SFP: ventilation and pressure gradients

Question 1

What is ventilation

Answer 1

The process of bringing in fresh air and removing stale air

Question 2

What is atmospheric pressure

Answer 2

0 cmH2O

Question 3

PA is…

Answer 3

Alveolar pressure

Question 4

Pa is…

Answer 4

Pressure in artery

Question 5

Is intrapleural pressure positive or negative

Answer 5

Negative; this creates a vacuum

Question 6

What is the formula for the pressure gradient across the lung

Answer 6

PL = PA – Pip

(alveolar pressure minus intrapleural pressure)

Question 7

What is the formula for pressure gradient across the chest wall

Answer 7

PW = Pip – Pb

(intrapleural pressure minus atmospheric pressure)

Question 8

What is the formula for trans airway pressure

Answer 8

Pta = Paw – Ppl

(airway pressure minus intrapleural pressure)

Question 9

What is the formula for trans respiratory pressure

Answer 9

Ptr = PA – Pb

(alveolar pressure minus atmospheric pressure)

Question 10

What is the function of the negative pressure in the intrapleural space

Answer 10

It helps keep the lungs open and keeps the chest wall in; without the negative pressure, the lungs would want to recoil and collapse and the chest wall wants to expand

Question 11

Give the atmospheric, intrapleural, and alveolar pressures at end expiration

Answer 11

0, -5, 0

Question 12

Give the atmospheric, intrapleural, and alveolar pressures during inspiration

Answer 12

0, -7, -2

Question 13

Give the atmospheric, intrapleural, and alveolar pressures at end inspiration

Answer 13

0, -8, 0

Question 14

Give the atmospheric, intrapleural, and alveolar pressures during expiration

Answer 14

0, -6, +2

Question 15

What is tidal volume

Answer 15

The volume of air you move in and out during one breathing cycle

Question 16

What is the formula for minute ventilation

Answer 16

Minute ventilation = tidal volume x frequency

Question 17

Describe movement of CO2 seen in alveolar air sampling

Answer 17

During inspiration, no movement of CO2 is seen. At the very start of expiration, the air exiting is fresh air from the dead space, so no CO2 is seen. As expiration continues, CO2 movement rises and eventually plateaus. As inspiration begins again, movement of CO2 declines

Question 18

What is end tidal? What is it reflective of

Answer 18

The value of partial tension of gas just prior to inspiration; The amount of CO2 in the alveolus

Question 19

What is normal end tidal value?

Answer 19

40

Question 20

What is alveolar dead space

Answer 20

Alveolar air not participating in gas exchange due to inadequate vascular perfusion

Question 21

What is anatomical dead space

Answer 21

Areas where no gas exchange occurs

Question 22

Is height or weight a better indicator of lung size and dead space

Answer 22

Height

Question 23

What is physiological dead space

Answer 23

The total wasted ventilation. It is the sum of anatomical and alveolar dead space

Question 24

What is the Bohr equation

Answer 24

VD = [(PACO2 – PECO2)/(PACO2)] x VT