Air Flow
How does sympathetic NS control air flow vs. parasympathetic?
Parasympathetic input constricts airways Sympathetic input relaxes/dilates airways
What does a V/Q = 0 mmHg mean?
Perfusion but NO ventilation where PAO2 is 40 mmHg (O2 content in alveolus because none taking it away) and PACO2 is 46 mmHg (nothing to take it away)
What happens in the iron lung when you increase P in tube?
Person's lung contracts and air flows out
What happens in the iron lung when you decrease P in tube?
Person's lung expand and pulls air in
What does placement of smooth muscle determine?
Places you can decrease diameter so you increase R and decrease airflow (Q)
How does pulmonary blood P and R differ from systemic?
Proportionally lower than systemic
What is V and Q in Zone 3? What's the ratio?
Q is highest V is higher Ratio is 0.6
What is V and Q in Zone 1? What's the ratio?
Q lowest V lower Ratio is 3.0
What's the air flow equation?
Q=deltaP/R
Why does resistance decrease as lung expands?
R decreases as lung expands because the diameter of the airway increases and thus R decreases Increase radius→increase lung volume; longer path length→greater R
What's the equation for air flow resistance?
R=viscosity x l / (r^4) Reduce airway radius, increase resistance
What are the main controls of air flow?
Sympathetic and parasympathetic control They do this by altering airway resistance and thus airflow
What's TLC? How do you find it in the gas dilution test?
Total lung capacity TLC= V2 (V of lung)- V1 (V of apparatus)
When is Spirometry used?
Useful in assessing lung conditions: asthma, emphysemia, bronchitis, COPD, pulmonary fibrosis
What does it mean if V/Q ratio is infinite?
Ventilation but NO perfusion where PaO2 is 150 mmHg (none getting into blood) and PaCO2 is 0 mmHg (none getting diffused out of system)
What can spirometry be used in conjunction with?
With Plethysmography to measure relative volume and flow of air
How does pulmonary blood flow equate to the systemic blood flow?
o Blood flow through the lungs about equal to that throughout the systemic blood flow despite vastly different sizes
How is flow primarily controlled by and why is this necessary? Does this alter overall resistance?
o Flow primarily controlled via vasoconstriction to make sure that blood gets to parts of lung that need it the most Normally doesn't alter overall resistance
What is the V/Q ratio? When does it occur and what is normal?
o Ratio of alveolar ventilation to pulmonary blood flow o Normal value ~80% for the whole lung o Occurs when breathing frequently, tidal volume and cardiac output are normal (during background respiration) o At 80%, arterial O2 at 100 mmHg, arterial CO2 at 40 mmHg
Why is hypoxic vasoconstriction necessary?
o Reduced flow to poorly ventilated areas is adaptive (diverts blood to areas of higher ventilation)
What's pulmonary blood flow?
o Superior vena cava + Inferior vena cava→R atrium→R ventricle→Pulmonary artery→Lungs→L atrium→L ventricle→Aorta o Pulmonary vasculature branches in a pattern similar to that seen on respiratory tree
What is the Q and V in Zone 2?
o Zone 2: Sweet spot where ratio is ~80%
What kind of pulmonary blood flow occurs in the different zones of the lungs? Why?
1: Low blood flow 2: Medium blood flow 3: High blood flow Due to gravity-->natural tendency for blood flow
What's used to treat asthma caused by the sympathetic NS?
Beta2-adrenergic agonists
Where is smooth muscle located in the respiratory tree?
Between cartilage Encircles airways in bronchi, bronchioles Encircles "mouths" of alveoli
Where is max resistance in the respiratory airway tree?
Between the trachea and bronchus
What Law does Iron Lung use?
Boyle's Law
What's the equation used in the Gas dilution test?
C1V1=C2V2
What activates sympathetic NS?
Circulating epineprhine from adrens
What does a low V/Q mean for PaO2 and PaCO2?
Decrease PaO2 Increase PaCO2
What are the 3 lung function tests (structural tests)?
Gas dilution Plethysompgraphy (Iron lung) Spirometry
What direction does air flow?
High P to Low P
What does a high V/Q mean for PaO2 and PaCO2?
Increase PaO2 Decrease PaCO2
What is asthma?
Inflammation causing severe smooth muscle contraction (bronchospasm)
What happens as you move down the airway?
Length gets shorter and thus a decreased R
What receptors activate parasympathetic NS?
Muscarinic receptors causing an constriction of airways
Is blood flow through the lungs uniform?
No
What's the equation used in Plethysmography Lung structural test?
P1 x V1 = P2 x V2 (Boyle's Law)
What's the PaO2 and PaCO2 in Zone 1?
PAO2 is 130 (O2 content high because of low blood flow so isn't being released) PACO2 is 28 (because it isn't being picked up)
What is the blood pressure in Zone 1? What does this cause the alveolar vessel to do?
alveolar pressure>arterial>venous pressures causes alveolar vessel to contract slightly
What is the blood pressure in Zone 2? What does this cause the alveolar vessel to do?
arterial>alveolar>venous pressures (not much difference between them)
What is the blood pressure in Zone 3? What does this cause the alveolar vessel to do?
arterial>venous>alveolar pressures P in vasculature > than alveolar vessel causing ale alveolar to expand a little bit
How do you use the Plethysmography test?
• Allows for more detailed assessments of the various volumes and capacities that make up total lung volume • When lungs expand then P decreases in the box causing air to be pulled in (P1 and V1 of box is known) • We can then measure P2 from the box and find V2 of person's lung to find TLC of lung
What's a R to L shunt? How can we test for that to prove it?
• Blood passes directly from the right ventricle to the left ventricle • Can test if this is really occurring by giving patient oxygen: Not helped by breathing pure oxygen (shunted blood never reaches the lung)
What's a physiologic shunt? What's an example of it?
• Blood returns to the heart un-oxygenated • Example: Blood in vasculature that serves the bronchial tree doesn't reach the alveoli Where V/Q is less than normal
How can you find the effective diameter of alveoli and what does this tell us compared to trachea?
• Can find effective diameter of alveoli by taking estimated number of ducts and multiply that by the 1/10 alveolar diameter. The diameter of the alveoli are 1000x> than trachea so there's a drastic decrease in R once you get down the airway tree
How does the Gas dilution test work?
• If you plug a person into a tube and open the valve (where they're hooked up to an apparatus where C1 V1 is known), you can measure C2 and find the new V2 given the above equation • TLC (total lung capacity) can be found by doing: TLC= V2 (V of lung) -V1 (V of apparatus)
How does High O2 affect vascular smooth muscle?
• In normal ventilation where PAO2 =100 mmHg in alveolus, then High O2 in alveolus causes vascular smooth muscle to relax
How does Low O2 affect vascular smooth muscle?
• In poor ventilation where PAO2 < 70 mmHg in alveolus, then Low O2 stimulates vascular smooth muscle to constrict vessel so blood flow to alveolus is decreased and blood is redirected to other parts of the lung
What's the PaO2 and PaCO2 in Zone 3? Why?
• PAO2 is 89 (has good perfusion, a lot of O2 getting to the blood) PACO2 is 42 (good perfusion, a lot of CO2 getting into alveolus)
