Ventilation/Mechanics I

Question 1

Vol of lungs at rest determined by?

Answer 1

coupling of chest wall and lungs:

one expands, other expands

Question 2

Coupling due to? (2)

Answer 2

1) intrapleural fluid

(b/w parietal and visceral)

2) sealed cavity (Boyle’s law)

Question 3

Intrapleural Pressure is?

Purpose?

Answer 3

P in pleural cavity < atmospheric P

keeps lungs expanded

keeps chest wall from overexpanding

Question 4

Which elastic force favors collapse?

Answer 4

lung (recoil)

Question 5

Which elastic force favors expansion?

Answer 5

chest wall

Question 6

Lung recoil forces due to? (2)

Answer 6

1) collagen and elastic fibers in interstitial matrix
2) surface tension in alveoli

Question 7

Chest wall elastic forces due to?

Answer 7

tendons and mm b/w ribs

Question 8

Antagonistic action of lung/chest forces creates?

Answer 8

negative intrapleural P

Question 9

Intrapleural pressure counteracts what?

Answer 9

elastic forces of wall and lung

Question 10

Atelectasis is?

Answer 10

abscence of gas from lung

due to failure to expand

Question 11

Punctured chest wall causes?

Answer 11

pneumothorax (air in pleural cavity)

Question 12

Traumatic pneumothorax from?

Answer 12

punctured chest wall

Question 13

Spontaneous pneumothorax from?

Answer 13

hole in lung

Question 14

Inspiration mm?

Answer 14

diaphragm

external intercostals

accessory (SCM, scalenes)

Question 15

Eupnea is?

Answer 15

respiration at rest

Question 16

What happens to pressure and volume during inspiration?

Answer 16

vol ↑

pressure ↓

Question 17

Expiration mm?

Answer 17

diaphragm

internal intercostals

abdominal mm

Question 18

What happens to intrapleural pressure during active expiration?

Answer 18

becomes positive

Question 19

What happens to pressure and volume during expiration?

Answer 19

vol ↓

pressure ↑

(cavity gets smaller)

Question 20

Inspiration at rest:

intrapleural pressure?

Answer 20

from -5 cm H2O to -8 cm H2O

Question 21

Inspiration at rest:

alveolar pressure (airway pressure)

Answer 21

from 0 to negative

pulls air in

Question 22

Expiration at rest:

alveolar pressure (airway pressure)

Answer 22

from neg to positive

pushes air out

Question 23

3 types of dead space?

Answer 23

1) anatomical
2) alveolar
3) physiological

Question 24

Anatomical Dead Space gas is?

Answer 24

vol of gas in conducting airways

~ 1ml/lb body wieght

Question 25

Anatomical Dead Space gas does?

Answer 25

humidifies

purifies

↓ velocity

Question 26

Alveolar Dead Space due to?

Answer 26

un-perfused alveoli

(not all capillaries are open at same time so some alveoli have air but not blood)

Question 27

Physiological Dead Space is?

Answer 27

anatomical DS + alveolar DS

Question 28

Tidal Vol (V_T) is?

Answer 28

vol of air moving in/out of lungs at rest

~ 500 ml

Question 29

Tidal Vol eqn

Answer 29

V_T = V_D + V_A

V_D = dead space vol

V_A = alveolar vent vol

Question 30

Dead space vol is?

Answer 30

amount of V_T not available for gas ex

~150 ml

Question 31

Alveolar vent vol is?

Answer 31

amount of V_T available for gas ex

~350 ml

Question 32

Alveolar minute ventilation is?

Answer 32

ºV_A = V_A x (breaths/min)

more accurate estimate of gas ex than ºV_T

Question 33

Alveolar Ventilation eqn

Answer 33

ºV_A = V_T - V_D

V_D = total dead space

Question 34

P_Aco₂ is good measure of what?

Answer 34

ventilation:

high P_Aco₂ = hypoventilating

low P_Aco₂ = hyperventilating