Pulm Physio Flashcards
oxy-hgb curve
what is a right shift?
- decreased affinity of O2 to hgb
- caused by inc temp/CO2/23DPG, acidosis, abn hgb
oxy-hgb curve
what is a left shift?
- increased affinity of O2 to hgb
- caused by dec temp/CO2/23DPG, alkalosis, methgb, carboxyhgb
oxy-hgb curve
what is p50?
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)
What is normal PO2 and when do you see a rapid dec in O2 sat on the oxy hub curve?
normal PO2 = 80-100 mmHg = >90% O2 sat
rapid dec O2 sat when PO2 < 60 mmHg
How is CO2 transported?
- primarily as bicarb to the lungs
- dissolved in plasma (more than O2)
- carbamino compounds
How do you determine O2 content?
1.34 (dissolved O2) x HCT x O2 sat (hgb bound)
Ventilation-Perfusion (V/Q) mismatches
impaired perfusion = high V/Q
+ ventilation, - flow = 1/0 = infinity = dead spacing
impaired ventilation = low V/Q
- ventilation, + flow = 0/1 = 1 = shunting
Describe the lung zones.
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
What is a normal VC?
70 ml/kg (5 L)
What is a normal TV?
500 ml
What is a normal TLC?
6 L (includes RV)
What is a normal RV?
1 L
What happens to lung volumes as you age?
VC dec
RV inc
What are the layers of the alveolar-capillary membrane?
- surfactant layer
- alveolar epithelium
- basement membrane
- interstitial space
- capillary endothelium
What are the major/accessory muscles of inspiration?
major = diaphragm, external intercostals accessory = SCM, scalene muscles
What are the accessory muscles of expiration?
internal intercostals, ABD muscles
What does surfactant do?
- dec surface tension
- inc compliance
- dec WOB
- prevents atelectasis
What is compliance?
change in volume/change in pressure
What forces dominate during:
- inspiration
- end inspiration
- expiration
- end expiration
- inspiration - diaphragm contraction
- end inspiration - diaphragm contraction
- expiration - lung recoil
- end expiration - lung recoil = chest recoil
What controls ventilation/RR?
CO2 levels which regulate pH
high CO2 = inc RR
low CO2 = dec RR
hypoxic drive kicks in w/ severe hypoxemia where O2 controls ventilation
Describe 4 steps to gas transport.
- ventilation of O2 to lungs
- diffusion of O2 from alveoli to capillary
- perfusion of O2 from capillary to systemic
- diffusion of O2 from systemic blood to tissues
