module 11 mechanics of breathing

Question 1

4 mechanics of breathing

Answer 1

airway resistance
lung compliance
opposing lung forces (elastic recoil vs chest wall expansion)
work of breathing

Question 2

lungs and recoil

Answer 2

lungs have natural recoil tendency

Question 3

chest wall prefers expansion

Answer 3

inspiration

• chest wall muscles contract elevating ribs, diaphragm moves down
  expiration:
• lung deflates passively d/t recoil and relaxation of diaphragm

Question 4

lung during heavy breathing (exercise)

Answer 4

elastic forces not strong enough to cause rapid expiration

• abd. muscles contract pushing up
• > compression of lungs

Question 5

muscles of inspiration

Answer 5

Major:

• intercostal muscles
• diaphragm
• recuts abdominis
  accessory: when major are tired
• serratus posterior superior
• sternocleidomastoid
• scalenus muscles
• intercostal muscles

Question 6

airway resistance

Answer 6

resistance = driving pressure/rate of airflow
influence by radius and pattern of gas flow
- resistance inc. as radius dec.
– radius dec. from trachea to terminal bronchioles

Question 7

pattern of gas flow

Answer 7

turbulent flow
- bronchospasm
laminar
transitional

Question 8

turbulent flow

Answer 8

nasal cavity -> large bronchi

- inc. friction and resistance

Question 9

laminar

Answer 9

small airways

smooth flow

Question 10

transitional flow (mixed)

Answer 10

large airway bifurcations

Question 11

newborns and resistance

Answer 11

increased until about 5 y/o

Question 12

lung compliance

Answer 12

compliance = change in volume/ change in pressure
- lung expandability and ease of lung inflation
2 factors
- chest wall expandability
- lung expandability

Question 13

peds and compliance

Answer 13

increased in neonates and peds < 3.5 yrs

- chest wall flexibility

Question 14

elderly and compliance

Answer 14

dec compliance

• chest wall rigidity
• dec. motility of ribs
• partial contraction of inspiratory muscles

Question 15

disease processes affecting compliance

Answer 15

• > stiffer lungs
• pneumonia
• pulmonary edema
• atelectasis
• ARDS
• pulmonary fibrosis
• obesity
• abd. distention
• pregnancy
• kyphosoliosis
• abd. surgery

Question 16

abnormal inc. in lung compliance w/ loss of elastic recoil

Answer 16

-> WOB d/t inc. effort to exhale

Question 17

functional components of respiratory system

Answer 17

neurochemical control of ventilation
mechanics of breathing
gas transport
control of pulmonary circulation

Question 18

neurochemical control

Answer 18

neural control: respiratory center
- medulla oblongata
- pons 
Chemoreceptors: 
- central
- peripheral 
Baroreceptors
Proprioceptors 
Environmental factors

Question 19

Stimulation to breathe

Answer 19

inc in arterial CO2

Question 20

respiratory center

Answer 20

efferent nerve impulses form brain -> diaphragm via phrenic nerve -> muscular contraction -> inhalation

Question 21

medullary center

Answer 21

dorsal respiratory group:
- stimulate inspiratory muscles: intercostal and diaphragm
- ramp signal: generated in increasing fashion. begin slowly and inc. for 2 seconds -> inspiration
abruptly stop for 3 seconds -> expiration

Question 22

upper pons

Answer 22

pneumotaxic center

• influence rate of respirations
• ends inspiration by inhibiting ramp

Question 23

lower pons

Answer 23

apneustic center

• pattern of respiration
• provide extra driving force for inspiratory neurons
• > prolonged inspiration

Question 24

sensory inputs

Answer 24

central chemoreceptors
peripheral chemoreceptors
Hering-Breuer stretch receptors
proprioceptors
baroreceptors 
environmental sensations

Question 25

central chemoreceptors

Answer 25

change in CO2 and pH

- increase

Question 26

peripheral chemoreceptors

Answer 26

aortic arch and carotid

sense dec. in arterial O2

Question 27

hering-breuer reflex

Answer 27

alveolar septa, bronchi, and bronchioles

• inflation of lungs -> vagus nerve stimulation to medulla -> inhibition of inspiration
• affects rate and duration
• primarily seen in neonates at and high tidal vol. (>1500mL)
• prevents overinflation

Question 28

proprioceptors

Answer 28

muscles and tendons

- body movement -> respiratory rate and depth to maintain O2

Question 29

baroreceptors

Answer 29

aortic arch and carotid

• sense change in BP
• • inc. BP -> dec. respiration
• • dec. BP -> inc. respiration

Question 30

environmental sensations

Answer 30

cold shower
pain
airway irritation
stress
smoking
infection 
fever
exercise

Question 31

Distribution of blood flow in lungs

Answer 31

affected by body position and exercise
- upright: blood flow dec. in upper regions of lungs (apices) compared to bases
- supine: blood to posterior is inc. more than anterior
affects of gravity

Question 32

Perfusion: pulmonary blood flow

Answer 32

pulmonary circulation is a low pressure system and distribution of blood flow is uneven

• zone 1
• zone 2
• zone 3

Question 33

Zone 1

Answer 33

upper regions of lungs
minimal blood flow
r/t enlarged alveolar sacs -> pressure > capillary pressure -> capillary collapse
- no gas exchange

Question 34

Zone 2

Answer 34

middle region of lungs
pulmonary artery pressure > pressure in alveoli during systole, but may fall below during diastole
- intermittent perfusion

Question 35

zone 3

Answer 35

bases of lungs
pulmonary arterial pressure > venous pressure > alveoli pressure
-> capillary vessels distended, dec. vascular resistance

Question 36

O2 requires high pressure gradient to diffuse

Answer 36

PO2 in alveoli: 104

PO2 in capillaries: 40

Question 37

affinity of hemoglobin for O2 and shifting of curve

Answer 37

normal curve: normal affinity of hgb for O2
left shift: inc. affinity of hgb for O2
- helps loading of O2 in lungs, decreased release to tissues
right shift: dec. affinity of hgb for O2
- aids in release of O2 to tissues

Question 38

factors shifting curve to left

Answer 38

increased affinity for O2

• dec. H+, inc. pH
• dec. PCO2
• dec. temp
• hypothyroidism
• carboxyhemoglobin

Question 39

factors shifting curve to right

Answer 39

decreased affinity for O2

• inc. H+, dec. pH
• inc. PCO2
• inc. temp
• hyperthyroidism
• anemia
• chronic hypoxemia
• • high altitude, congenital heart disease

Question 40

alveoli hypoxic vasoconstriction

Answer 40

alveolar hypoxia -> vasoconstriction r/t no diffusion at that alveoli, body sends blood elsewhere
chronic alveolar hypoxia -> chronic vasoconstriction -> chronic pulmonary HTN

Question 41

carbon dioxide diffusion and transport

Answer 41

dissolved in plasma (5-10%)
bicarbonate (60-70%)
carbamino compound on hgb (20-30%)

Question 42

respiratory membrane

Answer 42

what CO2 and O2 pass through for diffusion

• surfactant
• alveolar membrane
• interstitial fluid
• capillary membrane
• plasma
• RBC

Question 43

O2 concentration in alveoli and partial pressure controlled by

Answer 43

rate of absorption in blood

rate of entry of new O2 into lungs

Question 44

diffusion capacity impairment

Answer 44

alveolar thickening or capillary membrane

• pneumonia
• pulmonary edema
• interstitial lung disease
  dec. surface area
• emphysema
  inc. physical activity
• dec. time of RBC in capillary

Question 45

factors that determine ability to diffuse

Answer 45

surface area of alveoli and capillaries
integrity of capillary and alveolar membranes
available hemoglobin
solubility of gas
diffusion coefficient of the gas
differences in partial pressure (concentration)

Question 46

O2 transport mechanisms

Answer 46

dissolved in plasma ( 0.3mL O2/ 100mL blood)
bound to Hgb
- once at area of low O2 partial pressure hgb releases O2