Oxygen Delivery Flashcards by Lily Watkins

Define atmospheric pressure

The weight of different gases in the atmosphere causing a downward pressure

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At sea level, how much of mercury can atmospheric pressure support

One column of mercury (Hg), 760mm high, therefore 1 atmosphere =760mmHg

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What are gases measured in, in addition to mug

Torr

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What is 1 torr equal to

1 atmosphere/760mmHg

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Define partial pressure

The pressure of a single gas in a mixture

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What is the partial pressure AKA

Tension of a gas

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Define Dalton’s law

The total pressure of a gas mixture is equal to the sum of the partial pressure of the component gases

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How do you calculate the partial pressure

Multiply the total pressure (Pt) of all the gases by the fraction of composition of the gas you want

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Example of calculating the partial pressure:
- at sea level the Pt is 760mmHg
- O2 is approx 20.93% of atmospheric composition

What is the equation & answer

760 x .2093 =159.068 (159.1mmHg)

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Example of calculating the partial pressure:
- Pt of 2 gases is 760mmHg
- Gas A = 2/10
- Gas B = 8/10

What is partial pressure of each gas

Gas A - 760 x.2 = 152mmHg
Gas B - 760 x .8 = 608mmHg

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Define Henry’s law

The quantity of a gas that dissolves in a volume of liquid is directly proportional to the partial pressure of that gas, the pressure remaining contant

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What is the composition of dry atmospheric air

Nitrogen : 79.03% (600.60mmHg)
Oxygen : 20.93% (159.10mmHg)
Carbon dioxide : 0.04% (.30mmHg)
H2O : - -

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What is the composition of alveolar air

Nitrogen : 74.9% (569.24mmHg)
Oxygen : 13.6% (103.36mmHg)
Carbon dioxide : 5.3% (40.28mmHg)
H2O : 6.2% (47.12mmHg)

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What is key to note about atmospheric air vs alveolar air

They have the same total composition (760mmHg), but the components vary

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What is above any solution

The vapour of the solution (solvent!) which creates a vapour pressure

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What is the vapour pressure equivalent to

The P of the gas in the liquid

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What is the vapour pressure of H2O at 37 degrees, and why is it relevant

47mmHg, and because the water in AWs is equal to this d/t humidity saturation

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What is critical to note about diffusion within the body

Gases diffuse across the alveolar & capillary membranes to allow for gas exchange & venous blood to return to the lungs

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Provide examples of various pathologies that may impact how efficient gas exchange is

COPD, pulmonary edema, tumours, fibrosis

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What are the 5 factors affecting diffusion

Solubility of the gas in the fluid
Concentration or pressure gradient
Amount of SA available
Thickness of the membrane
Temp of the fluid

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How does diffusion work

Diffuses from high to low concentrations until an equilibrium is reached

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What is the average PO2 in the tissues and why can it vary

The average is assumed to be 40mmHg but may be lower in active tissues as it depends on metabolic demands

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What is the average PCO2 in venous blood, and how does CO2 get to venous blood

46mmHg, through diffusion as CO2 is a by product of cellular metabolism therefore higher in tissues causing it to move to venous blood

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Describe diffusion of O2 & CO2 in the lungs & tissues

Diffuses into/out of blood where the PO2 begins at 40, and PCO2 45
In the lungs & oxygenated blood:
PO2 = 100
PCO2 = 40
In the tissues O2 diffuses in and CO2 out, initial values are as follows but then move up to what the lungs have:
PO2 = 40
PCO2 = 45

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Describe diffusion of O2 & CO2 in the lungs & tissues

Diffuses into/out of blood where the PO2 begins at 40, and PCO2 45 In the lungs & oxygenated blood: PO2 = 100 PCO2 = 40 In the tissues O2 diffuses in and CO2 out, initial values are as follows but then move up to what the lungs have: PO2 = 40 PCO2 = 45

What are the values of PCO2 between the tissues and lungs, and how does the diffusion work

Venous blood = 46mmHg, alveolar air in lungs = 40mmHg, therefore diffusion goes from venous blood to lungs

At the normal PO2 of __, O2 is relatively __ to __

100mmHg, insoluble, plasma

Roughly __ of __ will dissolve into __of __

0.3mL, O2, 100mL, plasma

Why is it a problem that O2 does not dissolve into plasma in large amounts

Because it would not meet the metabolic demand

What are the 2 factors that impact the quantity of O2 being delivered to tissues

- Perfusion (ie blood flow) - Oxygenation (ie concentration of hemoglobin & the affinity of oxygen to it)

What is actual blood flow determined by

The health of the CVS (in addition to vasoconstriction & CO2)

What is the red pigment in blood due to

Hemoglobin

What are RBCs AKA

Erythrocytes

What is important to note about Hb

It has a strong affinity for O2

What carries the most (97-98%) of O2 around the body

Hb, through binding

Hb will combine __ - __ of O2 per every __ of blood

19-20mL, 100mL

What makes up hemoglobin

Heme (4 iron atoms) & globin (protein) portions

What is oxyhemoglobin, and what is the short form

Oxygen & hemoglobin combined, HbO2

Where is HbO2 formed, and why

In the alveolar beds, and it is due to the increased PO2 with decreased PCO2

What are the main components impacting oxygen affinity

Temperature, pH, CO2 & hydrogen ions

What is the difference between a left & upwards shift, vs a right & downwards shift

Left = increased affinity (O2 is left on read — will not diffuse into tissus easily) Right = decreased affinity (O2 Fs right off — O2 readily leaves the Hb)

What can cause a left & upward shift of the oxyhemoglobin dissociation curve

pH (decrease in H+ ions & increase in pH [>7.6] = alkaline state) Temp (decrease = hypothermia) CO2 (decrease in CO2 = alkaline state) 2,3-DPG (decrease in amount creates unbound hemoglobin, making it easier for O2 to bind & therefore increasing the affinity)

What can cause a right & upwards shift of the oxyhemoglobin dissociation curve

pH (increase in H+ ions & decrease in pH [<7.2] = alkaline state) Temp (increase = hyperthermia) CO2 (increase in CO2 = acidotic state) 2,3-DPG (increase in amount promotes it to bind to the deoxyhemoglobin, stabilizing the conformations & making it harder for Hb & O2 to bind therefore easier to offload)

Venous blood has an average of PO2 40mmHg, meaning what

~75% of Hb is saturated in “deoxygenated blood”

What is a good reminder to recall the oxyhemoglobin affinity curve correctly

Increase in source = decrease on the scale

For every drop in CO2 by 10mmHg, how much does pH increase by

0.08

Why might supplemental O2 benefit in a hyperventilating pt

The pt will be alkalotic, therefore O2 will be tightly bound. By applying supplemental O2 you can attempt to increase the amount of O2 dissolved in plasma

Under normal conditions through aerobic metabolism, how much CO2 is given off by every 100mL of blood at the lungs

4-5mL

CO2 is transported by the blood until eliminated by what two sources

The lungs and kidneys

What are the 3 ways CO2 is transported, and what % do they make up

— Carried in the form of bicarbonate (65-70%) — Combined with Hb [AKA carboxyhemoglobin] (23-25%) — Dissolved in plasma (7-10%)

CO2 is almost __ more soluble in __ than O2

20x, plasma

The chemical reaction forming bicarbonate is slow in __ but increases by __ when the CO2 enters the __ through the enzyme __

Plasma, 1000, RBC, carbonic anhydrase

What is the chemical reaction the forms bicarbonate

(With the help of carbonic anhydraise) CO2 + H2O = H2CO3 —> this reaction is the carbonic acid, which then dissociates to become an H+ ion & bicabrb H2CO3 = CO3 + H+

How are free hydrogen ions managed in the body

Buffered by deoxyhemoglobin in the venous blood

Where does bicarbonate go

It dissolves into plasma

What is the chloride shift

Where bicarbonate moves into a cell & Cl- moves out, at a 1:1 ratio. This occurs so electrochemical neutrality is maintained within the cell — the reverse happes in the lungs as CO2 is expelled

What does the Bohr Effect describe

Changes in affinity of O2-Hb as a result of the shift in blood pH that occurs on a breath-by-breath basis, where the changes occur at the lungs & tissues. It contributes the changes to a lowered pH & increase in CO2

What is the definition of hyperventilation

A MV (RR x TV) the exceeds the body’s metabolic demands

What is a normal pH

7.35-7.45

What is acidoic vs alkalotic

Acidotic — <7.35 Alkalotic — >7.45

Define hypoxemia

Blood gas analysis where O2 in arterial blood is <80mmHg & usually an SpO2 of <90%

Define hypoxia

The state of O2 deficiency/lack of O2, causing impairment of bodily functions

What are the 4 types of hypoxia

Hypoxic hypoxia, hypemic hypoxia, stagnant hypoxia, histotoxic hypoxia

Oxygen Delivery Flashcards

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