability, transparency and reliability of oxygen consumption measurements.
Topics: Energy Metabolism; Mitochondria; Oxygen Consumption; Reference Standards; Reproducibility of Results
PubMed: 35971004
DOI: 10.1038/s42255-022-00619-4 -
Journal of Muscle Research and Cell... Jun 2023This article lays out the determinants of maximal O consumption (VOmax) achieved during high intensity endurance exercise. It is not a traditional topical review but...
This article lays out the determinants of maximal O consumption (VOmax) achieved during high intensity endurance exercise. It is not a traditional topical review but rather an educational essay that intertwines chance observations made during an unrelated research project with a subsequent program of stepwise thought, analysis and experimentation to reveal how O is delivered to and used by the mitochondria. The centerpiece is the recognition that O is delivered by an inter-dependent system of transport components functioning as a "bucket brigade", made up of the lungs, heart, blood and circulation, and the muscles themselves, each of which affects O transport by similar amounts as they change. There is thus no single "limiting factor" to VOmax. Moreover, each component is shown to quantitatively affect the performance of the others. Mitochondrial respiration is integrated into the O transport system analysis to reveal its separate contribution to VOmax, and to show that mitochondrial PO at VOmax must be extremely low. Clinical application of the O transport systems analysis is described to separate central cardiopulmonary from peripheral tissue contributions to exercise limitation, illustrated by a study of patients with COPD. Finally, a short discussion of why muscles operating maximally must endure an almost anoxic state is offered. The hope is that in sum, both the increased understanding of O transport and the scientific approach to achieving that understanding described in the review can serve as a model for solving other complex problems going forward.
Topics: Humans; Oxygen Consumption; Muscles; Exercise
PubMed: 36434438
DOI: 10.1007/s10974-022-09636-y -
Intensive Care Medicine Apr 1996
Topics: Lung; Lung Diseases; Oxygen Consumption
PubMed: 8708162
DOI: 10.1007/BF01700446 -
Disease-a-month : DM Jul 1994The primary function of the heart and lungs is to generate a flow of oxygenated blood to respiring tissues to sustain aerobic metabolism. Teleologically, such a... (Review)
Review
The primary function of the heart and lungs is to generate a flow of oxygenated blood to respiring tissues to sustain aerobic metabolism. Teleologically, such a transport system has several basic requirements. It should be energy efficient, avoiding unnecessary cardiorespiratory work, but it should be sensitive to the fluctuating demands of cellular metabolism. Ideally, metabolic demand and oxygen distribution should be matched regionally when at rest, during exercise, and in different disease states. Finally, oxygen should pass efficiently across the extravascular tissue matrix. The mechanisms that control oxygen distribution are complex and not completely understood. In the critically ill patient, these mechanisms may have an important role in determining the clinical outcome. The relationship between oxygen delivery and consumption has not been clearly established despite considerable investigation during the last decade. However, these variables are often measured to define a population of critically ill patients in whom oxygen consumption is limited by oxygen delivery, the state of so-called delivery-dependent oxygen consumption or pathologic supply dependency. The recent literature in critical care and many leading intensive care units has emphasized the importance of raising oxygen delivery to "supranormal" levels in an attempt to satisfy the increased metabolic demands of these patients. This practice has been justified by the observation that increasing oxygen delivery improves oxygen debt and outcome in postoperative surgical patients requiring intensive care. In the severely hypovolemic patient, most physicians would agree that volume replacement to improve oxygen delivery must be beneficial. However, in patients with more complex problems, including sepsis, cardiovascular collapse, and hypoxic hypoxemia, controlled trials to examine the influence of such strategies on clinical outcome have produced conflicting data. Several methodologic factors may have contributed to these contradictory and often controversial results. These factors include failure to define the disease and patient population adequately, the relationship between the time of investigation and the evolution of the disease process, and the accuracy and frequency of measurement.(ABSTRACT TRUNCATED AT 400 WORDS)
Topics: Animals; Bacterial Infections; Critical Illness; Humans; Oxygen; Oxygen Consumption; Surgical Procedures, Operative
PubMed: 8020386
DOI: No ID Found -
Nutrition (Burbank, Los Angeles County,... 1993
Topics: Critical Care; Critical Illness; Energy Metabolism; Humans; Oxygen Consumption
PubMed: 8485333
DOI: No ID Found -
Respiration Physiology 1990The factors limiting VO2max in humans are analyzed according to a multifactorial model derived from the O2 conductance equation. In this context, alveolar ventilation... (Review)
Review
The factors limiting VO2max in humans are analyzed according to a multifactorial model derived from the O2 conductance equation. In this context, alveolar ventilation (VA) and lung O2 transfer (GL) are not considered to be limiting, at least at sea level, because changes in VA and/or in GL are not accompanied by changes in VO2max due to the shape of the O2 dissociation curve. Thus, the limits to VO2max are shared between blood O2 transport (FQ') and a peripheral factor. This last includes tissue O2 transfer (Ft') and mitochondrial O2 utilization (Fm'). In untrained subjects at sea level, blood O2 transport is found to be responsible for approximately 70% of the overall limits to VO2max (FQ' = 0.7), the rest depending on the peripheral factors. FQ', as well as the sum of Ft' and Fm', are unchanged after training or upon return to sea level following exposure to chronic hypoxia (altitude higher than 5000 m). In the latter condition, however, since tissue O2 transfer, which sets Ft', is facilitated, and mitochondrial O2 utilization, which sets Fm', is impaired, Ft' is reduced and Fm' increased as compared to control condition and/or after training.
Topics: Humans; Oxygen Consumption
PubMed: 2218094
DOI: 10.1016/0034-5687(90)90075-a -
Respiratory Physiology & Neurobiology Jan 2023The effects of temperature on breathing pattern and oxygen consumption are being investigated in juvenile tortoises and compared to adults, in order to understand...
The effects of temperature on breathing pattern and oxygen consumption are being investigated in juvenile tortoises and compared to adults, in order to understand physiological adjustments of the respiratory system as related to body size, especially regarding the energetic expenditure associated with growth. We analyzed the breathing pattern and oxygen consumption of juvenile and adult red-footed tortoises (Chelonoidis carbonarius, Cryptodira: Testudinidae). The animals (N = 9; body mass ranging from 0.03 Kg to 2.5 Kg) were exposed to normoxic-normocarbic conditions using open respirometry in order to determine the breathing pattern and oxygen consumption in three different temperatures (15, 25, 35 °C). The obtained results showed intermittent breathing pattern in all tested temperatures in juveniles and adults. Tidal volume was not affected by changes in temperature, while breathing frequency increased significantly with increasing temperature, leading to a significant increment in minute ventilation between 15 and 35 °C. Mass specific oxygen consumption increased significantly with temperature and juveniles showed greater values when compared to adults. The alterations in the ventilatory response to temperature changes occurred in order to maintain the oxygen supply with increased metabolic activity. The differences between juveniles and adults in breathing frequency lead to juveniles needing a lower ventilation rate to perform gas exchange while extracting more oxygen. While these differences might be attributed to a greater metabolic expenditure during development, scaling effects on respiratory variables might be the main contributors to the found differences.
Topics: Animals; Temperature; Turtles; Oxygen Consumption; Respiration; Oxygen
PubMed: 36252778
DOI: 10.1016/j.resp.2022.103978 -
Journal of Optometry 2022The study of oxygen consumption rate under" in vivo" human cornea during contact lens wear has been technically a challenge and several attempts have been made in the...
The study of oxygen consumption rate under" in vivo" human cornea during contact lens wear has been technically a challenge and several attempts have been made in the last 20 years to model the physiology of the human cornea during contact lens wear. Unfortunately, some of these models, based on a constant corneal oxygen consumption rate, produce areas on the cornea where the oxygen tension is negative, which has no physical sense. In order to avoid such inconsistency, different researchers have developed alternative models of oxygen consumption, which predict the likely oxygen metrics available at the interface cornea/post lens tear film by determination of oxygen flux, oxygen consumption, and oxygen tension through the different layers (endothelium, stroma, and epithelium). Although oxygen deficiency produces corneal edema, corneal swelling, hypoxia, acidosis, and other abnormalities, the estimation of the oxygen distribution below the impact of a contact lens wear is interesting to know which lens transmissibility was adequate to maintain the cornea and avoid epithelial and stromal anoxia. The estimation of minimum transmissibility for a lens for extended wear applications will be very useful for both clinicians and manufacturers. The aim of this work is to present a complete discussion based on Monod kinetics model that permits give an estimation of oxygen partial pressure distribution, the profile distribution of corneal flux and oxygen consumption rate, and finally the estimation of the relaxation mechanism of the cornea depending on the oxygen tension at the interface cornea/post lens tear film. Relaxation time in this context can quantify the capability of the corneal tissue to adapt to increasing concentrations of oxygen. It is proposed this parameter as a biological meaningful indicator of the interaction between contact lens polymers and living tissues such as the corneal cellular layer.
Topics: Contact Lenses, Hydrophilic; Cornea; Humans; Oxygen; Oxygen Consumption; Tears
PubMed: 33589396
DOI: 10.1016/j.optom.2020.12.002 -
Journal of Visualized Experiments : JoVE Jan 2019Regulated metabolic activity is essential for the normal functioning of living cells. Indeed, altered metabolic activity is causally linked with the progression of...
Regulated metabolic activity is essential for the normal functioning of living cells. Indeed, altered metabolic activity is causally linked with the progression of cancer, diabetes, neurodegeneration, and aging to name a few. For instance, changes in mitochondrial activity, the cell's metabolic powerhouse, have been characterized in many such diseases. Generally, the oxygen consumption rates of mitochondria were considered a reliable readout of mitochondrial activity and measurements in some of these studies were based on isolated mitochondria or cells. However, such conditions may not represent the complexity of a whole tissue. Recently, we have developed a novel method that enables the dynamic measurement of oxygen consumption rates from whole isolated fly heads. By utilizing this method, we have recorded lower oxygen consumption rates of the whole head segment in young versus aged flies. Secondly, we have discovered that lysine deacetylase inhibitors rapidly alter the oxygen consumption in the whole head. Our novel technique may therefore aid in uncovering new properties of various drugs, which may impact metabolic rates. Furthermore, our method may give a better understanding of metabolic behavior in an experimental setup that more closely resembles physiological states.
Topics: Animals; Diptera; Humans; Oxygen Consumption
PubMed: 30663674
DOI: 10.3791/58601 -
Compendium (Yardley, PA) Jan 2011Early recognition of failure of oxygen delivery and knowledge of how medications can alter oxygen delivery allow clinicians to institute appropriate therapies in a... (Review)
Review
Early recognition of failure of oxygen delivery and knowledge of how medications can alter oxygen delivery allow clinicians to institute appropriate therapies in a timely manner and can result in improved patient outcomes. Oxygen delivery can be estimated and evaluated using a variety of methods, including arterial blood gas sampling, blood lactate quantification, echocardiography, and direct cardiac output measurement. Delivery can be enhanced by manipulating the components of the oxygen delivery formula. Cardiac output, hemoglobin concentration, oxygen saturation, and oxygen tension can all be improved through therapeutic or pharmacologic intervention.
Topics: Animals; Blood Gas Analysis; Cardiac Output; Hemoglobins; Lactates; Monitoring, Physiologic; Oxygen; Oxygen Consumption
PubMed: 21882160
DOI: No ID Found