1 Mosby items and derived items © 2011, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. Chapter 5 Chapter 5 Oxygenation Assessments Oxygenation Assessments
Dec 13, 2015
1Mosby items and derived items © 2011, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
Chapter 5Chapter 5
Oxygenation AssessmentsOxygenation Assessments
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Oxygen Transport ReviewOxygen Transport Review
Oxygen is carried in the blood in two ways:Oxygen is carried in the blood in two ways:1.1. As dissolved oxygen in the blood plasmaAs dissolved oxygen in the blood plasma2.2. Bound to the hemoglobin (Hb)Bound to the hemoglobin (Hb)
Most oxygen is carried to the tissue cell bound to Most oxygen is carried to the tissue cell bound to the hemoglobin.the hemoglobin.
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Oxygen Dissolved in the Blood Oxygen Dissolved in the Blood PlasmaPlasma
At normal body temperature, about 0.003 mLAt normal body temperature, about 0.003 mLof oxygen (Oof oxygen (O22) will dissolve in each 100 mL of ) will dissolve in each 100 mL of
blood for every 1 mm Hg of POblood for every 1 mm Hg of PO22.. Thus when the PaOThus when the PaO22 is 100 mm Hg, about is 100 mm Hg, about
0.3 mL of dissolved O0.3 mL of dissolved O22 exists in every 100 mL exists in every 100 mL
of plasma: 0.003 × 100 mm Hg = 0.3 mLof plasma: 0.003 × 100 mm Hg = 0.3 mL Clinically, written as 0.3 volume percent (volClinically, written as 0.3 volume percent (vol
%)%) 0.3 vol% O0.3 vol% O22
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Hb value in normal man: 14 to 16 g/100 mLHb value in normal man: 14 to 16 g/100 mL Hb value in normal woman: 12 to 15 g/100 Hb value in normal woman: 12 to 15 g/100
mLmL Clinically, the weight measurement of Clinically, the weight measurement of
hemoglobin, in reference to 100 mL of blood, hemoglobin, in reference to 100 mL of blood, is known as the is known as the grams percent hemoglobin grams percent hemoglobin (g(g% Hb)% Hb)
Oxygen Bound to HemoglobinOxygen Bound to Hemoglobin
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Each g% Hb can carry 1.34 mL of OEach g% Hb can carry 1.34 mL of O22
Thus if the Hb level is 12 g% and if the Hb is Thus if the Hb level is 12 g% and if the Hb is fully saturated, about 15.72 vol% of Ofully saturated, about 15.72 vol% of O22 will be will be
bound to the Hb:bound to the Hb:
OO22 bound to Hb = 1.34 mL O bound to Hb = 1.34 mL O22 × 12 g% Hb × 12 g% Hb
= 15.72 vol% O= 15.72 vol% O22
Oxygen Bound to Hemoglobin Oxygen Bound to Hemoglobin (Cont’d)(Cont’d)
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At a normal PaOAt a normal PaO22 of 100 mm Hg, however, of 100 mm Hg, however,
the Hb saturation (SaOthe Hb saturation (SaO22) is only about 97% ) is only about 97%
because of these normal physiologic shunts:because of these normal physiologic shunts: Thebesian venous drainage into the left atriumThebesian venous drainage into the left atrium Bronchial venous drainage into the pulmonary Bronchial venous drainage into the pulmonary
veinsveins
Oxygen Bound to Hemoglobin Oxygen Bound to Hemoglobin (Cont’d)(Cont’d)
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Thus the amount of arterial oxygen in the Thus the amount of arterial oxygen in the calculation must be adjusted to 97%:calculation must be adjusted to 97%:
15.72 vol% O15.72 vol% O22
× .97× .97 15.24 vol% O15.24 vol% O22
Oxygen Bound to Hemoglobin Oxygen Bound to Hemoglobin (Cont’d)(Cont’d)
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To calculate the total amount of oxygen in To calculate the total amount of oxygen in 100 mL of blood, the following must be added 100 mL of blood, the following must be added together:together: Dissolved oxygen Dissolved oxygen Oxygen bound to hemoglobin Oxygen bound to hemoglobin
Total Oxygen ContentTotal Oxygen Content
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A 44-year-old woman with a long history of A 44-year-old woman with a long history of asthma arrives in the emergency room in asthma arrives in the emergency room in severe respiratory distress. Her vital signssevere respiratory distress. Her vital signsare respiratory rate 36 breaths/min, heart rate are respiratory rate 36 breaths/min, heart rate 130 bpm, and blood pressure 160/95 mm Hg. 130 bpm, and blood pressure 160/95 mm Hg. Her hemoglobin concentration is 10 g%, and Her hemoglobin concentration is 10 g%, and her PaOher PaO22 is 55 mm Hg (SaO is 55 mm Hg (SaO2 2 85%). Based on 85%). Based on
these data, the patient’s total oxygen content is these data, the patient’s total oxygen content is determined on the next slide:determined on the next slide:
Case ExampleCase Example
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55 PaO55 PaO22
× 0.003× 0.003 (dissolved O (dissolved O22 factor) factor)
0.165 vol% O0.165 vol% O22
1. Dissolved O1. Dissolved O22
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2. Oxygen Bound to Hemoglobin2. Oxygen Bound to Hemoglobin
10 g% Hb10 g% Hb × 1.34× 1.34 (O (O22 bound to Hb factor) bound to Hb factor)
13.4 vol% O13.4 vol% O22 (at SaO (at SaO22 of 100%) of 100%)
Above answer is then followed by the SaOAbove answer is then followed by the SaO2 2
factor:factor: 13.4 vol% O13.4 vol% O22
× .85 SaO× .85 SaO22
11.39 vol% O11.39 vol% O22 (at SaO(at SaO22 of 85%) of 85%)
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11.39 vol% O11.39 vol% O22 (bound to hemoglobin)(bound to hemoglobin)
+ 0.165 vol% O+ 0.165 vol% O22 (dissolved O(dissolved O22))
11.555 vol% O11.555 vol% O22 (total amount of O(total amount of O22/100 mL of blood)/100 mL of blood)
3. Total Oxygen Content3. Total Oxygen Content..
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The total oxygen content can be calculated inThe total oxygen content can be calculated inthe patient’s:the patient’s: Arterial blood (CaOArterial blood (CaO22)) Venous blood (CvOVenous blood (CvO22) ) Pulmonary capillary blood (CcOPulmonary capillary blood (CcO22))
Total Oxygen Content (Cont’d)Total Oxygen Content (Cont’d)
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CaOCaO22 = Oxygen content of arterial blood = Oxygen content of arterial blood
(Hb × 1.34 × SaO(Hb × 1.34 × SaO22) + (PaO) + (PaO22 × 0.003) × 0.003)
CvOCvO22 = Oxygen content of mixed venous blood = Oxygen content of mixed venous blood
(Hb × 1.34 × Sv(Hb × 1.34 × SvOO22) + (Pv) + (PvOO22 × 0.003) × 0.003)
CcOCcO22 = Oxygen content of pulmonary capillary = Oxygen content of pulmonary capillary
bloodblood (Hb × 1.34) + (PAO(Hb × 1.34) + (PAO22 × 0.003) × 0.003)
Total Oxygen Content (Cont’d)Total Oxygen Content (Cont’d)
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Oxygenation IndicesOxygenation Indices
Oxygen tension–based indicesOxygen tension–based indices Oxygen saturation and content indicesOxygen saturation and content indices
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Oxygen Tension–Based IndicesOxygen Tension–Based Indices
Arterial oxygen tension (PaOArterial oxygen tension (PaO22)) Alveolar-arterial oxygen tension difference Alveolar-arterial oxygen tension difference
(P[A-a]O(P[A-a]O22))
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Arterial Oxygen Tension (PaOArterial Oxygen Tension (PaO22))
Good indicator of the patient’s oxygenation Good indicator of the patient’s oxygenation statusstatus
The PaOThe PaO22, however, may be misleading in , however, may be misleading in
these clinical situations:these clinical situations: Low HbLow Hb Decreased cardiac outputDecreased cardiac output Peripheral shuntingPeripheral shunting Carbon monoxide and cyanide exposureCarbon monoxide and cyanide exposure
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Alveolar-Arterial Oxygen Tension Alveolar-Arterial Oxygen Tension Difference (P[A-a]ODifference (P[A-a]O22))
The P(A-a)OThe P(A-a)O2 2 is the oxygen tension difference is the oxygen tension difference
between the alveoli and arterial blood.between the alveoli and arterial blood.
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Alveolar-Arterial Oxygen Tension Alveolar-Arterial Oxygen Tension Difference (P[A-a]ODifference (P[A-a]O22) (Cont’d)) (Cont’d)
PAOPAO22 = FIO = FIO2 2 (P(PBB − PH − PH22OO) − PaCO) − PaCO22 (1.25) (1.25)
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Case Study ExampleCase Study Example
If a patient is receiving an FIOIf a patient is receiving an FIO22 of 0.30 on a day of 0.30 on a day
when the barometric pressure is 750 mm Hg, when the barometric pressure is 750 mm Hg, and if the patient’s PaCOand if the patient’s PaCO22 is 70 mm Hg and is 70 mm Hg and
PaOPaO22 is 60 mm Hg, the P(A-a)O is 60 mm Hg, the P(A-a)O22 can be can be
calculated as shown on the next slide:calculated as shown on the next slide:
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Case Study Example (Cont’d)Case Study Example (Cont’d)
PAOPAO22 = = FIOFIO2 2 (P(PBB − P − PHH22OO) − PaCO) − PaCO22 (1.25) (1.25)
= 0.30 (750 − 47) − 70 (1.25)= 0.30 (750 − 47) − 70 (1.25)= (703) 0.30 − 87.5= (703) 0.30 − 87.5= (210.9) − 87.5= (210.9) − 87.5= 123.4 mm Hg= 123.4 mm Hg
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Case Study Example (Cont’d)Case Study Example (Cont’d)
Using the PaOUsing the PaO22 obtained from the ABG: obtained from the ABG:
123.4 (PAO123.4 (PAO22))
− − 60.0 (PaO60.0 (PaO22))
63.4 mm Hg [P(A-a)O63.4 mm Hg [P(A-a)O22]]
The normal P(A-a)O2 ranges from 7 to 15 mm Hg and should not exceed 30 mm Hg.
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P(A-a)OP(A-a)O22 Increases Increases
Oxygen diffusion disorders Oxygen diffusion disorders Decreased V/Q ratiosDecreased V/Q ratios Right-to-left cardiac shuntingRight-to-left cardiac shunting AgeAge
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Note: The P(A-a)ONote: The P(A-a)O22
Loses sensitivity in patients breathing high FIOLoses sensitivity in patients breathing high FIO22
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Oxygen Saturation– and Oxygen Saturation– and Content–Based IndicesContent–Based Indices
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Oxygen Saturation– and Content–Based Oxygen Saturation– and Content–Based IndicesIndices
CaOCaO22 = (Hb × 1.34 × SaO = (Hb × 1.34 × SaO22) + (PaO) + (PaO22 × 0.003) × 0.003)
CvOCvO22 = (Hb × 1.34 × SvO = (Hb × 1.34 × SvO22) + (PvO) + (PvO22 × 0.003) × 0.003)
CcOCcO22 = (Hb × 1.34) + (PAO = (Hb × 1.34) + (PAO22 × 0.003) × 0.003)
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Most Common Oxygen Saturation–and Most Common Oxygen Saturation–and Content–Based IndicesContent–Based Indices
Total oxygen deliveryTotal oxygen delivery Arterial-venous oxygen content differenceArterial-venous oxygen content difference Oxygen consumptionOxygen consumption Oxygen extraction ratioOxygen extraction ratio Mixed venous oxygen saturationMixed venous oxygen saturation Pulmonary shunting Pulmonary shunting
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Total Oxygen DeliveryTotal Oxygen DeliveryDODO22 = Q = QTT × (CaO × (CaO22 × 10) × 10)
The total oxygen delivery is the amount of The total oxygen delivery is the amount of oxygen delivered to the peripheral tissue cells.oxygen delivered to the peripheral tissue cells.
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Total Oxygen DeliveryTotal Oxygen Delivery DO DO22 = Q = QTT × (CaO × (CaO22 × 10) (Cont’d) × 10) (Cont’d)
For example, if a patient has a cardiac output of For example, if a patient has a cardiac output of 4 L/min and a CaO4 L/min and a CaO22 of 15 vol%, the DO of 15 vol%, the DO2 2 is 600 is 600
mL of oxygen per minute—as calculated on the mL of oxygen per minute—as calculated on the next slide:next slide:
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Total Oxygen DeliveryTotal Oxygen Delivery
DODO22 = Q = QTT × (CaO × (CaO22 × 10) × 10)
= 4 L/min × (15 vol% × 10)= 4 L/min × (15 vol% × 10)= 600 mL O= 600 mL O22 per minute per minute
Normally, about 1000 mL/minNormally, about 1000 mL/min
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Total Oxygen Delivery (Cont’d)Total Oxygen Delivery (Cont’d)
Decreases:Decreases: Low PaOLow PaO22 Low SaOLow SaO22
Low HbLow Hb Low cardiac outputLow cardiac output
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Total Oxygen Delivery (Cont’d)Total Oxygen Delivery (Cont’d)
Increases:Increases: Increased PaOIncreased PaO22 Increased SaOIncreased SaO22
Increased HbIncreased Hb Increased cardiac outputIncreased cardiac output
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Arterial-Venous Oxygen Content Arterial-Venous Oxygen Content DifferenceDifference
C(a-v)OC(a-v)O22 = CaO = CaO22 − CvO − CvO22
The arterial-venous oxygen content difference The arterial-venous oxygen content difference (C[a-v]O(C[a-v]O22) is the difference between the CaO) is the difference between the CaO22
and the CvOand the CvO22—that is, CaO—that is, CaO22 − CvO − CvO22..
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Arterial-Venous Oxygen Content Arterial-Venous Oxygen Content DifferenceDifference
C(a-v)OC(a-v)O22 = CaO = CaO22 − CvO − CvO2 2 (Cont’d)(Cont’d)
For example, if a patient’s CaOFor example, if a patient’s CaO22 is 15 vol% and is 15 vol% and
the CvOthe CvO22 is 8 vol%, the C(a-v)O is 8 vol%, the C(a-v)O22 is 7 vol%—as is 7 vol%—as
calculated on the next slide:calculated on the next slide:
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Arterial-Venous Oxygen Arterial-Venous Oxygen Content DifferenceContent Difference
C(a-v)OC(a-v)O22 = CaO = CaO22 − CvO − CvO22
= 15 vol% − 8 vol%= 15 vol% − 8 vol%= 7 vol%= 7 vol%
Normally, 5 vol% Normally, 5 vol%
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Arterial-Venous Oxygen Arterial-Venous Oxygen Content Difference (Cont’d)Content Difference (Cont’d)
Increases:Increases: Decreased cardiac outputDecreased cardiac output ExerciseExercise SeizuresSeizures HyperthermiaHyperthermia
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Arterial-Venous Oxygen Arterial-Venous Oxygen Content Difference (Cont’d)Content Difference (Cont’d)
Decreases:Decreases: Increased cardiac outputIncreased cardiac output Skeletal relaxationSkeletal relaxation Peripheral shuntingPeripheral shunting CyanideCyanide HypothermiaHypothermia
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Oxygen ConsumptionOxygen ConsumptionVVOO22 = Q = QTT [C(a-v)O [C(a-v)O22] × 10] × 10
Oxygen (VOOxygen (VO22) consumption is the amount of ) consumption is the amount of
oxygen consumed by the peripheral tissue cells oxygen consumed by the peripheral tissue cells during a 1-minute period. during a 1-minute period.
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Oxygen ConsumptionOxygen ConsumptionVOVO22 = Q = QTT [C(a-v)O [C(a-v)O22] × 10 (Cont’d)] × 10 (Cont’d)
For example, if a patient has a cardiac output of For example, if a patient has a cardiac output of 4 L/min and a C(a-v)O4 L/min and a C(a-v)O22 of 6 vol%, the total of 6 vol%, the total
amount of oxygen consumed by the tissue cells amount of oxygen consumed by the tissue cells in 1 minute would be 240 mL—as calculated on in 1 minute would be 240 mL—as calculated on the next slide:the next slide:
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Oxygen ConsumptionOxygen Consumption
VOVO22 = Q = QTT [C(a-v)O [C(a-v)O22] × 10] × 10
= 4 L/min × 6 vol% × 10= 4 L/min × 6 vol% × 10= 240 mL O= 240 mL O22/min/min
Normal is 250 mL ONormal is 250 mL O22/min/min
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Oxygen Consumption (Cont’d)Oxygen Consumption (Cont’d)
Increases:Increases: SeizuresSeizures ExerciseExercise HyperthermiaHyperthermia Body sizeBody size
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Oxygen Consumption (Cont’d)Oxygen Consumption (Cont’d)
Decreases:Decreases: Skeletal muscle relaxationSkeletal muscle relaxation Peripheral shuntingPeripheral shunting Certain poisons (e.g., cyanide)Certain poisons (e.g., cyanide) HypothermiaHypothermia
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Oxygen Extraction RatioOxygen Extraction RatioOO22ER = ER = CaOCaO22 − CvO − CvO22
CaOCaO22The OThe O22ER is the amount of oxygen consumed ER is the amount of oxygen consumed
by the tissue cells divided by the total amount of by the tissue cells divided by the total amount of oxygen delivered.oxygen delivered.
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Oxygen Extraction RatioOxygen Extraction RatioOO22ER = ER = CaOCaO22 − CvO − CvO22
CaO CaO2 2 (Cont’d)(Cont’d)
For example, if a patient’s CaOFor example, if a patient’s CaO22 is 15 vol% and is 15 vol% and
the CvOthe CvO22 is 10 vol%, the O is 10 vol%, the O22ER would be 33%—ER would be 33%—
as calculated on the next slide:as calculated on the next slide:
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Oxygen Extraction RatioOxygen Extraction Ratio
OO22ER = ER = CaOCaO22 − CvO − CvO22
CaOCaO22= = 15 vol% − 10 vol%15 vol% − 10 vol%
15 vol%15 vol%= = 5 vol% 5 vol% 15 vol%15 vol%= 0.33= 0.33
Normal is 0.25% Normal is 0.25%
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Oxygen Extraction Ratio (Cont’d)Oxygen Extraction Ratio (Cont’d)
Increases:Increases: Decreased cardiac outputDecreased cardiac output Periods of increased OPeriods of increased O22 consumption consumption
Exercise, seizures, hyperthermiaExercise, seizures, hyperthermia AnemiaAnemia Decreased arterial oxygenation Decreased arterial oxygenation
↓ ↓ Hb, ↓ PaOHb, ↓ PaO22
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Oxygen Extraction Ratio (Cont’d)Oxygen Extraction Ratio (Cont’d)
Decreases:Decreases: Increased cardiac outputIncreased cardiac output Skeletal muscle relaxationSkeletal muscle relaxation Peripheral shuntingPeripheral shunting Certain poisons (e.g., cyanide)Certain poisons (e.g., cyanide) HypothermiaHypothermia Increased arterial oxygenation Increased arterial oxygenation
↑ ↑ Hb, ↑ PaOHb, ↑ PaO22
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Mixed Venous Oxygen SaturationMixed Venous Oxygen Saturation SvO SvO22
Signals changes in the:Signals changes in the: C(a-v)OC(a-v)O22
VOVO22
OO22ERER
Normally about 75%Normally about 75%
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Mixed Venous Oxygen SaturationMixed Venous Oxygen Saturation SvO SvO2 2 (Cont’d)(Cont’d)
Decreases:Decreases: Decreased cardiac outputDecreased cardiac output ExerciseExercise SeizuresSeizures HyperthermiaHyperthermia
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Mixed Venous Oxygen SaturationMixed Venous Oxygen Saturation SvO SvO2 2 (Cont’d)(Cont’d)
Increases:Increases: Increased cardiac outputIncreased cardiac output Skeletal muscle relaxationSkeletal muscle relaxation Peripheral shuntingPeripheral shunting Certain poisons (e.g., cyanide)Certain poisons (e.g., cyanide) HypothermiaHypothermia
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Pulmonary Shunt FactionPulmonary Shunt Faction
QQss = = CcOCcO22 − CaO − CaO22
QQTT CcOCcO22 − CvO − CvO22
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Ventilated Alveolus
Ventilated Alveolus
AlveolusAlveolus
Pulmonary capillaryPulmonary capillaryOxygenated
bloodOxygenated
blood
Nonoxygenated blood
Nonoxygenated blood
Normal alveolar-capillary unit.Normal alveolar-capillary unit.
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Ventilated Alveolus
Ventilated Alveolus
AlveolusAlveolus
Pulmonary capillaryPulmonary capillaryOxygenated
bloodOxygenated
blood
Nonoxygenated blood
Nonoxygenated blood
Anatomic shunt.Anatomic shunt.
Anatomic shunt
Anatomic shunt
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AlveolusAlveolus
Pulmonary capillaryPulmonary capillaryNonoxygenated
bloodNonoxygenated
blood
Nonoxygenated blood
Collapsed Alveolus
or
Consolidated or Fluid-Filled
Alveolus
Collapsed Alveolus
or
Consolidated or Fluid-Filled
Alveolus
Types of capillary shunts.Types of capillary shunts.
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AlveolusAlveolus
Pulmonary capillaryPulmonary capillaryNonoxygenated
bloodNonoxygenated
blood
Nonoxygenated blood
Alveolus with Decreased Ventilation
or
Alveolus with a Diffusion Defect
Alveolus with Decreased Ventilation
or
Alveolus with a Diffusion Defect
Types of relative or shuntlike effects.Types of relative or shuntlike effects.
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Pulmonary ShuntingPulmonary Shunting
Need following information:Need following information: Barometric pressure Barometric pressure PaOPaO2 2
PaCOPaCO2 2
PvOPvO22
Hb concentrationHb concentration PAOPAO22 (partial pressure of alveolar oxygen)(partial pressure of alveolar oxygen) FIOFIO22
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Case Example:Case Example:Automobile Accident VictimAutomobile Accident Victim
A 22-year-old man is on a volume-cycled A 22-year-old man is on a volume-cycled mechanical ventilator on a day when the mechanical ventilator on a day when the barometric pressure is 755 mm Hg. The patient barometric pressure is 755 mm Hg. The patient is receiving an FIOis receiving an FIO22 of 0.60. The following of 0.60. The following
clinical data are obtained:clinical data are obtained: Hb: 15 g/dLHb: 15 g/dL PaOPaO22: 65 mm Hg (SaO: 65 mm Hg (SaO22 = 90%) = 90%) PaCOPaCO22: 56 mm Hg: 56 mm Hg PvOPvO22: 35 mm Hg (SvO: 35 mm Hg (SvO22 = 65%) = 65%)
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Case Example:Case Example:Automobile Accident Victim (Cont’d)Automobile Accident Victim (Cont’d)
With this information the followingWith this information the followingcan now be calculated:can now be calculated: PAOPAO22
CcOCcO2 2
CaOCaO2 2
CvOCvO22
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Case Example:Case Example:Automobile Accident Victim (Cont’d)Automobile Accident Victim (Cont’d)
PAOPAO22 = (P= (PBB − PH − PH22O) FIOO) FIO22 − PaCO − PaCO22 (1.25) (1.25)
= (755 − 47) 0.60 − 56 (1.25) = (755 − 47) 0.60 − 56 (1.25) = (708) 0.60 − 70= (708) 0.60 − 70= 424.8 = 424.8 − 70− 70= 354.8 = 354.8
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Case Example:Case Example:Automobile Accident Victim (Cont’d)Automobile Accident Victim (Cont’d)
CcOCcO22 = (Hb × 1.34) + (PAO = (Hb × 1.34) + (PAO22 × 0.003) × 0.003)
= (15 × 1.34) + (354.8 × 0.003)= (15 × 1.34) + (354.8 × 0.003)= 20.1 + 1.064= 20.1 + 1.064= 21.164 (vol% = 21.164 (vol% OO22))
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Case Example:Case Example:Automobile Accident Victim (Cont’d)Automobile Accident Victim (Cont’d)
CaOCaO22 = (Hb × 1.34 × SaO = (Hb × 1.34 × SaO22) + (PaO) + (PaO22 × 0.003) × 0.003)
= (15 × 1.34 × 0.90) + (65 × 0.003)= (15 × 1.34 × 0.90) + (65 × 0.003)= 18.09 + 0.195= 18.09 + 0.195= 18.285 (vol% O= 18.285 (vol% O22))
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Case Example:Case Example:Automobile Accident Victim (Cont’d)Automobile Accident Victim (Cont’d) CvOCvO22 = (Hb × 1.34 × SvO= (Hb × 1.34 × SvO22) + (PvO) + (PvO22 × 0.003) × 0.003)
= (15 × 1.34 × 0.65) + (35 × 0.003)= (15 × 1.34 × 0.65) + (35 × 0.003) = 13.065 + 0.105= 13.065 + 0.105 = 13.17 (vol% O= 13.17 (vol% O22))
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Case Example:Case Example:Automobile Accident Victim (Cont’d)Automobile Accident Victim (Cont’d)
QQSS == CcOCcO22 − CaO − CaO
QQTT CcO CcO22 − CvO − CvO22
== 21.164 − 18.28521.164 − 18.28521.164 − 13.1721.164 − 13.17
== 2.8792.879 7.9947.994
== 0.360.36
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Table 5-2. Clinical Significance of Pulmonary Shunting Table 5-2. Clinical Significance of Pulmonary Shunting
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Table 5-3. Oxygenation Index Changes Commonly Seen in Respiratory Diseases Table 5-3. Oxygenation Index Changes Commonly Seen in Respiratory Diseases
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HypoxemiaHypoxemia
HypoxemiaHypoxemia refers to an abnormally low refers to an abnormally low arterial oxygen tension (PaOarterial oxygen tension (PaO22) and is ) and is
frequently associated with hypoxia. frequently associated with hypoxia. Although hypoxemia may suggest tissue Although hypoxemia may suggest tissue
hypoxia, it does not necessary mean the hypoxia, it does not necessary mean the absolute existence of tissue hypoxia.absolute existence of tissue hypoxia. For example, a low arterial oxygen level may be For example, a low arterial oxygen level may be
offset by an increased cardiac output.offset by an increased cardiac output.
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Table 5-4. Hypoxemia Classifications* Table 5-4. Hypoxemia Classifications*
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HypoxiaHypoxia
HypoxiaHypoxia refers to low or inadequate oxygen refers to low or inadequate oxygen for aerobic cellular metabolism.for aerobic cellular metabolism.
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Table 5-5. Types of Hypoxia Table 5-5. Types of Hypoxia
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Cor PulmonaleCor Pulmonale
The term used to denote:The term used to denote: Pulmonary arterial hypertensionPulmonary arterial hypertension Right hypertrophyRight hypertrophy Increased right ventricular workIncreased right ventricular work Right ventricular failureRight ventricular failure
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Cor Pulmonale (Cont’d)Cor Pulmonale (Cont’d)
Three major causes:Three major causes: Increased viscosity of blood (polycythemia)Increased viscosity of blood (polycythemia) Increased vascular resistanceIncreased vascular resistance
• Caused by hypoxic vasoconstrictionCaused by hypoxic vasoconstriction Obliteration of the pulmonary capillary bedObliteration of the pulmonary capillary bed
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PolycythemiaPolycythemia
Increased red blood cell levelIncreased red blood cell level
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Hypoxic Vasoconstriction Hypoxic Vasoconstriction of the Lungsof the Lungs
Caused by decreased Caused by decreased PAOPAO22
Generalized pulmonary vasoconstriction Generalized pulmonary vasoconstriction combined with polycythemia leads to:combined with polycythemia leads to: Cor pulmonaleCor pulmonale Distended neck veinsDistended neck veins Peripheral edema and pitting edemaPeripheral edema and pitting edema
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Pitting edema. (From Bloom A, Ireland J: Pitting edema. (From Bloom A, Ireland J: Color atlas of diabetesColor atlas of diabetes, ed 2,, ed 2,London, 1992, Mosby-Wolfe.)London, 1992, Mosby-Wolfe.)