O2

Front 1

Room Air composition of: N2, O2, CO2

Back 1

78%, 21%, 0.03%

Front 2

What is the pressure in compressed O2 tank?

Back 2

1900 PSIG or 14.3 PSIA

Front 3

1L of compressed gas yields ____ L of gas

Back 3

150 L gas / 1L compressed gas

Front 4

Liquid O2 is ___est and most _______.

Back 4

SAFest and most ECONOMICAL.

Front 5

1L of LIQUID O2 yields ___ L of gas

Back 5

850 L of O2 gas

Front 6

Boyle's Law

Back 6

PV = k; P1V1 = P2V2

Front 7

E cyclinder holds ___L O2 gas; H cylinder holds ___ L O2 gas.

Back 7

E = 660 L; H = 6,900 L

Front 8

Gas gauge reading is ____ reading and _____ _____ as the gas empties

Back 8

TRUE reading; STEADILY DECLINES.

Front 9

VO2 signifies....

Back 9

oxygen consumption by the tissues.

Front 10

Partial Pressure (pp) cascade of O2 follows it from _____ to _____.

Back 10

TRACHEAL INSPIRED O2 to MITOCHONDRIA.

Front 11

Alveolar pp represented as ___. What does it represent?

Back 11

PAO2 (capital A).

Is the concentration of O2 in the alveoli (~80-130) and is DRIVING END of O2 pp gradient between alveolus and pulmonary capillary blood.

Front 12

In serum: O2 enters RBC and _____ binds to Hgb per ________ _________ ______.

Back 12

REVERSIBLY

Oxyhemoglobin Dissociation Curve

Front 13

O2 combines with free H+ in _______ to make _____.

Back 13

Mitochondria

H2O

Front 14

Final pp at mitochondrial level is _____.

Back 14

0.5 torr

Front 15

Factors that affect mitochondrial delivery:

Back 15

Inspired O2 conc.
Minute Ventilation
Airway patency & resistance
Alveolar volume & gas consumption
PAO2
V/Q matching
Arterial & Venous pp of O2
CO and systemic B/P

Front 16

Formation of ATP occurs in ______ during ______ ______.

Back 16

Mitochondria

Krebs Cycle

Front 17

O2 used to make ATP by producing ____-_____ ________ _____.

Back 17

High-energy phosphate bonds

Front 18

1 molecule of glucos yields ___ ATP.

Back 18

38 ATP; 1270 kJ of energy

Front 19

Anaerobic metabolism yields ___ ATP & ____ ____.

Back 19

2 ATP and lactic acid.67 kJ energy

Front 20

What accounts for most (~90%) of VO2 (Oxygen consumption)?

Back 20

Transfer of O2 from Hgb to mitochondria.

Front 21

Transfer of O2 from Hgb to mitochondria occurs at capillary level on _________ of mitochondria.

Back 21

cap level on INNER MEMBRANE of mitochondria.

Front 22

What is final electron acceptor?

Back 22

O2

Front 23

Where and how is CO2 produced?

Back 23

Mitochondrial cytosol

via Krebs Cycles

Front 24

O2 levels in alveolus decrease d/t:

Back 24

Addition of H2O (47 torr)

Addition of CO2 (40 torr)

Removal of O2 from alveolus (O2 uptake)

Front 25

A-a DO2 Gradient
Normal?

Back 25

10 torr

30-50 torr at 100% FiO2 (anatomic shunt)

Front 26

Anatomic shunt:
Normal %?

Three veins involved:

Back 26

2-5 %

Bronchial, pleural, thebesian veins

Front 27

Equation of A-aDO2 (Alveolar - arterial Difference for O2):

Back 27

A-aDO2 = PAO2 - PaO2

PAO2 = (PB - PH2O)FiO2 - (PaCO2/0.8)

**Pg 10 of O2 packet**

Front 28

Respiratory exchange ratio (#)

Back 28

0.8

Front 29

Respiratory Exchange Ratio defined..

Back 29

VCO2 / VO2

Fraction of (VO2) oxygen consumption used for 1) oxidative phosphorylation on inner membrane of mitochondria & 2) associated CO2 production.

Front 30

What is normal A-aDO2?

Back 30

< 60 mmHg

Front 31

A-aDO2 often inaccurate when ____ fluctuates.

Back 31

FiO2 differences change A-aDO2.

Front 32

What ratio is more accurate for arterial/Alveolar O2 difference?

Back 32

a/A ratio

Relatively constant regardless of FiO2.

Front 33

Two ways O2 transported in blood.

Back 33

1) combo with Hgb

2) dissolved in plasma

Front 34

O2 transport is a function of 3 things:

Back 34

1) Cardiac Output

2) Hgb

3) Hgb affinity for O2

Front 35

1 gm of Hgb carries ____ mL of O2

Back 35

1.34 mL of O2.

(fully saturated, 98% at RA)

Front 36

O2 bound to Hgb and it's effect on partial pressure.

Back 36

O2 that is bound does NOT exert pp.

Front 37

Explain OxyHgb Dissoc Curve

Back 37

Graphically shows relationship between O2 tensions (PaO2) and O2 saturation (SpO2).

Front 38

Steep area of OxyHgb Dissoc curve range is __-__ and signifiies that small changes in ... (finish the thought)

Back 38

20-80 torr

small changes in... O2 tension (PaO2) can allow for high exchange of O2 in blood

Front 39

P50 (give normal value and explain)

Back 39

PaO2 at which SpO2 = 50%

Normal = 26 torr

Front 40

Bohr effect vs Haldane effect on Oxyhgb dissoc curve

Back 40

Bohr --> lower pH reduces O2 affinity for Hgb

Haldane --> increased oxygenation of hemoglobin promotes dissociation of carbon dioxide.

Front 41

Re: affinity, what happens to the oxyhgb dissoc curve when Hgb affinity for O2 is INCREASED?

Back 41

Shifts LEFT

Front 42

Re: affinity, what happens to the oxyhgb dissoc curve when Hgb affinity for O2 is DECREASED?

Back 42

Shifts RIGHT

Front 43

What variables shift oxyhgb dissoc curve to left?

Back 43

Alkalosis
Hypothermia
Decreased 2,3DPG
Abnormal Hgb (feta)
Carboxyhemoglobin
Methemoglobin

Front 44

What variables shift oxyhgb dissoc curve to right?

Back 44

Acidosis
Hyperthermia
Increased 2,3 DPG
Abnormal Hgb
Increased CO2

Front 45

Carbon Monoxide and Cyanide inhibit...

Back 45

oxidative phosphorylation

Front 46

What is 2,3 DPG?

Back 46

Enzyme system substrate in RBC.

Promoties O2 dissociation from Hgb by competing for O2 binding sites.

Front 47

Oxyhgb dissoc curve:

Which shift yields more O2 movement from blood to tissues? Which yields less?

Back 47

More O2 delivery... R

Less O2 delivery... L

Front 48

Define oxygen content.

Back 48

Total O2 dissolved in plasma and bound to Hgb

Front 49

CaO2 is... (give equation and explain)

Back 49

CaO2 = (Hgb x 1.34 x SaO2) + (PaO2 x 0.003).

O2 arterial content

Front 50

What is normal CaO2? CvO2?

Back 50

20 gm % (a)

15 gm % (v)

gm % = Grams of Hgb per 100 mL blood.

Front 51

Plasma carries ____ ml O2 / _____ / ____

Back 51

0.003-mL O2 / dL plasma / torr

Front 52

Explain difference between gm% and vol%.

Back 52

gm% = grams of Hgb per 100 mL blood.

vol% = mL of oxygen per 100 mL blood.

Front 53

Equation to calculate O2 transport from CaO2.

Back 53

TO2 = CaO2 x CO.

Front 54

How and why might oxygen transport (TO2) differ from oxygen delivery (DO2)?

Back 54

O2 transported can be greater than O2 delivered.

A-V Fistula

Front 55

Oxygen Delivery equation (DO2)

Back 55

DO2 = CO x CaO2

**This looks suspiciously like TO2 = CaO2 x CO. So TO2 must (usually) = DO2 (except with AV fistula or other abnormalities).

Front 56

Oxygen consumption equation:

Back 56

VO2 = CO x C(a-v)O2

*That's if no shunt.

Front 57

Normal O2 consumption value:

Back 57

250 mL/min

~3mL / kg / min

Front 58

VO2 (O2 consumption) decreases ___% under basal conditions (GA).

Back 58

15%

Front 59

Normal venous parameters:

PvO2 ____
SvO2 ____
Venous O2 content ____

Back 59

PvO2 = 40 torr
SvO2 = 70%
Venous O2 content = 15 gm%

Front 60

Under GA, shunt usually...

Back 60

Shunt worsens under GA.

Front 61

What percentage of CO is shunted under GA? What likely causes this?

Back 61

10-15%

Likely d/t atelectasis.

Front 62

V/Q mismatching made worse when CRNA uses...

Back 62

lower tidal volumes.

Front 63

List items that worsen shunting:

Back 63

1) inhalation agents
2) atelectasis
3) proximal obstruction (mucus)
4) Nitrogen washout

Front 64

Explain "Nitrogen washout"

Back 64

Pre-oxygenating with 100% FiO2 removes all N2 from alveoli which causes alveolar constriction. Dependent alveoli may close.

Front 65

What is minimum FiO2 to be used under GA?

Back 65

30%

Front 66

List items that worsen shunting:

Back 66

1) inhalation agents
2) atelectasis
3) proximal obstruction (mucus)
4) Nitrogen washout

Front 67

List items that worsen shunting:

Back 67

1) inhalation agents
2) atelectasis
3) proximal obstruction (mucus)
4) Nitrogen washout

Front 68

Primary carrier gas for inhalation agents is...

Back 68

O2 (duh)

Front 69

Explain "Nitrogen washout"

Back 69

Pre-oxygenating with 100% FiO2 removes all N2 from alveoli which causes alveolar constriction. Dependent alveoli may close.

Front 70

What is minimum FiO2 to be used under GA?

Back 70

30%

Front 71

4 advantages of O2 use in anesthesia:

Back 71

1) decreased post-op infection
2) decreased PONV
3) Improved oxygenation for marginally perfused tissues (lessens r/f tissue damage/bed sores)
4) Reduce risk of liability for hypoxia-related injuries.

Front 72

Explain "Nitrogen washout"

Back 72

Pre-oxygenating with 100% FiO2 removes all N2 from alveoli which causes alveolar constriction. Dependent alveoli may close.

Front 73

Primary carrier gas for inhalation agents is...

Back 73

O2 (duh)

Front 74

What is minimum FiO2 to be used under GA?

Back 74

30%

Front 75

4 advantages of O2 use in anesthesia:

Back 75

1) decreased post-op infection
2) decreased PONV
3) Improved oxygenation for marginally perfused tissues (lessens r/f tissue damage/bed sores)
4) Reduce risk of liability for hypoxia-related injuries.

Front 76

Primary carrier gas for inhalation agents is...

Back 76

O2 (duh)

Front 77

4 advantages of O2 use in anesthesia:

Back 77

1) decreased post-op infection
2) decreased PONV
3) Improved oxygenation for marginally perfused tissues (lessens r/f tissue damage/bed sores)
4) Reduce risk of liability for hypoxia-related injuries.

Front 78

Swine hemorrhagic shock model confirmed that ____ was more influential in slowing the rate of apneic desaturation than ____. Yielded a 5-fold increase in time until critical oxygen desaturation occured underscoring the importance of.... before emergent airway management.

Back 78

FiO2 >>> fluid resuscitation

Study outlined the importance in preoxygenating with 100% FiO2 prior to intubating, over RA.

Front 79

100% FiO2 + supine pt = ___

Back 79

decreased FRV

Front 80

Disadvantages of O2 use in Anesthesia:

Back 80

1) Conceals evolving pulmonary pathology
2) apparatus risk
3) Mucosal drying
4) Pt inconvenience
5) Resorption atelectasis d/t high O2 conc.

Front 81

Hyperbaric O2 does 2 main things:

Back 81

1) Increases hydrostatic pressure

2) Increases O2 tension (therapeutic AND bacteriostatic)

Front 82

As hyperbaric O2 increases hydrostatic pressure, three effects are:

Back 82

1) decreases bubble volume

2) increases gradient for N elimination

3) reduces hypoxia in downstream tissues

Front 83

Hyperbaric O2 uses:

Back 83

1) Treat decompression sickness

2) Increases tissue oxygenation (for crush injuries, compromised skin grafts)

3) Chronic osteomyelitis (HBO is bacteriostatic and slows clostridea growth when PO2 >250 torr.

4) CO poisoning, cyanide toxicity and acute severe anemia

Front 84

HBO toxicity after 6-8 hours:

Back 84

decreased tracheal mucous velocity

Front 85

HBO toxicity, CNS effects

Back 85

seizures and visual changes

Front 86

HBO toxicity, 12-24 hours.

Back 86

1) Tracheal/bronchial irritation (12hr)

2) Changes in bronchial function (12-24 hr)

Front 87

What specifically causes HBO toxicity (4 things)

Back 87

1) Superoxides

2) Singlet O2

3) Hydroxyl radical

4) Hydrogen peroxide

Front 88

CO poisoning: CO ____ binds to Hgb with ____ times the affinity as O2.

Back 88

REVERSIBLY binds Hgb.

CO has 200x affinity for Hgb as O2.

Front 89

Carboxyhemoglogin interferes with:

Causes curve shift to...

Back 89

Binding & dissociation of O2 and Hgb.

Shift to left.

Front 90

S&S of CO poisoning:

Back 90

1) HA, N/V, irritability

2) NOT cyanosis

3) PaO2 normal on ABG

4) Pulse Ox false high

Front 91

Easiest way to determine CO poisoning:

Back 91

CO-oximeter (can differentiate carboxyHgb and oxyhemoglobin)

Front 92

Explain 2 ways that carboxyhemoglobin decreases tissue oxygenation.

Back 92

1) CO takes up binding sites on Hgb meant for O2.

2) Causes left shift of dissociation curve, making Hgb-O2 affinity greater so Hgb holds on to O2 tighter, delivering less to tissues (due mostly to reduction in DPG).

Front 93

Anemia causes ____ shift.

Back 93

Right shift.

Front 94

Early warning signs of hypoxemia (think O2):

Back 94

SpO2 <90%

PaO2 <=60

Front 95

O2 analyzer determines value of...

Back 95

O2 concentration delivered by machine.

Front 96

OR standard for monitoring ventilation...

Back 96

ETCO2

Front 97

Normal ETCO2 35-45, what is this value is vol% ?

Back 97

4-6 vol%

Front 98

At rest humans produce ___ mL CO2 / kg / min

Back 98

2.5 mL CO2 / kg / min

Front 99

What is respiratory quotient (value and equation)?

Back 99

0.8

200 mL CO2 / 250 mL O2

aka

CO2 production / O2 consumption

Front 100

CO2 diffusion coefficient is ___ times that of O2.

Back 100

20x

CO2 diffusion coeff 20x > O2

Front 101

Where is ventilation monitored in CNS?

PNS?

Back 101

Medulla

Aortic & carotid bodies (chemoreceptors respond to changes in PaCO2 and PaO2, especially PaO2 <50 torr)

Front 102

Hypoxia vs hypoxemia (definitions)

Back 102

Hypoxia - Reduced O2 supply to tissues.

Hypoxemia - deficient oxygenation of the blood (PaO2 < 60 torr; PvO2 < 30 torr).

Front 103

When hypoxia occurs and inadequate oxygen delivered to mitochondria...

Back 103

Oxidative phosphorylation stops.

Anaerobic metabolism begins

Energy production drops

H+ and lactate levels rise

(Lactate/pyruvate ratio rises; ATP/ADP ratio falls!!!)

Front 104

CNS effects of hypoxia

Back 104

Cerebral vascular resistance initially decreases.

Autoregulation lost.

With complete cessation of blood flow or complete hypoxia:

1) electrical activity stops w/i seconds

2) Irreversible damage w/i 4-5 minutes.

Front 105

Most damage caused by severe cerebral hypoxia d/t ...

Back 105

Intracellular acidosis

Front 106

Why is cell damage less apparent when anoxia or severe hypoxia follows CHRONIC hypoxia?

Back 106

Less lactic acid is produced (less intracellular acidosis) as a result of the glucose depletion caused by chronic hypoxia.

Front 107

CV hypoxia effects:

Back 107

Decreased SVR and Increased HR.

(Reduces diastolic filling time and further decreases myocardial O2 supply.)

Front 108

Pulmonary Hypoxia effects

Back 108

Significant redistribution of pulmonary blood via:

-Hypoxic vasoconstriction (HPV)
-Mediated primarily by PAO2 & pumonary PaO2.

Front 109

_____ blocks natural hypoxic pulmonary vasoconstriction.

Back 109

Inhalation agents

Front 110

Explain HPV:

Back 110

Blood from HYPOventilated areas of lung redistributed to better ventilated ones. Constriction due to low pH.

See picture on pg 24 of O2 packet.

Front 111

Renal hypoxia effects:

Back 111

Depletion of HIGH ENERGY PHOSPHATE COMPOUNDS leads to renal damage.

Front 112

Hepatic hypoxia effects:

Back 112

Systemic vasodilation leads to increased O2 extraction by body and decreased O2 content in portal circulation. Hepatic autoregulation is lost in severe hypoxia.

Front 113

How do we compensate for hypoxia?

Back 113

1) Hyperventilation
2) Pulmonary redistribution
3) Increased Cardiac Ouput
4) Increased Hgb (chronic hypox)
5) Changes in O2 dissociation curve

Front 114

How do we compensate for chronic hypoxia?

Back 114

1) Increased # of alveoli
2) Increased concentration of Hgb
3) Incerased myoglobin in muscle
4) Decreased ventilatory response to hypoxia

Front 115

Acute responses to high altitude.

Treatment?

Back 115

H/A, nausea, sleep disturbance, pulmonary and verebral edema

Treat with carbonic anhydrase inhibitor (Diamox), steroids and slow descent.

Front 116

Two main causes of hypoxemia.

Back 116

Decreased PAO2

True intrapulmonary shunt

Front 117

How would each of the following hypoxemic pts respond to 100% FiO2:

1) Hypoventilation
2) Absolute shunt
3) V/Q mismatch
4) Diffusion abnormality
5) Decreased FiO2

Back 117

Only #2, absolute shunt, would not improve. Level of hypoventilators improvement will determine ultimately on whether RR is adequate.

Front 118

Define anatomic shunt (one main, two additional):

Back 118

1) Venous blood from bronchial, thebesian veins & L heart enters LA and LV. (approx 2-5% of CO)

Others:
2) Congenital VSDs
3) A-V Intrapulmonary fistulas

Front 119

What is happening is true/absolute shunt? Does increasing FiO2 help this patient?

Back 119

Blood from R-heart enters L-heart w/o exchanging alveolar gas

Mixes with oxygenated blood in L-heart and lowers O2 concentration.

Why? -- Blood is perfusing atelectatic lung units.

Increased FiO2 does NOT help.

Front 120

4 causes of true/absolute shunts...

Back 120

1) Lobar atelectasis
2) pulmonary edema
3) acute lung injury)
4) bilateral pneumonia

Front 121

Compensation for true shunt:

Back 121

1) Increased Cardiac Output

2) Decreased O2 utilization (causes increased A-a systemic shunt)

2) Changes in pulmonary distribution of perfusion to decrease shunt (HPV)

Front 122

Relative Shunt (V/Q mismatch)...

How common?

Increased FiO2 help?

Back 122

Relative shunt most common shunt seen in OR.

Responds well to FiO2. (Giving FiO2 easiest way to differentiate between true/absolute and relative shunt)

Front 123

Normal acceptable V/Q?

Back 123

> 0.75

Front 124

Ideal V/Q?

Lung bases?

Apices?

Entire lung?

Back 124

Ideal V/Q - 1.0

Lung bases - 0.63

Apices - 3.3

Entire lung - 0.85

Front 125

As shunt fractions increase/worsen CRNA keeps titrating up FiO2, what will eventually happen?

Back 125

FiO2 increases will eventually stop being effective (moving towards true shunt).

Front 126

Diffusion block caused by...

Back 126

Thickened alveolar/capillary membrane (e.g. cystic fibrosis).

Front 127

Clinical signs of acute hypoxemia...

Back 127

Subjective:

Anxiety, restlessness
Confusion
AMS
Dyspnea
Dimmed peripheral vision

Objective:

Diaphoretic
Seizures, unconsciousness
cyanosis
Inc C output
Inc SV
HTN, follow by hypotension
tachypnea
dysrhythmias
Tachycardia, followed by brady

Front 128

Risk factors for developing hypoxemia:

Back 128

Age
Hyperbaric conditions
obesity
Cardiopulmonary disease
smoking

Duration of anesthesia
Type of anesthesia
Operative site

Abdominal distension
Pain

Front 129

Calculating intrapulmonary shunt fraction:

QS/QT = A-aDO2 (0.003) / (CaO2 - CvO2) + (A-aDO2)(0.003)

Define variables and coefficient

Back 129

QS = Fraction of pulm blood NOT exposed to ventilated alveoli

QT = Total pulmonary blood flow

A-aDO2 = Alveolar to arterial difference for oxygen

CaO2 - CvO2 = Arterial to venous oxygen content difference (assume as 5 ml^-1)

0.003 = solubility coeff for O2 in plasma

Front 130

Calculate Intrapulmonary shunt fraction if:

A-aDO2 = 200mmHg

CaO2-CvO2 = 5ml/dl^-1

Back 130

=(200 x 0.003) / 5 + 200 (0.003)

= 0.6 / 5.6

= 0.107 = 10.7% (about normal)