respiratory physiology basics CPBC Flashcards
List the structures of the respiratory system from proximal to distal
nasal chambers, pharynx, larynx, trachea, primary bronchi, secondary bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs
what respiratory system structures take part in the gas exchange
respiratory bronchioles, alveolar ducts, alveolar sacs
what are club cells
- make glycosaminoglycans –> protects the bronchioles
- surfaces stem cells –> produce more bronchiole cells
what mediates the contraction or expansion of the lungs?
- collagen and elastin from fibroblasts
- no muscles
what is the ratio when comparing the thickness of RBCs and alveolar walls
alveolar walls are significantly thinner –> RBCs 7 times thicker
what are goblet cells
- produce mucous to catch unwanted material that is then brought up by cilia
- decrease in number from proximal to distal
what are the pores of Kohn?
interalveolar clefts –> allow fluid and cells to come in and out of alveoli
what are the 3 major cell types in the alveoli
- type I pneumocytes
- type II pneumocytes
- phagocytes (macrophages)
what is the main function of type I pneumocytes?
- most important for gas exchage
what is the main function of type II pneumocytes?
secrete surfactant to lower surface tension
what is the role of nitrogen in the lungs?
gaseous skeleton in small airways –> important for stability –> can be washed out when patient is placed on 100% oxygen
how does the pressure of pulmonary arteries compare to systemic pressure
only 1/6th of systemic pressure
what causes peribronchial cuffing
dilated lymphatics at junction between alveolar and extra-alveolar spaces
what is hypoxic vasoconstriction in the lungs?
closing of precapillary sphincters –> terminal bronchioles can go straight to postcapillary venule (=shunt)
what could open precapillary sphincters in the lungs?
higher O2 demand, e.g., exercise
explain the forces creating centripetal pressure in alveoli
- forces of attraction between molecules of liquid lining alveoli
- proposing forces of water and interface of alveoli –> inward collapsing pressure –> elastic recoil
Explain the Law of Laplace
collapsing pressure = 2x surface tension / radius
P = 2T/r
–> the greater the radius the smaller the collapsing pressure
what are the effects of surfactant?
- prevents transudation of fluid from capillaries to alveolar space
- prevents small alveoli emptying (air flow from small to larger alveoli)
prevents collapse of alveoli
reduces work of breathing (due to less negative pressure necessary to move air into alveoli)
what are the partial pressures of O2 and CO2 in the alveolus?
- PO2 = 100 mm Hg
- PCO2 = 40 mm Hg
what are the partial pressures of O2 and CO2 in the afferent alveolar capillaries?
PO2 = 40 mm Hg
PCO2 = 45 mm Hg
what are the partial pressures of O2 and CO2 in the efferent alveolar capillaries
- PO2 = 100 mm Hg
PCO2 = 40 mm Hg
what are the partial pressures of O2 and CO2 in the resting tissue cells/leaving systemic capillaries?
PO2 = 40 mm Hg
PCO2 = 45 mm Hg
what is Fick’s Law
gas movement across membrane proportional to transfer surface area and inversely proportional to thickness of membrane
–> large and thin alveolar wall enables more gas exchange than short and tick
what is the thickness of alveolar membranes?
1/3 micrometer
what is the equation for Fick’s law of diffusion?
Diffusion = SA x D x (P1-P2) / T
SA = surface area
D = diffusion constant of the particular gas
P1 and P2 pressures of the gas on either side of the membrane
T = thickness
Describe Boyle’s Law
P1V1 = P2V2
i. e., decreasing the volume will increase the pressure and increasing the volume will decrease the pressure
e. g., breath: increase volume –> decrease pressure –> negative pressure –> airflow into lungs
Describe Dalton’s Law
Ptotal = P1 + P2 + P3 …
i.e., within the alveolus the total pressure in the alveoli is the total sum of partial pressures
Describe Henry’s Law
CGas ~ PGas
i.e., at a constant temperature the concentration of a gas is going to be proportional to the pressure of the gas
how much ml of O2 does one gram of hemoglobin contain if it is 100% saturated?
~ 1.36 ml of O2
what is the normal Hg concentration of blood?
~ 15 g/dL
15 x 1.36 (ml/g O2) = 20 –> 20 ml/dL O2 in blood bound to Hg
what is the amount of dissolved O2 in blood per PaO2?
0.003 mL/dL/mm Hg PaO2
what is the amount of O2 in arterial blood, how much is dissolved and how much bound to Hg?
arterial blood ~ 19.8 mL/dL, 0.29 in solution and 19.5 bound to Hg
what is the venous Hg O2 saturation?
75%
what is the total O2 content of venous blood?
15.2 mL/dL
what is the P50 of the oxygen-hemoglobin saturation curve in dogs?
28.8
means at 28.8 pO2 –> 50% of Hg will be saturated with O2
what is the P50 of the oxygen-hemoglobin saturation curve in cats?
means at 36 pO2 –> 50% of Hg will be saturated with O2
what does a right shift of the oxygen-hemoglobin curve mean?
O2 is less Hg bound/ affinity of O2 to Hg decreases –> more O2 released from Hg to tissues
What is the mechanism of hypoventilation causing hypoxemia?
hypoventilation –> pACO2 goes up –> pAO2 must go down because sum of pressures must be constant –> if pACO2 goes up pAO2 goes down –> paO2 goes down –> Dalton’s law
How do you calculate alveolar pO2 (PAO2)
PAO2 = PIO2 - (PACO2 / R)
R = respiratory quitient –> fraction of CO2 produced to O2 consumed –> influenced by factors like diet
at sea level:
PAO2 = 150 - (PACO2 / 0.8)
when can you not use the formula PAO2 = 150 - (PACO2 / 0.8)?
when you’re not at sea level
use:
PiO2 (150 at sea level) = FiO2 (barometric pressure - water vapor pressure)
= FiO2 (PB - PH2O)
what is the equation for PiO2 when not at sea level?
PiO2 (150 at sea level) = FiO2 (barometric pressure - water vapor pressure)
= FiO2 (PB - PH2O)
in high altitude what happens to PaO2, A-a gradient and effect of supplemental oxygen?
PaO2 decreased
A-a gradient normal
O2 supplementation improves oxygenation
during hypoventilation what happens to PaO2, A-a gradient and effect of supplemental oxygen?
PaO2 decreased
A-a gradient normal
O2 supplementation improves oxygenation
during diffusion defect what happens to PaO2, A-a gradient and effect of supplemental oxygen?
PaO2 decreased
A-a gradient decreased
supplemental O2 will improve oxygenation
during V/Q defect what happens to PaO2, A-a gradient and effect of supplemental oxygen?
PaO2 decreased
A-a gradient increased
O2 supplementation will improve oxygenation
during R to L shunt what happens to PaO2, A-a gradient and effect of supplemental oxygen?
PaO2 decreased
A-a gradient increased
O2 supplementation will not improve oxygenation
