lecture 3

Question 1

what is compliance and elastic recoil?

Answer 1

compliance = the ease in which the lungs expand
elastic recoil = the tendency of the lungs tissue to return to its resting state of inspiration

Question 2

what does the compliance curve show?

Answer 2

it shows the change in volume relative to pressure

• there are separate curves inspiration and expiration

Question 3

how do you calculate alveolar pressure?

Answer 3

elastic recoil pressure (transpulmonary pressure) + intrapleural pressure

Question 4

what forces drives the intrapleural pressure?

Answer 4

muscle contraction and thoracic expansion

Question 5

what forces drives elastic recoil pressure?

Answer 5

elastin, collagen, tissue forces, and surface tension

Question 6

what are pulmonary function testing?

Answer 6

its a group of tests that measure how well the lungs inhale, exhale, and exchange gasses and is the gold standard for diagnosing lung diseases

Question 7

what is spirometry?

Answer 7

it measures the airflow and lung volumes during forced breathing maneuvers

Question 8

what are the main measurements of Spirometry?

Answer 8

• Forced vital capacity ( Total volume of air that can be forcefully exhaled after a deep inhalation
• Forced expiratory volume in 1 second (volume of air exhaled in the first second)
• FEV1 and FVC ratio

Question 9

what is pneumotachograph and how does it work?

Answer 9

its a technique used to measure airflow. pts,. breath through a tube with a resistor and the pressure transducer measures the pressure difference across the resistor

Question 10

what is ETCO2?

Answer 10

the maximum concentration of CO2 at the end of exhalation

Question 11

how is intrapleural pressure indirectly measured?

Answer 11

a small balloon catheter is inserted into the esophagus, the balloon is inflated to record the esophagus pressure because that pressure is relatively the same to the intrapleural pressure

Question 12

what clinical applications does measuring esophagus pressure have?

Answer 12

can assess
- lung mechanics
- ventilator settings
- prevent lung overdistension (barotrauma)

Question 13

why is airway pressure and alveolar pressure equal during static conditions?

Answer 13

because no airflow is taking place

Question 14

what is elastic resistance?

Answer 14

its the force needed to overcome lung and chest wall elasticity.

Question 15

what is non elastic resistance?

Answer 15

• airway resistance
• tissue resistance

Question 16

when measuring intrapleural pressure, what does dashed lines represent?

Answer 16

its the changes in intrapleural pressure needed to overcome elastic recoil of the alveoli

Question 17

when measuring intrapleural pressure, what does solid lines represent?

Answer 17

intrapleural pressure needed to overcome both elastic recoil and non elastic resistance

Question 18

what is the role of type 1 pneumocytes?

Answer 18

they are thin epithelial cells which is important for gas exchange

Question 19

what is the role for type 2 pneumocytes?

Answer 19

it secretes surfactant and reduces surface tension

Question 20

how can you calculate transpulmonary pressure under static conditions?

Answer 20

airway pressure - esophageal pressure

Question 21

how do you calculate lung compliance?

Answer 21

change in lung volume / change in transpulmonary pressure (elastic recoil of the lungs)

Question 22

define low compliance?

Answer 22

any change in pressure leads to a small change in volume

Question 23

define high compliance

Answer 23

the change in pressure leads to a large change in volume

Question 24

what is the x axis and y axis on the compliance curve

Answer 24

x = transpulmonary pressure
y = lung volume

Question 25

what is hysteresis?

Answer 25

the difference between the inspiration curve and expirationcirve on the compliance graph

Question 26

why does obesity reduce volume changes in the lungs and a reduced compliance

Answer 26

because the fat makes it harder for the diaphragm to move downward to expand the lungs

Question 27

why is hysteresis clinically important?

Answer 27

because surfactant function can be inferred

Question 28

how does pulmonary fibrosis cause low compliance

Answer 28

fibrosis tissue deposited in interstitial space which causes the lungs to become more stiff and harder to expand

Question 29

how does emphysema cause an increase in compliance?

Answer 29

because emphysema destroys alveolar walls and creates larger air spaces with fewer elastic fibers. its important to note that although there is an increase in compliance there is a loss of recoil which impairs exhalation

Question 30

what is the role of surfactant?

Answer 30

it reduces surface tension and prevents alveolar collapse when exhaling

Question 31

what is functional residual capacity?

Answer 31

the volume of airy left after a normal tidal exhalation (expiratory reserve volume + residual volume)

Question 32

what happens to the pressures when a pt. uses extreme efforts to exhale below FRC?

Answer 32

the intrapleural pressure rises above airway pressure

Question 33

what happens to the volume and pressure when a person is inspiring

Answer 33

volume and pressure increase * and both decrease when expiration takes place

Question 34

why are curves for inspiration and expiration different?

Answer 34

because they have different forces to overcome at each phase

Question 35

what are the 5 contributing factors to compliance?

Answer 35

1. alveolar recruitment 2. airway resistance 3. stress relaxation 4. gas absorption 5. surface tension