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74 Cards in this Set
- Front
- Back
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definition of tidal volume
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volume inspired with each normal breath
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definition of IRV
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volume that can be inspired over and above the tidal volume (with exercise)
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definition of ERV
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volume that can be expired after expiration of tidal volume
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definition of residual volume
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volume that remains in the lungs after a maximal expiration... Cannot be measured by spirometry
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definition of anatomic dead space
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volume of the conducting airways
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what is the "normal" anatomic dead space
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approx. 150 ml
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definition of physiologic dead space
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volume of the lungs that does not participate in gas exchange
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what is the equation for physiologic dead space?
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Vd = Vt * (PaCO2 - PeCO2)/PaCO2
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what is the equation for alveolar ventilation?
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alveolar ventilation = (Vt - Dead space) * breaths/min
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definition of functional residual capacity
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sum of ERV and RV; volume remaining in lungs after Vt is expired
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what is the normal FEV1?
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80% of the FVC
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What happens to FEV1 in obstructive lung diseases?
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FEV1 reduced more than FVC, so FEV1/FVC is decreased
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What happens to FEV1/FVC in restrictive lung disease?
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e.g. fibrosis, both FEV1 and FVC are reduced and FEV1/FVC is normal or increased
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what is the most important muscle for inspiration?
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diaphragm
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what is hysteresis
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the difference in the P-V curves of inspiration and expiration
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what happens to the FRC in a patient with emphysema and why?
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FRC increases due to increased compliance of the lung. The lung reduces its tendency to collapse and "traps" the air that failed to be expired from a normal cycle.
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What happens to the FRC in a patient with fibrosis?
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lung compliance is decreased, and tendency of the lung to collapse is increased, so FRC decreases
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what is the effect of surfactant on alveoli?
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it reduces the surface tension, and, therefore the opening pressure of the alveoli (Laplace's law). This results in a decreased tendency of alveoli to collapse
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where is surfactant produced?
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type II alveolar cells
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what is the primary composition of surfactant?
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dipalmitoyl phosphatidylcholine (DPPC)
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what is the earliest time surfactant is produced in the fetus?
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24 weeks
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how does one tell if a fetus is producing mature levels of surfactant?
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lecithin:sphingomyelin ratio > 2:1 in amniotic fluid
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according to Poiseuille's law, what is the relationship between resistance of an airway and the radius?
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R is inversely proportional to the r^4
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where is the major site of airway resistance?
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medium-sized bronchi
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What class (and example) of drug causes dilation of airways?
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Beta-2 agonists (e.g. isoproterenol)
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at what point in the breathing cycle is alveolar pressure equal to 0?
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at FRC, just before inspiration.
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how does one measure intrapleural pressure?
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with a balloon catheter in the esophagus
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why do patients with COPD expire through pursed lips?
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during forced expiration a positive intrapleural pressure is created that collapses the airways. Pursing the lips creates enough back-pressure to maintain airway patency
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What are general characteristics of COPD?
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obstructive disease with increased lung compliance. FEV1 is markedly decreased, FVC is decreased, FEV1/FVC is decreased and FRC is increased
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What are characteristics of a "pink puffer"
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primarily emphysema, have mild hypoxemia, normocapnia.
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what are characteristics of 'blue bloaters?'
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primarily bronchitis, have severe hypoxemia with cyanosis, do not maintain alveolar ventilation --> hypercapnia; right ventricular failure and systemic edema. must have productive cough for >3 consecutive months in >= 2 years
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what are characteristics of pulmonary fibrosis?
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restrictive disease with decreased lung compliance. inspiration is impaired; decrease in ALL lung volumes, FEV1/FVC is increased
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what is the equation to correct for water vapor and PO2 in humidified tracheal air?
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P(total) = (760mmHg - 47mmHg) * 0.21 = 150 mmHg P(O2)
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what is the normal P(O2) in normal humidified tracheal air?
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150 mmHg
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what limits gas exchange in pulmonary capillaries normally?
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perfusion --> partial pressures of gases equilibrate early in the capillary
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what limits gas exchange in the pulmonary capillaries under strenuous exercise?
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diffusion --> perfusion is increased to a point that maximum gas exchange is achieved limited by the rate at which the gases can cross the alveolar membranes
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what limits gas exchange in fibrosis?
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thickness of membrane increases
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what limits gas exchange in emphysema?
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surface area is decreased
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what molecule causes off-loading of O2 from Hb in tissues?
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2,3-diphosphoglycerate
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what is the composition of fetal Hb and how are its properties different from adult Hb?
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composition: 2 alpha and 2 gamma chains; this causes a left-shift in the saturation curve resulting in increased affinity for O2 due to decreased affinity to 2,3-DPG
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what is the equation for O2 content of blood?
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O2 content = (O2-binding capacity * % saturation) + dissolved O2
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which binding site of Hb has the highest affinity for O2? Why is this important?
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the fourth binding site --> it allows maximal loading of O2 in the lungs and unloading in the tissues
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What causes a right-shift in the Hb-O2 dissociation curve?
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increased P(CO2)
decreased pH increased temperature increased 2,3-DPG |
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What causes a left-shift in the Hb-O2 dissociation curve?
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decreased P(CO2)
increased pH decreased temperature decreased 2,3-DPG |
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what is normal pulmonary arterial pressure?
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15 mmHg
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Describe the pressure and perfusion relationships in Zone 1 alveoli
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alveolar pressure > arterial pressure > venous pressure
Q is greatly decreased, V is decreased and V/Q is increased blood flow is lowest |
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Describe the pressure and perfusion relationships in Zone 2 alveoli
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arterial pressure > alveolar pressure > venous pressure
Q, V and V/Q are "normal" gas transfer is maximized |
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Describe the pressure and perfusion relationships in Zone 3 alveoli
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arterial pressure > venous pressure > alveolar pressure
Q is greatly increased, V is increased and V/Q is reduced blood flow is highest |
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what is the effect of hypoxia on pulmonary vasculature?
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it causes vasoconstriction in order to redirect flow away from poorly ventilated hypoxic regions of the lung to those that are better ventilated
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Where are right-to left shunts seen and what is the result?
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Tetralogy of Fallot; result in a decrease in arterial P(O2)
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where are left-to-right shunts seen and what is the result?
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paten ductus arteriosus or traumatic injury; do not result in decrease in arterial P(O2). most are asymptomatic.
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What is the normal V/Q ratio?
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0.8
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What are the partial pressures of CO2 and O2 in pulmonary capillaries of obstructed airways?
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in a physiologic shunt, Pa values approach venous values: Pa(O2) = 40 mmHg and Pa(CO2) = 46 mmHg
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What are the partial pressures of CO2 and O2 in alveoli of obstructed pulmonary capillaries?
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in physiologic dead space, the partial pressures of O2 and CO2 approach that of humid air: P(O2) = 150 mmHg and P(CO2) = 0 mmHg
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Where is the medullary respiratory center located?
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in the reticular formation
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What is responsible for inspiration and generates basic rhythm of breathing?
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Dorsal respiratory group
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From where does the input to the dorsal respiratory group come?
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vagus (chemoreceptors and mechanoreceptors) and glossopharyngeal (chemoreceptors) nerves
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Where does the output of the dorsal respiratory group go?
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along the phrenic nerve to the diaphragm
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What is the function of the ventral respiratory group and when is it activated?
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function is expiration, activated during exercise
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What and where is the apneustic center?
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stimulates inspiration; located in lower pons
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Where/what is the pneumotaxic center?
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located in the upper pons and inhibits inspiration
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where are the central chemoreceptors for breathing and what stimuli increase breathing rate?
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medulla; decreased pH (or increased CO2 which combines with water to make H+) of CSF
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where are the peripheral chemoreceptors for breathing and what stimuli increase breathing rate?
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carotid and aortic bodies; decreased P(O2) (if <60mmHg), decreased pH, increased P(CO2)
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What are J receptors and what do they affect?
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located in alveolar walls, close to capillaries. they are activated by engorgement of pulmonary capillaries (as in left heart failure) to cause rapid shallow breathing
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what happens to the mean values of arterial P(O2) and P(CO2) during exercise
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they do not change
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what happens to physiologic dead space during exercise?
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it decreases
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what are physiologic adaptations in high altitude?
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alveolar P(O2) is decreased, arterial P(O2) is decreased (hypoxemia), hyperventilation, respiratory alkalosis, increased EPO, increased 2,3-DPG, hypoxic pulmonary vasoconstriction
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What structures perforate the diaphragm and at what levels?
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IVC (T8), esophagus (T10), vagus (T10), aorta (T12), thoracic duct (T12), azygous vein (T12).
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By what is the diaphragm innervated?
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phrenic nerve (C3, 4, 5) (keeps the diaphragm alive)
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What are the accessory muscles of inspiration?
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external intercostals, scalene muscles, sternocleidomastoids
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what are the accessory muscles of expiration?
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rectus abdominis, internal and external obliques, transversus abdominis, internal intercostals
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what molecule activates bradykinin?
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Kallikrein
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What is the effect of CO poisoning?
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causes a decrease in oxygen binding capacity of Hb with a left-shift in the oxygen dissociation curve
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Calculation of pulmonary vascular resistance?
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PVR = [P(pulm artery) - P(wedge)] / Cardiac outupt
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