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Week 42 > Mechanics I > Flashcards

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
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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
  • Airflow: Ventilation=bidirectional (inhale/exhale)
    • V=P1-P2/R
    • inhale: Pa
    • Exhale: Pa>Pb
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3
Q

Pleural space function:

A
  • Negative relative to Barometric pressure at rest
  • connects opposing forces:
    • Abdominal wall-expands
    • Lungs: Collapse
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4
Q

What is the resting lung volume:

A
  • when opposing forces are equal
    • abdominal wall
    • lungs
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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
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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
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7
Q

What will happen if you can’t contract the diaphragm?

A

intubtion or diaphragm stimulation

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8
Q

How do we exhale? (resting)

A
  • Passive process (does not require muscle contraction)
    • ​forced exhalation is active requiring expiratory muscles
      • ex: exercise
  • Steps:
    • inspiratory muscles relax
    • elastic recoil pulls inward on the lung surface
    • alveolar pressure increases
    • air flows out of the lungs
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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
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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
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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
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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
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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
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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
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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
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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
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17
Q

Esophageal pressure (Pes)

A
  • used to estimate pleural pressure
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18
Q
  1. @FRC before inspiration
  2. 50% inspiration
  3. End of inspiration
A
  1. @ FRC
    1. Volume=0
    2. Pleural pressure=-5
    3. Expiratory flow= 0
    4. Pa=0
  2. 50% inspiration:
    1. Volume= increased
    2. Ppl=decreased=-8
    3. Expiartory flow= decrease (-.5)
    4. Pa=decrease (-1)
  3. End of inspiration:
    1. Volume=Peak max
    2. Ppl=Most negative!
    3. Expiratory flow= 0
    4. 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
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

Week 42 (10 decks)

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