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80 Cards in this Set
- Front
- Back
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What structures make up the conducting zone?
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The nose, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles.
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What is the function of the conducting zone?
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To warm, humidify, and filter the air before it reaches the critical gas exchange region.
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How many divisions of the trachea/bronchi/bronchiole system are there?
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There are 23 such divisions.
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What effects does sympathetic innervation have on the conducting airway?
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The walls of the conducting airways contains smooth muscle.
Sympathetic adrenergic neurons (and circulating epinephrine released from the adrenal medulla) activate β2 receptors on bronchial smooth muscle, which leads to relaxation and dilation of the airways. |
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What effects does parasympathetic innervation have on the conducting airway?
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Parasympathetic cholinergic neurons activate muscarinic receptors, which leads to contraction and constriction of the airways.
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What type of drugs are used to treat asthma?
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β2-adrenergic agonists (e.g. epinephrine, isoproterenol, albuterol), which are used to dilate the airways.
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What structures make up the respiratory zone?
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Respiratory bronchioles, alveolar ducts, and the alveolar sacs.
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What are transitional structures?
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Respiratory bronchioles are transitional structures. Like the conducting airways, they have cilia and smooth muscle, but they are also considered part of the gas exchange region because alveoli occasionally bud off their walls.
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How many alveoli does each lung contain?
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Approximately 300 million alveoli.
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What is the role of type II pneumocytes?
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Type II pneumocytes synthesize surfactant and have regenerative capacity for the type I and type II pneumocytes.
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Which structures of the conducting zone contain cartilage?
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Only the trachea and bronchi contain cartilage.
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Where is pulmonary blood flow the highest? The lowest? Why?
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Pulmonary blood flow is highest at the base of the lungs. It is lowest at the apex (top) of the lungs. This is due to gravitational effects.
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What is tidal volume (Vt)?
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Normal, quiet breathing. It is approximately 500 mL and includes the volume of air that fills the alveoli plus the volume of air that fills the airways.
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What is inspiratory reserve volume?
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The additional volume that can be inspired above tidal volume. It is approximately 3000 mL.
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What is expiratory reserve volume?
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The additional volume that can be expired below tidal volume, approximately 1200 mL.
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What is the volume of gas that remains in the lungs after a maximal forced expiration?
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Residual volume, which is approximately 1200 mL. This cannot be measured by spirometry.
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What is the inspiratory capacity (IC)?
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The inspiratory capacity is composed of the tidal volume plus the inspiratory reserve volume.
Approximately 3500 mL (500 + 3000) |
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What is the functionary residual capacity (FRC)?
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FRC is the volume remaining in the lungs after a normal tidal volume is expired and can be thought of as the equilibrium volume of the lungs. It is composed of the expiratory reserve volume plus the residual volume.
Approximately 2400 mL (1200 + 1200) |
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What is the vital capacity?
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Vital capacity is the volume that can be expired after maximal inspiration. It is composed of the inspiratory capacity plus the expiratory reserve volume.
Approximately 4700 mL (3500 + 1200) |
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What is the volume of total lung capacity?
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Total lung capacity (TLC) includes all of the lung volumes (Vital capacity + residual volume).
It is approximately 5900 mL (4700 + 1200) |
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What is the anatomic dead space? What is its volume?
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The anatomic dead space is the volume of the conducting airways, including the nose (and/or mouth), trachea, bronchi, and bronchioles. The volume is approximately 150 mL.
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What is the definition of physiologic dead space?
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Physiologic dead space is the total volume of the lungs that does not participate in gas exchange. It includes the anatomic dead space of the conducting airways plus a functional dead space in the alveoli.
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What is a reason the physiologic dead space can become larger than the anatomic dead space?
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In normal persons, the physiologic dead space is nearly equal to the anatomic dead space. When the physiologic dead space is larger than the anatomic dead space, there may be a ventilation/perfusion defect.
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What is the equation to calculate the volume of physiologic dead space?
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Vd = Vt*(Paco2 - Peco2)/Paco2
Volume of the physiologic dead space is the tidal volume multiplied by a fraction that represents the dilution of alveolar Pco2 by dead space air. |
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What is the difference between minute ventilation and alveolar ventilation rates?
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Minute ventilation is the total rate of air movement into and out of the lungs. Alveolar ventilation rate is the same, but it corrects for the physiologic dead space.
Minute ventilation = Vt x Breaths/min Alveolar ventilation Va = (Vt-Vd) x Breaths/min Vt = tidal volume (mL) Vd = physiologic dead space (mL) |
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What is forced vital capacity (FVC)?
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Forced vital capacity is the total volume of air that can be forcibly expired after a maximal inspiration
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What is FEV1?
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FEV1 is the volume of air that can be forcibly expired in the first second.
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What is the value of FEV1/FVC in a normal person?
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FEV1/FVC = ~0.8, meaning that 80% of the vital capacity can be forcibly expired in the first second.
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What is the FEV1/FVC in a patient with asthma?
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In obstructive lung diseases like asthma, both FVC and FEV1 are decreased, but FEV1 is decreased more. Thus, FEV1/FVC is decreased.
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What is the FEV1/FVC in a patient with fibrosis?
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In patients with restrictive lung diseases such as fibrosis, both FVC and FEV1 are decreased, but they decrease the same or FEV1 is decreased less than FVC. Thus, in fibrosis FEV1/FVC is the same or increased.
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What is the most important muscle for inspiration?
What muscles are used for inspiration during exercise? |
The diaphragm.
During exercise, the external intercostal muscles and accessory muscles (scalene muscles and sternomastoids) |
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What muscles are used for expiration? During exercise?
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Expiration is normally a passive process.
During exercise (or disorders like asthma), the muscles of expiration include abdominal muscles, internal intercostal muscles, and internal and external obliques. |
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What happens during a pneumothorax?
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Normally, intrapleural pressure is -5 cm H2O. When a sharp object punctures the intrapleural space, air is introduced into the space, and intrapleural pressure suddenly becomes equal to atmospheric pressure.
- There is no longer a negative intrapleural pressure to hold the lungs open, and the lungs collapse. - There is no longer a negative intrapleural pressure to keep the chest wall from expanding, and the chest wall springs out. |
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What occurs when the volume is FRC?
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At FRC, because they are elastic structures, the lungs "want" to collapse and the chest wall "wants" to expand. At FRC, the collapsing force on the lungs is exactly equal to the expanding force on the chest wall. Thus, the combined system neither has a tendency to collapse nor to expand.
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What occurs when the volume is less than FRC?
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When the volume in the system is less than FRC (i.e., the subject makes a forced expiration), there is less volume in the lungs and collapsing (elastic) force of the lungs is smaller. The expanding force on the chest wall is greater, however, and the combined system "wants" to expand.
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What occurs when the volume is greater than FRC?
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When the volume in the system is greater than FRC (i.e., the subject inspires from the spirometer), there is more volume in the lungs and collapsing (elastic) force of the lungs is greater. The expanding force of the chest wall is smaller, and the combined system "wants" to collapse.
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What happens to compliance in patients with emphysema?
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Emphysema is associated with loss of elastic fibers in the lungs. As a result, the compliance of the lungs increases. As a result, at a given volume, the collapsing (elastic recoil) force on the lungs is decreased.
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Why do patients with emphysema have a barrel-shaped chest?
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Because of the decreased tendency to collapse, the combined lung and chest-wall system seeks a new higher FRC, where the two opposing forces (expansion and collapse) can be balanced. A patient with emphysema breathes at higher lung volumes, and will have a barrel-shaped chest.
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What happens to compliance in patients with fibrosis?
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Fibrosis is associated with stiffening of lung tissues and decreased compliance. The lung and chest-wall system will seek a new lower FRC.
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What does the law of Laplace state?
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The law of Laplace states that the pressure tending to collapse an alveolus is directly proportional to the surface tension generated by the molecules of liquid lining the alveolus and inversely proportional to alveolar radius.
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What is the formula for collapsing pressure (Law of Laplace)?
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P = 2T/r
P = Collapsing pressure on alveolus (dynes/cm^2) or Pressure required to keep alveolus open T = Surface tension (dynes/cm) r = Radius of the alveolus (cm) |
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In simple words, describe the law of Laplace.
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The tendency for an alveolus to collapse increases as the radius decreases.
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What is the most important constituent in surfactant?
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Dipalmitoyl phosphatidylcholine (DPPC).
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What occurs in neonatal respiratory distress syndrome?
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Surfactant is lacking. Infants born before gestational week 24 will never have surfactant, and infants born between weeks 24 and 35 will have uncertain surfactant status. Thus, without surfactant, small alveoli have increased surface tension and increased pressures, and will collapse. Lung compliance will be decreased and the work of inflating the lungs during breathing will be increased.
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What is the formula for pulmonary vascular resistance (PVR)?
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PVR = P(pulm.artery) - P(L.atrium)/ Cardiac Output
P(pulm.artery) = pressure in pulmonary artery P(L.atrium) = pulmonary wedge pressure |
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What does Poiseuille's law sate?
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Resistance is inversely proportional to the radius of an airway (to the fourth power), and directly proportional to the length of the airway and viscosity of inspired air.
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What is Poiseuille's law?
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R = 8ηl/πr^4
R = Resistance η = Viscosity of inspired air l = Length of the airway r = Radius of the airway |
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What are the sites of highest airway resistance?
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The medium-sized bronchi. Because of the parallel arrangement of the smallest airways, the total resistance is less than the individual resistance.
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What factors constrict the airways, decrease the radius, and increase the resistance to flow?
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Parasympathetic stimulation, irritants, and the slow-reacting substance of anaphylaxis (asthma)
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What factors relax the airways, increase the radius, and decrease the resistance to airflow?
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Sympathetic stimulation and sympathetic agonists (isoproterenol) dilate the airways via β2 receptors.
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What is the difference in intrapleural pressure when expiration (passive) and forced expiration?
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In passive expiration, intrapleural pressure (which was -6 cm H2O during inspiration) returns to its resting value (-3). During a forced expiration, intrapleural pressure actually becomes positive. This positive intrapleural pressure compresses the airways and makes expiration more difficult.
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What is asthma? What is it characterized by?
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Asthma is an obstructive disease in which expiration is impaired.
Characterized by: Decreased FVC Decreased FEV1 Decreased FEV1/FVC Air that should have been expired is not, leading to air trapping and increased FRC. |
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What is COPD? What is it characterized by?
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COPD is a combination of chronic bronchitis and emphysema. It is an obstructive disease with increased lung compliance in which expiration is impaired.
Characterized by: Decreased FVC, FEV1 Decreased FEV1/FVC Air that should have been expired is not, leading to air trapping, increased FRC, and a barrel-shaped chest. |
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What are "pink puffers"? "Blue bloaters"?
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"Pink puffers" (primarily emphysema) have mild hypoxemia and normocapnia (normal PCO2).
"Blue bloaters" (primarily bronchitis) have severe hypoxemia with cyanosis and hypercapnia (increased PCO2). They have right ventricular failure and systemic edema. |
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What condition leads to a decrease in all lung volumes, decreased lung compliance in which inspiration is impaired, and an increased FEV1/FVC?
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Fibrosis (restrictive disease).
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What are the values of partial pressure of O2 and CO2 for alveolar air, systemic arterial blood, and mixed venous blood?
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Alveolar air
PO2 = 100 mmHg PCO2 = 40 Systemic Arterial Blood PO2 = slighty <100 (due to physiologic shunt) PCO2 = 40 Mixed Venous Blood PO2 = 40 mmHg PCO2 = 46 |
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In hemoglobin, what is the heme moiety?
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Iron-containing porphyrin. The iron is in the ferrous state (Fe2+), which binds O2. Iron in the ferric state (Fe3+) does not bind O2.
Mnemonic: Ferris (Ferrous) was with 2 (Fe2+) people on his adventure. |
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What is hemoglobin F composed of?
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In fetal hemoglobin, the β chains are replaced by γ chains. Thus, fetal hemoglobin is α2γ2.
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At which values of PO2 is hemoglobin 100% saturated?
75% saturated? 50% saturated? |
100% saturated: PO2 = 100 mmHg
75% saturated: PO2 = 75 mmHg 50% saturated: PO2 = 50 mmHg |
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What does a shift to the right in the hemoglobin-O2 dissociation curve indicate? What causes this?
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Shifts to the right occur when the affinity of hemoglobin for O2 is decreased.
Causes: Increases in PCO2 Decreases in pH Increases in temperature (e.g. during exercise) Increases in 2,3-DPG concentration (e.g. living at high altitudes) |
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What does a shift to the left in the hemoglobin-O2 dissociation curve indicate?
What conditions cause this? |
Shifts to the left occur when the affinity of hemoglobin for O2 is increased.
Causes: Decreased PCO2 Increased pH Decreased temperature Decreased 2,3-DPG concentration |
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What is 2,3-DPG? When does 2,3-DPG production increase?
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2,3-diphosphoglycerate (2,3-DPG) is a byproduct of glycolysis in red blood cells. 2,3-DPG binds to the β chains of deoxyhemoglobin and reduces their affinity for O2.
2,3-DPG production increases under hypoxic conditions (i.e. high altitude). |
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Does HbF cause the curve to shift to the left? What about the binding of CO to hemoglobin?
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HbF: left shift.
HbF does not bind 2,3-DPG as strongly as adult hemoglobin, which results in increased affinity of HbF for O2. Carbon monoxide (CO) poisoning: left shift |
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What is the A-a gradient used for? What is the normal A-a gradient?
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A-a gradient = PAO2 - PaO2
Alveolar - arterial A-a gradient can be used to compare causes of hypoxemia. Normal A-a gradient < 10 mmHg |
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What is the A-a gradient for the following conditions?
High altitude Hypoventilation Diffusion defect (e.g. fibrosis) V/Q defect Right-to-left shunt |
High altitude: Normal
Hypoventilation: Normal Diffusion defect (e.g. fibrosis): Increased V/Q defect: Increased Right-to-left shunt: Increased |
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What are the three forms of CO2 in the blood?
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1. Dissolved CO2
2. Carbaminohemoglobin 3. HCO3- (major form, 90%) |
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How does CO2 get converted to HCO3-? Where is it converted?
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CO2 diffuses into RBCs, where it combines with H2O to form H2CO3. This reaction is catalyzed by carbonic anhydrase.
H+ and HCO3- are dissociated from H2CO3. HCO3- leaves the RBC in exchange for Cl- (chloride shift). |
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What are the three zones? What is the comparison of the pressures?
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Zone 1: blood flow is lowest
Alveolar pressure > arterial pressure > venous pressure Zone 2: blood flow is medium Arterial pressure > alveolar pressure > venous pressure Zone 3: blood flow is highest Arterial pressure > venous pressure > alveolar pressure |
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In the lung, what happens during hypoxia? Why?
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Hypoxia causes vasoconstriction. Physiologically, this effect is important because local vasoconstriction redirects blood away from poorly ventilated, hypoxic regions of the lung and toward well-ventilated regions.
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What is the normal V/Q ratio?
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V/Q = 0.8
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Where is blood flow highest? Where is ventilation highest?
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Blood flow AND ventilation are highest at the base of the lungs.
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Where is the V/Q ratio highest? Where is the V/Q ratio lowest?
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The V/Q ratio is highest at the apex (3.0), and lowest at the base (0.6).
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What is a shunt? What can cause a shunt?
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V/Q = 0
When the airways are completely blocked (e.g. by a steak caught in the trachea). |
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What is dead space?
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V/Q = infinite.
When the blood flow to a lung is completely blocked (e.g. by an embolism) |
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What nerves relay sensory information? Where does the information go?
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Vagus nerve and glossopharyngeal nerve relays information to the dorsal respiratory group.
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In what nerve does the output to the diaphragm travel?
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Phrenic nerve
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Where are the central and peripheral chemoreceptors located?
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Central chemoreceptors are in the medulla.
Peripheral chemoreceptors are in the carotid and aortic bodies. |
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How does increased CO2 activate the central chemoreceptors?
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CO2 diffuses from arterial blood into the CSF (CO2 is lipid soluble). In the CSF, CO2 combines with H2O to produce H+ and HCO3-. The resulting H+ acts directly on the central chemoreceptors. Thus, increases in PCO2 and [H+] stimulate breathing, and decreases in PCO2 and [H+] inhibit breathing.
Metabolic acidosis -> hyperventilation |
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In response to exercise, does the arterial PO2 and PCO2 change? What about the Venous PCO2? V/Q ratios?
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The arterial PO2 and PCO2 do not change in response to exercise. Venous PCO2 does increase.
The V/Q ratios are more evenly distributed in the lung during exercise. |
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In the context of adaptation to high altitude, what are the changes to the following parameters:
Alveolar PO2 Arterial PO2 Ventilation rate Arterial pH Hemoglobin concentration 2,3-DPG concentration Hemoglobin-O2 curve Pulmonary vascular resistance |
Alveolar PO2: decreased (resulting from decreased barometric pressure)
Arterial PO2: decreased (hypoxemia) Ventilation rate: increased Arterial pH: Increased (respiratory alkalosis) Hemoglobin concentration: Increased (polycythemia) 2,3-DPG: Increased Hemoglobin-O2 curve: shift to right Pulmonary vascular resistance: increased (hypoxic vasoconstriction) |
