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SA respiratory > S2) Ventilation and Lung Mechanics > Flashcards

S2) Ventilation and Lung Mechanics Flashcards

1
Q

Breathing rate and depth is controlled to allow for certain processes.

Identify 5 processes

A
  • Eating/drinking
  • Speech
  • Defecation
  • Parturition (giving birth)
  • Change in metabolic requirements (sleep/exercise)
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2
Q

Which two structures both need to function to ensure healthy respiration?

A
  • Lung parenchyma
  • Respiratory airways
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3
Q

Inspiration is an active form of tidal breathing.

Describe the processes involved

A
  • Diaphragm contracts and moves down
  • Ext. intercostals contract and elevate ribs
  • Thoracic cavity volume expands
  • Intrapulmonary pressure decreases
  • Intrathoracic pressure falls below atmospheric pressure and air flows in
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4
Q

Expiration is an passive form of tidal breathing.

Describe the processes involved

A
  • Muscle contraction ceases
  • Muscles relax
  • Elastic recoil of the lungs results in return to the resting end-expiratory level
  • Air flows out
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5
Q

What is resting expiratory level?

A

Resting expiratory level refers to the state of equilibrium in the respiratory system before you breathe in and after you breathe out

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6
Q

Identify and describe the forces acting on the lung at the equilibrium position at the end of quiet expiration

A
  • Inward: lung’s elasticity and surface tension generate an inwardly directed force that favours small lung volumes
  • Outward: elastic elements of muscles and various connective tissue associated with the rib favour the outward movement of the chest wall

Result = opposing forces balance each other and create a negative pressure gradient in intrapleural space

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7
Q

What is tidal volume?

A

Tidal volume is the lung volume representing the normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied/ volume of air that enters and leaves the lungs with each breath

anatomical dead space + alveolar ventilation

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8
Q

What is inspiratory reserve volume?

A

Inspiratory reserve volume is the additional air that can be forcibly inhaled after the inspiration of a normal tidal volume

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9
Q

What is expiratory reserve volume?

A

Expiratory reserve volume is the additional air that can be forcibly exhaled after the expiration of a normal tidal volume

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10
Q

What is residual volume?

A

Residual volume is the volume of air still remaining in the lungs after the expiratory reserve volume is exhaled

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11
Q

What is Inspiratory Capacity?

A

Inspiratory capacity is the maximum amount of air that can be inspired i.e. inspiratory reserve + tidal volumes

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12
Q

What is Functional Residual Capacity?

A

Functional residual capacity is the volume of air in the lungs at the end of a passive exhalation

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13
Q

What is vital capacity?

A

- Vital capacity is the total amount of air that can be expired after fully inhaling

- Vital capacity = inspiratory capacity + expiratory reserve OR inspiratory reserve volume + TV + expiratory reserve volume

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14
Q

What is Total lung volume?

A

- Total lung volume is the maximum amount of air that can fill the lungs

- Total lung volume = vital capacity + residual volume

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15
Q

What determines the functional residual capacity?

A
  • The balance of elastic forces of the chest wall, favouring outward expansion
  • The elasticity and surface tension of the lung, favouring a smaller lung volume
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16
Q

What role do the pleural membranes have in ventilation

A
  • The pleural membranes constitute the pleural seal which holds the lungs to the chest wall
  • Hence, as the chest wall expands, the lung is forced to follow
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17
Q

Describe the structure and function of the pleural membranes

A
  • Structure: double-walled sacs enclosing each lung
  • Function: slide over each other to enable smooth expansion of the lung

parietal pleura - lines the inside of each hemi-thorax

visceral - lines outside of lung (shiny)

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18
Q

What is the pleural space/cavity?

A
  • The pleural space is the space between the visceral and parietal pleural membranes
  • Contains 10-20 ml pleural fluid (lubricant)
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19
Q

Identify the muscles of quiet inspiration and expiration

A
  • Inspiration: diaphragm and external intercostal muscles
  • Expiration: due to elastic recoil, no muscles used
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20
Q

Describe the mechanism of quiet expiration and the role of elastic recoil

A

In quiet expiration, when muscle contraction ceases, the elastic recoil of the lung results in the thoracic cavity and the lung returning to the original equilibrium position (passive process)

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21
Q

Identify the accessory muscles of forced inspiration

A
  • Sternocleidomastoid
  • Scalene
  • Pectoralis major & minor
  • Trapezius
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22
Q

Identify the accesory muscles of forced expiration

A
  • Internal intercostals
  • Muscles of the abdominal wall
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23
Q

In the older adult, resting end-expiratory level (FRC) is relatively higher than in the young person.

Why?

A
  • FRC = functional residual capacity = volume of air in the lungs after a quiet expiration:
    • emphysema = increased FRC
  • fibrosis = reduced FRC
  • The balance between the chest wall (recoiling out) and the lung (recoiling in) has changed
  • Lung tissue has lost its elasticity
24
Q

What is compliance?

A

Compliance is the relationship between pressure and volume (how much something can stretch)

C = Δvolume/Δpressure

volume and pressure are inversely proportional

25
Q

Describe how the stiffness/slackness of the lungs influences compliance

A
  • Stiff lungs = low compliance (fibrosis)
  • Slack lungs = high compliance (emphysema – less elastin)
26
Q

Identify the factors which affect compliance of the lung

A
  • Elastic fibres (elastin)
  • Fibrosis (disease)
  • Surface tension
27
Q

What effect does surface tension have?

A
  • water has a high infinity, so stick together, water lines the outside of the alveoli so:
  • Makes inflation of alveolus harder
  • Makes smaller alveoli tend to collapse into larger ones
28
Q

Surfactant reduces surface tension.

How does it do this?

A
  • Allows the lung to inflate more easily (increased compliance)
  • Helps to regulate alveolar size
  • Prevents alveolar collapse
29
Q

Describe the structure of surfactant

A
  • Complex mixture of lipids and proteins
  • Secreted by alveolar cells
  • used to disrupt the surface tension of water so the alveoli can expand
30
Q

Describe the production and depletion of surfactant

A
  • Production begins between 25-28 weeks gestational age
  • Diminished in Acute Respiratory Distress Syndrome (ARDS)
31
Q

Ventilation is measured through minute ventilation.

What is the minute ventilation for 15 breaths per minute with a tidal volume of 0.5 L?

A

Minute ventilation = 15 x 0.5 L/min

= 7.5 L/min

32
Q

Where in the bronchial tree is the main site of airways resistance?

A

Upper respiratory tract

33
Q

How can airways resistance be increased?

A
  • Increased mucus
  • Hypertrophy of the smooth muscle and/or oedema
  • Loss of radial traction
34
Q

A small change in radius makes a big difference in resistance.

How is resistance of airways calculated?

A
  • Resistance = Pressure ÷ Flow (units kPa.L-1.s)
  • Resistance α 1/r4
35
Q

Provide examples of clinical conditions which manifest the following:

  • Increased mucus
  • Hypertrophy of the smooth muscle and/or oedema
  • Loss of radial traction
A
  • Increased mucus: chronic bronchitis
  • Hypertrophy of the smooth muscle and/or oedema: asthma
  • Loss of radial traction (pulling) : emphysema
36
Q

Why does air flow into the pleural cavity during pneumothorax?

A
  • Normally, a negative pressure gradient in the pleural space keeps the two pleurae together & facilitates ventilation
  • When punctured, air flows from high→low pressure, from the atmosphere into the space until it reaches equilibrium
37
Q

Why do the lungs recoil when air enters the pleural cavity (in pneumothorax)?

A
  • If air enters the pleural space between the parietal and visceral pleura, the -4cm H2O pressure gradient disappears
  • This gradient normally keeps the lung against the chest wall, hence, the lung recoils and collapses
38
Q

A tube is placed in the pleural space to drain the air in pneumothorax.

How could damage be minimised during this procedure?

A
  • Tube is inserted through the intercostal space under ultrasound guidance
  • Tube is inserted above superior border of lower rib as intercostal nerves and vessels run along the inferior border (4/5th intercostal space, mid-axillary line)
39
Q

Identify 4 intra-abdominal structures that could be damaged due to a stab wound to the chest

A
  • Nerves (intercostal and phrenic)
  • Intercostal vessels (veins and arteries)
  • Diaphragm
  • Aorta
40
Q

Why would lack of surfactant cause difficulty breathing?

A
  • Less surfactant increases surface tension in alveoli and they don’t inflate properly
  • Lungs are stiffer and compliance is lower
41
Q

What is Respiratory distress of the newborn?

A

- Neonatal respiratory distress syndrome is a condition occurring in premature infants caused by developmental insufficiency of pulmonary surfactant production and structural immaturity in the lungs

-There is an insufficient amount of surfactant to inflate and ventilate the lungs

42
Q

Why would a premature baby with Respiratory Distress Syndrome have intercostal recession?

A
  • Intercostal muscles are immature not strong enough to expand the ribcage
  • Hence, soft tissues between the lungs draw inwards against the negative pressure
43
Q

conducting portion (anatomical dead space) of the respiratory tract

A
  • nasal cavity
  • pharynx
  • larynx
  • trachea
  • primary bronchi
  • secondary bronchi
  • bronchioles
  • terminal bronchioles
44
Q

respiratory portion

A
  • respiratory bronchioles
  • alveolar ducts
  • alveoli
45
Q

definition of anatomical dead space

A
  • volume of air in conducting airways
46
Q

definition of alveolar dead space

A
  • air in alveoli that don’t take part in gas exchange due to damage
47
Q

physiological dead space

A

anatomic dead space + alveolar dead space

48
Q

total pulmonary ventilation formula (min Vol)

A

tidal vol x respiratory rate (16-20min)

49
Q

alveolar ventilation

A

(tidal volume - dead space) x respiratory rate

50
Q

difference between respiration and ventilation

A

respiration - exchange of gasses across a membrane

ventilation -physical action of breathing in and out

51
Q

relevance of negative intrapleural pressure

A
  • lungs have a natural inward elastic recoil
  • chest wall has an outward elastic recoil

= opposing pressure which prevents collapsing of alveoli and lungs

52
Q

diagram explaining the difference between atmospheric pressure and intrapulmonary pressure

A
53
Q

relationship between compliance and elastic recoil

A

inversely proportional,

the more something can stretch (compliance) the harder it is to return back to the normal size ( elastic recoil)

54
Q

advantage of tubes connected in parallel

A
  • reduces overall airway resistance
  • connecting parallel branches creates alternative routes
  • highest resistance in upper airways so easier for air to flow deeper into the lungs
55
Q

accessory muscles of inspiration

A
  • sterniocleiodmaster
  • scalene
  • serratus anterior
  • pec major
56
Q

accessory muscles of expiration

A
  • internal intercostal
  • abdominal wall muscles
57
Q

graph of lung volume and capacity

A

SA respiratory (23 decks)

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