How do you calculate respiratory shunt?

Published by Anaya Cole on

How do you calculate respiratory shunt?

The pulmonary shunt fraction was calculated using the established classical equation: Qs/Qt = (Cc,O2 – Ca,O2)/(Cc,O2 – Cv,O2), in which Qs/Qt is the RLS as a fraction of the cardiac output, Cc,O2 is the oxygen content at the end of the pulmonary capillary, Ca,O2 is the oxygen content of arterial blood and Cv,O2 is the …

What is shunt in respiratory physiology?

A pulmonary shunt refers to the passage of deoxygenated blood from the right side of the heart to the left without participation in gas exchange in the pulmonary capillaries.

What does the shunt equation tell you?

The Shunt equation quantifies the extent to which venous blood bypasses oxygenation in the capillaries of the lung. “Shunt” and “dead space“ are terms used to describe conditions where either blood flow or ventilation do not interact with each other in the lung, as they should for efficient gas exchange to take place.

What is lung shunt fraction?

The lung shunt fraction (LSF) is calculated as the counts from the lung ROI divided by the total counts for the lung and liver ROI (from the geometric mean image) (Fig. 1).

What causes shunting in the lungs?

Causes of shunt include pneumonia, pulmonary edema, acute respiratory distress syndrome (ARDS), alveolar collapse, and pulmonary arteriovenous communication.

How do you calculate SVR and PVR?


  1. PVR = 80*(PAP – PCWP)/CO, normal 100-200 dyn-s/cm5.
  2. SVR = 80*(MAP – CVP)/CO, normal 900-1200 dyn-s/cm5.

What is shunt write its expression?

A resistor having a very low value of resistance connected in parallel with other resistor is caused shunt. The range of ammeter reading can be extended by connecting a shunt resistance to it. The shunt is used in the galvanometer for measuring the large current. It is used as diodes also.

What is shunt law?

(a)The shunt is a device which allows electric current to pass around another point in the circuit by creating a low resistance path. (b)Ampere’s circuital law states that the line integral of the magnetic field around some closed loop is equal to the net current enclosed by this path. Ampere’s circuital law ∮Bdl=μ0I.

What is shunt in biology?

(shunt) In medicine, a passage that is made to allow blood or other fluid to move from one part of the body to another. For example, a surgeon may implant a tube to drain cerebrospinal fluid from the brain to the abdomen.

How do you calculate VQ ratio?

This is calculated by multiplying the tidal volume (volume of air inhaled and exhaled in a single breath) by the respiratory rate. In an average man, the ventilation rate is roughly 6L/min. The perfusion (Q) of the lungs refers to the total volume of blood reaching the pulmonary capillaries in a given time period.

How do you calculate the Shunt equation?

The shunt equation, otherwise known as the Berggren equation, is used to calculate the shunt fraction: Qs/Qt = (Cc O2 – Ca O2) / (Cc O2 – Cv O2)

What is the true shunt for lung units?

However, for lung units with “true” shunt, V/Q = 0, and no amount of extra inspired oxygen is going to improve their oxygenation. As a consequence of this, breathing a high FiO 2 essentially eliminates the contribution of V/Q scatter to the total shunt fraction, and what is left over is the “true” shunt.

What is the mixed venous blood content in the Shunt equation?

Thus, the mixed venous blood content is 97.5ml/L, and the fully oxygenated end-capilary blood content is 130ml/L. The shunt equation can now be used to determine how much mixed venous blood one would need to add to the capillary blood to create the systemic arterial oxygen content, which is 117ml/L: Qs/Qt = (130-117) / ( 130 – 97.5) = 0.4

What is the relationship between shunt fraction and oxygen difference?

The relationship between the different fractions must therefore remain a ratio, rather than a real oxygen difference in ml. Hence the shunt fraction is usually represented as Qs/Qt.

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