Term
| What are the principles of pulmonary gas exchange? |
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Definition
| Gas exchange in the body involves diffusion across the respiratory membrane and diffusion across tissue capillaries |
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Term
| What is the difference between alveolar and atmospheric air? |
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Definition
- Atmospheric - primarily O2 and N2
- Alveolar - Less O2, similar N2, more CO2/H2O
**N2 is actually the highest in both |
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Term
| How does PO2/CO2 in alveoli compare to atomspheric? |
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Definition
Alveolar:
- PO2 is lower than atmospheric, there is less oxygen
- PCO2 is higher than atmospheric, there is more CO2 |
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Term
| What 3 factors determine alveolar PO2/PCO2? |
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Definition
- Partial pressure of O2 in the atmosphere - Decrease PO2 in atm = decr PO2 alveolar
- Rate of O2 consumption/CO2 production ie metabolism - increased metabolism = decreased alveolar PO2 and increased alveolar PCO2
- Alveolar ventilation - Increased ventilation = increased alveolar PO2 and decreased PCO2 |
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Term
| How do hyperbaric oxygen changers work? |
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Definition
| Contain O2 at a pressure of >1 atm - use to rapidly increase alveolar oxygen to treat CO poisoning, shock, gangrene, tetanus, asphyxiation. |
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Term
| How does oxygen toxicity occur? |
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Definition
| At PO2 over 2 atm, generates free radicals leading to tissue damage. |
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Term
| How does O2 consumption affect alveolar PO2? |
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Definition
- a higher ratio of O2 consumption = lower alveolar PO2
- A higher ratio of CO2 production = higher alveolar PCO2 |
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Term
| How does hypo/hyperventilation affect alveolar PO2? |
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Definition
- Hypoventilation - increased CO2, metabolism is higher than ventilation
- Hyperventilation - decreased CO2, metabolism is low compared to ventilation
**exercise proportionally increases metabolism = no change in PO2/CO2 |
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Term
| What is O2/CO2 Consumption Balance? |
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Definition
- O2 consumed by the body = O2 added to blood
- CO2 produced by cells = CO2 that leaves the blood and is expired |
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Term
| How do partial pressure gradients affect the alveolar membrane? |
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Definition
- normal PP gradient is higher in alveoli than pulmonary, resulting flow of O2 from alveoli to pulmonary capillaries
- CO2 pressure is lower in alveoli than pulmonary circuit, resulting in flow from pulmonary capillaries into alveoli
**Gradient of O2 is steeper, but solubility of CO2 is 20x higher = same amounts exchanged.
**PP in capillaries and alveoli are nearly the same |
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Term
| How does high altitude affect partial pressure gradient? |
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Definition
| PO2 is lower, resulting in lower PO2 of the pulmonary system |
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Term
| What are the characteristics of the respiratory membrane? |
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Definition
- TSA of alveoli affects O2/CO2 exchange
- Thickness affects exchange. Scarring impairs exchange.
**TSA reduced in emphysema, edema, infections, pulmonary fibrosis |
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Term
| What is Ventilation/Perfusion coupling? |
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Definition
Coupling between ventilation and blood flow - more = more exchange.
- When pressure is LOW, not all capillaries are open
- When pressure is HIGH, more are open to exchange
**More blood is supplied to well ventilated areas |
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Term
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Definition
When V/Q does not equal 1, imperfect coupling occurs.
- In emphysema, collapse (V/Q < 1) and destruction of blood vessels (V/Q > 1)
** V/Q < 1 - less air flow, from an obstruction or asthma
** V/Q > 1 - less blood flow, from an embolism or tissue damage |
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Term
| How is oxygen found in the blood? |
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Definition
- 1.5% freely dissolved
- 98.5% bound to Hb |
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Term
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Definition
Protein in RBCs w/ 4 subunits that binds O2. Each subunit has iron-containing heme. Binds 4 O2s.
**Oxygen carrying capacity = 200 ml/L. reduced in anemia. |
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Term
| What are causes of anemia? |
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Definition
- Low #s of RBCs - Blood loss, destruction, bone marrow
- Decreased Hb - iron deficiency or low B12
- Abnormal Hb - Thallasemia, sickle cell
**Fatigue, paleness, SoB, chills |
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Term
| What is the equation for O2 binding to Hb? |
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Definition
nO2 + dHb = Hb(O2)n
%saturation = amount of O2 bound/maximum that can be bound * 100%. Impacted by blood PO2, PCO2, pH, temp, DPG
**Increasing PO2 increases amount of bound oxygen! |
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Term
| What are characteristics of the O2-Hb saturation curve? |
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Definition
- 40 mmHg in resting tissue
- Drops below 40 during exercise
- Increases to 60 in high altitude |
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Term
| How does O2-Hb affect blood PO2? |
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Definition
It is sequestered, so not at all.
Oxygen diffusion only controlled by free O2
**Hb acts as a sink |
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Term
| Why does most alveolar O2 end up bound to Hb? |
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Definition
| Until Hb is saturated, blood PO2 is lower than the alveoli, resulting in a partial pressure gradient |
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Term
| How does O2 transfer from Hb to tissue capillaries? |
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Definition
| PO2 is higher in the blood than in the tissue capillaries, resulting in diffusion out of the blood |
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Term
| How does PCO2, pH, DPG, and temp affect Hb? |
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Definition
An increase will shift the curve to the right --> Hb has LOWER affinity for O2
**Higher in the tissue capillaries --> release of O2 into cells.
**DPG binds directly to RBCs, releasing O2 for cells in anemia, high altitudes, and COPD |
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Term
| How is CO2 present in the blood? |
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Definition
- 10% freely dissolved
- 30% bound to Hb
- 60% converted to bicarb, catalyzed by CA in RBCs |
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Term
| How does the bicarbonate reaction take place? |
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Definition
In RBCs, transported into plasma by an exchanger.
H+ high in tissue capillaries and venous blood. Can also bind to Hb.
** Hb acts as a BUFFER for H+ - H+ does not damage. |
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Term
| What happens to the H+ formed by the bicarb reaction? |
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Definition
| As venous blood goes to the lungs, H+ is displaced by O2 from Hb, and reacts w/ bicarb --> CO2 and H2O |
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Term
| What respiratory acid/base disorders are possible? |
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Definition
- Respiratory acidosis - Increased arterial H+ due to CO2 retention from hypoventilation
- Respiratory alkalosis - Decreased H+ due to increased CO2 elimination from hyperventilation
- Hypercapnia - increased arterial CO due to hypoventilation from respiratory depression, blockage. |
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