Lecture 4/1 Flashcards
Test 3
Explain the capnography waveform
Early: No CO2
Transitional: CO2 begins (increases)
Plateau slope: after transition phase
should match blood gases
Indicates how much air is in the lung
Why is there a slope in the capnography wave?
It increases bc CO2 is continuously being off/unloaded by blood in the lungs/alveoli during exhalation
Longer expiration = more unloading = increased CO2 on capnograph
You see the highest CO2 on the capnograph wave at the end of _______.
Exhalation
2 seconds into exhalation
or 4 secends into resp cycle
T/F: During inspiration, capnograph wave will be at its lowest point
T
Where is end tidal?
Value at the end of the plateu on capnograph wave
What is the alveolar concentration of CO2 in between breaths? What is the quantity of CO2 in 3L of lung air? What is the alveolar concentration of CO2 when adding a breath of fresh air? What is the new PCO2?
PACO2= 40 mmHg
FRC = 3L
40/760 =0.0526 –> 5.26%
0.0526 x 3 =0.158 –> 158ml
Fresh air: PCO2 = 0 mmHg
350 cc of fresh alveolar air
158ml/3350ml =0.0472 –> 4.72%
0.0472 x 760 =35.872 mmHg –> 36 mmHg
How much does alveolar PCO2 fluctuate during inspiration/expiration?
+/- 4 mmHg
Inspiration: 36 mmHg
Expiration: 40 mmHg (increased CO2 unloading in lungs)
What causes abnormal slopes on the capnograph waveforms?
Increases slope: Asthma, Bronchospasm
Inverted slope: Emphysema dt high lung compliance –> tendency for small airway collapse
Base of lungs collapse before apex –> concentration of CO2 from apex more dilute
T/F: Top of the lung gets less fresh air
F
Gets more fresh air than the base
Why is there a delay in inspiration in the capnograph wave?
It doesnt instantly detect inspiration bc the long airway hose in the circuit & low flow rate
What are capnographs highly sensitive to?
Moisture –> Need moisture trap
Can cause malfunction & inaccurate readings
(Machines cost 20,000$)
Alveolar deadspace shouldnt have _____ in it. What does this do to your capnograph
CO2
Lowers the height of plateau/slope
If ETCO2 < PACO2, what does this mean?
You have alveolar deadspace
What is Bohr’s equation used for?
Estimate how much alveolar dead space you have using expired air
Where does CO2 in ME come from?
Alveoli that are ventilated and perfused!!!
No bad alveoli!!!!
Equation: Bohr’s Equation
Vd / Vt = ((PPACO2) - PPECO2)) / PPACO2)
What are the 2 units of the pulmonary system compliance? What are the 2 barriers to putting air into the lungs?
- Lungs: want to recoil on themselves –> hard to put air in
- Chest: top heavy or laying suping –> chest pressure more positive –> forcing air out (compliance reduced)
Apex of lung sits above _____
rib 1
The chest wall at FRC has the tendency to recoil ______
outward
What causes the PPl -5 cmH20 ?
The lungs wanting to recoil inward
The chest wanting to recoil outward
What happens when the lungs lose elastic recoil?
Less inward recoil –> forces out of balace –> chest allowed to recoil outward more
Increased lung volumes (Obstructive lung diseases)
BARREL CHEST
More positive Pleural pressure
-5 cmH2O –> -2.5 cmH2O
You need a transpulmonary pressure of _____ to reach TLC in normal lungs. Obstructive? Restrictive?
30 cmH2O
Obstructive: Less (10)
restrictive: More
Equation: Compliance
ΔV / ΔP
What is normal pulmonary (lung) compliance at FRC?
0.2 L/cmH2O
