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Respiratory > Lung physiology > Flashcards

Lung physiology Flashcards

1
Q

What are muscles involved in inspiration?

A

Diaphragm- 70% of volume change phrenic C3-5
innervation
External intercostals- lift ribs 2-12
widen thoracic cavity
Scalenes- lift ribs 1&2
Pectoralis major- lift ribs 3-5
Sternocleido.- elevates sternum
Muscles relax to allow passive expiration

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2
Q

What innervates the diaphragm?

A

C3, 4, 5
Phrenic
Keep the diaphragm alive

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3
Q

Function external intercostal?

A

Lift ribs 2-12
Widen thoracic cavity

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4
Q

Function scalenes?

A

Lift ribs 1 and 2

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5
Q

Function pectoralis major?

A

Lift ribs 3-5

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6
Q

Function sternocleidomastoids?

A

Elevate sternum

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7
Q

What occurs to achieve passive expiration?

A

Muscle relaxation

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8
Q

What muscles used during active expiration?

A

Internal intercostals- depress ribs 1-11
Rectus abdominis- depress lower ribes
- compress abdominal organs and diaphragm

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8
Q

What muscles used during active expiration?

A

Internal intercostals- depress ribs 1-11
Rectus abdominis- depress lower ribes
- compress abdominal organs and diaphragm

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9
Q

Define:
PaCO2
PACO2
PaO2
PAO2
PIO2

V’A
V’CO2

A

PaCO2 arterial CO2
PACO2 Alveolar CO2
PaO2 arterial O2
PAO2 Alveolar O2 (~14kPa)
PIO2 Pressure of inspired O2
V’A Alveolar ventilation
V’CO2 CO2 production

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10
Q

What does ‘a’ represent?

A

arterial

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11
Q

What does ‘A’ represent

A

Alveolar

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12
Q

At what point is Hb fully saturated through capillary bed?

A

Fully sat 25% WAY THROUGH

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13
Q

What occurs when hypoxia?

A

Hypoxia
Pulmonary vasoconstriction
Maximise ventilation-perfusion
Optimal gas exchange

Altered posture

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14
Q

How is CO2 transported?

A

Bound haemoglobin
In plasma (dissolved CO2 as HCO3-)

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15
Q

Define Boyle’s law?

A

Boyle’s Law: P1V1=P2V2

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16
Q

How does Boyle’s law apply to ventilation?

A

Inspiritary muscles contract
Thoracic cavity volume increases
Allows air to flow into lungs:
1) increased transpulmonary pressure (Palveolar – Pintraplueral)
2) alveolar pressure lower than atmospheric
3) expiration caused by decreasing transpulmonary pressure
4) ribcage pressing down on lungs
5) alveolar pressure increases above atmospheric
6) air flow out

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17
Q

What limits lung expansion?

A

Compliance- ability stretch and expand
Determined by amount elastic tissue and surface tension in alveoli

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18
Q

What reduces surface tension in alveoli?

A

Surfactant

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19
Q

Define normal pH?

A

7.35-7.45

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20
Q

What is Henderson Hasellback equation for pH?

A

pH = pKₐ + log([A⁻]/[HA])

pH=6.1 + log10([HCO3-]/[0.03PCO2])

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21
Q

Equation for dissociation of CO2?

A

CO2 + H2O to H2CO3 to H+ + HCO3-

22
Q

What enzyme is involved in the dissociation of CO2?

A

Carbonic anhydrase

23
Q

How is pH maintained?

A

CO2 dissociation
renal secretion/reabsorption
protein buffers

24
Q

Characteristics of respiratory acidosis?

A

Low pH
High HCO3-
High pCO2

25
Q

What are causes of respiratory acidosis?

A

Lack respiratory drive
Restriction airways
Hypoventilation
COPD2

Impaired CO2 elimination cause hypercapnia (smaller 6kPA)

26
Q

What compensates respiratory acidosis?

A

Retention and production HC03-
H+ secretion

27
Q

Characteristics of respiratory alkalosis?

A

High pH
Low HCO3-
Low CO2

28
Q

What is the cause of respiratory alkalosis?

A

Hyperventilation, fever
Loss CO2 causes hypocapnia
H2CO3 converted CO2 meaning less H+
pH raised

29
Q

Define tidal volume?

A

Volume inhaled/exhaled in normal breath
500ml

30
Q

Define inspiratory reserve?

A

Max air that can be inhaled minus tidal volume
3L

31
Q

Define expiratory reserve volume?

A

Mac air that can be exhaled minus tidal volume
1.2L

32
Q

Define residual volume?

A

Air remaining in lungs after max expiration to prevent collapse
1.2L

33
Q

Define vital capacity?

A

Max air expired after max inspiration
4.7L
(ERV +TV + IRV)

34
Q

Define inspiratory capacity?

A

Max inhalation after normal tidal expiration
3.5L
(IRV + TV)

35
Q

Define functional residual capacity?

A

Air in lungs after tidal expiration
2.4L
(RV+ERV)

36
Q

Define total lung capacity

A

Total volume of air in lungs after maximal inspiration
5.9L
(RV+VC)

37
Q

Define FEV1? Amount?

A

Forced exp. Volume in 1 second
80% of vital capacity in healthy person

38
Q

Define FVC?

A

forced vital capacity- max air expired under max force after max inspiration

39
Q

Define PEF?

A

Peak air flow
Highest velocity of air measured during FVC
Flow will decrease linearly in healthy person after PEF

40
Q

Define DLCO?

A

Diffusing capacity of lung for carbon dioxide
Measure efficiency gas exchange
Known [CO] inhaled, 10 sec breath hold, expired [CO] measured
Reduced with COPD

41
Q

What will an airway obstruction cause? (Lung vol)
Causes
Ratio?

A

Decreasing FEV1
Increasing RV
Increasing TLC
FVC similar

Ratio FEV1/FVC reduced below 0.7
e.g. COPD, asthma

42
Q

Define airway restriction?
Causes?
Ratio?

A

Reduced compliance of lungs
Reduce FEV1 and FVC- ratio same
Everything else reduced
Pulmonary fibrosis

42
Q

Define airway restriction?
Causes?
Ratio?

A

Reduced compliance of lungs
Reduce FEV1 and FVC- ratio same
Everything else reduced
Pulmonary fibrosis

43
Q

Label:
Tidal volume
Inspiratory reserve
Expiratory reserve
Residual volume
Vital capacity
Insp. capacity
Functional residual capacity
Total lung capacity

A
44
Q

How to calculate vital capacity?

A

ERV+TV+IRV
4.7L

45
Q

How to calculate inspiratory capacity?

A

IRV+TV
3.5L

46
Q

How to calculate functional residual capacity?

A

ERV+VC
2.4L

47
Q

How to calculate total lung capacity?

A

RV+VC
5.9L

48
Q

State process of inspiration?

A

Diaphragm- flattens
External intercostal muscles- elevate ribs and sternum- extend thoracic

Increase volume thoracic cavity- lungs increase
Decrease pressure in lungs- Boyles law
Pressure higher environment than lungs
Air move down pressure gradient

49
Q

Explain process passive expiration?

A

Relaxation inspiratory muscles
Diaphragm- return resting position- reduce thoracic cavity
External intercostal relax- depress rib and sternum
Decrease volume thoracic cavity- increase pressure
Pressure inside lungs greater external environment
Air moves out lung
Down pressure gradient

50
Q

Explain forced breathing? When used?

A

Exercise
Active inspiration- contraction accessory muscles
Scalenes – elevates the upper ribs.
Sternocleidomastoid – elevates the sternum.
Pectoralis major and minor – pulls ribs outwards.
Serratus anterior – elevates the ribs (when the scapulae are fixed).
Latissimus dorsi – elevates the lower ribs

Increase volume thoracic cavity

51
Q

Outline how active expiration occurs?

A

Anterolateral abdominal wall – increases the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity.
Internal intercostal – depresses the ribs.
Innermost intercostal – depresses the ribs.

Decrease volume thoracic cavity

Respiratory (8 decks)

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