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A low PaO 2 indicates that the patient's current minute ventilation (whether high or normal) is not enough to allow adequate oxygen diffusion into the blood. Therefore, the A–a gradient essentially demonstrates a high respiratory effort (low arterial PaCO 2) relative to the achieved level of oxygenation (arterial PaO 2). A high A–a gradient ...
A high gradient (> 1.1 g/dL, >11 g/L) indicates the ascites is due to portal hypertension, either liver related or non-liver related, with approximately 97% accuracy. [2] This is due to increased hydrostatic pressure within the blood vessels of the hepatic portal system , which in turn forces water into the peritoneal cavity but leaves proteins ...
More specifically, optimal levels are generally close to a central tendency of the values found in the population. However, usual and optimal levels may differ substantially, most notably among vitamins and blood lipids, so these tables give limits on both standard and optimal (or target) ranges.
For example, in the 1930s Widmark measured alcohol and blood by mass, and thus reported his concentrations in units of g/kg or mg/g, weight alcohol per weight blood. Blood is denser than water and 1 mL of blood has a mass of approximately 1.055 grams, thus a mass-volume BAC of 1 g/L corresponds to a mass-mass BAC of 0.948 mg/g.
If one were to consider humidified air (with less oxygen), then the ideal v/q ratio would be in the vicinity of 1.0, thus leading to concept of ventilation-perfusion equality or ventilation-perfusion matching. This matching may be assessed in the lung as a whole, or in individual or in sub-groups of gas-exchanging units in the lung.
The proportion of AST to ALT in hepatocytes is about 2.5:1, but because AST is removed from serum by the liver sinusoidal cells twice as quickly (serum half-life t 1/2 = 18 hr) compared to ALT (t 1/2 = 36 hr), so the resulting serum levels of AST and ALT are about equal in healthy individuals, resulting in a normal AST/ALT ratio around 1.
Mathematically, if the change in the numerator is similar to the change in the denominator, the delta ratio will be close to 1. Since the anions are unable to diffuse out of the bloodstream, while bicarbonate and hydrogen ions diffuse with ease (as H 2 CO 3, carbonic acid), the usual result will be closer to a delta ratio of 1 to 2.
A P a O 2 /F I O 2 ratio less than or equal to 250 mmHg is one of the minor criteria for severe community acquired pneumonia (i.e., possible indication for inpatient treatment). A P a O 2 /F I O 2 ratio less than or equal to 333 mmHg is one of the variables in the SMART-COP risk score for intensive respiratory or vasopressor support in ...