Ventilation Mechanics

Question 1

ventilation

Answer 1

movement of air in and out of the lungs

Question 2

respiration

Answer 2

exchange of gases (oxygen and carbon dioxide) at the tissue, b/w tissue and blood, and b/w blood and lung

Question 3

aerobic tissue respiration

Answer 3

refers to O2 utilization and CO2 production by metabolizing tissues with an ATP endproduct

Question 4

respiratory quotient (RQ)

Answer 4

volume of CO2 released/volume of CO2 consumed

Question 5

anaerobic tissue respiration

Answer 5

refers to the production of ATP w/o utilization of oxygen; only few ATP and lots of endproduct

Question 6

how is CO2 produced in anaerobic respiration?

Answer 6

due to lactic acid production which breaks down into CO2 and water:
carbohydrates → lactic acid (La:H) → La- + H+ H+ + HCO3- ←→ H2CO3 ←→ H2O + CO2

Question 7

partial pressure

Answer 7

the pressure of each gas in a mixture

Question 8

Boyle’s Law

Answer 8

PV = k, where pressure and volume are inversely proportional; differences in air pressure drives movement of air into and out of lungs

Question 9

quiet inspiration

Answer 9

downward movement of diaphragm (1-2cm) + contraction of external ICs = increased thoracic capacity and decreased pressure

Question 10

forced inspiration

Answer 10

downward movement of diaphragm (8-10cm) + contraction of external ICs + accessory muscles = increased thoracic capacity and decreased pressure

Question 11

quiet expiration

Answer 11

elastic recoil of lungs and relaxation of musculature

Question 12

forced exhalation

Answer 12

internal intercostals and abdominal muscles contract and increase lung pressure to expel air

Question 13

what force allows the lungs to move with the thoracic wall and diaphragm?

Answer 13

hydrostatic force (created by the pleural fluid)

Question 14

spirometry

Answer 14

a measurement of breathing (or lung volumes) with a spirometer

Question 15

spirometer

Answer 15

instrument used to measure breathing that consists of a dome that has been turned upside down and is floating in a water tank; the dome will rise when person breathes into tube and drops when person inhales

Question 16

tidal volume (TV)

Answer 16

amount of air inhaled or exhaled with each breath under resting conditions (~0.5L)

Question 17

inspiratory reserve volume (IRV)

Answer 17

excess air breathed in w/ accessory muscle recruitment

Question 18

expiratory reserve volume (ERV)

Answer 18

the volume of additional air that can be forcibly exhaled after a normal exhalation w/ use of accessory muscles

Question 19

vital capacity (VC)

Answer 19

the max. amount of air that can be moved in and out of lungs, measured during forceful breathing (TV + IRV + ERV)

Question 20

residual volume (RV)

Answer 20

amount of air remaining in the lungs to prevent alveoli collapse

Question 21

total lung capacity (TLC)

Answer 21

maximum amount of air contained in lungs after a maximum inspiratory effort (VC + RV)

Question 22

functional residual capacity (FRC)

Answer 22

volume of air lungs naturally obtain when no muscles of respiration are engaged (end of quiet expiration; inward elastic recoil of lung = outward recoil of thoracic cage)

Question 23

minute ventilation

Answer 23

tidal volume x respiratory rate

Question 24

alveolar ventilation

Answer 24

rate of fresh air moving in and out of alveoli; equal to respiratory rate x (VT - dead space)

Question 25

dead space

Answer 25

the volume of air occupying the non-respiratory segments of the airways (e.g. nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles) and does not participate in gas exchange

Question 26

what are the impedances to ventilation?

Answer 26

elastance and resistance

Question 27

elastance

Answer 27

a measure of the stiffness of the lungs

Question 28

low elastance indicates:

Answer 28

compliance, such as in emphysema (compliance = 1/elastance)

Question 29

high elastance indicates:

Answer 29

stiffness, such as in fibrosis and low surfactant

Question 30

elastic tissues of the lung are:

Answer 30

highly compliant

Question 31

surface tension of water and compliance

Answer 31

has low compliance compared to lung elastic tissue; water lining alveoli decreases lung compliance (increases elastance)

Question 32

what is the effect of surfactant on compliance?

Answer 32

it reduces the surface tension of water and therefore the effort needed to breathe (prod. continually after 27-28 weeks of gestation)

Question 33

resistance

Answer 33

related to the pressure needed to maintain air flow and can be likened to "drag" (pressure difference on both ends of a tube); rate of flow = change in pressure; equation is ∝ 1 / r^4

Question 34

what happens ti lungs with high resistance?

Answer 34

obstruction, such as in asthma and COPD

Question 35

which factor has the biggest influence on resistance?

Answer 35

airway diameter (caliber)

Question 36

ventilation and pleural pressure

Answer 36

changes in lung vol. occur when the muscles of ventilation move the chest wall and prod. changes in pleural pressure (the lungs are recruited)

Question 37

intrapulmonary pressure

Answer 37

pressure within the alveoli

Question 38

pleural pressure

Answer 38

pressure in the pleural cavity

Question 39

positive ventilation

Answer 39

the lungs are inflated by increasing pressure inside the alveoli (similar to mechanical ventilation)

Question 40

normal ventilation

Answer 40

lungs are expanded by reducing pressure surrounding lungs to sub-atmospheric pressure (-ve pressure)

Question 41

what affects pleural pressure?

Answer 41

pneumothorax or excess fluid accum.

Question 42

pleural pressure

Answer 42

always negative during quiet breathing due to competition between elastic recoil of lung and rib cage (expand), more negative during inspiration (i.e. fluctuates during breathing cycle)

Question 43

what is the intrapulmonary pressure during inspiration?

Answer 43

negative (less pressure)

Question 44

what is the intrapulmonary pressure during expiration?

Answer 44

positive (more pressure)

Question 45

what happens when the intrapulmonary pressure is the same as the atmosphere?

Answer 45

there is no airflow

Question 46

before inspiration

Answer 46

- no breathing; resp. muscles are relaxed - lung volume is functional residual capacity - equally matched forces between lung elastic recoil and thoracic cage elastance to result in a negative pleural pressure

Question 47

during inspiration

Answer 47

- muscles of respiration expand thoracic cage - outward forces are greater than inner forces resulting in a more negative plural pressure - (muscle forces + thoracic cage elastance > recoil)

Question 48

end of inspiration

Answer 48

- inspiratory muscles active, holding lung at fixed volume - increased lung elastic recoil due to stretching, thoracic cage elastance + muscle forces tends to make chest wall expand - forces equally matched to result in even more -ve pleural pressure (forces pull on pleural space) - intrapulm. pressure is zero = no airflow

Question 49

during expiration

Answer 49

- inspiratory muscles inactive (allows passive recoil of lung for expiration) - lung elastic recoil is increased and is larger than thoracic wall elastance (causing lungs' volume to decrease) - outward forces are less than inward forces and intrapulm pressure becomes less -ve

Question 50

pleural pressure at rest

Answer 50

it fluctuates during the breathing cycle but is almost always atmospheric (negative; during inspiration)