Mechanics I Flashcards
1
Q
What is the primary function of the Respiratory System:
A
- Gas exchange
- bulk air movement (ventilation)
- Gas transfer (Diffusion)
- Gas delivery (transport/perfusion)
- Regulation (match supply with demand
2
Q
How does air flow?
A
- Air movement depends on the:
- pressure difference b/w
- barometric pressure
- alveolar pressure
- can’t control barometric pressure, so have to change alveolar pressure to breathe
- resistance
- pressure difference b/w
- Airflow: Ventilation=bidirectional (inhale/exhale)
- V=P1-P2/R
- inhale: Pa
- Exhale: Pa>Pb
3
Q
Pleural space function:
A
- Negative relative to Barometric pressure at rest
- connects opposing forces:
- Abdominal wall-expands
- Lungs: Collapse
4
Q
What is the resting lung volume:
A
- when opposing forces are equal
- abdominal wall
- lungs
5
Q
How does inspiration occur?
A
- Active process-contract inspiratory muscles
- diaphgram mainly
- external intercostal m.
- need Pa
- Activate inspiratory muscles
- Increase Thorax volume
- Intrathorax pressure decreases
- Air into lungs
6
Q
Muscles of inspiration:
A
During relaxed resting/tidal breathing
- Diaphragm-produces 75% of inspiratory force during relaxed tidal breathing
- dome shape at rest
- flattens when contracts
- increases height of thoracic cavity
- elevates lower ribs
- External Intercostal muscles-produces 25% of inspiratory force during relaxed tidal breathing
- elevate ribs
- Accessory muscles: Heavy breathing, deep breathes
- scalene
- sternocleidomastoid
- parasternal intercostal
7
Q
What will happen if you can’t contract the diaphragm?
A
intubtion or diaphragm stimulation
8
Q
How do we exhale? (resting)
A
-
Passive process (does not require muscle contraction)
- forced exhalation is active requiring expiratory muscles
- ex: exercise
- forced exhalation is active requiring expiratory muscles
- Steps:
- inspiratory muscles relax
- elastic recoil pulls inward on the lung surface
- alveolar pressure increases
- air flows out of the lungs
9
Q
Muscles of forced exhalation:
A
- Abdominal muscles compress–>elevate diaphragm
- internal oblique
- external oblique
- transverse abdominis
- Rectus abdominis
- Triangularis sterni-depress sternum
- Internal intercostal-depress ribs
10
Q
What is lung recoil?
A
- Elastin fibers
- tie alveoli together
- link alveoli, airways (conducting airways-bronchioles), blood vessels to lung surface
- factor into interdependence
11
Q
Interdependence:
A
- Elastin fibers connect lung to respiratory system
- &surfactant
- forces applied to one unit are transferred and applied to adjacent units
- makes inflation of lungs easier
- Expiration:Deflation:
- stabilizes alveoli during deflation
- adjacent alveoli provide structural stabilization that limits alveolar collapse
12
Q
How was negative pressure ventilation used in Polio treatment?
A
- Polio
- designed to inflate the lungs by pressure gradients
- similar to normal ventilation
13
Q
Functional Residual Capacity(FCR)
A
- amount of air left in your lungs at the end of a tidal breathe
- equilibrium point of thorax between
- chest wall
- lungs
14
Q
Pressure Gradients
A
- Transthoracic pressure (Prs)
- Transrespiratory pressure
- =Pa-Pb=PL+Pw
- direct determinant of air flow
- Transpulmonary pressure (PL)
- Pa-Ppl
- pressure across the lung wall
- stretched or compressed
- Transmural chest wall pressure (Pw)
- Ppl-Pb
15
Q
Pressures: General
A
- Pressure at the mouth is atmospheric (barometric)
- Barometric pressure is referenced as zero
- pressures are relative to barometric pressure
- Typically expressed in cmH2O, rather than mmHg
- more accurate for low pressures
16
Q
What are the 3 main pressure that drive inspiration or expiration:
A
- Alveolar pressure=Pa
- Pleural Pressure=Ppl or Pip
- Barometric pressure: Pb
17
Q
Esophageal pressure (Pes)
A
- used to estimate pleural pressure
18
Q
- @FRC before inspiration
- 50% inspiration
- End of inspiration
A
- @ FRC
- Volume=0
- Pleural pressure=-5
- Expiratory flow= 0
- Pa=0
- 50% inspiration:
- Volume= increased
- Ppl=decreased=-8
- Expiartory flow= decrease (-.5)
- Pa=decrease (-1)
- End of inspiration:
- Volume=Peak max
- Ppl=Most negative!
- Expiratory flow= 0
- Pa=0
19
Q
What drives air flow?
A
differences in Pa and Pb
20
Q
In a normal individual how do you check for normal breathing mechanics:
A
- Smooth synchronized movement of chest and abdomen circumference in parallel
- airflow slight lag
21
Q
Pneumothorax
A
- Intrapleural space open to atmosphere (not sealed)
- Ppl=Pb
- punctured lung
- Loss of funcitonal attachment between chest wall andl ung
- activation of inspiratory muscle pulls air into pleural space
- radiolucency where lungs would be
22
Q
Tidal Volume
A
- change in volume during one respiratory cycle at rest
- normal adult=500-750mL
23
Q
Residual Volume
A
- volume of air left in the lung after the end of max exhalation
- adults=1.2L
24
Q
Vital Capacity:
A
- Total lung volume available for active respiration (4.75L)
- End of max inhalation to end of max exhalation
25
Q
Total lung capacity:
A
- Volume of air in lungs @ max inspiration
- adults=6L
26
Q
Compliance:
A
- how easily the lungs can expand (exhale or inhale)
- delta V/dPpl
- Lungs=less compliant at high lung volumes
- Emphysema
- breakdown of lung tissue
- lose lung elastic recoil
- Chest wasll recoil>
- INCREASE LUNG COMPLIANCE
- high lung volume
- Pulmonar fibrosis:
- scar tissue in lungs(more stiff)
- lung elastic recoil>>
- Decrease Lung compliance
- more pressure to expand=harder
- low lung volume
*
27
Q
Surface tension
A
- Attraction of water molecules at an air water interface
- Big factor in lungs elastic recoil
- causes a pressure on alveoli
- If surface tension is the same in both alveoli, pressure will be lowest in larger aleolus, and higher in the smaller alveolus
- Air will follow the pressure gradient: Smaller alveoli will collapse/empty into larger alveoli
- effects alveolar fluid balance
- increased surface tension promotes formation of pulmonary edema where radius is smallest
28
Q
Alveoli: Pressure resulting from Surface tension
A
- If surface tension is the same in both alveoli, pressure will be lowest in larger aleolus, and higher in the smaller alveolus
- Air will follow the pressure gradient:
- Smaller alveoli will collapse/empty into larger alveoli
29
Q
Law of Laplace
A
- P=T/r
- T=surface tension
- P=pressure
- Radius
- Pressure is proportional to surface tension
- inversely proptional to radius
30
Q
Effect of surface tension on alveolar fluid balance
A
- increased surface tension promotes formation of pulmonary edema where radius is smallest
31
Q
Surfactant
A
- reduces surface tension
- lower in smaller alveoli bc surfactant is more concentrated
- stabilizes alveoli
- prevents alveoli from collapsing
- equalize pressure–>won’t go to larger alveoli
- keeps alveoli dry
- prevents water being drawn into alveoli from interstitial fluid
- responsible for hysteresis
32
Q
Composition of surfactant:
A
- Phospholipid-77%
- DPPC-62%
- Neutral lipids-13%
- cholesterol
- Surfactant Apoprotein-8%
- SP
33
Q
Surfactant system developement
A
- Not full mature until week 36
34
Q
Fetal lung maturity test
A
- testing amniotic fluid for biochemical markers associated with surfactant production
35
Q
Type II pneumocytes
A
- produces surfactant
- cell differentation week 17-26
- accelerated by glucocorticoids in premature babies
- regulation of secretion:
- Stimulated by:
- Stretch of alveolar septa (walls)
- B-adrenergic agonists
- Stimulated by:
36
Q
IRDs
A
- Infant respiratory disease syndrome
- premature infants born before type II cells have mtured
- surfactant deficiency
- Tx: synthetic surfactant=survanta or glucocorticoids
37
Q
ARDs
A
- Acute Respiratory Distress syndrome
- Adults
- damage type 2 pneumocytes
- causes:
- aspiration of stomach acid (GERD)
- Smoke or other toxic fumes (Fire not cigs)
- Pneumonia
- Shock
- Sepsis
- trauma (bruising of lungs)
- viral infection
38
Q
PAP
A
- Pulmonary alveolar proteinosis
- progressive accumulation of surfactant
- impairs gas exchange
39
Q
Hysteresis
A
- Hysteresis
- difference in change of volume between inhalation and exhalation
- due to difference in air/liquid interface=surfactant
- inflate lungs with saline=less hysteresis
- greater compliance=Shift up and left
- Lower compliance in air
40
Q
A
41
Q
Dynamic Compliance
A
- Measured @ rest=FRC
- from Residual volume (RV) to Total lung capacity (TLC)
- used for Lung compliance ONLY
- C=dV/dP
- Increased compliance=steep slope
- shift up and left
- pulmonary emphysema
- Decreased compliance=flat slope
- shift down and right
- ARDs or pulmonary edema
42
Q
Surfactant effect on Dynamic Compliance:
sufficient surfactant
A
- sufficient surfactant
- maintains FRC
- increases compliance
- facilitates lung expansion
- delays lung closing
43
Q
Deficiency in surfactant causes:
A
- increase surface tension
- increased alveolar fluid
- decreased lung compliance
- collapsed alveoli
