Airway Resistance

Question 1

How can you describe airway resistance?

Answer 1

The rate at which a certain volume of gas flows through the bronchial airway is the function of the pressure gradient between the mouth and the alveoli and the resistance created by the airway to the flow of gas.

Question 2

The inelastic properties of airway resistance include what 2 divisions?

Answer 2

Viscous (tissue movement)

Frictional (airway diameter, flow rate, gas viscosity)

Question 3

What is included in the elastic properties of airway resistance?

Answer 3

Compliance
-lung elasticity
Surface tension

Question 4

What is the formula for airway resistance?

Answer 4

Pressure difference between

The flow rate

Question 5

What law is use for airway resistance?

Answer 5

Poiseuille’s law

Question 6

When poiseuille’s law is rearranged for flow, what happens to flow if the radius is decreased by 1/2 with the pressure remaining constant?

Answer 6

The flow is reduced to 1/16 of the original.

The equation States that flow is directly proportional to change in pressure and the radius of the airway.

inversely proportional to the length and the viscosity of the gas.

Question 7

what is the general term for the pressure difference between 2 systems?

Answer 7

Pressure gradient

Question 8

when poiseuille’s law rearranged for pressure, what adjustment can be made in driving pressure to maintain the same flowrate when the radius of the tube is reduced by 50%?

Answer 8

the pressure must be increased 16 times the original

Question 9

a lung that loses elastic fibers will exhibit what?

Answer 9

increased lung compliance

Question 10

what is airway resistance?

explain in terms relating to formula

Answer 10

it is dirived by the pressure difference between mouth and alveoli over the flow in l/sec

Question 11

what 3 factors can affect Raw?

Answer 11

patterns of gas flow
characteristic of gas being breathed
diameter and length of airway

Question 12

what does surfactant do to the surface tension in the alveoli?

Answer 12

it decreases the surface tension

Question 13

what is normal airway resistance value?

Answer 13

0.6 to 2.6 cm H20/L/sec

Question 14

what does air trapping and hyperinflation do to lung compliance?

Answer 14

It decreases lung compliance due to inability to accept more air then what is already there.

Question 15

what is the total lung/thorax compliance in a normal patient?

why?

Answer 15

0.1 L/cm H20.

the lung and thorax individually have a compliance of
0.2 L/cm H20. but since they work in opposition of each other. the compliance drops to 0.1 L/cm H20

Question 16

when poiseuille’s law rearranged for flow with pressure remaining constant, what would happen if the radius of the tube is reduced by 50%?

Answer 16

the flow would be reduced to 1/16 the original

Question 17

at what point(s) in the respiration cycle will the alveolar and atmospheric pressure be equal?

Answer 17

end-inspiration and end-expiration

Question 18

what happens to hemodynamic stability during a tension pneumothorax?

Answer 18

the rising pressure in the pleural space builds to a point where it decreases venous return and cardiac output. which also decreases BP

Question 19

what forces must be overcome to move air into the respiratory system?

Answer 19

tissue movement
elastic forces
airway resistance
surface tension

Question 20

what is the reciprocal of compliance?

Answer 20

elastance

compliance eq = change vol/change pressure

elastance eq = change in pressure/change vol

Question 21

what is dead space ventilation?

Answer 21

situations where v/q is high.
ventilation is normal but capillary perfusion is low.
narrow or blocked capillaries like pulmonary embolism.

Question 22

what is shunting?

Answer 22

its when v/q is low.
low to no ventillation but adequate perfusion

blocked/plugged airway