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CVR Lectures > Lung Physiology 1: General principles > Flashcards

Lung Physiology 1: General principles Flashcards

1
Q

What is the requirement of the respiratory pump?

A
  • To move 5 litres / minute of inspired gas
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2
Q

What is the respiration pump doing?

A
  • Negative intra-alveolar pressure draws air in (inspiration) to generate flow
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3
Q

What is involved with the respiratory pump?

A

Bones, muscles, pleura, peripheral nerves and airways

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4
Q

What muscles are involved in the respiratory pump during inspiration?

A
  • Diaphragm 70% of volume change (phrenic C3-5 innervation)
  • External intercostals – lift ribs 2-12, widen thoracic cavity
  • Muscles relax to allow passive expiration
  • Diaphragm is contracted in this state (flattened so increase volume of thorax)
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5
Q

What muscles are involved in the respiratory pump during expiration?

A
  • Internal intercostals – depresses ribs 1-11
  • Rectus abdominis – depresses lower ribs, compresses abdominal organs and diaphragm
  • Diaphragm is relaxed in this state (domed so reduced volume of the thorax)
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6
Q

What nerves are involved in respiration?

A
  • Sensory (assessing flow, stretch)
    (afferent via vagus nerve - 10th cranial nerve which helps spacial awareness so when our eyes are closed we know where the thorax is for e.g.)
  • Autonomic; sympathetic and parasympathetic
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7
Q

What is a resting lung volume and how do we change it?

A
  • Chest wall and lungs have elastic properties and a resting (unstressed) volume
  • To change this volume requires force
  • Release of force leads to a return to the resting volume
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8
Q

What is ventilation?

A

Flow of O2 in and CO2 out
- Total combined surface area for gas exchange is 50-100 m2

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9
Q

What is perfusion?

A

When the body delivers blood through the capillary bed into tissue and so it requires an adequate pulmonary blood supply

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10
Q

What is dead space and how many mls do we have?

A

The volume of air not contributing to ventilation
- some lost to anatomic (nasal, larynx) approx 150mls
- some lost to alveolar approx 25mls
anatomic + alveolar = 175mls dead space

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11
Q

How is the heart supplied with blood?

A
  • Right and left coronary arteries
  • Left split into circumflex and anterior inter ventricular branch
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12
Q

How are the bronchioles circulated (blood)?

A
  • Blood supply to the lungs via branches of the bronchial arteries and also supply peri-bronchial tissue and visceral pleura
  • Venous drainage via bronchial veins draining ultimately to superior vena cava
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13
Q

How is pulmonary circulation?

A
  • Right and left pulmonary arteries run out of right ventricle
  • Much lower pressure 24mm/10mm
  • There is 17 orders of branching
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14
Q

What is the broncho-vascular bundle?

A
  • A pulmonary artery and bronchus airway run in parallel with each other
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15
Q

How many capillaries per alveolus?

A

1000 capillary

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16
Q

At rest when is haemoglobin fully saturated?

A

25% through the capillary bed

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17
Q

When are capillaries perfused with blood

A

At the most dependent parts of the lung are preferentially perfused with blood at rest

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18
Q

What does perfusion of capillaries depend on?

A
  • pulmonary artery pressure
  • pulmonary venous pressure
  • alveolar pressure
19
Q

What happens if we have a hypoxic pulmonary?

A
  • this is a cut in the lung
  • If the lung is damaged, we stop blood going there via vasoconstriction as it is a waste if there is no air getting there anyway
20
Q

What is PaCO2?

A

arterial CO2

21
Q

What is PACO2?

A

Alveolar CO2

22
Q

What is PaO2?

A

arterial O2

23
Q

What is PAO2?

A

Alveolar O2

24
Q

What is PiO2?

A

Pressure of inspired oxygen

25
Q

What is FiO2?

A

Fraction of inspired oxygen (0.21)

26
Q

What is V’A?

A

rate of Alveolar ventilation

27
Q

What is V’CO2

A

Rate of CO2 production

28
Q

What is the equation for PaCO2?

A

PaCO2 = kV.CO2 / V.A
- Normally PaCO2 = 4-6kPa

29
Q

What are the three ways CO2 is carried?

A
  1. bound to haemoglobin
  2. plasma dissolved
  3. As carbonic acid (HCO3-)
30
Q

What is the alveolar gas equation?

A

PAO2 = PiO2 - PaCO2/R

31
Q

What are some causes of low PaO2?

A

(hypoxaemia)
- Alveolar hypoventilation
- Reduced PiO2
- V/Q mismatch (ventilation/perfusion)

32
Q

What are some causes of high CO2?

A
  • increased CO2 production
  • Reduced minute ventilation
  • Increased dead space
33
Q

How does O2 associate with Hb?

A

As each O2 molecule binds, it alters the conformation of haemoglobin, making subsequent binding easier (cooperative binding)

34
Q

What is the shape of the O2/Hb dissociation curve?

A

Non-linear (sigmoid shape)

35
Q

What influences the O2/Hb dissociation?

A

H+ (pH)
Temp
CO2

36
Q

What blood gases can we measure?

A

PaCO2, PaO2, pH, HCO3-

37
Q

What is the normal pH?

A

Normal pH = 7.35 – 7.45

38
Q

How does the body maintain control of pH?

A
  • CO2 elimination from lungs one mechanism to maintain pH
  • Buffers e.g. carbonic acid and bicarbonate buffer
  • Blood and tissue buffers (kidneys)
  • Lungs control pH by controlling CO2
39
Q

What is the carbonic acid equilibrium equation?

A

CO2 + H2O  H2CO3  H+ and HCO3-

40
Q

What is the Henderson-Hasselbalch equation?

A

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

41
Q

What happens to the equation if our CO2 increases?

A
  • If we under ventilate, CO2 increases so more acidic so pH drops
  • As PaCO2 increases, HCO3- also increases (equation shifts to the right) which rebalances the equation and pH
42
Q

What is Respiratory acidosis?

A

There is an increased PaCO2, so a decreased pH, mild increase in HCO3-

43
Q

What is Respiratory alkalosis?

A

There is a decreased PaCO2, so higher pH, so mild decrease in HCO3-

44
Q

What is metabolic acidosis and alkalosis?

A

Acidosis- reduced bicarbonate and decreased pH
Alkalosis - increased bicarbonate and increased pH

CVR Lectures (28 decks)

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