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
Total lung capacity:
* Volume of air in lungs @ max inspiration
* adults=6L
26
Compliance:
* 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
Surface tension
* 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
Alveoli: Pressure resulting from Surface tension
* 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
Law of Laplace
* P=T/r
* T=surface tension
* P=pressure
* Radius
* Pressure is proportional to surface tension
* inversely proptional to radius
30
Effect of surface tension on alveolar fluid balance
* increased surface tension promotes formation of pulmonary edema where radius is smallest
31
Surfactant
* 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
Composition of surfactant:
* Phospholipid-77%
* DPPC-62%
* Neutral lipids-13%
* cholesterol
* Surfactant Apoprotein-8%
* SP
33
Surfactant system developement
* Not full mature until week 36
34
Fetal lung maturity test
* testing amniotic fluid for biochemical markers associated with surfactant production
35
Type II pneumocytes
* 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
36
IRDs
* Infant respiratory disease syndrome
* premature infants born before type II cells have mtured
* surfactant deficiency
* Tx: synthetic surfactant=survanta or glucocorticoids
37
ARDs
* 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
PAP
* Pulmonary alveolar proteinosis
* progressive accumulation of surfactant
* impairs gas exchange
39
Hysteresis
* 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
41
Dynamic Compliance
* 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
Surfactant effect on Dynamic Compliance:
sufficient surfactant
* sufficient surfactant
* maintains FRC
* increases compliance
* facilitates lung expansion
* delays lung closing
43
Deficiency in surfactant causes:
* increase surface tension
* increased alveolar fluid
* decreased lung compliance
* collapsed alveoli
