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Control of Breathing Flashcards

1
Q

What respiratory control centres of the brainstem control breathing?

A
  • Inspiratory centre (medulla)
  • Expiratory centre (medulla)
  • Pneumotaxic centre (pons)
  • Apneuristic centre (pons)
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2
Q

What (3) factors control breathing?

A
  • Cerebral cortex: can exert voluntary control over breathing as well as centres involved in emotion and pain
  • Peripheral chemoreceptors (in vascular system) & central chemoreceptors (in brain): detect changes to O2 and CO2
  • Stretch receptors (in lungs) & activity receptors (in muscles and joints)
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3
Q

What are (4) airway characteristics?

A
  • Rich blood supply
  • Large surface area
  • Tissues have intrinsic elastic properties
  • Fluid lubrication (ensure rapid diffusion + counteract physical forces like surface tension)
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3
Q

Pontine Centres.

A

influence output from the medullary respiratory centres

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3
Q

Medullary Respiration Centres.

A

provide output to respiratory muscles

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4
Q

How does high levels of CO2 affect the body?

A

changes the body’s pH = toxic

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4
Q

What is partial pressure measured in?

A

kilopascals (kPa) or millimetres of mercury (mmHg)

E.g.: (0.133kPa = 1mmHg)

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5
Q

What is PaPO2?

A

Partial pressure of oxygen dissolved in plasma of arterial blood

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6
Q

What is PO2/PCO2?

A

Partial pressure of oxygen / carbon dioxide in the air

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7
Q

What is PvCO2?

A

Partial pressure of carbon dioxide dissolved in plasma of venous blood

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8
Q

What is partial pressure?

A

the concentration of each gas in the body

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9
Q

What are (3) factors affecting gas solubility?

A
  • Partial pressure of gas
  • Partial pressure of gas in liquid phase
  • Solubility of a gas
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10
Q

How does partial pressure of gas affect gas solubility?

A

The greater the partial pressure the faster it will dissolve into the liquid phase

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11
Q

How does partial pressure of gas in liquid phase affect gas solubility?

A

If the partial pressure of a gas in the liquid phase becomes higher than its partial pressure in the gas phase, some of the dissolved gas will re-enter the gas phase

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12
Q

What (3) key factors will influence gaseous exchange?

A
  • Gas partial pressure and gas solubility
  • Matching of alveolar ventilation with pulmonary blood perfusion
  • Structural characteristics of the respiratory membrane
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13
Q

What is ventilation (V)?

A

volume of air entering the alveoli

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14
Q

What is perfusion (Q)?

A

volume of blood flowing through the lungs

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15
Q

What is the ventilation/perfusion mismatch?

A

inadequacy of V or Q will significantly impact the oxygenation of the blood and the removal of CO₂

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16
Q

When side lying should the patient’s ‘bad’ lung be faced up or down (in terms of VQ)?

A

Up (so not lying on the bad side)

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17
Q

Where (in a healthy adult) is self-ventilating lung ventilation optimal?

A

lower 1/3 of lung (dependent region)

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18
Q

Which regions of the lung have a greater initial volume?

A

non-dependent (upper) lung

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19
Q

Which regions of the lung are partially expanded?

A

dependent (lower) lung

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20
Q

Why are the dependent (lower) lung regions partially expanded?

A

so they still have the capacity of further expansion + volume change

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21
Q

What is perfusion influenced & affected by?

A
  • Gravity
  • The interaction of alveolar, arterial + tissue pressure
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22
Q

What is perfusion?

A

the passage of blood, a blood substitute, or other fluid through the blood vessels or other natural channels in an organ or tissue

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23
Q

Does the distribution of perfusion increase up/down the lung?

A

Down

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24
Q

What (2) ways can Oxygen be carried in?

A
  • Bound to haemoglobin (Hb) in red blood cells (RBCs) (98.5%)
  • Dissolved in plasma (1.5% … this is how we measure PaO₂)
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25
Q

What does oxygen bind to in the blood?

A

Haem molecules in haemoglobin

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26
Q

How much O2 is reversible bound or released is determined by what?

A
  • Partial pressure of oxygen in blood (PO2)
  • Temperature
  • Blood pH
  • The partial pressure of carbon dioxide (PCO2) + therefore concentration of H+ ions
  • Blood concentration of BPG (2,3-Biophosglycerate) produced by RBC
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27
Q

How much CO2 do respiring cells produce per minute?

A

200ml

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28
Q

What (3) ways does blood carry CO2 in the lungs?

A
  • Dissolved as CO2 in blood plasma (7-10%)
  • Chemically bound to Hb in RBC’s as carbaminohaemoglobin (20%)
  • Bicarbonate ions in plasma (~70%)
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29
Q

What is carbaminohaemoglobin?

A

CO2 binds to globin portion of molecule

30
Q

What happens when CO2 diffuses into red blood cells?

A

It combines with water to form carbonic acid.

31
Q

Which enzyme speeds up the reaction between CO2 and water in RBCs?

A

carbonic anhydrase

32
Q

Why is carbonic acid in red blood cells considered unstable?

A

It quickly dissociates into hydrogen ions and bicarbonate ions

33
Q

What role do hydrogen ions play after being released from carbonic acid in RBCs?

A

They bind to haemoglobin and facilitate the release of oxygen

34
Q

What is the normal pH of arterial blood?

A

7.35-7.45 pH

35
Q

What is the normal pH of venous blood?

A

7.31-7.41 pH

36
Q

How does blood become more acidic?

A

increased CO2 = increased H+ = decreased pH

37
Q

How does blood become more alkali?

A

decreased CO2 = decreased H+ = increased pH

38
Q

Tidal Volume (Vt)

A

Volume of air inhaled or exhaled during a single normal breath

39
Q

What is Tidal Volume (Vt) in men vs women?

A

Men: 500ml
Women: 50ml

40
Q

Inspiratory reserve Volume (IRV)

A

Maximum amount of air that can be inspired on top of a normal tidal inspiration

41
Q

What is Inspiratory Reserve Volume (IRV) in men vs women?

A

Men: 3000ml
Women: 1900ml

42
Q

What is Expiratory reserve volume (ERV) in men vs women?

A

Men: 1100ml
Women: 700ml

43
Q

Expiratory reserve volume (ERV)

A

Maximum amount of air that can be exhaled following a normal tidal expiration

44
Q

Residual volume (RV)

A

Volume of air remaining in the lung after a maximal expiration

45
Q

What is Residual volume (RV) in men vs women?

A

Men: 1200ml
Women: 1100ml

46
Q

What is Minimal Volume (MV) in men vs women?

A

Men & Women: 30-120ml

47
Q

Minimal volume (MV)

A

Amount of air that would remain if the lungs collapsed

48
Q

Total Lung Capacity (TLC)?

A

Total volume of the lungs at the end of a max inspiration
TLC=VT+IRV+ERV+RV

49
Q

Vital Capacity (VC)

A

Maximum amount of air that can be inspired and expired in a single breath
VC=VT+IRV+ERV

50
Q

Inspiratory Capacity (IC)

A

Maximum volume of air that can be inspired after a normal tidal expiration
IC=VT+IRV

51
Q

Functional Residual capacity (FRC)

A

Volume of air remaining in the lungs at the end of normal tidal expiration
FRC=ERV+RV

52
Q

What is total lung capacity (TLC) in men vs women?

A

Men: 5800ml
Women: 4200ml

53
Q

What is vital capacity (VC) in men vs women?

A

Men: 4600ml
Women: 3100ml

54
Q

What is inspiratory capacity (IC) in men vs women?

A

Men: 3500ml
Women: 2400ml

55
Q

What is functional residual capacity (FRC) in men vs women?

A

Men: 2300ml
Women: 1800ml

56
Q

If airways are blocked, what allows air to move (in order to minimise airway collapse)?

A

Collateral Ventilation

57
Q

What is Pendelluft?

A

The movement of air between areas of differing compliance or resistance

(If one area of lung has greater resistance than the other it will take longer to fill, e.g. asthma, ARDS)

58
Q

What does oscillation do?

A
  • Improve mucus rheology (i.e. flow)
  • Improve expiratory airflow bias
  • Create shearing forces which move mucus off the airway walls
59
Q

How does airway clearance work?

A
  • Collateral ventilation
  • Interdependence
  • Pendelluft
  • Expiratory flow bias
  • Enhances oscillatory effect
59
Q

What is interdependence?

A

If tidal volume is increased during inspiration expanding alveoli will exert a traction force on the surrounding alveoli

60
Q

How does interdependence help?

A

Helps to re-expand surrounding alveoli that have collapsed surrounding alveoli that have collapsed

61
Q

What is V/Q matching essential for?

A

Efficient gas exchange

62
Q

What is V/Q affected by?

A

Body position

63
Q

What does the ‘V’ in V/Q stand for?

A

The amount of air reaching the alveoli

64
Q

What does ‘Q’ in V/Q stand for?

A

The amount of blood reaching the alveoli

65
Q

What are the main (2) determining factors of PaO2 & PaCO2?

A
  • The amount of air reaching the alveoli (V)
  • The amount of blood reaching the alveoli (Q)
66
Q

What does the V/Q ratio assess?

A

How well matched the PaO2 + PaCO2 variables are

67
Q

What is a ‘V/Q Mismatch’?

A

When the ventilation + perfusion in gas exchange aren’t matched

68
Q

What is the normal value for the V/Q ratio?

A

Ratio = 0.8

(alveolar ventilation is about 4l/min and pulmonary capillary blood flow about 5l/min = 4:5 ratio)

69
Q

What does a V/Q approaching 1 indicate?

A

Higher probability of optimal oxygenation of blood

70
Q

What does it mean when the V/Q ratio is greater than 1?

A

Circulation is obstructed but ventilation is normal

71
Q

What does it mean when the V/Q ratio is less than 1?

A

An airway is obstructed, and there is no effective ventilation but adequate perfusion

72
Q

What is a ‘shunt’?

A

An area with no ventilation

73
Q

What is ‘dead space’?

A

An area with no perfusion

74
Q

What are the considerations for V/Q matching?

A
  • Contraindications
  • Underlying cardiopulmonary pathology
  • Lines, intubation etc
  • BMI
  • Skin intergrity
  • Nursing care needs
  • Haemodynamic instability
  • Need for monitoring during after repositioning

Physiotherapy (62 decks)

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