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CVR > DeCoursey Respiratory Mechanics I > Flashcards

DeCoursey Respiratory Mechanics I Flashcards

1
Q

Which pressures are greater when air flows Out?

In?

A

Out- Pressure Alveolar> Pressure B/Air

in- Pressure Air/B > Pressure Alveolar

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2
Q

Boyles Law is?

A

PV/T= Constant in an enclosed container

P1V1=P2V2- for fixed amount of gas (enclosed container) at constant temp

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3
Q

Membranes Surrounding of lungs?

A
  1. Visceral Pleura- internal boundary, attached to lung
  2. Parietal pleura- outside boundary, lines the chest wall

Space between forms the potential space- pleural space

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4
Q

What 3 conditions can come from disruption to the visceral space/pleurae

A
  1. Pneumothorax- air enters the potential spae
  2. Pleural effusion- fluid enters the potential space
  3. Empysema- fluid enters the same in severe infection
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5
Q

What is the favorable volumes of the lung and chest wall?

Why don’t they reach these values?

A

Lung- 800ml
Chest wall- 4500ml

They don’t reach these values because they are virtually attached by the pleura

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6
Q

What happens during pnemothorax?

A

Pleural has negative pressure so when you poke a hole, air enters the potential space and the chest wall expands and the lungs collapse

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7
Q

Why is pleural pressure negative at FRC?

ADD TO/Review THIS CARD

A

Lungs pull inward, chest wall pulls outward

pleural pressure «< Alveolar Pressure alwayss!

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8
Q

Steps of breathing in

A
  1. Contract inspiration muscles (diaphragm and external intercostal)
  2. Decrease in Pleural Pressure
  3. Increase in Alveolar Volume
  4. Decrease Alveolar pressure
  5. Air in (Palveolar&laquo_space;Pressure atmos.)
  6. Return Pressure Alveolar to Pressure atmos.
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9
Q

Steps of breathing out

What happens in increased ventilation?

A
  1. Relax inspiration muscles (passive) causes elastic recoil of the lungs
  2. Increase in pleural pressure
  3. Decrease in Alveolar volume
  4. Increase in Alevolar pressure
  5. Air out (alveolar pressure» Atm pressure)
  6. Return to Palv to Patm

Increased ventiliation internal intercostal become active and pull inward and downward on ribs opposing the external intercostals

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10
Q

Importance of diaphragm in respiration

A
  1. It’s the main inspiration muscle
  2. When this dome shaped muscle contracts it pushes the abdominal contents
    down and forward increasing lateral dimension of thoracic cavity
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11
Q

Four forces that have to be overcome by respiratory muscles?

A
  1. Elastic recoil of chest cavity
  2. Elastic recoil of lungs
  3. Surface tension
  4. Airway resistance
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12
Q

What is elastic recoil of lungs measured by?

A

Compliance= DeltaV/DeltaP

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13
Q

How does compliance change with volume in the lungs?

A

At high volumes the pressure volume curve is flatter and compliance is low- same work produces smaller change in volume when compliance is low

At moderate volumes (near FRC), the compliance is high (steep slope) because the lung is unfolding and can easily increase volume

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14
Q

4 situations where compliance is reduced

A
  1. Pulmonary Fibrosis
  2. Alveolar edema-makes alveoli harder to inflate
  3. Unventilated Lung regions-collapsed alveoli or increased surface tension
  4. Increase in pulmonary venous pressure- causes lungs to be engorged with blood
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15
Q

What happens in pulmonary fibrosis?

A

Infiltration of lymphocytes/plasma cells–> increased fibroblast–> these lay down collagen thickening the alveolar walls

Ultimately decreasing compliance

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16
Q

When is compliance too high?

A

Pulmonary Emphysema- due to the change in the elastic recoil of the lung tissue

17
Q

Define COPD

A

Airway obstruction due to chronic bronchitis, emphysema or a mixture of the two.

18
Q

Why is Pressurepleural&laquo_space;Pressure Alveolar ALWAYS

A

The lungs are always pulling inward decreasing alveolar volume and increasing alveolar pressure above whatever the pleural pressure is

19
Q

At what percentage of TLC capacity is chest wall relaxed?

A

80% So this means the chest is pulling outward over most physiological ranges

20
Q

What happens at values near 100% of VC?

A

Both the chest wall and lungs are pulling inward so respiratory muscle have to work hard to inflate lungs to TLC

21
Q

Diseases that affect compliance of the chest wall

A

These are more rare than affect compliance of lung but

  1. Ankolsing spondylitis (spinal joint inflammation)
  2. Kyphoscoliosis
  3. Obesity
22
Q

What is complaince of the system compared to lungs and chest wall alone?

A

Compliance of the system is less (flatter slope)

23
Q

What is happening at FRC with forces? What percentage of Vital capacity?

A

Inward of lung is equal and opposite to outward of chest cavity so the system is at rest/equilibrium

About 40%

24
Q

What is surface tension? What does it do in the lungs?

A

Its the tension force at the interface between two phases.

IN the lungs there is an air/water interface that tends to collapse the alveoli

25
Q

Explain the saline/air experiment of surface tension

A

For Saline the lungs inflate and deflate easily and the same because we have eliminated the air/water surface tension

With air it takes 3-4 more work to inflate lungs
Also there is hysteresis-meaning deflation and inflation follow different curves. This is partially due to pulmonary surfactant.

26
Q

Define atelectasis

Law that determines atelectasis

A

collapsed alveoli

LaPlaces law

27
Q

LePlaces Law

A

P= 2(T)ension Surface/radius in sphere

Small radius collapse more
Large radius stay open

28
Q

Effects of surfactant

A
  1. Reduce Surface tension and atelectasis
  2. Increase compliance
  3. Reduce work of breathinig
29
Q

How does surfactant work?

Where is it secretated from?

A

It’s a thin layer of fluid that lines the alveolus that reduces surface tension by opposing intermolecular forces.
Hydrophobic- towards air
Hydrophilic towards water

Secreted from Type II alveolar endothelial cells

30
Q

Surfactant in fetus appears when?

Premature lacking surfactant have?

A

Type appears ~6 months and surfactant Week 24-35 (7-8 months)

Infant Respiratory Distress Syndrome leading cause of death in premature

31
Q

Two forces that oppose atelectasis

A
  1. Surfactant

2. Interconnectedness of lung tissue- when alveoli begins to collapse it pulls on neighboring alveoli and they pull back

32
Q

Where is surfactant packaged?

What is it composed of?

A

Lamellar bodies

DPCC

33
Q

Where do you find Type I and Type II alveolar epithelial cells?

A

Type 1- thin, flat that lines 95% of alvelar surface

Type 2- cubodial in the corners of alveoli

34
Q

Situations that reduce surfactant

A

PAAAID ASS O

  1. Pulmonary Embolu- prevents “food” from getting to Type II so no production
  2. Acidosis
  3. Atelectasis
  4. ARDS (adult resp. distress syndrom)
  5. IRDS (infant)
  6. Drowning
  7. Abdominal Surgery
  8. Smoking
  9. Shock
  10. Oxygen related abnormalities (low/too much O2)
35
Q

Increase surfatant

A
  1. Mechanical Stretch (Yawning)
  2. Birth (hormonal effects)
  3. Secretagogues (Beta agonist)
36
Q

Discuss elastic recoil at
High volumes
Low Volumes

A

High- elastic recoil is stronger– makes sense, lower compliance so can’t inflate much more

Low volume- counter-intuitive large pressure is required to inflate because surface tension is greatest at smaller volumes. So you have to pass a critical opening pressure

Think balloon hard to start but once it starts its easeir

CVR (13 decks)

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