Pulm Physio

Question 1

oxy-hgb curve

what is a right shift?

Answer 1

• decreased affinity of O2 to hgb

- caused by inc temp/CO2/23DPG, acidosis, abn hgb

Question 2

oxy-hgb curve

what is a left shift?

Answer 2

• increased affinity of O2 to hgb

- caused by dec temp/CO2/23DPG, alkalosis, methgb, carboxyhgb

Question 3

oxy-hgb curve

what is p50?

Answer 3

normal p50 = 50% O2 sat w/ PO2 of 27 mmHg
if p50 is low = left shift (inc affinity)
if p50 is high = right shift (dec affinity)

Question 4

What is normal PO2 and when do you see a rapid dec in O2 sat on the oxy hub curve?

Answer 4

normal PO2 = 80-100 mmHg = >90% O2 sat

rapid dec O2 sat when PO2 < 60 mmHg

Question 5

How is CO2 transported?

Answer 5

• primarily as bicarb to the lungs
• dissolved in plasma (more than O2)
• carbamino compounds

Question 6

How do you determine O2 content?

Answer 6

1.34 (dissolved O2) x HCT x O2 sat (hgb bound)

Question 7

Ventilation-Perfusion (V/Q) mismatches

Answer 7

impaired perfusion = high V/Q
+ ventilation, - flow = 1/0 = infinity = dead spacing

impaired ventilation = low V/Q
- ventilation, + flow = 0/1 = 1 = shunting

Question 8

Describe the lung zones.

Answer 8

Zone 1 - PA > Pa > Pv = no blood flow (apex)
Zone 2 - Pa > PA > Pv = + blood flow but compressed venous
Zone 3 - Pa > Pv > PA = blood flow fluctuates

Question 9

What is a normal VC?

Answer 9

70 ml/kg (5 L)

Question 10

What is a normal TV?

Answer 10

500 ml

Question 11

What is a normal TLC?

Answer 11

6 L (includes RV)

Question 12

What is a normal RV?

Answer 12

1 L

Question 13

What happens to lung volumes as you age?

Answer 13

VC dec

RV inc

Question 14

What are the layers of the alveolar-capillary membrane?

Answer 14

1. surfactant layer
2. alveolar epithelium
3. basement membrane
4. interstitial space
5. capillary endothelium

Question 15

What are the major/accessory muscles of inspiration?

Answer 15

major = diaphragm, external intercostals
accessory = SCM, scalene muscles

Question 16

What are the accessory muscles of expiration?

Answer 16

internal intercostals, ABD muscles

Question 17

What does surfactant do?

Answer 17

• dec surface tension
• inc compliance
• dec WOB
• prevents atelectasis

Question 18

What is compliance?

Answer 18

change in volume/change in pressure

Question 19

What forces dominate during:

1. inspiration
2. end inspiration
3. expiration
4. end expiration

Answer 19

1. inspiration - diaphragm contraction
2. end inspiration - diaphragm contraction
3. expiration - lung recoil
4. end expiration - lung recoil = chest recoil

Question 20

What controls ventilation/RR?

Answer 20

CO2 levels which regulate pH
high CO2 = inc RR
low CO2 = dec RR
hypoxic drive kicks in w/ severe hypoxemia where O2 controls ventilation

Question 21

Describe 4 steps to gas transport.

Answer 21

1. ventilation of O2 to lungs
2. diffusion of O2 from alveoli to capillary
3. perfusion of O2 from capillary to systemic
4. diffusion of O2 from systemic blood to tissues