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26 Cards in this Set
- Front
- Back
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Where does gas exchange actually occur? Where does it not occur?
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Gas exchanges with the pulmonary capillary blood only in the alveoli and the respiratory bronchioles (acinus). The tracheobronchial system, the larynx, and pharynx are not useful in gas exchange (anatomic dead space).
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What affects the levels of anatomic dead space in different people?
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ADS is equal in ml to body wt in lbs
ADS depends on positions, sex, size, age. ADS decreases with PSNS stimulation ADS icnreases with sympathetic stimulations |
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What is the average tidal volume that a person breathes in?
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The average person breathes in a tidal volume of 450ml.
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How much of the tidal volume ends up in the alveoli? in the dead space?
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About 2/3rds of the tidal volume (300ml) ends up in the alveoli and about 1/3rd of the tidal volume (150ml) occupies dead space.
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If you are breathing 10 breaths per minute, what will be the ventilation at the alveoli? the dead space? the mouth?
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For the Alveoli: 300ml/breath x 10 breaths per min = 3L/min
For the Dead Space: 150ml/breath x 10 breaths/min = 1.5 L per minute For the mouth: 3.0L/min + 1.5L/min = 4.5L/min |
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How is air conditioned as it passes through the airway system?
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It is warmed: 98.6 degrees
It is mositened: fully saturated with water vapor (P-H20 = 47mmHg at 37 degrees C) It is cleaned -- free of particles larger than 10 microns |
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What are the 2 types of lung disease?
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Obstructive Lung Diseases
-Asthma -Chronic Bronchitis -Emphysema -COPD Restrictive Lung Diseases -Interstitial Fibrosis -Chest Wall Abnormalities |
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Compare interstitial fibrosis, asthma, chronic bronchitis, emphysema, and COPD.
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In interstitial fibrosis, fibrous strands are deposited in the interstitial spaces ebtween alveolar membranes and capillaries, but the airways are normal.
In asthma, the airways are constricted by muscle spasms and edema, but the alveoli are normal In chronic bronchitis, the airways become plugged by excessive secretions from hypertrophied submucosal glands and increased numbers of goblet cells, but the alveoli are normal. In emphysema, the distal alveoli have lost their septa and have become confluent and distended. COPD is a variable combination of chronic bronchitis and emphysema. |
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Pathophysiology of interstitial fibrosis
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Undigestible particles deposited in interstitium.
Chronic irritation (e.g. silica, asbestos) in interstitium leads to scarring. Alveolar-capillary membrane is thickened. Pathway for O2 tranport is lengthened. Lungs are small and stiff and difficult to expand on inspiration. The airways are normal. |
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Pathophysiology of chronic bronchitis
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Irritation (e.g. smoking) can cause the proliferation of mucus cells and the loss of ciliated cells. This leads to stagnant mucus buildup, which can grow irritant bacteria and stimulate an inflammatory response (WBC recruitment, vasodilation). There are more submucosal glands (>40% of wall thickness).
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Pathophysiology of asthma
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Hypertrophied smooth muscle cells that are hyperreactive (to vagal stimulation-- e.g. metacholine test)
-vasodilation --> edema -increased mucus, eosinophils -normal alveoli |
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Describe the structural changes in emphysema
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In emphysema the walls of the small airways are very thin.
Imbalance in trypsin-like enzyme release and inactivation by antitrypsin in acinus Collagen fibers in alveolar septa and small airways are degraded Small airways (like cellophane) collapse on expiration Air is trapped |
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Describe the values obtained by spirometry, and what the patient has to do to produce those values.
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Function Residual Capacity: Patient quietly breathes out, leaving roughly 2 liters in the lungs.
Tidal volume:After having exhaled, the patient breathes in and out normally. This volume is the tidal volume, roughly half a liter. Vital Capacity: Back at baseline, patient breathes in as deeply as possible and then forces all the air out of his lungs to get the Vital Capacity. Residual Volume: Because it's impossible to force all the air out, the RV = ~1L. Total Lung Capacity: is the sum of the Vital Capacity and the Residual Volume. |
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What could decrease the vital capacity of lungs?
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-stiff lungs (e.g. pulmonary edema, interstitial fibrosis)
-deformed chest (e.g. kyphoscoliosis, obesity) -space occupying lesions (e.g. pleural effusion, cysts) -collapsed lung (pneumothorax) -muscle weakness (polio, Guillain-Barre) |
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When lung compliance increases, TLC...
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When lung compliance increases (emphysema), TLC increases (barrel chest).
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When chest wall compliance decreases, RV...
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When chest wall compliance decreases (kyphoscoliosis), RV increases.
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What cannot be measured by spirometry alone? How are these values obtained?
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The RV, FRC, and TLC cannot be measured by spirometry alone, because one does not know the amount of air left in the lungs after breathing out.
These values can be obtained through helium dilution, or measuring FRC via Thoracic gas volume. |
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How does helium dilution work?
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Helium dilution is where a known volume/concentration of helium is allowed to equilibriate with a patient's lungs. The concentration (the same in and out of the lung) can be used to calculate the volume.
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How do the spirometry graphs of emphysema and interstitial fibrosis compare to normal?
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A patient with emphysema typically has a large RV, FRC (baseline), and total lung capacity.
On the other hand, the lungs of a patient with interstitial fibrosis are scarred, shriveled up, and small. It is no surprise that all the lung volumes are small in this condition. |
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Describe the Functional Residual Capacity, and how it is affected by different conditions.
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FRC is the lung volume where the outward pull of the chest wall is balanced by the inward pull of the lung
FRC is increased in emphysema FRC is decreased in interstitial frbrosis FRC is less than the thoracic gas volume in pts with emphysema because of gas pockets. |
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What are the alveolar, intrathoracic, and intra-abdominal pressures at rest and during a quiet inspiration?
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At rest, the alveolar pressure is 760mmHg, Intraabdominal pressure is 760mmHg, and intrathoracic pressure 758mmHg.
During inspiration, alveolar pressure is 758mmHg, intraabdominal pressure is 762mmHg, and intrathoracic pressure is 756mmHg. |
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Describe the alveolar, intrathoracic, and intraabdominal pressures in
1) a woman exercising 2) an asthmatic woman 3) a woman with interstitial fibrosis |
These three women are using their accessory muscles of inspiration to lower intrathoracic pressure to the same level of 710mmHg. The alveolar pressure will be a little higher (e.g. 715) in the exercising and asthmatic women, but it will be substantially higher (750) in the interstitial fibrosis patient. Ventilation will be similar with IF, asthma, but much higher in the exercising woman.
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How is dynamic lung compliance related to the frequency of breathing in a normal person?
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Dynami lung compliance is snormally independent of the frequency of breathing. However, in a patient with early emphysema the dynamic compliance decreases as the respiration rate increases.
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When is chest wall compliance decreased? What is it normally?
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Chest wall compliance is decreased in deformities of the thoracic spine, e.g., kyposcoliosis. It is decreased in marked obesity which can lead to hypoventilaiton at night. Chest wall compliance is normally about equal to lung compliance.
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What is the L/S Ratio? What does it tell you?
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The Lecithin/Sphingomyelin ratio tells you the risk for insufficient surfactant production in a newborn. If it is less than 2 (esp. 1.5) than there is concern that the baby will be born in respiratory distress. The obstetrician might then try to delay delivery or give steroids to mature the surfactant production.
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Recite how decreased surfactant leads to Respiratory Distress
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Decreased Surfactant --> Increased surface tension --> 1) Non-compliant lungs -> Increased work of breathing -> Respiratory distress 2) Increased alveolar recoil -> a) interstitial/intraalveolar edema -> hypoxemia -> cyanosis b) decreased lung volume -> atelectasis -> i) increased pulmonary vascular resistance -> Increased RV, RA pressures -> shunting of deoxy Hb through PFO -> hypoxemia ii) Decreased Va/Qc ratio -> Hypoxemia
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