斯塔林方程

斯塔林方程（Starling equation），是表示流体经由毛细管膜运动所产生的静水压力及渗透压力（即所谓的斯塔林力）之流体运作方程式。发现者是英国生理学家恩斯特·斯他林（Ernest Henry Starling）。
毛细管流体运动可能会出现三个过程的作为结果：
斯塔林方程仅仅是指经由毛细管膜的流体运动所产生滤过的结果。
c is the capillary hydrostatic pressure
By convention, outward force is defined as positive, and inward force is defined as negative. The solution to the equation is known as the net filtration or net fluid movement ("J""v"). If positive, fluid will tend to "leave" the capillary (filtration). If negative, fluid will tend to "enter" the capillary (absorption). This equation has a number of important physiologic implications, especially when pathologic processes grossly alter one or more of the variables. Note that previously it was believed that at steady state the arterial capillaries filter fluid and the venous capillaries reabsorb it, as shown by the diagram. Though many physiology textbooks still use this misconception, modern evidence shows that in most cases venular blood pressure exceeds the opposing pressure, thus maintaining a positive outward force. This indicates that capillaries are normally in a state of filtration along their entire length.
Pressures are often measured in millimetres of mercury (mmHg), and the filtration coefficient in millilitres per minute per millimetre of mercury (ml·min−1·mmHg−1).
In essence the equation says that the net filtration ("J""v") is proportional to the net driving force. The first four variables in the list above are the forces that contribute to the net driving force.
滤过系数.
The filtration coefficient is the constant of proportionality. A high value indicates a highly water permeable capillary. A low value indicates a low capillary permeability.
The filtration coefficient is the product of two components:
反射系数.
The reflection coefficient (σ) is often thought of as a correction factor. The idea is that the difference in oncotic pressures contributes to the net driving force because most capillaries in the body are fairly impermeable to the large molecular weight proteins. (The term "ultrafiltration" is usually used to refer to this situation where the large molecules are retained by a semipermeable membrane but water and low molecular weight solutes can pass through the membrane).
Many body capillaries do have a small permeability to proteins (such as albumins). This small protein leakage has two important effects:
Both these effects decrease the contribution of the oncotic pressure gradient to the net driving force. The reflection coefficient (σ) is used to correct the magnitude of the measured gradient to 'correct for' the ineffectiveness of some of the oncotic pressure gradient. It can have a value from 0 up to 1.
近似值.
Following are approximated values for the variables in the equation for both arterioles and venules:
Some albumin escapes from the capillaries and enters the interstitial fluid where it would produce a flow of water equivalent to that produced by a hydrostatic pressure of +3 mmHg. Thus, the difference in protein concentration would produce a flow of fluid into the vessel at the venous end equivalent to 28 − 3 = 25 mmHg of hydrostatic pressure. The total oncotic pressure present at the venous end could be considered as +25 mmHg.
In the beginning (arteriolar end) of a capillary, there is a net driving force (formula_1) outwards from the capillary of +9 mmHg. In the end (venular end), on the other hand, there is a net driving force of −8 mmHg.
Assuming that the net driving force declines linearly, then there is a mean net driving force outwards from the capillary as a whole, which also results in that more fluid exits a capillary than re-enters it. The lymphatic system drains this excess.
临床应用价值.
The principles behind the equation are considered useful for explaining physiological phenomena happening at the capillary (e.g. the formation of edema), but the impossibility of easily measuring all six variables together in actual patients makes it more difficult to apply it in daily practice.
Research data has suggested that the Starling equation may not accurately reflect physiological processes at a capillary level, and that it needs to be modified to include the role of the glycocalyx.