Vascular physiology & lungs at extremes

Question 1

(Pouiseuille’s Law) Resistance =

Answer 1

(8 x L x viscosity)/ pie x radius

Question 2

What is Ohm’s Law?

Answer 2

Pressure (in pulmonary circulation) = flow (CO) x resistance (pulmonary vascular resistance)

Question 3

What is the calculation for Ohm’s law?

Answer 3

mPAP - PAWP = CO x PVR

Question 4

What are 3 diseases of the pulmonary circulation?

Answer 4

VQ mismatch
Increased PVR
Shunt

Question 5

What is pressure at 0m (surface)?

Answer 5

1 atm

Question 6

Rule to remember about pressure and depth of sea water?

Answer 6

Every 10m water = 1 atm

Question 7

What is Boyle’s law?

Answer 7

P1V1 = P2V2 @ constant temperature

Question 8

How do you calculate atm from sea level depth (m)?

Answer 8

(m/10) + 1 = atm

Question 9

What is Henry’s law?

Answer 9

Amount of gas dissolved in a liquid @ given temp. is directly proportional to the partial pressure of the gas

Question 10

How does Henry’s law affect divers?

Answer 10

More gas dissolves in the tissues at depth
If ascending at a rate that exceeds the body’s capacity to clear this excess gas –> inert bubbles form in tissues –> decompression illness

Question 11

What are the 3 diving reflexes with free diving?

Answer 11

Aponea
Bradycardia
Peripheral vasoconstriction

Question 12

What is PiO2? Can it change?

Answer 12

Pressure of inspired oxygen - can change

Question 13

What is FiO2? Can it change?

Answer 13

Fraction of inspired oxygen - cannot change

Question 14

What is the value for FiO2?

Answer 14

0.21

Question 15

How do you measure the pressure of inspired gas?

Answer 15

Pigas = Patm x Figas

Question 16

What is Patm at sea level?

Answer 16

100kPa

Question 17

What is extremely high altitude?

Answer 17

18000ft

Question 18

What does the alveolar gas equation show?

Answer 18

PaCO2 is inversely proportional to alveolar ventilation

Question 19

PAO2 =

Answer 19

PiO2 - PaCO2/R

Question 20

PaO2 =

Answer 20

PAO2 - A-aDO2

Question 21

What is A-aDO2?

Answer 21

1kPa

Question 22

At sea level, PaCO2=6kPa. What is PAO2?

What is PaO2 at sea level?

Answer 22

PAO2 = 21 - 6/0.8 = 13.5 kPa
PaO2 = 13.5 - 1 = 12.5 kPa

Question 23

Normal PaO2 at sea level?

Answer 23

10.5 - 13.5 kPa

Question 24

Normal PaCO2 at sea level?

Answer 24

4.5 - 6.0 kPa

Question 25

What is the barometric pressure at the summit of Everest?

Answer 25

33.5 kPa (1/3 of Patm)

Question 26

What happens to pressure as altitude increases?

Answer 26

Pressure decreases (not linear relationship)

Question 27

What happens to PiO2 with increasing altitude?

Answer 27

PiO2 decreases

Question 28

What normal effect does altitude have on the lungs?

Answer 28

Hypoxia –> hyperventilation

Alkalosis compensated for by renal HCO3- excretion