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80 Cards in this Set
- Front
- Back
diffusion
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Gas movement between the lungs and tissues occurs via simple diffusion
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Identify where the highest/lowest PO2 & PCO2 are found.
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Highest PO2 in air, lowest in cells. Highest PCO2 in cells, lowest in air.
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Define PAO2
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Alveolar partial pressure of oxygen
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Calculate PAO2
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PAO2=FIO2x (PB-47) - PACO2
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List normal values for PO2 and PCO2 of the venous blood returning to the lungs from the right side of the heart.
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PO2=100 mmHg
PCO2=40 mmHg |
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State how many times faster CO2 diffuses across the avleolar capillary than does O2?
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CO2 diffuses 20 times faster than O2
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Describe P50
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P50=partial pressure of O2 at which the Hb is 50% saturated, standardized to a pH of 7.40
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pH saturation value for a normal P50
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7.40
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PO2 saturation value for a normal P50
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26.6 mmHg
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Hb saturation value for a normal P50
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50%
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Define the Haldane effect
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the more oxygen that is bound to a hemoglobin molecule, the less CO2 will bind to that molecule
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Identify a normal A-a gradient P(A-a) O2
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Normal A-a gradient is 5-10 mmHg on room air, and no more than 65mmHg when 100% is breathed
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Describe what it means if the A-a gradient is elevated.
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if the gradient is high, it indicates a large difference between the alveolar and arterial PO2 values.
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A-a gradient formula
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P(A-a) O2 = PAO2-PaO2
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Describe the Bohr Effect
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pH alters the bonding of O2 to hemoglobin - this is known as the Bohr effect
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Conditions/factors that cause a decrease in Hb affinity for O2
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Acute acidosis
High CO2 Increased temperature High levels of 2,3-DPG Abnormal hemoglobin |
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Conditions/factors that cause an increase in Hb affinity for O2
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Acute alkalosis
Decreased PCO2 Decreased temperature Low levels of 2,3-DPG Carboxyhemoglobin Methemoglobin Abnormal hemoglobin |
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Shift in the oxyhemoglobin (O2Hb) dissociation curve to the Right.
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Decreased affinity for O2
More tissue oxygenation Increased H+ (lower pH) Increased PCO2 Increased Temp Increased 2,3-DPG |
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Shift in the oxyhemoglobin (O2Hb) dissociation curve to the Left.
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Increased affinity for O2
Less tissue oxygenation Decreased H+ (higher pH) Decreased PCO2 Decreased temp Decreased 2,3-DPG |
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What is the formula to calculate the total oxygen content of arterial and venous blood?
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CaO2=(PaO2 x 0.003) + (1.34 x Hb x SaO2)
CvO2=(PvO2 x 0.003) + (1.34 x Hb x SvO2) |
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Normal value for CaO2
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16-20 ml/dl
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Normal value for CvO2
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14-15 ml/dl
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Normal value PaO2
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>80 torr
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Normal value PvO2
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37-43 torr
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Normal value SaO2
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>95%
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Normal value SvO2
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70-76%
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Normal value Hb
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12-16 grams/100 ml blood or grams percent g%
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PaO2 is related to what form of oxygen?
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Physically dissolved oxygen
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What is the formula for Dissolved O2?
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ml/dl=PO2x0.003
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Identify the 2 components responsible for carrying oxygen in the blood.
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dissolved in the plasma & erythrocyte intracellular fluid - the majority of O2 is carried in a reversible chemical combination with hemoglobin (Hb) inside the RBC.
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Calculate the saturation of the arterial blood (SaO2) using the appropriate formula.
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SaO2=[HbO2/total Hb] x 100
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Identify the hemoglobin saturation of the arterial blood (SaO2) that correlates with a PO2 of 65 mmHg
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SaO2 90%
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Calculate cardiac output using the Fick Formula
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Qt=VO2/[C(a-v) O2x10]
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Compare Carbon Monoxide's (CO) affinity for hemoglobin to that of Oxygen's
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hemoglobin's affinity for carbon monoxide is more than 200 times greater than it is for oxygen
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Define PaCO2
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Dissolved plasma carbon dioxide
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What does decreased PaCO2 mean?
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it means the patient is having more ventilation
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What does an increase in PaCO2 mean?
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it means the patient is having less ventilation
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Explain the major ways that CO2 is transported in the blood - give the percentages for each for
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Dissolved in physical solution 8%, chemically combined with protein 12%, ionized as bicarbonate 80%
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Calculate oxygen delivery (DO2)
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DO2= C.O. x (CaO2 x 10)
C.O. = cardiac output |
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Define the term Hypoxia
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when oxygen delivery falls short of cellular needs, hypoxia occurs.
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When the pH is increased (hydrogen ion concentration (H+) is decreased), in which direction will the HbO2 Dissociation curve shift?
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To the "left"
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In what direction does the oxygen (HbO2) Dissociation Curve shift when the pH is decreased?
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To the "right"
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The Ventilation/Perfusion ratio (V/Q) represents:
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Changes in alveolar ventilation (VA) and pulmonary capillary blood flow (Qc)
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In which direction will the O2 Dissociation Curve shift, due to an increase in body temperature?
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To the right
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100% O2 may not be sufficient to achieve satisfactory arterial oxygen content under what condition?
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Hypoxemia due to physiological shunting.
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The impact of changes in blood pH on hemoglobin's affinity for oxygen is called the
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Bohr effect
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How would you describe hypoxia?
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tissue O2 delivery is inadequate to meet cellular needs
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What is the overall main goal of acid-base homeostasis?
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Maintain a normal blood pH
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With respect to the excretion of H+ and reabsorption, how will the kidneys respond if the blood PaCO2 is high?
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Excrete H+ and retain HCO3-
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What is the most common cause of hyperventilation in patients with respiratory disease?
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low arterial PaO2 (hypoxemia)
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An increase in body temperature will shift the oxygen dissociation curve in what direction?
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Right
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The _____Effect alters the position of the HbO2 Dissociation curve.
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Bohr
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In healthy young adults, what is considered a normal of PAO2-PaO2 gradient (A-a Gradient)?
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5 to 10 mmHg
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What contains the highest level of PCO2?
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Cells
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The normal total oxygen content of the blood is approximately____________
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19.5 mEq/L
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What is the normal CaO2-CvO2 (arteriovenous oxygen content difference) in a healthy adult at rest?
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5 mL/dL
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Which of the following approximate a normal P50?
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26.6
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A PaO2 of 100 mmHg is normally associated with a hemoglobin saturation (SaO2) of _______.
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97%
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What would be the approximate hemoglobin saturation (SaO2) associated with a PaO2 of 65 mmHg?
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90%
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Where is the lowest PO2 normally found?
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Cells
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The majority of oxygen (O2) is carried:
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Chemically combined with Hb
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The majority of carbon dioxide is carried:
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As bicarbonate ion (HCO3)
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Calculate Oxygen Delivery (DO2)
CaO2=16ml/dl & cardiac output 6.0 L/min. |
DO2= 6 (16x10)
DO2= 6 (160) DO2= 960 ml |
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There is a total of 14 g/dL hemoglobin (Hb) in the blood, of which 7.5 g is HbO2. What is the calculated SaO2 (%)?
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SaO2 = 7.5/14x100
SaO2 = 54% |
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While receiving an oxygen concentration (FIO2) of 65%, a patient's PaO2 is 50 mmHg. What is most likely causing this problem?
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Significant shunting is present
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Hyperventilation is normally seen as the compensatory mechanism for___________.
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Metabolic Acidosis
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Why is the bicarbonate buffer system, considered an open buffer system?
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Its acid component (carbonic acid) is volatile.
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What is the ratio of HCO3- to dissolved CO2 that results in a pH of 7.40?
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20:1
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What describes respiratory alkalosis?
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The PaCO2 is less than 35 mmHg
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Primary metabolic alkalosis is associated with_____________?
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An increase in buffer base
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What might be used to correct metabolic alkalosis?
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Restoring normal fluid volume
Restoring normal K+ and Cl- levels |
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An increase in the hydrogen ion concentration [H+] of the blood due only to an increase in the arterial PCO2 (hypercapnia), best describes which acid-base disorder?
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Acute respiratory acidosis
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Interpret the following set of ABG values: pH 7.22, PCO2 60mm Hg, HCO3 24 mEq/L
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Acute (uncompensated) respiratory acidosis
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Describe the state of "alkalemia"?
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the HCO2:CO2 ratio exceeds 30:1 and The blood pH exceeds 7.45
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What is the normal range of PAO2 - PaO2 gradient (A-a gradient) for a healthy young adult breathing room air?
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5 to 10 mmHg
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Which equation describes O2 delivery to the tissues?
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DO2 = Qt [CaO2 x 10]
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Describe the PaO2. What is it?
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Oxygen dissolved in the blood plasma.
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Under what conditions may even the delivery of 100% O2 not be sufficient to acheive a satisfactory arterial oxygen content?
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When physiologic shunting is present.
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A patient with a normal PaO2, SaO2 and cardiac output is exhibiting signs and symptoms of tissue hypoxia. What is the most likely cause?
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Anemic hypoxia
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How is the vast majority of O2 carried in the blood?
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Combined with Hb
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