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Week Six > Week Six > Flashcards

Week Six Flashcards

Knock It Out the Park Like Bruce

1
Q

VBG vs. ABG

A

Allows for easier access, less pain and fewer complications associated with it.

  • -> Venous - arterial PCO2, pH and HCO3- differ only in NARROW range.
  • Venous PO2 DIFFERS GREATLY because normal level in tissues is 40 while arterial is 100 mmHG.
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2
Q

Metabolic Acidosis WITHOUT increased anion gap

A

Diarrhea
Carbonic Anhydrase Inhibitors
Renal tubular Acidosis
Hyperalimenation (IV feeding)

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3
Q

Metabolic Acidosis WITH increased anion gap

A 
"MULEPAK"
M: Methanol ingestion
U: Uremia
L: Lactic acidosis
E: Ethylene glycol ingestion
P: Paraldehyde ingestion
A: Aspirin overdose
K: Katoacidosis
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4
Q

Renal Maintenance of pH

A
  1. Regulation of plasma [HCO3-] - Kidney generates just enough bicarb to neutralize net acid production from metabolism.
  2. Excretes fixed metabolic acids (NH4+) and phosphoric acid (H2PO4-).
  3. Reabsorption of filtered bicarb in early PCT
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5
Q

Pulmonary Maintenance of pH

A

Balances CO2 excretion with metabolic CO2 production.
- Monitors arterial PCO2 by central chemoreceptors which will then increase or decrease alveolar ventilation depending on the level of arterial CO2.

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6
Q

Anion Gap

A

Indicates concentration of unmeasured anions such as protein, phosphate, sulfate and citrate.
- Help differentiate between metabolic acidosis cause by addition of acid or loss of HCO3-

Anion Gap = [Na+] - ([Cl-]+[HCO3-])

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7
Q

Buffer

A

Substance that can reversibly bind H+

  • Provide limited but immediate limitations on pH change; resist changes to pH.
  • Kidneys secrete and synthesize HCO3- as buffering system.
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8
Q

3 Ways CO2 is Carried in Lungs for Expiration

A
  1. Bicarbonate - majority
  2. Bound to protein (esp. Hgb)
  3. Dissolved in plasma (CO2, 20 times more soluble than O2)

CO2 + H2O ⇄ H2CO3 ⇄ (H+) + HCO3-
enzyme = carbonic anhydrase

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9
Q

Erythropoietin

A

Glycoprotein growth factor that promotes differentiation of proerythroblasts into RBCs.
- Induced in kidney in response to hypoxia.

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10
Q

OxyHgb Dissociation Curve: Shifts to RIght

A

Decrease of Hgb to O2 –> Increases p50 –> Unloading of 02 in tissues is facilitated

a. Increased PCO2, decreases pH
b. Increases Temperature
c. Increases 2,3-DPG (increases hypoxic conditions such as high altitudes to facilitate delivery of O2 to tissues as an adaptive mechanism.

RELEASE O2

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11
Q

OxyHgb Dissociation Curve: Shifts to Left

A

Increase of Hgb for O2 –> p50 –> Unloading of O2 in tissues is difficult (binding of O2 is tighter)

a. Decreases PCO2, increases pH
b. Decreases pH
c. Decreases 2-3-DPG
d. Hgb F
e. Carbon monoxide - has higher affinity for Hgb than O2

Loves O2

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12
Q

p50

A

PO2 at which Hgb is 50% saturated (2/4 heme sites bound to O2)

  • Decrease in p50 –> affinity for 02 increases - O2 bound more tightly to Hgb.
  • Increase in p50 –> affinity for O2 decreases - Frees up O2 from Hgb.
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13
Q

OxyHgb Dissociation Curve

A

Sigmodal shape –> positive cooperativity

  • binding of 1st molecule of O2 to heme group increases affinity for second and so forth
  • Body able to tolerate changes in PaO2-O2 has highest affinity for Hgb.
  • Very small changes in PaO2 will affect O2 affinity for Hgb –> causing big changes in Hgb saturation.

See Note Card for Respective graph

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14
Q

O2 Content

A

Actual amount of O2 per volume of blood.

  • Includes dissolved O2 and O2 bound to Hgb
  • O2 bound = O2 capacity of Hgb x % Hgb saturation
  • Dissolved O2 = PaO2 x ((0.003 mL O2/mmHg)/(100mL blood))
  • O2 bound + dissolved O2 = Total O2 content
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15
Q

Hgb Saturation

A

Amount of heme groups on each molecule of Hgb that are bound to oxygen

100% saturation = all 4 Heme groups on each Hgb molecule are bound to oxygen

% Hgb saturation = ((O2 bound to Hgb)/(O2 capacity of Hgb)) x 100%

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16
Q

O2 Carrying Capacity

A
  • Dependent on amount of Hgb present
  • -> the more Hgb, the higher the carrying capacity
  • Increased carrying capacity at higher altitudes

((1.34 mL O2)/(1 g Hgb)) x [Hbg in blood]

17
Q

Hemoglobin S

A

Abnormal variant of Hgb that causes sickle cell disease

  • Beta subunits are abnormal
  • Affinity for O2 is LESS than Hgb A
  • In deoxygenated form, forms sickle shaped rods on RBCs
18
Q

Fetal Hemoglobin

A

Hemoglobin F (alpha 2, gamma 2)

  • Higher affinity for O2
  • Facilitates O2 movement from mother to fetus
  • Gradually replaced by Hgb A within 1st year of life.
19
Q

Methemoglobin

A
  • Iron component is in ferric state (Fe3+)

- Does NOT bind O2

20
Q

Hemoglobin A

A

Adult Hemoglobin (alpha 2, beta 2)

  • binds 4 molecules O2 per Hgb
  • Iron must be in ferrous state (Fe2+) for oxygen to bind.
21
Q

Altitude Changes: Immediate vs. Early Adaptive

A

Immediate (<24 hrs): because O2 is decreased and CO2 is increased, you begin to breath rapidly to expire the CO2 (leftward shift)
- No change in Hgb or 2,3-DPG
Early Adaptive (72 Hrs): Start to get cellular compensation - allowing body to adapt to high altitude (Right shift)
- Increased Hgb to get elevated carrying capacity of O2.

22
Q

Fick’s Law of Diffusion

A

Vx = ((D x A x change in p)/(change in X))

D = Diffusion coefficient
A = Surface area of alveoli
Change in p = Difference in partial pressure
Change in X = Thickness of alveolar membrane
Vx = Rate of diffusion

23
Q

Dalton’s Law

A

Partial pressure of a gas in a mixture of gases is the pressure the gas would exert if it occupied the total volume of the mixture.

Px = Pb x F

Px = Partial pressure
F = Fractional concentration of dry gas
Pb = Total pressure
24
Q

Acute Altitude Sickness

A
  • Barometric pressure will be different at different altitudes – higher altitudes cause decreased O2 which changes partial pressure gradient, decreasing rate of O2 diffusion (Fick’s Law) – physiological change
  • If you administer 100% O2 you increase fraction of O2 in inspired air, increased partial pressure gradient thus increases rate of O2 diffusion
25
Q

Affects of Interstitial Fibrosis

A
  • Causes increased membrane thickness – space between capillary and alveolar space is widened (filled with collagen and CT tissue)
  • Rate of O2 diffusion will be decreased due to increased membrane thickness – will not diffuse well through all the collagen –> Fick’s Law
  • Results in SOB + fatigue
26
Q

Affects of COPD, Emphysema

A
  • Rate of oxygen diffusion will be decreased due to increase in availability of functional S.A. for diffusion in the alveoli (Fick’s Law).
  • Loss of pockets which help alveoli increase the S.A. for diffusion.
  • Decreased diffusion of O2 will lead to SOB and fatigue because you can’t keep up with tissue metabolism – not able to unload adequate amount of O2 in tissues.
27
Q

Respiratory Zone

A

Where gas exchange occurs

  • Alveoli increases surface area
  • Capillaries
  • Very thin interstitium because you don’t want a thick barrier to have to go through for diffusion.
  • Simple squamous epithelium
28
Q

Conducting Zone

A

Cleans the air that will be entering the respiratory zone.

  • Humidifies the air
  • Contains mucous, cilia, smooth muscle (dilation/constriction)
  • Surrounded by cartilage –> support
29
Q

Systemic Circulation

A

Left ventricle –> right atrium

- Supplies tissues before returning to Right atrium of heart.

30
Q

Pulmonary Circulation

A

Right ventricle –> lungs –> left atrium

- CO2 is exchanged for O2 in the capillaries of the lungs – oxygenates blood

31
Q

Compensation

A

Body’s attempt to maintain pH within normal limits

  • metabolic compensates for respiratory
  • respiratory compensates for metabolic
  • can be: none, partial or fully compensated
32
Q

Normal Ranges of plasma pH, paCO2 + Bicarb

A

Plasma pH: 7.35 - 7.45
CO2 (acid): 45 - 35
HCO3- (base): 22 - 26
(acidic - basic)

33
Q

Main pH Buffer Systems

A
  1. Buffers (like phosphates)
  2. Changes in ventilation and CO2 excretion can occur over seconds to minutes to provide rapid second line defense against pH change.
  3. Renal system H+ excretion and HCO3- synthesis is final line of defense, acting over hrs –> days prevent sustained pH change.
34
Q

Henderson-Hasselbach Equation

A

pH = pKa + log ([A-]/[HA])

pH = pKa + log ([HCO3-]/[H2CO3-])

Bicarb:Carbonic Acid = 20:1

Week Six (1 decks)

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