Respiratory physiology

Question 1

Inspiratory reserve volume

Answer 1

air that can still be breathed in during normal inspiration;

Question 2

Tidal volume

Answer 2

air that moves into lung with each quiet inspiration, typically 500 cc

Question 3

Expir reserve volume

Answer 3

volume that can still be expired after a normal expiration

Question 4

how to remember lung volumes

Answer 4

LITER; lung, inspir reserve volume, tidal volume, expir reserve volume, residual volume

Question 5

residual volme

Answer 5

the air left in the lung after you have already expired as much air as you can

Question 6

inspiratory capacity

Answer 6

IRV + TV

Question 7

functional residual capacity

Answer 7

RV + ERV; volume of gas in lung after normal expiration

Question 8

Vital capacity

Answer 8

TV+IRV+ERV; max volume of gas that can be expired after max inspiration

Question 9

total lung capacity

Answer 9

just like it sounds

Question 10

Physiologic dead space

Answer 10

the space in the lung where you don’t have gas exchange; this includes the conducting airways plus the alveolar dead space; apex of healthy lung is the largest contributer of alveolar dead space because you don’t have blood flow up there; VDead=(VT x PaCO2 -PECO2)/PaCO2

Question 11

Minute ventilation

Answer 11

VE= VT x RR

Question 12

Alveolar ventilation

Answer 12

VA= (VT-VD) x RR; volume of gas per unit time that acutally reaches the alveoli

Question 13

Compliance of lung

Answer 13

decreased in pulmonary fibrosis, pneumonia, pulm edema; increaed in emphysema, normal aging

Question 14

Hemoglobin molecule

Answer 14

Composed of 4 polypeptide subunits (2 alpha, 2 beta) and exist in 2 forms: T (taut, deoxygenated and also has low affinity for oxygen) and R (relaxed, oxygenated);

Question 15

Which conditions favor the taut (deoxygenated) form of the hemoglobin?

Answer 15

increased chloride, increased H+ (low pH), CO2, 2,3-BPG, and temperature; these all shift the dissociation curve to the right and lead to increaed oxygn unloading

Question 16

Fetal hemoglobin

Answer 16

2 alpha and 2 gamma subunits; has lower affinitiy for 2,3 BPG than adult hemoglobin, which means more affinity for oxygen

Question 17

2 types of hemoglobin modifications that lead to tissue hypoxia from decrease o2 sat and decreased o2 content

Answer 17

methemoglobin and carboxyhemoglobin

Question 18

methemaglobin

Answer 18

oxidized form of Hb (Fe3+) that does not bind oxygen as readily (normal has Fe2+) but has increased affinity for cyanide; may present wth cyanosis and chocolate colored blood; induced methemoglobinemia may be used to treat cyanide poisoning

Question 19

carboxyhemoglobin

Answer 19

form of Hb bound to CO in place of oxygen; caues decreased oxygen binding capacity with left shif in curve; decreased O2 binding in the tissues; CO binds to Hb with affinitity 200 x greater than o2

Question 20

What causes a right shift in the oxygen dissoc curve?

Answer 20

gives the Hb less affinity for oxygen; almost everything shift the curve right: acid, CO2, exercise, 2,3BPG, altitude, temperature

Question 21

oxygen content of blood

Answer 21

oxygen binding capacity x % saturation + dissolved O2

Question 22

A-a gradient

Answer 22

alveolar PO2 minus arterial PO2

Question 23

Causes of increased A-a gradient

Answer 23

shunting, V/Q mismatch, fibrosis (impairs diffusion)

Question 24

Hypoxemia versus hypoxia versus ischemia

Answer 24

hypoxemia is low oxygen in the blood; hypoxia is decreased ox delivery to the tissue; ischemia is loss of blood flow

Question 25

Hypoxemia with normal A-a gradient

Answer 25

altitude, decreased ventilation (opioid use)

Question 26

Hypoxemia with increased A-a gradient

Answer 26

V/Q mismatch, diffusion limitation, right to left shunt

Question 27

Hypoxia

Answer 27

Decreased cardiac output, hypoxemia, anemia, CO poisoning

Question 28

Ischemia

Answer 28

Impeded arterial flow, decreased venous drainage

Question 29

V/Q at the apex versus base of the lung

Answer 29

At the apex, it is much greater than 1; at the base, it is much less than 1; ideal is 1

Question 30

Both ventilation and perfusion are greater at the base of the lung

Answer 30

But proportionally, there is more perfusion than ventilation at the bottom and more ventilation than perfusion at the apex

Question 31

With increased exercise

Answer 31

vasodilation at the apex, so V/Q approaches 1 at the apex

Question 32

CO2 is transported from tissues to lungs in 3 forms

Answer 32

HCO3- (90%), carbaminohemoglobin or HbCO2 (5%), dissolved CO2 (5%)

Question 33

What is the Haldane effect?

Answer 33

In the lungs, oxygenation of Hb promotes dissociation of H+ from Hb; this shift equilibriu toward CO2 formation, and CO2 is released from RBCs

Question 34

What is the Bohr effect?

Answer 34

In peripheral tissue, increased H+ from tissue metabolism shifts curve to right, unloading O2

Question 35

Response to high altitude

Answer 35

Decreased PO2 leads to increased ventilation; EPO increases; 2,3 BPG increases (more Oxygen released); cellular changes (increase mitochondria); increased renal excretion of bicarb to compensate for resp alkalosis (can augment with acetazolamide); chronic hypoxia pulm vasoconstriction results in RVH

Question 36

Response to exercise

Answer 36

Increased CO2 production; increased oxygen consumption; increased ventilation rate to mee ox demand; V/Q ratio apex to base becomes more uniform; increased pulm blood flow due to increased CO; decreased pH during strenuous exercise (2/2 lactic acidosis); no chnage in PaO2 and PaCO2 but increased in venous CO2 content and decreased in venous O2 content