Search results for "Oxygen–haemoglobin dissociation curve"
showing 7 items of 7 documents
Une méthode rapide et simple pour l'estimation de la position de la courbe de dissociation de l'oxyhémoglobine
1989
The methods currently available for assessing the oxyhaemoglobin dissociation curve parameters are expensive, lengthy, require a large volume of blood, and the results obtained are modified by anaesthetic gases. The equipment required for the method described includes: a microtonometre, microcuvettes, 3 gas bottles containing different oxygen, carbon dioxide and nitrogen mixtures (4.5%, 5.6%, 89.9%; 3.5%, 5.6%, 90.9%; 2.5%, 5.6%, 91.9% respectively), a microxymetre, and a micropHmetre. The samples in the microcuvettes are incubated at 37 degrees C in a gas flow of 45 ml.min-1 from the bottles. SO2 is then read using the microxymetre. P50, i.e. PO2 at 50% saturation, is calculated, as well a…
Can Tumor Oxygenation be Improved by Reducing Cellular Oxygen Consumption?
1999
Tumor hypoxia, which can be found in many experimental and human tumors is an important factor influencing the therapeutic efficacy of standard radiotherapy, O2-dependent chemotherapy and photodynamic therapy (Hall, 1994) and might be responsible for the development of aggressive tumor cell subpopulations (Graeber et al., 1996). Since this oxygen deficiency results from a disparity between O2 supply to the tumor tissue and the oxygen demand of the cells, several attempts have been undertaken to improve tumor oxygenation primarily by increasing the arterial oxygen supply. The O2 supply to the tumor cells can be improved by (a) increasing the arterial O2 content (by breathing hyperoxic gases …
The Interdependence of Respiratory Gas Values and pH as a Function of Base Excess in Human Blood at 37°C
1973
The accurate estimation of the transport function of human blood for respiratory gases as well as the respiratory gas exchange in human body requires detailed knowledge of the respiratory gas partial pressures and the acid-base status in the blood. Because there is an interdependence between the different respiratory gas parameters described as Bohr and Haldane effect (3,4), it is possible to obtain a general picture of the whole transport system, if these interrelations are known.
Oxygen-haemoglobin dissociation curve in hypoxic rats of first or second generation.
1993
SUMMARY 1. Albino Wistar rats were raised in a normobaric hypoxic environment (10% O2 in N2). Two generations of hypoxic rats were observed for changes in their haemoglobin-oxygen (Hb-O2) dissociation curves (ODC), 2,3-diphosphoglycerate (2,3-DPG), haemoglobin (Hb), and Hill coefficients at P50 (n50). The first generation were called (H1) and the second generation (H2). The control group (N) had a normoxic environment. 2. Thirty-five rats (13 N rats, 12 H1 rats and 10 H2 rats) were used. The 2,3-DPG was significantly higher in both hypoxic groups when compared with N rats (2.02 ± 0.51 mmol/L) but 2,3-DPG of H2 rats was significantly lower than that of H1 rats (H1 = 3.48±0.58 mmol/L and H2 =…
Observation of ventilation-induced Spo(2) oscillations in pigs: first step to noninvasive detection of cyclic recruitment of atelectasis?
2010
High arterial partial oxygen pressure (Pao(2)) oscillations within the respiratory cycle were described recently in experimental acute lung injury. This phenomenon has been related to cyclic recruitment of atelectasis and varying pulmonary shunt fractions. Noninvasive detection of Spo(2) (oxygen saturation measured by pulse oximetry) as an indicator of cyclic collapse of atelectasis, instead of recording Pao(2) oscillations, could be of clinical interest in critical care. Spo(2) oscillations were recorded continuously in three different cases of lung damage to demonstrate the technical feasibility of this approach. To deduce Pao(2) from Spo(2), a mathematical model of the hemoglobin dissoci…
TISSUE OXYGENATION AND TISSUE METABOLISM IN THE BRAIN CORTEX DURING PRONOUNCED ARTERIAL HYPOCAPNIA
1981
Publisher Summary This chapter describes the tissue oxygenation and tissue metabolism in the brain cortex during pronounced arterial hypocapnia. Acute arterial hypocapnia induced by hyperventilation leads to typical reactions in the circulation and the metabolism of the brain tissue. With a lowering of arterial CO2 tension, the cerebro-vascular resistance (CVR) increases resulting in a decrease of cerebral blood flow. The changes in CVR are a consequence of decreasing hydrogen ion and potassium ion concentrations in the perivascular space of the brain arterioles. The corresponding changes in the brain metabolism are characterized by elevated concentrations of lactate and pyruvate and an inc…
Tumor Oxygenation Under Normobaric and Hyperbaric Hyperoxia
1997
Tumor hypoxia is an important factor limiting the efficiency of sparsely ionizing ra-diation and O2-dependent chemotherapy. Since the tumor pO2 is the result of a dynamic steady state between oxygen supply and O2 consumption of the tumor tissue, hypoxia could be reduced either by increasing the O2-supply or by reducing the O2 demand of the tumor cells. The O2 supply can be improved for instance by (i) increasing the arterial oxy-gen partial pressure, (ii) improving (and homogenizing) the tumor perfusion, or (iii) en-hancing the O2 release from blood into the tissue by right-shifting the HbO2 dissociation curve. Theoretically, it should also be possible to improve tumor oxygenation by a rela…