Section 5 Lecture 4 Flashcards
alveolar pressure increases between ___ and decreases between ____:
middle of inspiration to middle of expiration, middle of expiration to middle of inspiration
When is alveolar pressure negative?
inspiration
When is intracellular pressure increasing?
expiration
Range of intracellular pressure:
-6 to -3 mm Hg
When is intrapleural pressure decreasing?
inspiration
How to measure pleural pressure:
esophageal balloon
Average volume of air exchanged in and out of lungs per breath:
500 mL
What is the flow limitation in inspiration?
None
distending pressure =
arterial pressure - pleural pressure
Arterial pressure =
pressure tending to collapse lung + pleural pressure
distending pressure =
pressure tending to collapse lung
These are equal at FRC:
Barometric and atmospheric pressures
Average pleural pressure:
-3 cm H2O
P(el) is equals and opposite to:
P(cw) P(el) = pressure tending to collapse lung, P(cw) = chest wall pressure
Sequence of events leading to inspiration:
inspiratory muscles contraction, chest wall expansion, P(pl) becomes more subatmospheric, lung expands, P(A) becomes sub-atmospheric, air flows into alveoli
No pull on lung to expand, lung collapses:
peumothorax
When can a pneumothorax occur from the inside?
if the P(pleural) is very positive, tumor, infection, or over expansion
True or False? Increasing surface tension makes it easier to reinstall a collapsed lung.
F. decreasing surface tension
True or False? Intracellular pressure matches atmospheric when the normal lung is at rest.
F. sub-atmospheric
How is the rib cage affected if there is a pneumothorax?
rib cage expands slightly (air flows in and lung collapses)
When does the lung volume plateau?
maximum vital capacity
True or False? The lung is always trying to collapse so it always has a positive pressure.
T.
What is positive pressure generated by?
recoil of lungs
True or False? Both chest wall and chest wall and lung (respiratory system) pressures can be both negative and positive.
T
% vital capacity at neutral point:
60%
% TLC at FRC:
40%
Which is more positive at FRC, chest wall pressure or respiratory system pressure?
respiratory system pressure
The slope of the lung pressure vs % vital capacity graph is linear until what % vital capacity?
75%
At what % vital capacity are lung pressure and respiratory system pressure equal?
about 55%
% TLC at RV:
25%
How is surface tension offset?
surfactant
Compliance dec w these 2 diseases:
Resp Distress Syndrome, Firbrosis
Low compliance require (larger/ smaller) translung pressure
larger
Emphysema destroys:
elastic recoil of lung, inc compliance
Translung P:
diff bw pleural and atmospheric
Compliance =
delta V/ delta P
Lungs compliance =
delta V/ delta P(pleural)
Average compliance:
0.2L / cm H2O
Is the lungs more or less distensible at high volumes?
less
What does compliance affect?
work of breathing
This disease results in inelastic scar-tissue:
Fibrotic Lung disease
This diseases results from a lack of surfactant in the lungs:
RDS
Compliance increases with this disease:
emphysema
If compliance is increased, will the translung pressure vs vital capacity graph shift up or down?
up
What corrects for the decreased compliance at higher volumes?
specific compliance
Types of phospholipids in surfactant:
DPPC, PG
Functions of proteins in surfactant:
regulate surfactant turnover, immune regulation, formation of tubular myelin
What causes the release of surfactant?
Beta adreneric agonist, activators of PKC, leukotrienes, purinergic agonist
How is surfactant cleared?
repute, lymphatics, macrophages
Which has higher pressure, small or large bubble if they have the same surface tension?
small bubble (P = 2T/r)
Law of LaPlace:
P = 2T/r
Without surfactant would the lower lung volumes require greater or less transmural pressure to keep the lungs expanded?
greater
What, besides surfactant, prevents alveoli from collapsing/
interdependence, channels that equalize pressure
Does compliance increase or decrease with increase in volume?
decrease
What does the slope of the P-V curve represent?
compliance
Does the slope (compliance) increase or decrease as delta p increases.
decreases
normal compliance value:
0.2 L/cm H2O (200 mL of air per 1cm H2O = 200mL/cm H2O
Which is on the x-axis in the P-V curve?
Pressure
Is the slope of the graph for a patient with emphysema greater or less than the normal curve?
greater. Remember: steeper curve (delta v/ delta P) = increases compliance. emphysema = high compliance (about 400 mL/cm H2O)
Is the slope of the graph for a patient with fibrosis greater or less than the normal curve?
less (Remember: steeper curve (delta v/ delta P) = increases compliance). fibrosis = low compliance (about 100 mL/cm H2O)
The work of breathing can be determined by the area under the curve of which graph?
Flow - Volume Loop
How would filling the lungs with fluid affected surface tension?
no surface tension
Is more or less pressure required to increase volume of lungs when filled with air vs. water
more
Does the compliance of the lungs increase or decrease when inflated with water?
increases
Is water inflation or air inflation non-compressible?
water inflation
Factors affecting lungs recoil;
elastic fibers (1/3) and surface tension (2/3)
How are compliance and recoil changed with fibrosis?
recoil increases. compliance decreases
How are compliance and recoil changed with emphysema?
recoil decreases, compliance increases
Diseases that cause changes in airway resistance:
asthma and emphysema
Shorthand calculation for airflow resistance:
1/r^4
What % of the total oxygen consumption and total cardiac output is used for moderate exercise?
1-3%
What % of the oxygen consumption is used in patients with pulmonary disease?
20-30% or more
What does lung recoil primarily influence?
tidal volume (V(T))
How is the tidal volume affected with an increase in compliance?
increases tidal volume
The lungs and chest walls can get up to what % of cardiac output?
20%
Expiratory flow rate (Vdot (E)) =
V(T) X frequency
What does airflow resistance primarily influence?
frequency
What factors can alter the viscosity of the air?
humidity and altitude
What can h=physically obstruct the upper airways?
mucus and other factors
These cause bronchoconstriction:
parasympathetic neurons (muscarinic receptors), histamine, leukotrienes
Factors affecting airway resistance:
length, viscosity, radius, mucus, edema, contraction of bronchial smooth muscle, increase air density (scuba diving)
What causes bronochodilation?
CO2, epinephrine (Beta 2- receptors)
How to calculate the total resistance for a system in series:
R1 + R2 + …
How to calculate the total resistance for a systems in parallel:
1/R1 + 1/R2 +…
Does resistance to airflow increase or decrease as lung volume increase?
decreases
What pulls open the airways?
negative pleural pressure of inhalation
What causes the flow to be turbulent in the larger airways?
higher resistance and in series (and parallel)
True or False? Resistance in the large airways in only in series.
F. both series and parallel
Reynold’s Number =
(2r (airwaY) v (airflow) d (of air))/ viscosity (of air)
Laminar flow will predominate when Reynold’s number is
less than 2000
How will airflow be affected if the Reynold’s number is less than 2000?
airflow for a given pressure will increase
If Reynold’s number is greater than ____ turbulent flow will predominate.
2000
What 2 factors can increase turbulent flow?
increase in airflow velocity or increase in airway radius
Expirated ventilation is aka:
minute ventilation
Expired ventilation =
tidal volume X frequency (breathes per minute)
The optimum level of work is at how many breathes per minute?
15
How many mL is our expired ventilation (minute ventilation)?
6000 ml/min
Tidal volume for emphysema and pulmonary fibrosis relative to normal:
doubles to 1000ml for emphysema and about half to 200 for pulmonary fibrosis (breaths per minutes follow the same pattern)
Factors affected the rate of airflow through the airways:
Laminar vs. turbulent flow, airflow resistance in series and parallel, “flow limitation” (during expiration) and the “equals pressure point”
Factors that increase airway resistance:
mucus, edema, contraction of smooth muscle, inspired gas density and viscosity
How is inspiratory muscle effort affected with volume increases?
it increases
How is recoil of lung affected with volume increases?
it increases
How is airway resistance affected with volume increases?
it decreases
What does RV stand for?
Residual Volume
What fraction of tidal volume is expired during FEV(1)?
2/3
Peak flow rate in L/sec for both inspiration and expiration:
about 10 L/sec (at 25% of volume expired)
PEFR =
Maximal effort
What region represents the flow limitation?
effort-independent region
How does the maximum effort curve for a patient with asthma or emphysema compare to the normal curve?
lower than, generate less pressure
Is the expiratory flow or volume greater or less in a patient with emphysema or asthma?
less
True or False? The reserve volume for patients with emphysema or asthma is larger than normal.
F. smaller
average transpulmonary pressure:
30 cm H2O
Average transairway pressure:
30 cm H2O
Average pleural pressure:
-30 cm H2O
How will the pressure be affected if the gas velocity is increased?
pressure decreases
What is transairway pressure?
pressure difference between the airway opening and the alveolus.
What is transpulmonary pressure?
difference between the alveolar pressure and the intrapleural pressure in the lungs
Both transpulmonary and transairway pressures are calculated by subtracting this from a value:
pleural pressure
What becomes negative, transpulmonary or transairway pressure?
transairway
How is the resistive drop altered in a diseased state?
greater resistive drop
How is the equals pressure point affected in the diseased state?
it is close to alveoli in non-cartilage airways
How does the body try and offset the airway resistance in diseased state?
increase lungs volume
What will happen as airway resistance continues to increase?
crackles and rales on inspiration
When is airway compression required?
beyond the equal pressure point in expiration (negative transairway pressure)
