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Hypoxia can be due to external causes, when the breathing gas is hypoxic, or internal causes, such as reduced effectiveness of gas transfer in the lungs, reduced capacity of the blood to carry oxygen, compromised general or local perfusion, or inability of the affected tissues to extract oxygen from, or metabolically process, an adequate supply ...
Tissue hypoxia refers to low levels of oxygen in the tissues of the body and the term hypoxia is a general term for low levels of oxygen. [2] Hypoxemia is usually caused by pulmonary disease whereas tissue oxygenation requires additionally adequate circulation of blood and perfusion of tissue to meet metabolic demands. [4]
Intrauterine hypoxia (also known as fetal hypoxia) occurs when the fetus is deprived of an adequate supply of oxygen. It may be due to a variety of reasons such as prolapse or occlusion of the umbilical cord , placental infarction , maternal diabetes (prepregnancy or gestational diabetes ) [ 1 ] and maternal smoking .
Histopathology of placenta with increased syncytial knotting of chorionic villi, with two knots pointed out. The following characteristics of placentas have been said to be associated with placental insufficiency, however all of them occur in normal healthy placentas and full term healthy births, so none of them can be used to accurately diagnose placental insufficiency: [citation needed]
The dilation of these blood vessels causes overperfusion relative to ventilation, leading to ventilation-perfusion mismatch and hypoxemia. There is an increased gradient between the partial pressure of oxygen in the alveoli of the lung and adjacent arteries (alveolar-arterial [A-a] gradient) while breathing room air.
Basically, understanding of the etiology of perinatal asphyxia provides the platform on which to build on its pathophysiology. The general principles guiding the causes and the pathophysiology of perinatal asphyxia are grouped into antepartum causes and intra partum causes. As these are the various points to which insults can occur to the foetus.
Hypoxic hypoxia – Limited oxygen in the environment causes reduced brain function. Divers, aviators, [ 24 ] mountain climbers, and fire fighters are all at risk for this kind of cerebral hypoxia. The term also includes oxygen deprivation due to obstructions in the lungs.
Silent hypoxia (also known as happy hypoxia) [1] [2] is generalised hypoxia that does not coincide with shortness of breath. [ 3 ] [ 4 ] [ 5 ] This presentation is known to be a complication of COVID-19 , [ 6 ] [ 7 ] and is also known in walking pneumonia , [ 8 ] altitude sickness , [ 9 ] [ 10 ] [ 11 ] and rebreather diving .