Respiratory Flashcards
Why is there less resistance in the pulmonary circulation as compared to systemic?
to ensure that the rate of flow is equal to systemic because the pressure in the systemic circulation is greater so the decreased resistance in the pulmonary circulation makes up for that. Qdot=pressure difference/resistance
What two physiologic mechanisms can occur to keep resistance low during exercise, etc when pressure increases?
-recruitment of more vessels
-distension, so increased radius of vessels
Describe vascular resistance in the alveoli and how complete occlusion in limited
initially with an inspiration, resistance increases because alveolar vessels are compressed, but then extralveolar vessels can be expanded by the manual pull on CT to pull them open
Where can you measure blood pressure directly via a catheter with a transducer placed into venous circulation?
-right atrium
-right ventricle
-pulmonary arteries
How would you measure blood pressure in the pulmonary vein and left atria?
indirectly estimate by pulmonary wedge pressure
Describe pulmonary wedge pressure
catheter is fed into right heart then into pulmonary circulation where a balloon at the end of the catheter is opened.this occludes the arteriole, and as long as the capillary/venule is continuous, the indirect pressure flowing back from other venules is equivalent to the left atrial pressure
Describe hypoxic pulmonary vasoconstriction
occurs in times of hypoxia and is adaptive to reduce blood flow to regions of the lungs that are poorly ventilated. this response locally matches ventilation/profusion to normal
How is hypoxic pulmonary vasoconstriction modulated?
pulmonary endothelial cells release vasodilating (PGI2,ANF, NO) or vasoconstricting agents (thromboxane or endothelin-1)
what can result from damage to pulmonary endothelial cells?
can result in decrease to vascular tone molecules as well as increase pro-inflammatory and procoagulant factors due to the necrosis of cells. this all favors vasoconstriction and coagulation
True/False: fetal lungs participate in gas exhange
false
fetal pulmonary circulation is characterized as what three things?
-high pressure
-high resistance
-low flow
Why is blood flow favored through the foramen ovale and the ductus arteriosis in fetal circulation
because Po2 is low, this results in prolonged vasoconstriction, this causes higher resistance in the pulmonary circulation as compared to the systemic circulation
At birth what causes the diversion of blood into pulmonary circulation?
the pressure in the pulmonary circulation falls rapidly and less to systemic as the ductus closes and active pulmonary vasodilation occurs. this increase in left atrial pressure which closes the foramen ovale
Pulmonary vasodilation at birth is a response to what?
mechanical effects of ventilation mediated by histamine and PGD2 from mast cells and rising PO2
Pulmonary vasodilation at birth is a response to what?
mechanical effects of ventilation mediated by histamine and PGD2 from mast cells and rising PO2
Fluid flex out of pulmonary capillaries is determined by what two things?
relative hydrostatic pressure and oncotic pressure
What is the reserve to help prevent alveolar edema?
lymphatics
Briefly describe two situations that would lead to pulmonary edema
-increased pressure in the left atria causing back flow and increased hydrostatic pressure
-increased capillary permeability
True/False: conducting airways (i.e bronchus and bronchioles) are involved in gas exchange
false
What respiratory structures are responsible for gas exhange?
the lung parenchyma (alveolar septa and alveoli)
What is total lung capacity
the volume of gas that can be contained within the maximally inflated lungs
Define tidal volume
the volume of a single expired breath
Define vital capacity
the maximal volume that can be expelled from the lungs after maximal inspiration
Define residual volume
the volume of gas that remains in the lungs after maximal expiration
Define functional residual volume
the volume remaining in the lungs at the end of a normal tidal expiration
How would you measure all the standard lung volumes in a conscious cooperative patient?
spirometry
What is the total pressure of ambient air?
760mmHg
What is the partial pressure of H2O?
47mmHg
What is the normal PIO2?
150mmHg
Define respiratory dead space
lung compartment with ventilation but no blood flow (so no gas exchange)
What does minute ventilation measure?
total gas flow in and out of the lungs per minute, this includes dead space + alveolar ventilation
What value is an accurate estimate for PACO2?
PaCO2
What information do you need to be able to calcualte PAO2?
PIO2 and lab measured PaCO2
What is the basic foundation of how air enters the lungs?
The alveolar pressure has to be less than atmospheric
Why is there a loss of velocity of air in periphery airways?
the same vol of inspired air is distributed among many airways as total cross sectional area increases rapidly in terminal airways
What are the 2 ways lungs can be inflated? when would each be used?
-Negative pressure which is normal circumstances
-Positive pressure which would be manual inflation under sedation etc
___ within alveolar walls contributes to the passive delflation of the lungs
elastin
____ within the pulmonary interstitium resists further expansion at high lung volumes
collagen
Define lung compliance
the change in volume as expanding pressure is applied
True/False: compliance of lung parenchyma is the same for negative pressure and positive pressure inflation
True
what would increase compliance?
loss of elastic tissue
what would decrease compliance?
CT proliferation or interstitial fluid
What is the force that acts to reduce alveolar surface area and volume which contributes to the passive recoil of lungs?
surface tension
True/False: a saline filled lung will have less compliance than an air filled lung. Why?
False because the saline filled lung obliterates the air-liquid interface making it have a lower tendency to recoil as compared to the air filled lung
small alveoli have a tendency to collapse into larger ones with surface tensions which then require large distending pressures to reopen them. What substance reduces surface tension then reducing pressure needed to reopen alveoli?
surfactant
What is surfactant
a phospholipid synthesized by type II cells
if an alveoli begins to collapse what manual mechanism helps to keep them open
the tension on the walls exerted through collagen fibers by neighboring alveoli
The chest wall tends to recoil in which direction?
outward
define relaxation volume (Vrx)
the equilibrium point where inward recoil of the lungs is balanced by the outward recoil of the chest
How can airway resistance be assessed in conscious compliant patients (humans)
determined by the volume that can be forcefully expired in 1 second (FEV1)
What circumstances can slow diffusion of gas across the air-blood barrier?
-decreased PO2
-thickening if the alveolar membrane
What molecule is used to measure diffusion?
carbon monoxide
What is the normal concentration of Hb in blood?
15g Hb/100mL blood
Why is the relationship between PO2 and Hb saturation non linear?
due to the changes in oxygen affinity for Hb as oxygen molecules progressively bind
What is the major mechanism of transport of CO2?
bicarbonate
hypoxemia is defined as below what value?
PaO2<85mmgHg
What is the most common cause of hypoxemia?
ventilation profusion mismatch
What is the most common cause of hypercapnia
hypoventilation
What is the major stimulus for increasing ventilation?
increased PaCO2
When is the V/Q ratio 0?
When there is no ventilation. so when there is a complete collapse or obstruction of an airway (aka a shunt)
When is there dead space/ V/Q ratio is infinity
when there is no perfusion so no gas exchange occurs (ie completely occluded capillary supply)
True/False: the A-a gradient is a sensitive indicator of V/Q mismatch
true
a low V/Q ratio indicate ___
impaired ventilation
a high V/Q ratio indicates ___
impaired circualtion
increased V/Q ratio leads to ____ PCO2
reduced
True/False: increasing inspired oxygen (FIO2) will not improve hypoxia due to V/Q inequity
False, it will improve hypoxia UNLESS there is a great inequity which will yield less response to FIO2
What condition of V/Q mismatch is resistant to correction by increasing FIO2? why?
shunts because there is no ventilation, so higher inspired oxygen will not raise the alveolar O2
What is the normal range of the A-a gradient?
4-6mmHg
True/False: there is no discrete respiratory center
true
What receptors are important for minute to minute control of ventilation?
chemoreceptors
What mechanoreceptor is responsible for the reflex that helps to prevent overinflation of the lung?
stretch receptor
What receptor augment inspiratory activity and constricts airways to promote rapid shallow breathing that limits penetration of noxious agents?
irritant receptors
Define eupnea
normal, quiet breathing
Define Tachypnea
increased respiratory rate
Define Hyperpnea
increased rate and depth of respiration
Define Dyspnea
refers to the subjective sensation of breathlessness
Define orthopnea
dyspnea while recumbent
Define apnea
cessation of breathing
Define cheyne-stokes respiration
abnormal pattern of waxing and waning tidal volume and periodic apnea
Define Kussmaul breathing
regular, rapid rate with large tidal volume
What cells synthesize surfactant?
epithelial type II cells
Deposition of gasses and vapors in airways depends on ____
solubility
Deposition of particles in airways depends on ___
particle size and breathing patterns
Where does mucociliary transport occur?
in airways down to terminal bronchioles
What is responsible for clearance of particles in alveoli?
alveolar macrophages
What is the predominant immunoglobulin in secretions from the nasal mucosa and upper airways?
IgA
there is ___ flow of blood vs. water at the gas exchange surface in gills
countercurrent
Since most amphibian larvae have ineffective lungs they use ____ to move water
buccal pumping
Why do amphibian lungs have limited surface area for diffusion?
their lungs, while internal, have rudimentary septation and few if any developed alveoli
True/false: birds have a diaphragm
false, they have a common thoraco-abdominal cavity
What have birds evolved anatomically to allow gas exchange to occur at both inspiration and respiration?
separation of ventilation and gas exchange
In avian parabronchi, sequential capillary loops have a ____ blood flow pattern vs air
cross current
True/False: avian parabronchi are rigid
true
True/False: there is gas exchange in avian air sacs
false
Why must avian keels be able to move freely
to allow body cavity and air sac volume to change since the lungs (parabronchi) are rigid
what is the sequential order of most to least efficient gas change between mammals, fish, and avian
fish, avian, mammals
Why is the avian blood gas barrier so extremely thin?
because the parabronchi do not expand and contract with each breath so less structural support is needed than in alveolar lungs
Why would collateral ventilation across interlobular septae be beneficial and detrimental
beneficial because it determines consequences of airway obstruction, detrimental because it allows for the lateral flow of pathogens
