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SFIII Test 2 > Respiratory Mechanics II > Flashcards

Respiratory Mechanics II Flashcards

1
Q

What is specific compliance?

A

Normalizes the compliance value to the FRC to account for volume differences when calculating compliance

SC = Compliance/FRC

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2
Q

What is the total pulmonary compliance?

A

Definecd as the sum of the lung and the chest wall compliance

1/total C = 1/lung compliance + 1/chest wall compliance

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3
Q

How is compliance measured?

A

Spirometry

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4
Q

What is the cause of emphysema?

A

Elastin is a prominent component of lung tissue and is degraded by elastase. Elastase is inhibited by alpha 1 - antitrypsin

Deficiency in a1-antitrypsin or inhibition by smoking will lead to widespread tissue destruction and cause emphysema

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5
Q

What is alveolar simplification?

A

Term used to describe the tissue destruction seen in emphysema

Refers to the loss of structure, entire alveoli are missing, replaced by big open spaces

Causes a larger than normal FRC

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6
Q

What is centrilobular emphysema?

A

Most common morphological subtype

Affects the central portion of secondary pulmonary lobules, around the central respiratory bronchioles, typically in the superior part of the lungs

Associated with long-standing cigarette smoking

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7
Q

What in panacinar emphysema?

A

Destroys the entire alveolus uuniformly and is predominant in the lower half of the lungs

Commonly associated with domozygous AAT deficiency or Ritalin-induced lung emphysema

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8
Q

What are some causes of decreased compliance?

A

Interstitial lung disease (fibrosis)

Loss of surfactant

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9
Q

What are some causes of increased compliance?

A

Emphysema

Age

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10
Q

Where is the largest airway resistance?

A

The largest airways

The smaller airways are incredibly numerous and arranged in parallel, therefore the they will have a much lower total resistance (because for parallel 1/Rt = 1/R1 + 1/R2…)

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11
Q

Where is the largest airflow velocity?

A

Largest airways

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12
Q

What value is the pleural pressure during normal exhalation and why is this significant

A

The Ppl always remains negative during a passive exhalation

This means that the air way is subjected to expansile forces along its length, these forces keep the airway open during normal passive exhalation

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13
Q

What is dynamic compression?

A

During forced exhalation, the pleural pressure becomes positive due to contraction of the extra muscles

At some point the pressure outside (pleural) the airway is greater than the pressure inside, causing the airway to collapse under the increased transmural forces.

More effort just causes the airways to collapse more and increase resistance

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14
Q

How does the Bernoulli Principle apply to the airway?

A

Applies to the inside of the airway; the faster the airflow, the lower the pressure exerted on the inside of the walls of the airway, promoting collapse

Largest airways have smallest side wall pressured due to highest velocity

This is why the large airways have cartilaginous rings, to prevent total collapse

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15
Q

What is radial traction?

A

Refers to the action of lung tissue on airway walls, tending to hold them open

Referred to as tethering of airways

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16
Q

How is radial traction implicated in emphysema?

A

Tissue damage makes their airways very soft and pliable

Forced exhalation causes increased velocity and therefore decreased pressure. Combined with the positive pleural pressure their is a high tendency for airway collpase and substantial increase in resistance

17
Q

How is radial traction implicated in asthma?

A

Asthma causes airway constriction, meaning the same volume of air has to move through a narrower airway

This increases flow velocity and consequently lower pressure inside the airway, which promotes collapse and increase in airway resistance

18
Q

Why is airway collapse a problem?

A

The collapsed units are not ventilated, but they are still being perfused

Meaning they act as right-to-left shunts impairing gas exchange

19
Q

What is tethering of airways?

A

Refers to them being attached to their neighbors, promoting stability of alveoli and resist collapse

20
Q

What happens to tethering forces in emphysema?

A

Tethering forces are reduced in emphysema due to tissue loss

21
Q

What is tidal volume?

A

Volume of air inspired or expired with each breath

Normal value = 500mL

22
Q

What is dead space volume?

A

Air which a person breathes bu is not used for gas exchange

Fills conducting pathways only (e.g. nose, pharynx, and trachea)

Normal value = 150mL

23
Q

What is residual volume?

A

Amount of air in lungs which can’t be exhaled or pushed out

Normal value = 1-2 L

24
Q

What is total lung capacity?

A

Volume of air in the lungs after a maximal inspiratory effort

Normal value = 6 L

25
Q

What is forced vital capacity (FVC)?

A

Amount of air that can be exhaled as quickly during a forced exhalation

Normal value = 4.6 L

26
Q

What is the forced expiratory volume in 1 second (FEV1)?

A

Amount wchaled in the first second

Should be about 80% of the FVC

Normal value = 3.8 L

27
Q

What is the functional residual capacity (FRC)?

A

Volume of air in the lung when the lung and chest wall have equal recoil force

Normal value = 2.3 L

28
Q

What parameters cannot be measured directly by spirometry?

A

Any parameter with RV in it

RV, FRC and TLC

29
Q

What is the helium dilution technique?

A

Patient breathes from a bag of known helium concentration until the helium matches in inspired air and exhaled gas

Measure the concentration in the bag, it will depend on the FRC and can be calculated

Used to measure FRC

30
Q

What are the effects of body position and age on FRC?

A

Lying down decreases FRC by about 10-15%

Age causes decrease in elastic recoil and an increase in compliance, leading to an increase in FRC

31
Q

How do obesity and pregnancy affect the FRC?

A

Both decrease the FRC because there is more mass pushing up on the diaphragm

32
Q

How would a lung resection affect the FRC?

A

Decreases in because there is less volume

33
Q

How does kyphoscoliosis affect the FRC?

A

Decreases

34
Q

How does emphysema affect the FRC?

A

Increases it due to increased compliance

SFIII Test 2 (14 decks)

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