1 - Perfusion & Ventilation

Question 1

What does the pulmonary variable P stand for?

Answer 1

Pressure

Question 2

What does the pulmonary variable C stand for?

Answer 2

Content

Question 3

What does the pulmonary variable V stand for?

Answer 3

Volume (gas)

Question 4

What does the pulmonary variable F stand for?

Answer 4

Fractional concentration

Question 5

What does the pulmonary variable Q stand for?

Answer 5

Volume (blood) (aka perfusion)

Question 6

What does the pulmonary variable S stand for?

Answer 6

Saturation

Question 7

What does the pulmonary variable A stand for?

Answer 7

Alveolar

Question 8

What does the pulmonary variable I stand for?

Answer 8

Inspired

Question 9

What does the pulmonary variable D stand for?

Answer 9

Dead space

Question 10

What does the pulmonary variable E stand for?

Answer 10

Expired

Question 11

What does the pulmonary variable T stand for?

Answer 11

Tidal

Question 12

What does the pulmonary variable a stand for?

Answer 12

arterial

Question 13

What does the pulmonary variable v stand for?

Answer 13

venous

Question 14

What does the pulmonary variable c stand for?

Answer 14

capillary

Question 15

What are the normal systolic and diastolic pressures in the pulmonary system? How do they compare to the systemic system?

Answer 15

Systolic = 25 mmHg (systemic = 120 mmHg)

Diastolic = 8 mmHg (systemic = 80 mmHg)

Question 16

How does the pulmonary system function with pressures significantly lower than those of the systemic system?

Answer 16

Pulmonary system has much less resistance, so it requires a lower pressure and smaller pressure drop

Question 17

Increased pulmonary arterial pressure [increases/decreases] resistance and [increases/decreases] blood flow.

Answer 17

Decreases resistance, increases blood flow (this is due to high compliance)

Question 18

What is the equation for transmural pressure?

Answer 18

P(Tm) = P(iv) - P(A)

Question 19

In regards to transmural pressure, high P(iv) and low P(A) [dilates/compresses] vessels and [increases/decreases] resistance.

Answer 19

dilates vessels, decreases resistance

Question 20

In regards to transmural pressure, low P(iv) and high P(A) [dilates/compresses] vessels and [increases/decreases] resistance.

Answer 20

compresses vessels, increases resistance

Question 21

Increased lung volume [dilates/compresses] alveolar vessels and [dilates/compresses] extra-alveolar vessels. How does this impact resistance?

Answer 21

compresses alveolar vessels (increased resistance), dilates extra-alveolar vessels (decreased resistance)

Question 22

With a PAO2 of less than 60 mmHg, pulmonary vessels [dilate/constrict]. Why?

Answer 22

Constrict; this shunts the blood flow away from a poorly perfused alveolus.

Question 23

What is the diagnosis criteria for pulmonary hypertension?

Answer 23

mean pulmonary pressure over 25 mmHg (normal 15 mmHg) at rest or 35 mmHg during exercise

Question 24

At what pulmonary capillary pressure does pulmonary edema occur?

Answer 24

Pulmonary capillary pressure over 25 mmHg

Question 25

What is the progression of pulmonary edema?

Answer 25

flooding of peri-capillary interstitial spaces --> crescentic filling of alveoli --> flooding of individual alveoli with loss of gas exchange

Question 26

How do you calculate the partial pressure of oxygen in atmospheric (dry) air? How do you calculate it once it has been humidified in the tracheal?

Answer 26

Atmospheric air: P(O2) = P(total) * oxygen proportion of air --> P(O2) = 760 mmHg * 0.21 Tracheal air: P(O2) = [P(total) - P(H2O)] * oxygen proportion of air --> P(O2) = [P(total) - P(H2O)] * 0.21

Question 27

What are the normal partial pressures of O2 and CO2 in alveolar air?

Answer 27

``` P(A)O2 = 104 mmHg P(A)CO2 = 40 mmHg ```

Question 28

What is the equation for minute ventilation? What are the normal values for these variables?

Answer 28

minute ventilation = respiratory rate x tidal volume ``` RR = 12-20 breaths/min TV = 500 ml/breath ```

Question 29

How much of tidal volume is anatomic dead space in a healthy individual?

Answer 29

Of a 500 ml tidal volume, 150 ml fills the conducting airways

Question 30

What is the equation for alveolar ventilation?

Answer 30

Alveolar ventilation = RR x (tidal volume - anatomic dead space volume)

Question 31

How can you calculate residual volume?

Answer 31

Helium dilution test: | C1 * V1 = C2 * V2 = C2 * (V1 + FRC)

Question 32

At what lung capacity is resistance the lowest?

Answer 32

Functional residual capacity (FRC)

Question 33

If a lung area has decreased ventilation, the lung will respond with [hypoxic vasoconstriction/hypocapnic bronchoconstriction].

Answer 33

hypoxic vasoconstriction

Question 34

If a lung area has increased ventilation, the lung will respond with [hypoxic vasoconstriction/hypocapnic bronchoconstriction].

Answer 34

hypocapnic bronchoconstriction

Question 35

What are the factors that influence pulmonary vascular resistance?

Answer 35

- compliance of a vessel - sympathetic/parasympathetic tone - lung volume - hypoxia - hypercapnia - low pH

Question 36

What is the definition of a shunt?

Answer 36

An area that is perfused but not ventilated

Question 37

Pulmonary edema can occur when intravascular hydrostatic pressure is too [high/low] and intravascular oncotic pressure is too [high/low].

Answer 37

high hydrostatic pressure, low oncotic pressure

Question 38

Pulmonary edema with alveolar flooding leads to hypoxemia by creating a ___.

Answer 38

Shunt

Question 39

What is the difference between cardiogenic and non-cardiogenic pulmonary edema?

Answer 39

Pulmonary edema from increased intravascular pressure is cardiogenic; pulmonary edema from increased alveolar-capillary permeability is non-cardiogenic

Question 40

What are the partial pressures of O2 and CO2 in atmospheric, tracheal, and alveolar conditions?

Answer 40

Atmospheric: PO2 = 160 mmHg, PCO2 = 0 mmHg Tracheal: PO2 = 150 mmHg, PCO2 = 0 mmHg Alveolar: PO2 = 104 mmHg, PCO2, = 40 mmHg

Question 41

Using VCO2 and PACO2, what is the equation for alveolar ventilation?

Answer 41

VA = 0.863 * (VCO2/PACO2)