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Inhalant Anesthesia and Partial Intravenous Anesthesia
Published in Michele Barletta, Jane Quandt, Rachel Reed, Equine Anesthesia and Pain Management, 2023
Inhalation anesthetics are administered as a vaporized gas. It is the partial pressure of this gas in the central nervous system that produces general anesthesia. The partial pressure of the gas must reach the lung via ventilation.From the lung, the gas travels to the target tissues (central nervous system) primarily by means of the vascular system.
Basic medicine: physiology
Published in Roy Palmer, Diana Wetherill, Medicine for Lawyers, 2020
The partial pressure of oxygen (pO2) is about 95 mmHg in arterial blood but only 40 mmHg in venous blood because so much oxygen is extracted for use by cells during the passage of blood through the tissues. Nearly all oxygen transport occurs as oxyhaemoglobin, whereas carbon dioxide is much more soluble in blood and is carried largely as carbonic acid. The affinity of haemoglobin for oxygen is affected by both pH and temperature. Skeletal muscle contains a protein (myoglobin) that resembles haemoglobin but has a much lower affinity for oxygen; it can store some oxygen in muscle for release when the blood supply is reduced. Arterial blood is normally 97% saturated with oxygen; oxygen saturation can be measured fairly simply and is a guide to inadequate respiration (hypoxia). A more accurate assessment requires an arterial blood sample to be obtained for measurement of pO2.
Pathophysiology of Spinal Cord Injury in a Rat Model of Decompression Sickness
Published in John J. Lemasters, Constance Oliver, Cell Biology of Trauma, 2020
Decompression sickness, a disease that affects divers and high-altitude fliers, is induced by a rapid decrease in ambient pressure. During decompression the difference in partial pressure of gas between body tissues and the environment causes the gas dissolved in the tissues to diffuse out into the blood. In the pulmonary microcirculation the gas diffuses from the blood to the air. Eventually the partial pressure of gas in body tissues equilibrates with the alveolar partial pressure of gas. During decompression, the decrease in ambient pressure diminishes the solubility of the gas in tissues. If the decrease in pressure occurs too rapidly to allow equilibration of the gas tension in the tissue with the ambient pressure, large amounts of free gas form. Formation of gas bubbles further retards the elimination of gas from tissues; the elimination of nitrogen is affected the most because this gas is metabolically inert and can be eliminated only by the circulation.1
Comparison of two oxygen saturation targets to decide on hospital discharge of infants with viral bronchiolitis living at high altitudes: a cost-effectiveness analysis
Published in Current Medical Research and Opinion, 2022
Carlos E. Rodriguez-Martinez, Monica P. Sossa-Briceño, Jefferson Antonio Buendia
The use of a high-altitude adjusted SpO2 threshold to decide on hospital discharge when all other discharge criteria are met is supported from a physiological perspective. As the altitude above sea level increases, the barometric pressure falls, affecting the inspired partial pressures of oxygen and resulting in a physiological hypoxemia referred to as hypobaric hypoxia25–27. Hypobaric hypoxia is responsible for the changes in physiology that occur at high altitudes and for considering that at high altitude settings, SpO2 < 85%, as used in the present study, may be more appropriate for identifying infants most in need for supporting oxygen therapy. Additionally, the use of a lower SpO2 threshold has been shown to be not only effective, avoiding unnecessarily prolonged hospitalizations, but also safe in the short term, without a subsequent increase in healthcare reattendance within 28 days when compared to the use of the usual SpO2 thresholds21.
Supraventricular tachycardia after respiratory syncytial virus infection in a newborn
Published in Baylor University Medical Center Proceedings, 2022
Seda Aydoğan, Nurdan Dinlen Fettah, Ali Ulaş Tuğcu, Ece Koyuncu, Tamer Yoldaş, Ayşegül Zenciroğlu
A 3760 g G1P1Y1 male baby born to a 24-year-old mother by vaginal delivery at 40 weeks of gestation was admitted at 17 days of age. He had a cough that began 4 days before hospital admission. His body weight was 4000 g, his axillary body temperature was 36°C, and his arterial oxygen saturation was 94% on room air. In the cardiovascular system examination, S1-S2 was rhythmical, no murmur was heard, the heart rate was 136 beats/min, and arterial blood pressure was 68–39 mm Hg. In the respiratory system examination, the respiratory rate was 64 breaths/min, bilateral thin crepitant rales were present, and intercostal retractions were present. Laboratory findings included a white blood cell count of 6400/mm3, hemoglobin of 14.9 g/dL, platelet count of 411.000/mm3, and C-reactive protein of <3 mg/L. The patient’s biochemical values were normal. For arterial blood gases, the partial pressure of oxygen was 62 mm Hg and the partial pressure of carbon dioxide was 45 mm Hg. No increase in aeration and cardiomegaly was detected on the chest x-ray. A nasopharyngeal swab sample was taken from the patient at the time of admission, and a viral panel study was performed. RSV was positive based on a polymerase chain reaction test. Our patient was not given β-agonist treatment or any antibiotics; only supportive treatment was applied.
Effect of first order chemical reactions through tissue-blood interface on the partial pressure distribution of inhaled gas
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
In the human respiratory system pressure is caused by the movement of molecules against the surface, and in the process of diffusion of gas in blood, or tissue-blood capillary (Hall and Guyton 2010; Bhattacharya and Matthay 2013). The pressure exerted by the gas (i.e. oxygen, carbon dioxide, nitrogen, helium, etc.), alone is defined as the partial pressure of that gas, which can be used to estimate the diffusion of a gas. Partial pressure is controlled by the solubility of a gas in fluid, the cross-sectional area of the tube, the distance through which the gas must diffuse and the molecular weight of that gas, in the fluid. Additional factors on which diffusion of the inhaled gas through the membrane depend are thickness and surface area of the membrane, the diffusion coefficient of the gas in the material of the membrane, and the partial pressure difference of the gas between tissue-blood capillary (Hall and Guyton 2010).