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128 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Diffusion is limited by which two factors?
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Surface Area / Volume ratio
Distance |
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Diffusion becomes more effective with increasing distance.
True or False? |
False
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What are the functions of the turbinates?
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Expand the surface area
Produce turbulent flow |
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What are the characteristics of daughter branches in the respiratory system?
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Cross-sectional area increases
Length decreases |
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What is the total cross-sectional area for gas transport?
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~70 square meters
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Where is the flow of gas most likely laminar in the respiratory system?
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Lower airway
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Velocity of flow decreases as gas travels down the airway.
True or False? |
True
(flow becomes more laminar) |
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What type of flow does gas undergo in the upper airway and trachea?
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Turbulent flow due to high velocity and convoluted structures
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What type of gas flow is apparent in the terminal airway (respiratory bronchioles, alveolar ducts)?
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Diffusional
(there is no bulk flow) |
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What is the relationship between air flow velocity and cross-sectional area?
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Inversely proportional
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In the upper airway cilia move the gel layer backward and down while the cilia move in the opposite direction in the trachea and bronchi.
True or False |
True
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What is responsible for the air conditioning function of the lower respiratory tree?
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Mucociliary ladder
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What are the functions of the upper airway?
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Filtration
Temperature & humidity adjustment |
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What three factors does the filtration function of the respiratory system depend on?
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Inertia
Sedimentation Diffusion |
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What is the mechanism for trapping particulates in the upper airway?
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Turbulent flow and inertia drive the particulate matter into the mucous layer
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What is the mechanism for trapping particulate matter in the region of the airway in which flow is mainly laminar?
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Sedimentation
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What is the mechanism for trapping particulate matter in the alveolar ducts?
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Diffusion
(since there is no bulk flow) |
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Where and how are particles greater than one micron trapped in the respiratory system?
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Nose and mouth
Turbulence / Inertia |
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What is the primary function of the upper airway?
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Air Conditioning
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Air conditioning is controlled by which factors?
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Surface area
Airflow patterns Sub-mucosal blood flow |
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What is the function of sub-mucosal blood flow?
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It delivers heat and water to the upper airway during respiration to ensure the inspired gas doesn't overly cool or dehydrate
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What are the non-respiratory functions of the lungs?
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Reservoir for the LV
Circulatory filter Chemical filter |
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Why is the lung an ideal place to have a chemical filter?
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The lungs receive the entire cardiac output
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All of the following are almost completely removed by the lung (≥80%) EXCEPT:
A. Prostaglandins B. Leukotrienes C. Serotonin D. Norepinephrine E. ATP / AMP |
Norepinephrine is only 30% removed
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What are the two main muscles of inspiration?
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Diaphragm
External intercostals |
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What are the main muscles used during forces expiration?
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Internal intercostals
Abdominal muscles |
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What is the physiological function of intrapleural fluid?
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It locks the parietal and visceral pleura together so that the lungs and thorax move together during respiration
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In which direction is the elastic force vector of the thorax at the end of expiration?
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Outward
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In which direction is the elastic force vector of the lungs at the end of expiration?
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Inward
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What is the alveolar pressure at the end of expiration?
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Zero
(no gas movement) |
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Why is the resting intrapleural pressure sub-atmospheric?
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Because of the elastic recoil of the lungs and expansion of the thorax
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What is the intrapleural pressure at the end of inspiration compared to at the end of expiration?
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It's more negative
(the elastic recoil of the lung has increased) |
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What is the major assumption in the nitrogen washout technique?
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All the nitrogen collected in the bad comes from the FRC
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Using the nitrogen washout technique you measure a nitrogen concentration of 0.035 in a washout bag equal to 100 liters, what is the FRC?
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4.4 L
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Using the helium dilution technique you measure the initial [He] to be 0.2 in a volume of 1 liter
After equilibration the [He] is measured to be 0.05 What is the FRC? |
3 L
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What is the minute ventilation of a patient with a respiratory rate of 28 breaths / minute?
What would happen to this patients arterial PCO2? |
14 L
Arterial PCO2 would decrease |
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Why is alveolar ventilation more important than minute ventilation?
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Alveolar ventilation gives you the functional input of oxygen and output of carbon dioxide
(in other words: alveolar ventilation represents the amount of fresh gas getting to the alveoli) |
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What happens to a patients alveolar ventilation if they breath through a tube?
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Alveolar ventilation decreases because the volume of dead space increases
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What is the minute ventilation of a patient if their frequency is 12, tidal volume is 500 ml, and dead space is 150 ml?
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6 L/minute
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What is the rate of fresh gas reaching the alveoli of a patient if their frequency is 12, tidal volume is 500 ml, and dead space is 150 ml?
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4.2 L/min
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What happens to alveolar ventilation as you decrease tidal volume?
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Alveolar ventilation decreases
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If the rate of carbon dioxide production remained unchanged, what will happen to the arterial partial pressure of carbon dioxide if alveolar ventilation is doubled?
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The partial pressure of arterial carbon dioxide will be halved
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Alveolar ventilation is _________ proportional to the arterial/alveolar partial pressure of carbon dioxide.
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inversely
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What method is used to determine the volume of anatomical dead space?
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Fowler's method
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What is the definition of physiological dead space?
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It is the volume in which ventilation is not associated with gas exchange
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If the partial pressure of expired carbon dioxide is equal to 0.3 and the arterial partial pressure is 0.43, what is the volume of the physiological dead space (assuming 500 ml for tidal volume)?
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151 ml
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What is the alveolar partial pressure of oxygen if the alveolar partial pressure of carbon dioxide is 50 mm Hg?
Assume R = 1 |
100 mm Hg
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What are the ideal alveolar partial pressures of oxygen and carbon dioxide?
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100 mm Hg for oxygen
40 mm Hg for carbon dioxide |
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Why does the partial pressure of alveolar oxygen decrease then increase during early inspiration?
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The inspired dead space air contains less oxygen and more carbon dioxide due to the previous expiration
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What are the structures that oxygen must pass in the blood-gas barrier in order to reach plasma?
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1. Alveolar fluid
2. Alveolar epithelium 3. Interstitial space 4. Capillary endothelium |
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Under normal resting conditions how much time does blood spend in a pulmonary capillary?
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0.75 seconds
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What limits a molecule if it doesn't reach equilibrium between alveoli and blood by the end of capillary?
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Diffusion limited
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If the time blood spends in a pulmonary capillary is reduced by one third, will oxygen reach equilibrium between the alveoli and blood?
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Yes
Oxygen requires at least 0.25 seconds to reach equilibrium |
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What limits a molecule if it reaches equilibrium between alveoli and blood in 0.75 seconds?
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Perfusion (flow) limited
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What is an example of a molecule that is diffusion limited?
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Carbon monoxide
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Is it wise to use a flow limited molecule to measure the diffusion characteristics of a semipermeable barrier?
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NO
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Why does nitrous oxide reach equilibrium in a pulmonary capillary faster than oxygen?
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Nitrous oxide does not react with hemoglobin
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Why doesn't carbon monoxide reach equilibrium in a pulmonary capillary?
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All of the carbon monoxide is tied up to hemoglobin due to its high affinity, thus it never reaches an appreciable partial pressure in the blood
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Where are the sites of resistance in the pulmonary circulation?
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Capillaries
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What are the two types of vessels involved in pulmonary resistance?
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Alveolar and extra-alveolar vessels
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Alveolar vessels
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Located in the alveolar wall
Affected by alveolar pressure Increased alveolar pressure compresses |
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Extra-alveolar vessels
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Tethered to the lung parenchyma
Affected by lung volume Decreased lung volume compresses |
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What happens to pulmonary vascular resistance as arterial or venous pressure is increased?
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Pulmonary vascular resistance decreases
*this is unique |
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What is the mechanism behind the relationship between pulmonary resistance and arterial/venous pressure?
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Recruitment of more vessels (lower pressures)
Distention of vessels (higher pressures) Result: decreased pulmonary resistance |
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Why does pulmonary vascular resistance increase as lung volume increases away from FRC?
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As the lung expands the extra-alveolar vessels are pulled open, thus resistance should go down; however, alveolar walls are thinning out causing compression of the alveolar vessels, thus resistance increases
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Why does pulmonary vascular resistance increase as lung volume decreases away from FRC?
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As you compress the lung you will physically compress the extra-alveolar vessels, thus increasing resistance
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As oxygen partial pressure ________, blood flow decreases.
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decreases
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Hypoxic vasoconstriction is caused by reduced alveolar oxygen partial pressure.
True or False |
True
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What is the significance of hypoxic vasoconstriction?
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To direct blood flow away from poorly ventilated regions of the lung
(adjusts the V/Q ratio) |
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What is the physiological mechanism for keeping the lungs dry?
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Pulmonary hydrostatic pressures are low and colloid osmotic pressures are normal
This leads to a low filtration pressure |
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What are two ways for fluid removal in the lung?
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Alveoli
Perivascular spaces |
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The amount of gas in a liquid is dependent upon __________ and __________.
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solubility; partial pressure
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How much oxygen is dissolved in 100 ml of blood plasma at a partial pressure of 100 mm Hg?
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0.3 ml oxygen / 100 ml blood
(oxygen solubility = 0.003 ml / 100 ml blood / mm Hg) |
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How much oxygen can 15 grams of hemoglobin bind (fully saturated)?
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20.85 ml of oxygen
(1g of hemoglobin binds 1.39 ml of oxygen) |
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If 15 grams of hemoglobin is 97.5% saturated, what is the total blood oxygen content in 100 ml of blood?
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20.6 ml of oxygen
(20.3 is bound; 0.3 is dissolved) |
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What happens to the oxy-hemoglobin dissociation curve when blood reaches tissue capillaries?
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Right Shift
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How does an increase in carbon dioxide affect the oxy-hemoglobin dissociation curve?
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Right shift
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How does an decrease in hydrogen ion concentration affect the oxy-hemoglobin dissociation curve?
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Left shift
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How does an increase in 2,3-DPG affect the oxy-hemoglobin dissociation curve?
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Right shift
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How does an decrease in temperature affect the oxy-hemoglobin dissociation curve?
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Left shift
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How does chronic hypoxia or high altitudes affect the oxy-hemoglobin dissociation curve?
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Right shift
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How does carbon monoxide affect the oxy-hemoglobin dissociation curve?
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It decreases the amount of Hb available for oxygen binding and shifts the curve to the left by increasing the Hb-oxygen affinity
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What is the oxygen carrying capacity of an anemic patient with a hemoglobin concentration of 10g?
(assume normal [Hb] = 15g) |
13.75 ml oxygen / 100 ml blood
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The work of breathing includes which two things?
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Expanding the chest (stretching muscles and cartilage)
Moving gas |
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What is the mechanism behind pulmonary surfactants ability to prevent alveoli of different sizes from collapsing?
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Surfactant makes the surface tension a function of area
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What are four causes of hypoxemia?
(A-a oxygen difference) |
Hypoventilation
Diffusion limitation Shunt V/Q mismatch |
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The partial pressure of oxygen in alveolar gas is determined by which two things?
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Removal of oxygen by pulmonary capillary blood
Replacement of oxygen by alveolar ventilation |
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What are two sources of anatomical shunts that contribute to the A-a oxygen difference?
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Bronchial artery emptying into the pulmonary veins
Thebesian veins |
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Administering 100% oxygen to a patient with a shunt increases arterial oxygen partial pressure.
True or False? |
False
(the added oxygen will only affect the non-shunt circulation) |
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How do you know a patient with an A-a difference has a shunt?
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If you administer 100% oxygen and it doesn't help
Hypoxemia due to shunts cannot be abolished by giving 100% oxygen |
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Why isn't administering 100% oxygen to a patient with an A-a difference due to shunt helpful?
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The shunted blood that bypasses ventilated alveoli is never exposed to the higher alveolar oxygen pressure
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Why don't shunts increase arterial partial pressures of carbon dioxide?
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Because chemoreceptors sense any elevation and respond by increasing ventilation
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What determines the oxygen concentration in the alveoli?
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The V/Q ratio
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If the V/Q ratio is altered by blocking perfusion, what will be the composition of the alveolar gas?
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It will be that of inspired gas
O2 = 150 mm Hg CO2 = 0 |
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If the V/Q ratio is altered by blocking ventilation, what will be the composition of the alveolar gas?
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Mixed venous blood
O2 = 40 mm Hg CO2 = 45 mm Hg |
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What is the V/Q ratio at the apex of the lungs?
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It is abnormally high because there is less ventilation and perfusion
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Alveolar partial pressures of oxygen decrease as you move down the lung.
True or False? |
True
(CO2 decreases less) |
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Where is alveolar carbon dioxide the highest in the lung?
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Base
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The concentration difference between the base and apex of oxygen is larger than the carbon dioxide difference.
True or False |
False
CO2 difference = 7 ml O2 difference = 0.8 ml |
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Why is the alveolar oxygen partial pressure at the apex 40 mm Hg more than at the base?
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Very low blood flow at the apex
(O2 isn't being taken away by the pulmonary capillaries) |
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Why is the partial pressure difference of oxygen between the base and apex 40 mm Hg while the difference in carbon dioxide is only 14 mm Hg?
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The difference in CO2 output between the base and apex is much less because it is closely related to ventilation
Ventilation decreases as you go from base to apex; however, the changes are more drastic for perfusion (thus oxygen) |
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The regions with the highest V/Q ratios have the greatest impact on arterial oxygen concentrations.
True or False? |
False
(regions with low V/Q ratios have the greatest impact) |
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If the majority of the blood leaving the lung comes from the base, how does this affect the A-a oxygen difference?
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It would increase the A-a difference because the base of the lung has much less oxygen than the apex, but the base has much greater blood flow
Thus, increased blood flow at the poorly oxygenated base decreases arterial PO2 |
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How do you differentiate between hypoventilation and V/Q inequalities?
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During hypoventilation the A-a gradient should be normal
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What does hypoxemia with a normal A-a gradient suggest?
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Hypoventilation
Low FiO2 (or diffusion block) |
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What does hypoxemia with an increased A-a gradient suggest?
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V/Q mismatch (asthma, COPD)
Shunt (shunts include: patent foramen ovale, alveolar collapse, pneumonia, pulmonary edema, or intrapulmonary shunt) |
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How can one differentiate between the difference causes of an increased A-a gradient?
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Supplemental oxygen will not correct hypoxemia resulting from a shunt
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The blood gases of a hypoxic patient were: PO2 = 50 and PCO2 = 76 (R=0.8)
What is the treatment? |
PAO2 = (PIO2 - PACO2) / R
PAO2 = 55 mm Hg A-a = 55 - 50 = 5 mm Hg (normal) This patient is hypoventilating, give supplemental oxygen |
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What part of the medulla is responsible for inspiration?
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Dorsal respiratory group (DRG)
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What part of the medulla is responsible for expiration?
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Ventral respiratory group (VRG)
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This respiratory center in the pons tends to have an excitatory effect on the DRG, and prolongs the ramps of action potentials
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Apneustic center
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This respiratory center in the pons tends to inhibit inspiration
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Pneumotaxic center
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This respiratory center in the pons is thought to fine-tune respiratory rhythm because a normal rhythm can be achieved in its absence
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Pneumotaxic center
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Where would you section the brainstem in order to obtain the minimum number of neurons needed for respiration?
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Between the apneustic and medullary centers
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What is the Hering-Breuer reflex?
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It is triggered to prevent overinflation of the lungs
Inflation tends to inhibit further inspiratory muscle activity Involved pulmonary stretch receptors present in the smooth muscle of the airways |
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Peripheral chemoreceptors have the lowest perfusion rates in the body.
True or False? |
False
They have the highest perfusion rates |
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Peripheral chemoreceptors are located in the aortic arch and carotid bodies and are slower to respond than central receptors.
True or False? |
Peripheral chemoreceptors are FASTER to respond
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Why are the peripheral chemoreceptors thought to sample arterial blood?
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They have a very high perfusion and metabolic rate, but the arterio-venous oxygen difference is very small, thus they respond to arterial and not venous oxygen
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The peripheral chemoreceptors are responsible for all the increase in ventilation that occurs in response to arterial hypoxia.
True or False? |
True
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What are peripheral chemoreceptors most sensitive to?
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Oxygen > CO2 > H+
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The sensitivity of peripheral chemoreceptors begins around 500 mm Hg of oxygen.
True or False? |
True
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High carbon dioxide and low oxygen levels act synergistically through peripheral chemoreceptors to stimulate ventilation.
True or False? |
True
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What is the mechanism for increasing ventilation by stimulating central chemoreceptors?
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Increase plasma CO2 causes in increase in CSF CO2, which increases H+ and stimulates the chemoreceptor to increase breathing
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How does the carbon dioxide level in the blood regulate ventilation?
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It does so chiefly by its effect on the pH of the CSF
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What is the significance of the reduced buffering capacity of the CSF?
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Changes in CSF pH for a given change in carbon dioxide are much greater than in blood
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What happens when the displacement in CSF pH is prolonged?
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The CSF eventually imported bicarbonate to bring the pH towards normal; however, blood carbon dioxide level may remain high because it takes the kidneys 2-3 days to adjust
This is important in people with chronic lung disease (CO2 retention) and those exposed to 3% atm CO2 |
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What is the significance of the hypoxic drive to ventilation in patients with severe lung disease?
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Chronic CO2 retention reduces chemoreceptor sensitivity because the CSF has imported bicarbonate to correct the pH, thus they have lost their main ventilatory drive
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The initial depression in blood pH has also been abolished by the kidneys, thus little pH stimulation on peripheral chemoreceptors
Arterial hypoxemia becomes the chief stimulus to ventilation, and ventilation ca become grossly depressed if the patient is give 100% oxygen |
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The ventilatory response to oxygen is important at high altitude and in patients with lung disease.
True or False? |
True
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