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Respiratory system > Ventilation > Flashcards

Ventilation Flashcards

1
Q

What is ventilation?

A

Movement of air

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2
Q

What is tidal volume?

A

volume of air inspired and expired during regular breathing

500 mL in a 70 kg man.

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3
Q

What is inspiratory reserve volume (IRV)?

A

volume of air that can be inspired after a tidal inspiration

2.7 L in a 70 kg man

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4
Q

What is the expiratory reserve volume (ERV)?

A

volume of air that can be expired after a tidal expiration

1.3 L in a 70 kg man

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5
Q

What is residual volume (RV)?

A

volume of air that cannot be emptied from the lungs

1.2 L in health adults

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6
Q

What is total lung capacity (TLC)?

A

maximum capacity of the lungs
(TLC) = RV + IRV + TV + ERV
6 L in a 70 kg man

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7
Q

What is functional lung capacity (FRC)?

A

volume of air in the lungs following a tidal expiration at rest
(FRC) = RV + IRV
• Equilibrium of mechanical forces of lung
• Needs to be imbalanced to stimulate ventilation

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8
Q

What is inspiratory capacity (IC)?

A

maximum volume of air the lungs can draw in from the equilibrium FRC point
(IC) = TV + IRV

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9
Q

What is vital capacity (VC)?

A

volume of air between the maximum and minimum achievable volumes
(VC) = TLC – RV; or, TV + IRV + ERV

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10
Q

How does a normal inspiratory trace look? What happens in a respiratory trace when a deep breath is taken?

A

see notes

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11
Q

What factors cause differences in lung capacity?

A

Height, body size, sex, age, genetic, areobic fitness, disease

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12
Q

What is the conducting zone?

A
  • 16 generations
  • No gas exhange
  • Ca. 150ml
  • anatomical dead space
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13
Q

What is the function of the conducting zone?

A

Defense (mucus)
Speech (layrnx)
Warming and humidying air for gass exchange

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14
Q

How does the speed of air change as it moves down the airway?

A

Slowed as cross sectional area increases

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15
Q

What is the respiratory zone?

A

Alveoli (parenchymal airway tissue)

Mostly terminal but some repiratory bronchioles have some

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16
Q

What is dead space?

A

parts of the airways that do not participate in gas exchange

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17
Q

What are the types of dead space?

A
  1. Anatomical:
    - All of conducting airway and upper respiratory tract (nasal cavity to larynx)
  2. Alveolar dead space/non perfused parenchyma
    - respiratory tissues unable to participate in gas exchange
    - Usually due to absent blood flow
    - In healthy person 0
  3. Physiological dead space:
    - Sum of anatomical and alveolar dead space
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18
Q

How would you decrease deadspace?

A

Trachestomy

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19
Q

How would you increase deadspace?

A

Snorkelling

Anaesthetic circuites

20
Q

What is alveolar ventilation?

A

difference between tidal volume and dead space

Valv = VT – VD

21
Q

What are the natural direction of recoil of the chest wall and lungs?

A

Chest wall: out

Lungs: in

22
Q

When are the chest wall and lung forces at equilibrium?

A

FRC

23
Q

What balances of forces causes inspiration?

A

Inspiratory muscle effort and chest recoil is larger than lung recoil

24
Q

What balances of forces causes expiration?

A

lung recoil and expiratory muscle effort is more than chest recoil

25
Q

What is the intrapleural cavity pressure in healthy individuals?

A

Negative

-5 cmH2O

26
Q

How is airflow stimulated?

A
  • Increasing atmospheric e.g positiv pressure breathing (ventilator)
  • Decreasing intrapleural pressure e.g negative pressure breathing (normal)
27
Q

How does negative pressure breathing occur?

A
  1. diaphragm contracts downward towards the abdomen (decrease in intrapleural pressure)
  2. the external intercostals pull the ribcage outwards and upwards
  3. Creates partial vacuum
  4. decrease in pressure
  5. visceral pleura is pulled outwards which inflates the lungs
    • Alveolar pressure below atmospheral pressure
  6. Expand until pressures equal out
28
Q

What happens during positive pressure breathing?

A
  1. increase in alveolar pressure
  2. expansion of lung tissue against the resistance of the thoracic wall
  3. increase in pleural pressure which causes an expansion of the chest wall

intra-pleural volume is fixed and resistant to change

29
Q

What is haemothorax?

A
  • accumulation of blood in the pleural cavity
    • Accumulates slowly
    • Reduces space to inflate
    • Increases effort to inhale
    • Limits overall achievable volume
30
Q

What is pneumothorax?

A
  • Puncture
    • Lung tension compromised
    • Resistance of outward and inward force disappears
    • Lung recoils and chest expands
31
Q

What are the 3 transmural pressures (across tissue pressures)?

A

pressures inside relative to the pressure outside: always pressure inside minus pressure outside

  1. transpulmonary pressure: difference in pressure between the alveolar sacs and the pleural cavity
    • (PTP= Ppl– Palv)
  2. transthoracic pressure: difference in pressure between the pleural cavity and the atmosphere
    • (PTT= Patm– Ppl)
  3. transrespiratory system pressure: difference in pressure between the alveolar sacs and the atmosphere
    • Dictates ariflow
    • (PRS= Patm– Palv)
32
Q

What are atmospheric, alveolar and pleural cavity forces at rest?

A

P(atm)=0
P(alv)=0
P(pl)= -5

33
Q

How are lung volumes calculated?

A
  • breathing in and out with a nose clip to recreate the spirometry trace
  • maximal expiration from TLC as “hard and fast” as possible
34
Q

What does spirometry measure?

A
  • forced vital capacity (FVC)

- forced expiratory volume in 1 second (FEV1)

35
Q

What is FVC/FVC1 used for?

A
  • Diagnosis of obstructive and restrictive lung disease
36
Q

What causes OLD?

A
  • structural abnormalities in the airway that increase resistance to airflow
37
Q

How does an OLD curve look?

A
  • have a shallower curve

- FVC is reduced because RV is larger than normal due to air trapping and emphysema

38
Q

How does a RLD curve look?

A
  • initial rate of expiration is largely unchanged

- FVC is markedly reduced.

39
Q

What is required for effective gas exchange?

A
  • atmospheric air in alveolar sac

- Adquate perfusion from pulmonary capillary close to it

40
Q

What is wasted ventilation?

A

Ventilated alveoli with no blood supply

41
Q

What is wasted perfusion?

A

Pulmonary capillaries that perfuse non-ventilated alveoli

42
Q

What part of the lung ventilates more readily?

A
  • Base
  • Effect of gravity on transmural pressure
  • makes basal lung tissue more compliant
43
Q

What is peak expiratory flow (PEF)?

A

maximum rate that the lungs can be emptied

Tested using noseclip

44
Q

How is PEF measured?

A

Wright peak flow meter
done three times and the highest value is used
compared with the charts

45
Q

How is peak expiratory flow rate calculated?

A

Gradient of graph

L/min

46
Q

What is the difference in PEF in asthma and COPD?

A

COPD would have stable PEF

asthma would have variable PEF.

Respiratory system (20 decks)

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