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TRANSITION BLOCK 1 > Respiratory Physiology > Flashcards

Respiratory Physiology Flashcards

1
Q

What are the 4 stages of Respiration?

A
  1. Ventilation (gas exchange from atmosphere to alveoli)
  2. Gas Exchange from alveoli to blood
  3. Transport of O2 and CO2 in blood
  4. Exchange of O2 and CO2 in tissues
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2
Q

How is air moved into the lungs using Boyle’s law?

A
  • normally pressure in alveoli = atmospheric pressure
    => Need to decrease this pressure to move air in
  • diaphragm flattens and external intercostals move ribs to increase thoracic volume
    => pressure drops and air can move in down pressure gradient
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3
Q

How is air moved out of the lungs following Boyle’s Law?

A

Passive relaxation of the diaphragm and external intercostal muscles causes thoracic cavity volume to reduce

=> intra-alveolar pressure increases to above that of the atmosphere
=> air is expelled from lungs down pressure gradient

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4
Q

What are the major inspiratory muscles?

A

Diaphragm

External intercostals

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5
Q

What are the accessory inspiratory muscles?

A

Sternocleidomastoid
scalenus
Pectoral muscles

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6
Q

What muscles can be used in active expiration?

A

Internal intercostals

abdominal muscles

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7
Q

What is the transmural pressure gradient and what does it cause?

A

intra-alveolar pressure - 760 mm Hg pushes OUT
intrapleural pressure - 756 mm Hg pushes IN
=> OUT > IN

4 mm Hg difference = transmural pressure gradient
=> stretches lungs OUT to fill the larger thoracic cavity.

Atmospheric pressure - 760 mm Hg pushes IN
Intrapleural pressure - 756 mm Hg pushes OUT
=> IN > OUT
4 mm Hg difference => pushes IN and compresses the thoracic wall

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8
Q

The external intercostal muscles move the ribs and sternum up and out. What is this mechanism called?

A

“bucket-handle” mechanism

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9
Q

Describe how the intra-alveolar and intra-pleural pressure change during INspiration and EXpiration?

A

Inspiration - both decrease
Expiration = both increase

this keeps transmural pressure gradient almost constant

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10
Q

What happens when the transmural pressure gradient is abolished? I.e. in a pneumothorax?

A
  • Pressures attempt to reach equilibrium (all 760mmHg)
    => lung collapses to its unstretched size
    => chest wall springs outward
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11
Q

What is responsible for elastic recoil of lungs?

A
  • Elastic connective tissue

- Alveolar surface tension

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12
Q

What is the alveolar surface tension and how does it help recoil?

A

Attraction between water molecules at liquid air interface

=> produces a force which resists the stretching of the lungs

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13
Q

What substance is made by the alveoli to ensure the surface tension doesnt get too high (or else they will colllapse)?

A

Surfactant

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14
Q

Smaller ALveoli have a higher tendency to collapse. TRUE/FALSE?

A

TRUE

- due to La Place’s law

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15
Q

What is the consequence of not having enough surfactant as a newborn?

A

Respiratory Distress of Newborn

- Baby makes strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs

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16
Q

What is meant by Tidal Volume and what is a normal value for this?

A

Volume of air entering/leaving lungs in a normal single breath
= usually 0.5L

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17
Q

How much air can be inspired over and above tidal volume using accessory muscles? And what is this called?

A

Inspiratory Reserve Volume = 3.0L

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18
Q

What is the maximum volume of air we can inspire in one breath? What is this called and how can it be calculated?

A

Inspiratory Capacity = 3.5L

Normal Tidal Volume + Inspiratory Reserve Vol.

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19
Q

How much extra air can be actively expired after a normal breath? What is this called?

A

1.0L

Expiratory Reserve Volume

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20
Q

How much air will remain in the lungs EVEN after a maximal expiration?

A

Residual Volume 1.2L

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21
Q

What is the Functional Residual Capacity? How can it be calculated?

A

Volume of air still in the lungs after normal expiration
Expiratory Reserve Volume + Residual Volume
1.0 + 1.2 => 2.2L

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22
Q

What is the Vital Capacity and what is a normal volume for this?

A

Maximal inspiration and expiration

=> TV (0.5) + IRV (3.0) + ERV (1.0) = 4.5L

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23
Q

What is the Total Lung Capacity and how is this different from the vital capacity?

A

TLC = Vital capacity AND the residual volume that cannot be moved out of the lungs

=> VC (4.5) + RV (1.2) = 5.7L

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24
Q

When can the residual volume in the lungs increase?

A

When elastic recoil of the lungs is lost

e.g. in emphysema

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25
Q

What is the difference between the FVC and the FEV1?

A

FVC = Forced Vital Capacity
=> Max. volume that can be forcibly expelled from lungs following a maximum inspiration

FEV1 = Forced Expiratory Volume in 1 second
=> Volume of air expired during the first second when measuring FVC

26
Q

Measuring FVC and FEV1 is collectively known as what?

A

Spirometry

27
Q

A normal FEV1/FVC ratio is more than what percentage?

A

> 70%

28
Q

Describe Spirometry findings if a patient has OBSTRUCTIVE disease (i.e. asthma/COPD)

A

FEV1 = LOW
FVC = NORMAL
=> FEV1/FVC Ratio = LOW (<70%)

29
Q

Describe the spirometry findings seen in patients with a RESTRICTIVE lung disease (i.e. Interstitial Lung Disease)

A

FEV1 = LOW
FVC = LOW
=> FEV1/FVC Ratio = NORMAL

30
Q

Patients can have mixed Obstructive and Restrictive disease. TRUE/FALSE?

A

TRUE

- this often presents as FEV1, FVC and ratio ALL LOW on spirometry

31
Q

What determines how resistant an airway is?

A

diameter of airway
=> Parasympathetic stimulation = bronchoconstriction
Sympathetic stimulation = bronchodilatation

32
Q

What is dynamic airway compression and when is it used?

A
  • Used during active expiration to put pressure on alveoli and airways
  • Pressure on alveolus helps push air out of lungs
33
Q

When is dynamic airway compression not desirable?

A
  • In patients with obstructive disease

- it makes active expiration more difficult for them by compressing the airway

34
Q

What is Peak Flow used to assess?

A
  • Airway function in obstructive lung disease (e.g. asthma and COPD)
35
Q

How is a Peak Flow measurement taken?

A
  • patient gives short sharp blow into the peak flow meter
  • best of three attempts taken
  • compared to normal for their height and weight
36
Q

What is meant by pulmonary compliance?

A
  • Effort to inflate the lungs

- If less compliant, it takes more work to inflate

37
Q

What can cause a decrease in pulmonary compliance?

A
  • pulmonary fibrosis
  • pulmonary oedema
  • lung collapse
  • pneumonia
  • absence of surfactant
38
Q

What symptom does a decreased pulmonary compliance usually cause?

A
  • causes lungs to become stiff
    => patients become short of breath on exertion
    => may cause restrictive spirometry pattern also
39
Q

What happens in INCREASED pulmonary compliance?

A
  • lungs can inflate, but struggle to recoil
    => often they are hyperinflated and patients have to work harder to get the air out
    (e.g. emphysema)
40
Q

Pulmonary compliance increases with age. TRUE/FALSE?

A

TRUE

41
Q

What can increase the work of breathing?

A
  • decreased pulmonary compliance
  • increased airway resistance
  • decreased elastic recoil
  • Need for increased ventilation
42
Q

What is the difference between Pulmonary Ventilation and Alveolar Ventilation?

A
  • some air remains in airways and cant take part in gas exchange (dead space)
    => This cannot get to alveoli to take part in alveolar ventilation
43
Q

Is it more advantageous to increase the rate or depth of breathing when exercising?

A

Depth
- Increasing rate of breathing has no effect on the dead space
=> need to increase depth of breathing to increase alveolar ventilation

44
Q

Transfer of gas from lung -> blood depends upon what?

A

Ventilation - rate that gas is passing through lungs

Perfusion - rate that blood is passing through the lungs

45
Q

In what area of the lung are ventilation and perfusion at their lowest? What effect does this have on the V/Q ratio

A
  • apex (top) of lung = poorest perfusion and ventilation

=> this causes V/Q ratio to rise

46
Q

What is meant specifically by the ALVEOLAR dead space?

A
  • air in the alveolar airways

- BUT no blood in perfusing that area in order to perform gas exchange

47
Q

There is usually a small mismatch in ventilation/perfusion between the PO2 in arterial blood and in the alveoli. TRUE/FALSE?

A

TRUE

  • Large gradient would indicate problems with gas exchange
  • OR right to left shunt in the heart
48
Q

Describe each step of the respiratory tree.

A

CONDUCTING ZONE

  • Trachea
  • Bronchi
  • Bronchioles
  • Terminal Bronchioles

TRANSITIONAL and RESP ZONES

  • Respiratory bronchioles
  • alveolar ducts
  • alveolar sacs
49
Q

What are the four factors which influence gas exchange in alveoli?

A
  1. partial pressures of O2 and CO2
  2. diffusion coefficient (how soluble gas is in membrane)
  3. surface area
  4. Thickness of alveolar membrane (e.g. interstitial fluid)
50
Q

HOw is O2 transported around the body?

A
  • bound to Hb
  • Hb has 4 haem groups, each carries one O2
    => maximally saturated
51
Q

What is the primary factor that determines how saturated Hb are with O2 in body?

A

PO2

  • this is highest in lungs and most Hb are maximally saturated in lungs
  • oxygen begins to dissociate in tissues with lower pO2
52
Q

What are the 3 main ways that O2 dedlivery to tissues can be impaired?

A

Respiratory disease
Heart failure
Anaemia

53
Q

Describe why the oxy-haemoglobin dissociation curve is sigmoid shaped?

A

Binding of one O2 to Hb increases the affinity of Hb for O2

54
Q

What happens when the Bohr Effect shifts the Oxy-haemoglobin dissociation curve to the right?

A
  • increased release of O2 in tissues
55
Q

What causes the Bohr Effect to shift the Oxy-haemoglobin dissociation curve to the right?

A

INCREASE IN:

  • 2,3-Biphosphoglycerate
  • Temperature
  • [H+]
  • PCO2
56
Q

Compare the Oxy-haemoglobin dissociation curve for foetal and adult Hb and explain why they are different

A

Foetal haemoglobin = 2 alpha and 2 gamma subunits

=> HbF interact less with 2,3- Biphosphoglycerate

=> higher affinity for O2 than HbA

=> curve shifted to the left

=> This allows O2 transfer from mother to foetus even if the PO2 is low

57
Q

Where is myoglobin found and what is its function?

A
  • present in skeletal and cardiac muscles
  • releases O2 at very low PO2
    => short-term storage of O2 for anaerobic conditions
58
Q

How many O2 molecules can be carried by myoglobin at any one time?

A

One

- only one haem group per myoglobin molecule

59
Q

Describe the shape of the oxy-myoglobin dissociation curve in comparison to the oxy-Hb dissociation curve

A

Hyperbolic (not sigmoidal)

60
Q

What does myoglobin in the blood indicate has occurred?

A

Muscle damage

TRANSITION BLOCK 1 (4 decks)

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