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Pulmonary Exam > Mechanics of the Respiratory System > Flashcards

Mechanics of the Respiratory System Flashcards

1
Q

Describe negative-pressure breathing

A

Lowering alveolar pressure below atmospheric pressure

Atmospheric pressure is congenitally referred to as 0cm H2O

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2
Q

Describe positive-pressure breathing

A

Increasing the pressure at the nose or mouth above alveolar pressure.

Used on patients unable to generate a pressure gradient between the atmosphere and the alveoli by normal negative-pressure breathing

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3
Q

How does negative-pressure breathing work

A

A pressure gradient is developed where the pressure in the alveoli falls below atmospheric pressure and air flows in

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4
Q

What is Boyle’s law

A

at constant temperature the product of the pressure and the volume of a gas is constant

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5
Q

Describe the transmural pressure gradient

A

Generated by the muscles of inspiration, transmural pressure

Alveoli expand passively in response to an increased distending pressure across the alveolar wall

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6
Q

How is the transmural pressure gradient calculated

A

Subtracting the outside pressure (intrapleural pressure) from the inside pressure (alveolar pressure)

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7
Q

How do the lung and chest wall interact at the end of expiration

A

They attempt to move in opposite directions

The lung is tending to decrease its volume due to elastic recoil of the alveolar walls

The chest wall is tending to increase its volume because of its outward elastic recoil

The intrapleural pressure is normally (-5cm)

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8
Q

How is alveolar pressure calculated

A

Intrapleural pressure + Alveolar elastic recoil pressure = alveolar pressure

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9
Q

What are the 3 inspiratory muscles

A
  1. Diaphragm
  2. External Intercostal
  3. Accessory muscles of inspiration
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10
Q

Contraction of what 3 muscles raises and enlarges the ribcage

A
  1. External intercostal
  2. Parasternal intercostal
  3. Scalene muscles

These muscles increase the anteroposterior dimension of the chest by rotating the ribs upward.
Innervated by nerves leaving the spinal cord at the 1st to 11th thoracic segments

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11
Q

What is interdependence

A

Pressure at the pleural surface is transmitted through the alveolar walls to more centrally located alveoli and small airways, pulling them open

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12
Q

What are the main muscles of active expiration

A

muscles of the abdominal walls

inter intercostal muscles

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13
Q

List the branches of the airway from largest to smallest

A

Conducting Zones

  1. Trachea
  2. Bronchi
  3. Bronchioles
  4. Terminal bronchioles

Respiratory Zones

  1. Respiratory bronchioles
  2. Alveolar ducts
  3. Alveolar sacs
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14
Q

What are the conducting zone branches of the respiratory system

A

Conducting Zones

  1. Trachea
  2. Bronchi
  3. Bronchioles
  4. Terminal bronchioles
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15
Q

What are the respiratory zone branches of the respiratory system

A

Respiratory Zones

  1. Respiratory bronchioles
  2. Alveolar ducts
  3. Alveolar sacs
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16
Q

What is the anatomic dead space

A

Space in the conducting zone where air does not reach the alveoli

17
Q

What are the events of normal inspiration

A
  1. Brain initiates inspiratory effort.
  2. Nerves carry the inspiratory command to the inspiratory muscles.
  3. Diaphragm ( and / or external intercostal muscles) contracts.
  4. Thoracic volume increases as the chest wall expands.*
  5. Intrapleural pressure becomes more negative. *
  6. Alveolar transmural pressure gradient increases. *
  7. Alveoli expand (according to their individual compliance curves) in response to the increased transmural pressure gradient. This increases alveolar elastic recoil. *
  8. Alveolar pressure falls below atmospheric pressure as the alveolar volume increases, thus establishing a pressure gradient for airflow. *
18
Q

What are the events of normal expiration

A
  1. Brain ceases inspiratory command.
  2. Inspiratory muscles relax.
  3. Thoracic volume decreases, causing intrapleural pressure to become less negative and decreasing the alveolar transmural pressure gradient. †
  4. Decreased alveolar transmural pressure gradient allows the increased alveolar elastic recoil to return the alveoli to their preinspiratory volumes. †
  5. Decreased alveolar volume increases alveolar pressure above atmospheric pressure, thus establishing a pressure gradient for airflow. †
  6. Air flows out of the alveoli until alveolar pressure equilibrates with atmospheric pressure.
19
Q

How is the pressure gradient calculated? AKA Transpulmonary pressure

A

transmural pressure = alveolar pressure - intrapleural pressure

in a resting lung:
Transmural pressure = 0 - (-5) = +5 mmH2O

20
Q

Describe the pressure-volume curve

A

as the transpulmonary pressure increases (becomes more positive) the % of lung volume increases

21
Q

What is Forced Vital Capacity (FVC)

A

Maximal expiratory effort made to force air from lungs

22
Q

What are examples of Restrictive diseases?

A

Fibrosis

23
Q

What are Obstructive diseases and what are some examples?

A

Problems with being unable to fully blow out a breath, usually a problem with increased alveolar compliance. Airway collapse and gas trapping occurs.

Asthma

Bronchitis

Emphysemia

24
Q

What is Tidal Volume

A

The Volume of air entering or leaving the nose or mouth per breath

25
Q

What is Residual Volume?

A

The amount of air left in the lungs after expelling a breath

26
Q

What is the Forced Expiratory Volume in 1 second (FEV1)

A

The volume of air expired in the first second

27
Q

What is the FEV1/FVC

A

In index of expiratory airway resistance

In normal subjects it is about .80; that is at least 80% of the FVC is expired in the first second

The person starts at TLC and expires all the air they can, in obstructive disease it is usually around .50, only about 50% is expired in the first second

It is normal or high in restrictive diseases

28
Q

What is a flow-volume curve

A

Used to asses airway resistance and is obtained by having the subject make repeated expiratory maneuvers with different degrees of effort

29
Q

What is effort-dependent and effort-independent curves of the flow-volume curve

A

Effort-dependent: As the subject exhales with heater effort, flow rates increase

Effort-independent: At low lung volumes, the expiratory efforts of different initial intensities all merge into the same curve

30
Q

Why is the peak expiratory flow (PEF) decreased in restrictive diseases?

A

The TLC is decreased (and therefore the VC)

The effort-independent part is usually similar to normal lungs

FEV1/FVC may be normal or increased because the lung has low volume and because alveolar elastic recoil pressure may be increased

31
Q

Why is the peak expiratory flow (PEF) and FEV1/FVC decreased in obstructive lung disease

A

The alveolar elastic recoil pressure is decreased

The effort-independent portion of the flow-volume curve is depressed inwards: flow rates are low for any relative volume

32
Q

What is a fixed obstruction

A

Obstructions not affected by the inspiratory or expiratory effort

33
Q

What is a variable obstruction

A

Changes in the transmural pressure gradient caused by the inspiratory or expiratory effort result in changes in the cross-sectional area of the obstruction

34
Q

What is intrapleural pressure

A

AKA the intrathoracic pressure, the pressure in the pleural cavity

Normally around (-5)cmH2O on end expiration

If it is increased above normal due to air entering the pleural cavity the lung way collapse

It decreases during inspiration, pulling the alveolar open and increasing transpulmonary pressurek

Pulmonary Exam (9 decks)

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