Flashcards in Pulmonary Phys Pearls Deck (37)
What is lung dead space?
Can be anatomic (conducting paths take up lung space roughly 140L) or physiologic (disease states) however it is the portion of the lung that does not participate in O2 exchange.
What is vital capacity?
the sum of tidal volume, inspiratory reserve volume and expiratory reserve volume.
Essentially is the volume of air that can be forcibly expired after full inspiration.
Which three lung measurements cannot be measured by spirometry?
Functional residual capacitance (Residual volume + expiratory reserve volume)
Total lung volume (all four volume ammounts)
What is FEV1 and what is normal?
This is the ammount of lung volume that can be forcibly exhaled in one second.
Normally its 80% of the forced vital capacity.
Describe how FEV1 and FVC are affected by obstructive lung disease.
with asthma or COPD Both are decreased however, FEV1 is reduced more than the FVC and so FEV1/FVC is decreased.
Describe how FEV1 and FVC are affected by restrictive lung disese.
With restrictive diseases such as fibrosis, both are reduced however FEV1 is reduced less than FVC and so FEV1/FVC is increased.
What equation describes compliance of the respiratory and vascular system?
Compliance is = Volume / Pressure
This ultimately describes the distensability of the chest wall. It is inversely related to elastance which is the elasticity of the chest wall (how well it snaps back)
What feature of the lungs cause the inhalation and exhalation curves to appear different?
In other words, the lungs need to overcome surface tension when being inflated and thus the curve is sigmoid in shape compared to the exponential exhale curve.
Why is intraplearal space generally negative?
The chest wall naturally wants to expand where as the lungs naturally want to collapse.
Thus the two forces interact and create a relatively negative pressure.
A barrel shaped chest should make you think of?
Emphysema where the FRC (functional residual capacity) is increased leading to distended lungs and chest.
THIS IS OBSTRUCTIVE
How will the lungs react with fibrosis?
this is a restrictive condition. It is difficult TO GET AIR INTO THE LUNGS and thus the lungs will tend to collapse.
Describe the relationship between alveolar radius and surface tension.
As radius increases the alveoli needs less pressure to remain open. Thus less likely to collapse.
surfactant helps make up the size diffrence.
What cell types make surfactact?
Type II alveolar cells.
What test can determine if an infant is making enough surfactant?
A lecthicin:sphingomyelin ratio of 2:1
What is the biggest factor effecting airway resistance?
By passouilles law 8Nl/pir^4
Where is the major site of airway resistance?
Medium sized bronchi.
How does the symapthetic nervous system effect the airway compared to the parasympathetic?
Sympathetic dialates via B2
Describe profusion vs diffusion properties at the alveolar/capillary junction.
Profusion depends on the saturation of blood and can only be increased by a faster heart rate.
Diffusion depends on the alveolar thickness and the solubility of the gas.
What is methemeglobin?
This is hemoglobin with the iron moiety in the Fe3+ stage.
It cannot bind oxygen.
What is hemoglobin S?
Sickle cell disease.
Alpha subunits normal beta subunits are abnormal leading to sickle cell stickyness when deoxygenated. `
What is hemoglobin P50?
The point at which 50% of all hemogobin is bound.
Typically at an O2 content of 25 mmHg.
During which scenario is 2,3 BPG increased?
During times of chronic hypoxemia.
How does carbonmonoxide poisoning shift the Hgb graph?
Shifts it to the left making it more difficult to release O2.
What is the difference between hypoxemia and hypoxia?
Hypoxemia is decreased arterial pO2 from diffusion defects, V/Q defects, or right to left shunts.
Hypoxia is decreased O2 delivery to tissues.
What does the A-a gradient describe?
Describes the O2 content in the Alveoli (A) and the arteriole (a)
Normal gradient is between 0-10 mmHg.
When would the A-a gradient be increased?
If alveolar O2 is not making its way into arteriolar space.
How does the kidney help when there is hpoxia?
It secretes EPO which increases erythrocyte synthesis from the bone. Signalled via hypoxia inducible factor `1 alpha.
What are the three forms of CO2 in the blood and what is the majority?
Dissolved CO2 (small)
Carbaminohemoglobin bound to Hgb (small)
HCO3- which is major form 90%
What reaction does carbonic anhydrase perform?
Carbonic anhydrous combines CO2 with H20 to form H2CO3 which then dissociates into H+ and CO3-
The H+ binds the Hgb and the HCO3- enters the plasma via a chloride channe.
What buffers the H+ formed in the blood?
How does blood flow through the lung change from supine to standing?
When standing most of the blood flow is in zone 3 the bottom of the lungs. When supine the blood flow in the lungs is equal in all three zones.
In the lungs what happens in hypoxemia?
Hypoxemia cause the lung arteries to vasoconstrict to shunt blood flow away from dead space of low O2
Why would fetal lungs have a high pressured blood flow?
Because fetal lungs are hypoxemic and thus have vasoconstriction naturally occuring. This reverses after birth after the first breath is taken .
When thinking of the V/Q ratio between the apex and base where is it larger?
The V/Q at the apex is greater as ventilation is high and perfusion is low.
It is low in the base.
What part of the brain controls breathing?
The brain stem specifically in the reticular formation and dorsal respiratorygroup.
Think vegas nerve and glossopharyngeal.
Which portion of the rbain stem is responsible for inspiration vs expiration?
Inspiration is from the dorsal respiratory group of the reticular formation.
Exhilation is from the ventral respiratory group of the reticular formation specifically only during exercise.