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Cases > Case 5 - Resporatory > Flashcards

Case 5 - Resporatory Flashcards

1
Q

How do you calculate alveolar ventilation?

A

= (tidal volume - dead space volume) X respiratory rate = (500 - 150) X 12 = 4200 ml/min

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2
Q

How is V:Q ratio defended and controlled locally?

A

A little air flow and large blood flow will cause 1) CO2 to dilate airways to increase airflow 2) O2 to vasodilate pulmonary vessels to decrease blood flow See case 5 notes as well as diagram from sherwood.

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3
Q

How is the respiratory centre controlled

A

See diagram in case 5 notes

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4
Q

What is the role of the Dorsal Repsiratory Group in breathing?

A

1) Contains mostly inspiratory neurones terminating at inspiratory muscles 2) firing initiates inspirating, inspiratory muscle relax when firing stops

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5
Q

Where the location of the pneumotaxic and apneustic centres and what do they do?

A

Pneumotaxic centre - sends impulses to DRG to help switchin off firing and thus preventing inspiration Apneustic centre - prevents switching off of inspiratory firing, boosts inspiration

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6
Q

What is the function of the pre-Botzinger complex?

A

Generation of respiratory rhythm - display pacemaker activity (self-induced action potentials)

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7
Q

You are interpreting an arterial blood gas. What are the normal values of pO2? pCO2? pH?

A

pO2 - 75-100 mmHg pCO2 - 35-45 mmHg Normal pH - 7.35 - 7.45

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8
Q

What is the average pulmonary ventilation and how is it calculated?

A

Pulmonary ventilation = 6000 ml/min = 500 ml/ min X 12 breaths = tidal volume x resp. Rate

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9
Q

What is the function the the pulmonary circulation?

A

1) to bring deoxygenated venous blood into contact with alveoli BUT ALSO to.. 2) protect the body from thrombi/emboli 3) metabolism of vasoactive substances - angiotensin | to angiotensin || 4) blood reservoir mobilised in shocked states

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10
Q

What do the pulmonary arteries do once they reach the lung?

A

Branch to form a dense capillary network to facilitate gas exchange

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11
Q

What are the features of pulmonary capillaries?

A
  1. Low pressure (25/8) unlike in systemic where pressure in aorta is 100 mm Hg
  2. Low resistance
  3. forms a mesh capillary network allowing blood to flow as a single sheet
  4. thin walls, adding to low pressure, right ventricle pressure exceeds that of pulmonary artery quickly - minimum work is needed to pump blood to pulmonary artery
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12
Q

What are the features of pulmonary arteries and arterioles? What makes them different to systemic arteries?

A
  1. Carry deoxygenated blood
  2. Less elastin and less smooth muscle
  3. thinner walls that arta
  4. all in all, they are less able to constrict that systemic arteries
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13
Q

What are the regional differences in perfusion and ventilation in the lung?

A
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14
Q

Describe the zones of the lungs in terms or arterial (Pa) and alveolar (PA) pressure.

A
  1. The further you go down the lugs, the more perfused the alveoli are
  2. thus Pa increases as you go further down the lungs and exceeds alveolar pressure, allowing more gas exchange to take place
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15
Q
  1. what is the normal value of alveolar ventilation?
  2. What is the normal ventilation:perfusion ratio in healthy individuals?
A
  1. Tidal volume - dead space X respiratory rate = 500-150 x 12 = 4200 ml (can be between 4 to 6 litres)
  2. As close to 1 as possible, so between 0.8 and 1.2
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16
Q

What are the reasons someone may have hypoxaemia? (Low oxygen in the blood)

A
  1. V:Q inequality
  2. shunting of blood
  3. hypoventilation - holding breath
  4. diffusion limitation
17
Q
  • What is pulmonary wedge pressure?
A

Pressure measured by

wedging a catheter with an inflated balloon in a small pulmonary arterial branch

Measures….

  • Changes in pulmonary venous pressure and left atrial pressure
18
Q
  • why measure pulmonary capillary wedge pressure?
A

Reflects changes in pulmonary venous and left atrial pressure

  • evaluating pulmonary hypertension (caused by increased vascular resistance)
19
Q

what is the pulmonary vascular resistance in comparison to systemic?

A
  • Pulmonary vascular resistance is 1/10th that of systemic (10 mmHg) because..
  • Blood is pumped at a much lower pressure from right ventricle to p. Artery
20
Q

How is pulmonary vascular resistance measured?

A

PVR = (mean pulmonary arterial pressure - PCWP) / cardiac output

21
Q

Why is pulmonary vascular resistance so low?

A

General factors:

according to Poisuille’s Law…

  • Large radius
  • Blood viscosity is low

Factors unique to the lung

  • High lung volume
22
Q

In terms of pulmonary blood flow, why is pulmonary vascular resistance so low?

A

Capillary recruitement

  • increase in cardiac output
  • closed capillaries open so you have more perfused vessels, decreasing resistance
  • Dominates at low pulmonary arterial pressure

capillary distention

  • Increasing the diameter of vessels
  • decreases resistance
23
Q

What are the values for pulmonary hypertension?

A
  • Mean arterial arterial pressure = more than 25 mmHg ( more than 30 mmHg when exercising)
  • elevated pulmonary vascuar resistance
24
Q

What is cor pulmonale?

A
  • Right enlargement and ventricular heart failure
  • due to….
  • Hypoxia (usually in COPD patients) Or tissue damage causing vascular damage
  • causes 1) pulmonary vasoconstriction and 2) increased blood viscosity
  • Increase in pulmonary vasular resistance
  • pulmonary hypertension
  • right ventricular hypertrophy!
25
Q

What are the signs and symptoms of cor pulmonale

A

CASERS of cor pulmonale - remember

C- cyanosis

A - ascites

S - shortness of breath

E - enlargment of neck and facial veins

R - raised JVP

S - swelling of ankles and feet ( peripheral oedema)

26
Q

What are alveoli made up of?

A

Ciliated cuboidal epithelium

see image *

27
Q

Outline the histology of the lung

A
28
Q

What type of epithelium is found is found at the respiratory mucosa?

A

Tall columnar pseudostratified epithelium

29
Q

Describe the components of the trache, bronchus, bronchioles, squamous epithelium

A
30
Q

What is the normal PaO2 and PaCO2 in kPa?

A

PaCO2 - is 5.1 kPa

PaO2 -

  • depends on inspired PO2
  • age - value decreases with age

10.8 (older healthy) to 12.5 kPa (younger healthy)

31
Q

What is type 1 Oxygenation failure?

A

PaO2 is below 8 kPa

PaCO2 is normal

Occurs when there is a major shunt from right to left (V:Q abnormality)

32
Q

What is type 2 ventilation failure?

A

PaO2 is below 8 kPa

paCO2 is above 6 kPa

Occurs when ventilation is not enough to excrete CO2 being produced

33
Q

What causes type 1 respiaory failure?

A

1) low altitude
2) v:Q mismatch
3) Shunt (intracardiac or intrapulmonary)
4) diffusion impairment (thickened membrane)

34
Q

What causes type 2 ventilation failure?

A

Inadequate ventilation

35
Q

Outline the following;

normal parameters of HcO3-, pCO2, pO2, and pH

What is the anion gap?

A
36
Q

How would you calculate the A-a gradient?

A

Calculate PAO2 by

  1. 21 - (pCO2/0.8)
  2. then PAO2 - PaO2
37
Q

A patient’s arterial blood gas comes back and the results are as following;

pH 7.49, PCO2 3.9, PO2 13.5, HCO3 24,

what abnormailty is demonstrated?

A

Respiratory alkalosis

38
Q

A patient’s arterial blood gas comes back and the results are as following;

pH 7.14, PCO2 9.3 KPa, HCO3 23

what is the abnormality ?

A

Respiratory acidosis

Cases (15 decks)

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