Resp Exam 2 Valley Questions

Question 1

Liters of alveolar ventilation and liters of pulmonary blood flow

What is average VQ ratio?

**Healthy adult

Answer 1

Alveolar vent: 4L/min
Pulmonary blood flow: 5L/min

VQ ratio: 0.8

Question 2

V/Q ratio between 0 and unity indicates what?

0 < VQ < 1

Answer 2

Relative shunt

Question 3

V/Q ratio that is greater than one?

VQ > 1

Answer 3

Dead space

Question 4

Importance of maintaining normal ventilation-to-perfusion relationship

Answer 4

Keep PaCO2 and PaO2 in normal range

Question 5

Lung unit that exhibits absolute shunt, what is the V/Q ratio?

What about ventilation and perfusion?

Answer 5

Absolute shunt = VQ 0
V= 0, perfusion (variable)

HPV can decrease perfusion

Question 6

What is the V/Q ratio in a lung unit that is ventilated but completely nonperfused?

Ie: PE

Answer 6

VQ = infinity

V= (variable)
Q= 0

**O can NEVER be a denominator (answer will always be infinity)

Question 7

Numeric values for absolute dead space and absolute shunt:

Answer 7

Dead space= infinity
Shunt= 0

Question 8

Compared w/ apex of lung, the base of the lung exhibits (when individual is awake and upright) higher or lower VQ ratio?

Answer 8

Lower

Question 9

Max PaO2 achievable in young healthy adult breathing RA

Answer 9

104mmHg

Question 10

Normal PaO2 in adult breathing RA

Answer 10

80-100mmHg

Question 11

If oxygen saturation is 90% (SaO2), what will the PO2 be?

Where is the blood with PO2 found?

Answer 11

SaO2 = 90%
PO2 = 60mmHg

This is arterial blood

Question 12

What is PO2 if O2 sat of hgb is 70%?

Where in circulation is blood with this PO2 found?

Answer 12

SaO2 = 70%
PO2 = 40mmHg

This would be mixed venous blood

Question 13

Normal arteriovenous oxygen content difference

Answer 13

5mL/ O2/ 100 mL blood

Question 14

How can you calculate how much oxygen is dissolved in blood?

What law applies?

Answer 14

PO2 x 0.003

Units are mL/O2/ 100 mL blood

Henry’s Law

Question 15

Two factors that determine the amount of oxygen carried by hemoglobin

Answer 15

PO2
Amount of hemoglobin

Question 16

How much O2 is carried by each gram of hemoglobin when saturated?

Answer 16

1.36 (Nagelhout) of O2 is carried by each gram of saturated hgb

Question 17

Significance of flat portion of oxyhemoglobin dissociation curve

Answer 17

Flat = loading of oxygen

** Large changes in pp of PaO2 produce small changes in SaO2

Question 18

Significance of steep portion of oxyhemoglobin dissociation curve

Answer 18

Steep = unloading of oxygen

** Large amounts of oxygen are unloaded from hgb = large decrease in SaO2 in response to small change in pp of O2

Question 19

P50 is

Answer 19

O2 pp where hgb is 50% saturated

Question 20

Normal P50 is

Answer 20

27mmHg

Question 21

What happens to P50 when oxyhemoglobin dissociation curve shifts right?

Answer 21

Increases

** > 28mmHg

Question 22

What happens to P50 when oxyhemoglobin dissociation curve shifts left?

Answer 22

Decreases

** < 26mmHg

Question 23

5 conditions that cause right shift

Answer 23

Increased temp
Increased pp of CO2
Increased 2, 3 DPG (DBG is interchangeable)
Increased H ions (decreased pH)
Sickle cell

Question 24

7 conditions that cause left shift

Answer 24

Decreased temp
Decreased pp of CO2
Decreased H ions (increased pH)
Decreased 2, 3 DPG
Fetal hgb
CO poisoning
Methemoglobin

Question 25

Increased CO2, which way does curve shift? Where in circulation does this occur?

Answer 25

Right Occurs as blood flows through caps of tissues **important bc more O2 IS released from hgb

Question 26

Decreased CO2, which way does curve shift? Where in circulation does this occur?

Answer 26

Left (think left in lung) Occurs in pulmonary capillaries as CO2 is being blown off-- O2 LOADING

Question 27

Bohr effect

Answer 27

Caused by CO2 entering or leaving blood Increased PCO2 --> shifts right --> unloads oxygen from hgb Decreased PCO2 in pulm capillaries --> shifts left --> loading of oxygen onto hgb

Question 28

How many grams of hgb must be in reduced form to produce cyanosis?

Answer 28

5 grams of hgb per 100 mL of blood must be in reduced form (without O2)

Question 29

Which direction do inhalational agents or IV general anesthetics shift the curve?

Answer 29

To the right

Question 30

Total quantity of O2 delivered to and used by tissues each min:

Answer 30

250 mL/min of O2

Question 31

During monitoring of mixed venous: suddenly goes from 74% to 40%. What are the most likely causes?

Answer 31

Decrease in CO Hypovolemia

Question 32

Venous blood oxygen saturation provides what information

Answer 32

Relationship between oxygen delivery and oxygen consumption

Question 33

What are 3 ways CO2 is transported in blood (give percentages)

Answer 33

Dissolved 5-10% Bicarbonate ions 80-90% Bound to hgb 5-10% (carbamino)

Question 34

What is CO2 in vol % in RA? What is the partial pressure of CO2 in RA?

Answer 34

0.03% 0.3mmHg

Question 35

Solubilities of O2 and CO2 in the blood

Answer 35

O2 - 0.003 CO2 - 0.067

Question 36

Diffusion coefficients of O2 and CO2 in the blood

Answer 36

O2 - 1 (reference point) CO2 - 20

Question 37

When PO2 decreases, does the blood CO2 curve shifts left or right? Where in circulation does this occur?

Answer 37

PO2 decreases, CO2 shifts left (more CO2 is carried by blood) This occurs as oxygen diffuses out of capillaries of systemic tissues **LOADING of CO2 in blood

Question 38

When PO2 increases, does the blood CO2 curve shift left or right? Where in circulation does this occur?

Answer 38

PO2 increases, CO2 shifts right (less CO2 is carried by blood) Occurs as blood flows through pulmonary capillaries in lungs *UNLOADING OF CO2

Question 39

Haldane effect

Answer 39

Changes in PO2 alter the amount of CO2 in blood IN THE LUNGS- increase in PO2 causes CO2 to shift right and unload CO2 IN THE TISSUES- decrease in PO2 causes CO2 to shift left and load CO2

Question 40

Role of carbonic anhydrase in RBC

Answer 40

Catalyzes (accelerates) conversion of H2O and CO2 to carbonic acid and then to bicarb ions

Question 41

After it is formed, bicarbonate moves out of RBC into plasma in exchange for what? What is this called?

Answer 41

Exchanges Cl- ions Chloride shift called Hamburger shift

Question 42

Primary respiratory centers and where they are located:

Answer 42

VRG DRG Located in medulla

Question 43

Secondary respiratory centers and where are they located:

Answer 43

Apneustic Pneumotaxic Located in pons

Question 44

Single most important factor responsible for **directly** stimulating central chemoreceptors

Answer 44

Hydrogen ions in CSF

Question 45

How are hydrogen ions generated in CSF?

Answer 45

CO2 diffuses into CSF Converted by carbonic anhydrase Yielded to bicarbonate ions and H ions

Question 46

To what 3 physiologic parameters do peripheral chemoreceptors (carotid and aortic) respond? Which stimulates them most?

Answer 46

PaO2, PaCO2, and pH Most stimulated by PaO2, but not until < 60

Question 47

Peak effect with peripheral chemoreceptor @ which PaO2 level?

Answer 47

30 mmHg

Question 48

What 3 exogenous substances stimulate peripheral chemoreceptors?

Answer 48

Nicotine, Doxapram and cyanide

Question 49

How much of the ventilatory response to an increase in PaCO2 is mediated by central or peripheral chemoreceptors?

Answer 49

Vent response to increased PaCO2 is central chemoreceptors (7x more powerful than peripheral)

Question 50

What normally drives ventilation?

Answer 50

CO2 Physiologic respiratory stimulant ** S I N G L E most important regulator of alveolar ventilation = PaCO2

Question 51

When are peripheral chemoreceptors stimulated?

Answer 51

Decreased arterial O2, especially from 60-80 Peak at 30

Question 52

Which two changes will increase ventilation most: increase in PaCO2 or decrease in pH?

Answer 52

Increase in PaCO2

Question 53

What triggers Hering-Breuer reflex?

Answer 53

Lung inflation triggers reflex Inspiration is inhibited (minor role in ventilation) **Not activated until TV is > 1.5 L

Question 54

Pulmonary stretch receptors within smooth muscle of small airways involved in Hering-Breuer reflex trigger sensory (afferent) impulses that travel along which nerve?

Answer 54

Vagus nerve carries afferent (sensory) impulses of Hering-Breuer