respiratory physio 3

Question 1

what is the breathing sequence during inspiration?

Answer 1

1) brain initiates inspiratory effort
2) nerves carry the inspiratory command to the inspiratory muscles
3) diaphragm and/or intercostals contract
4) thoracic volume increases as the chest wall expands
5) intraplural pressure becomes neg
6) alveolar transmural pressure grad increases
7) alveoli expand in response to increased transmural pressure gradient. this increases alveolar elastic recoil
8) alveolar pressure falls below atmospheric pressure as the alveolar volume increases, thus establishing a pressure grad for airflow
9) air flows into the alveoli until alveolar pressure equilibrates with atmospheric pressure

Question 2

breathing sequence for expiration?

Answer 2

1) brain ceases inspiratory command
2) inspiratory muscles contract
3) thoracic volume decreases, causing intrapleural pressure to become less neg and decreasing the alveolar transmural pressure grad
4) decreased alveolar transmural pressure grad allows the increased alveolar elastic recoil to return alveoli to their pre-inspiratory volumes
5) decreased alveolar volume increases alveolar pressure above atmospheric pressure thus establishing a pressure grad for airflow
6) air flows out of the alveoli until alveolar pressure equilibrates with atmospheric pressure

Question 3

what is a tell-tale sign that expiration is in a pathologic state?

Answer 3

-if there is an effort on the patient’s part to exhale

should be passive

Question 4

Hooke’s law

Answer 4

for an elastic structure, the increase in length (or volume ) varies directly with the increase in force or pressure until the elastic limit is reached and the item breaks
-applies to lungs and ventilation

Question 5

what is lung compliance?

Answer 5

the extent of lung expansion for each increase in transpulmonary pressure

• reflects lung dispensability
• IT IS THE STEEPNESS OF THE PRESSURE/VOLUME CURVE- if the curve is steep, there is a lot of compliance
• if there is a problem, there is a decrease in the slope

Question 6

on a pressure volume curve, why is the slope steeper for expiration than for inspiration?

Answer 6

the slope is steeper for expiration because there is no active buildup of pressure. it is just a collapse
whereas inspiration builds up pressure and thus leads to a more sigmoidal curve

Question 7

what are two determinants to lung compliance

Answer 7

• elastic forces of lung tissue- elastin and collagen

- elastic forces of surface tension- water molecules on alveoli

Question 8

how does residual volume play a role in the pressure volume curve?

Answer 8

• it is the semi plateau of inspiration- super important as it would take soooo much longer to gain enough pressure for inspiration without it.

Question 9

how is compliance related to elasticity and elastic/recoil

Answer 9

• compliance is the inverse of elasticity/recoil

- as elasticity/recoil go up, compliance decreases

Question 10

hysteresis

Answer 10

• between the inspiration and expiration
• difference in inspiration and expiration limbs of pressure volume loop
• due to surface tension

Question 11

what is laplaces law?

Answer 11

P = 2T/r
P= pressure tending to collapse an alveolus 
T = alveolar surface tension
r= alveolar radius

=increase tension, increase pressure that collapses the alveolus
= increase radius, decrease the pressure

Question 12

what can counteract laplace’s law? what is responsible? what does it do? what does it prevent and what’s the main component

Answer 12

• type II epithelial cells
• secretes surfactant -decreases surface tension of the alveolar aqueous surface ( decreases T on laplace’s equation)
• prevents atelectasis (collapse lung) following expiration
• main component- lecithin

Question 13

how can we see whether a fetus’ lungs are maturing well enough? how do you treat?

Answer 13

• in utero, baby has equal amounts of sphingomyelin and lecithin production but as you reach week 32 of gestation, the lungs begin to mature and you get a decrease in sphingomyelin and increase in lecithin.
• if you take a sample of amniotic fluid and look at the lecithin/ sphingomyelin ratio and it is low, you know that there is not enough maturation in the lungs

TREATMENT- CORTICOSTEROIDS, PEEP VENTILATION, SURFACTANT

Question 14

what is the normal movement of the lungs compared to the chest wall?

Answer 14

the lungs tend to collapse while the chest wall springs out

Question 15

what occurs with the pressure volume curve when a patient has emphysema? what kind of changes do we see?

Answer 15

• with emphysema patients, they have a decrease in elastic fibers leading to an increase in compliance and a INCREASING OF THE PRESSURE VOLUME SLOPE.
• ALSO SEE AN INCREASE IN THE FUNCTIONAL RESIDUAL CAPACITY AS THERE IS MORE AIR TRAPPED IN THE LUNGS AFTER EXPIRATION
• get a higher volume breathing
• barrel shaped chest

Question 16

what does decreased lung compliance do to the pressure volume curve? to functional residual capacity? what are some examples of decreased lung compliance?

Answer 16

• decreases the pressure volume slope and decreases the functional residual compliance
• ex: collapsed alveoli such as in atelectasis from pneumonia, tb, or tumor, pulmonary edema, lung fibrosis

Question 17

how do you calculate pulmonary resistance?

Answer 17

R = (8 nl)/ pie r^4
R = airway resistance
n = viscosity of inspired air
l = length of the airway
r = radius of the airway- small airways can decrease radius most because they have smooth muscle and no cartilage

Question 18

what bronchioles have the highest resistance? when do you see them manifest as probs?

Answer 18

• medium sized bronchioles

- asthma and bronchitis

Question 19

what occurs with the pulmonary resistance when the parasympathetics are activated? what receptors does this act on and what clinical conditions do you see that in? treatment?

Answer 19

• get an increase in resistance
• receptors = M3
• see this in asthma, and muscarinic agonists admin
• treatment- use a blocker or dilator like epi or albuterol

Question 20

what occurs with the pulmonary resistance when the sympathetics are activated? what receptors does this act on and what clinical conditions do you see that in?

Answer 20

• decrease in resistance
• receptors = beta 2
• see this when administering epi and albuterol

Question 21

what occurs with lung resistance when there is a high lung volume? when do you see this?

Answer 21

• decrease in resistance but increase in traction

- seen during exercise