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Carriage of Oxygen in Blood
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
When blood Pco2, hydrogen ion concentration and temperature increase (as in a working muscle), the oxygen dissociation curve is shifted to the right of the oxygen dissociation curve when haemoglobin releases oxygen more easily. This is known as the Bohr effect. In pulmonary capillaries, when Pco2 and hydrogen ion concentration fall, the affinity of haemoglobin for oxygen increases, favouring oxygen uptake into the blood. This Bohr shift of the oxygen–haemoglobin dissociation curve therefore favours haemoglobin oxygen uptake in the lungs and oxygen delivery in the tissues. Also, 2,3-diphosphoglycerate reduces the affinity of haemoglobin for oxygen, shifting the dissociation curve to the right.
Miscellaneous poisons
Published in Jason Payne-James, Richard Jones, Simpson's Forensic Medicine, 2019
Jason Payne-James, Richard Jones
The affinity of Hb for CO is up to 250 times greater than that for oxygen and the presence of CO results in a shift of the oxygen–haemoglobin dissociation curve to the left, causing decreased oxygen-carrying capacity and impaired delivery of oxygen to the tissues. Cellular hypoxia results and cardiac function is diminished because of hypoxia. The link between levels of CO and effects is not direct. The amount of uptake is governed by a number of variables, all of which are interrelated and include: relative concentrations of CO and oxygen, alveolar ventilation, duration and intensity of exposure. However, chronic exposure to high levels of CO leads to CO binding to proteins with less affinity than haemoglobin, such as myoglobin and cytochromes of the P450 system, particularly a3. Differential affinity may also account for some of the variations in response to exposure. Hypoxic stress caused by CO exposure alone would not seem to account for some of the longer-term effects and it is believed that CO also initiates a cascade of events culminating in oxidative stress.
SBA Answers and Explanations
Published in Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury, SBAs for the MRCS Part A, 2018
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury
The oxygen–haemoglobin dissociation curve relates percentage saturation of the oxygen (O2) carrying power of haemoglobin (Hb) to the saturation of oxygen (Po2). This curve has a characteristic sigmoid shape. Combination of the first haem in the Hb molecule with O2 increases the affinity of the second haem for O2, and oxygenation of the second increases the affinity of the third, and so on, so that the affinity of Hb for the fourth O2 molecule is many times that for the first. This is known as co-operativity. The decrease in O2 affinity of Hb when the pH of blood falls is called the Bohr effect.
Evaluation of aerosolized epoprostenol for hypoxemia in non-intubated patients with coronavirus disease 2019
Published in Hospital Practice, 2022
Vivek Kataria, Klayton Ryman, Ginger Tsai-Nguyen, Yosafe Wakwaya, Ariel Modrykamien
The threshold for response to therapy in our cohort was chosen in consideration of the disease process of SARS-CoV-2. Notably, previous studies utilizing aEPO via noninvasive routes defined the response to therapy as an improvement in the partial pressure of arterial oxygen (PaO2) or SpO2 to FiO2 by 20% [11–13]. Since the PaO2-to-FiO2 ratio is not validated in HFNC, routine arterial blood gases were not obtained. Moreover, SpO2-to-FiO2 ratio was not selected to demonstrate the impact on oxygenation in consideration of the oxygen-hemoglobin dissociation curve. Due to the sigmoidal curve, at saturations above 90–92%, further increases in PaO2 have a limited impact on further oxygen saturation[17]. Thus, the maintenance of SpO2 > 92% with a sustained reduction in FiO2 was selected to reflect the response to therapy and its impact on oxygenation.
Are infectious diseases and microbiology new fields for thermal therapy research?
Published in International Journal of Hyperthermia, 2018
Heat induces a prompt increase in blood flow accompanied by the dilation of vessels and an increase in the permeability of the vascular wall in normal tissues [2,48–50]. At the same time, increased blood temperatures result in a reduced affinity of haemoglobin for oxygen and thus a rightward shift of the Oxygen–Haemoglobin Dissociation Curve. When the temperature of muscle tissue is higher than 37 °C, oxygen can be unloaded from haemoglobin more easily (lowered oxygen affinity). These changes lead to an overall increase in oxygen availability and improved oxygenation status [51]. Oxygen is necessary for cellular survival and is lethal to some bacteria, especially anaerobes [52]. Heating tumours to higher temperatures typically causes a transient increase in perfusion during heating, followed by vascular collapse; however, such vascular collapse generally occurs at temperatures that cause a substantial blood flow increase in certain normal tissues [53]. Increased blood flow and permeability of the vascular wall may help antibiotics and components of the immune system easily diffuse through the target tissue.
Secondary erythrocytosis due to hemoglobin San Diego
Published in Baylor University Medical Center Proceedings, 2021
Hb SD was first described in 1974 in a Filipino family.3 Since then, some cases have been described in different countries.4–14 The literature review revealed that Hb SD could be diagnosed in all patient populations (from as young as 5 years to as old as 79 years). Hemoglobin values ranged from 15.8 to 22.5 g/dL. The P50 oxygen-hemoglobin dissociation curve value was reduced in all cases.4–14 In one patient, Hb SD coexisted with β0 thalassemia.7 Another patient had heterozygosity for both Hb SD and hemoglobin S.9 Many patients had a strong family history of erythrocytosis or confirmed Hb SD.3–5,8,12–14