Lecture 9 2/1/24

Question 1

Which processes are involved with delivering gases within the body?

Answer 1

-ventilation
-circulation
-perfusion
-diffusion

Question 2

What is ventilation?

Answer 2

movement of gas into and out of the lung

Question 3

What is minute ventilation?

Answer 3

total volume of air breathed per minute

Question 4

What is tidal volume?

Answer 4

the volume of each breath

Question 5

What is respiratory frequency?

Answer 5

the number of breaths per minute

Question 6

What are the characteristics of pulmonary circulation?

Answer 6

-receives total output of right ventricle
-low pressure and low resistance
-involved in gas exchange

Question 7

What is perfusion?

Answer 7

delivery of blood in capillaries surrounding the alveolar space in the lungs

Question 8

What is a V/Q ratio?

Answer 8

comparison of ventilation to perfusion

Question 9

What is diffusion?

Answer 9

flow of particles from a region of high pressure to a region of low pressure

Question 10

Where does gas movement take place?

Answer 10

-within alveoli: air to air
-across alveoli into blood: air to liquid
-from blood into tissues: liquid to tissues

Question 11

What are the general characteristics of conducting airways?

Answer 11

-conduits to get air to alveoli
-no gas exchange occurs

Question 12

Which spaces comprise anatomic dead space?

Answer 12

-nasal cavity
-pharynx
-larynx
-trachea
-bronchi
-bronchioles

Question 13

What are the characteristics of alveolar dead space?

Answer 13

-caused by poor perfusion of alveoli
-prevents gas exchange
-blood flow is disrupted/absent while alveolus is ventilated

Question 14

What is physiologic dead space?

Answer 14

alveolar dead space + anatomic dead space

Question 15

Why is it important to minimize the amount of plastic tubing when ventilating a patient?

Answer 15

decrease the amount of dead space contributed by the tubing

Question 16

What is the importance of calculating the tidal volume minus the dead space volume?

Answer 16

it represents the actual volume of gas available for gas exchange

Question 17

What are the characteristics of minute ventilation?

Answer 17

-amount of fresh gas entering lungs per minute
-estimated by resp. rate x tidal vol. in simplest form

Question 18

What is alveolar ventilation?

Answer 18

amount of fresh gas reaching the alveoli per minute

Question 19

How can alveolar ventilation be increased?

Answer 19

-increase tidal volume
-increase respiratory rate

Question 20

Why is it possible to measure alveolar ventilation?

Answer 20

-no gas exchange occurs in the anatomic dead space, thus all CO2 must come from alveolar gas
-measuring CO2 in clinic can provide a measure of alveolar ventilation

Question 21

What are the characteristics of the dead space/tidal volume ratio?

Answer 21

-identifies the fraction of each breath that ventilates dead space
-can change with disease and exercise
-changes tend to reflect alveolar/physiologic dead space changes

Question 22

What is the purpose of dead space?

Answer 22

-warming and moistening of air
-particle clearance

Question 23

What are the general steps of inhalation?

Answer 23

-resp. muscles contract
-thorax expands
-lung stretches
-neg. pressure forces air into lungs

Question 24

What are the general steps of expiration?

Answer 24

-resp. muscles relax
-thoracic volume decreases
-lung compresses
-increased pressure forces air out of lungs

Question 25

What are the characteristics of exhalation?

Answer 25

-does not require muscular effort in normal animals at rest -can be assisted by muscle contraction during exercise or due to disease

Question 26

Why are horses unique in terms of exhalation?

Answer 26

they have an activate phase of contraction when normal and at rest

Question 27

What are the characteristics of the diaphragm?

Answer 27

-most important inspiratory muscle -innervated by phrenic nerve -contraction pulls diaphragm caudally to expand thoracic cavity

Question 28

What is the main function of external intercostal contraction?

Answer 28

pull ribs rostral and outward to expand thoracic cavity volume

Question 29

What is the main function of the abductor muscles?

Answer 29

prevent collapse of the nares/upper airways during inspiration

Question 30

How does the pressure in the alveolar space differ based on the phase of respiration?

Answer 30

-pos. pressure for expiration -neg. pressure for inspiration

Question 31

What is the resting pressure of the pleural space?

Answer 31

-4 cmH2O

Question 32

What happens as the lungs deflate and fall away from the chest wall?

Answer 32

generates negative pressure

Question 33

What is the inspiratory pressure of the intrapleural space?

Answer 33

-8 cmH2O

Question 34

What are the characteristics of transpulmonary pressure?

Answer 34

-difference between pressures within the airways and the pleural pressures -driving force behind expanding and contracting lungs

Question 35

What is distensibility?

Answer 35

the ability of the lung to stretch

Question 36

What is elasticity?

Answer 36

the capability of a strained body to recover its size and shape after deformation

Question 37

What is compliance?

Answer 37

change in the dimension of a structure for a change in applied force

Question 38

What is the relationship between compliance and elasticity?

Answer 38

compliance is the inverse of elasticity

Question 39

What is residual volume?

Answer 39

air that remains in the lung after it is exposed to atmospheric pressure

Question 40

What is functional residual capacity?

Answer 40

air left in the lung at the end of normal expiration

Question 41

What is total lung capacity?

Answer 41

maximum amount of air that can be in the lungs

Question 42

What are the limiting factors of total lung capacity?

Answer 42

-collagen in pleural surface -rib cage

Question 43

What is surface tension?

Answer 43

elastic tendency of a fluid surface to acquire the least surface area possible

Question 44

Why is surface tension important in the alveolus?

Answer 44

-water molecules have tendency to go towards alveolar membrane -makes water layer in alveolus thinner, favoring collapse

Question 45

Which alveoli are more likely to collapse due to surface tension?

Answer 45

those with a smaller radius

Question 46

What are the characteristics of surfactant?

Answer 46

-produced by type II pneumocytes -has hydrophilic and hydrophobic ends -opposes natural attraction between the water molecules -reduces surface tension

Question 47

Why is surfactant important to the alveolus?

Answer 47

-promotes alveolar stability -increases lung compliance (makes inflation of lungs easier)

Question 48

What determines lower airway resistance?

Answer 48

-length -radius

Question 49

How does inspiration impact airway resistance?

Answer 49

-increased radius -decreased resistance

Question 50

How does contraction of bronchial smooth muscle impact airway resistance?

Answer 50

-decreased radius -increased resistance

Question 51

Which breath function is more exaggerated during resp. distress?

Answer 51

expiration

Question 52

Which portion of the nervous system stimulates airway muscle contraction?

Answer 52

parasympathetic system

Question 53

Which type of receptor mediates airway dilation?

Answer 53

beta-2 adrenergic receptor