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MD3001 - Respiratory Clinical > Blood Gas Analysis > Flashcards

Blood Gas Analysis Flashcards

1
Q

1kPa =

A

7.5mmHg

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2
Q

What are the main buffers in the body?

A
  • proteins
  • haemoglobin
  • carbonic acid/bicarbonate
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3
Q

What are the 2 main organs or excretion?

A

lungs and kidneys

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4
Q

When do acid-base disturbances occur?

A
  • problem with ventilation
  • problem with renal function
  • overwhelming acid or base load the body cant handle
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5
Q

What are the normal values for:

  • pH
  • pO2
  • pCO2
  • Bicarbonate

in arterial blood gases?

A
  • pH = 7.35-7.45
  • pO2 = 12-13 kPa
  • pCO2 = 4.5-5.6 kPa
  • Bicarbonate = 22-26 mmol/L (standard)
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6
Q

How is the standard bicarbonate calculated?

A

calculated frim the actual bicarbonate assuming 37°C and paCO2 of 5.3kPa

**Compensates for changes in CO2

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7
Q

What does thw standard bicarbonate show?

A

reflects the metabolic componenet of acid-base balance

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8
Q

What is step 1 in looking at arterial blood gases?

A

Look at the pO2

Is the patient hypoxic?

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9
Q

What are the adverse effects of high oxygen levels?

A
  • Increases risk of hypercapnic respiratory failure in acute exacerbations of COPD
  • Increased mortality survivors of cardiac arrest
  • increased mortality intensive care patients
  • increased mortality in acute severe asthma
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10
Q

What can high oxygen levels generate? and what are the consequences of this?

A
  • Generate free radicals
    • Lung toxicity
    • collapse of alveoli due atelectasis
    • irritating mucois membranes
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11
Q

What are the two main oxygen targets in hypoxia?

A
  • Normal = 94-98%
  • Type 2 resp. failure = 88-92%
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12
Q

What are the theraputic uses of high inspired concentration of oxygen?

A
  • pneumothorax
    • high oxygen conc. decreases the volume of N2 due to concentration gradient
  • carbon monoxide poisoning
    • pulse oximetry cannot differentiate between CO and O2 bound to Hb
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13
Q

Draw a diagram indicating how oxygen partial pressure changes in different parts of the body

A
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14
Q

What is the normal alveolar-arterial (A-a) gradient

A

less than 3kPa

expect arterial pO2 to be approx. 2/3 FiO2

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15
Q

What is the P/F ratio?

A

PaO2/FiO2

kPa divided by the fraction of inspired oxygen (0.2)

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16
Q

Give the P/F ratio in:

  • healthy person
  • acute lung injury
  • Acute respiratory distress syndrome
A
  • healthy = >50
  • acute lung injury = < 40
  • ARDS = <26.7
17
Q

What is step 2 in looking at arterial blood gases?

A

Assess the pH

  • <7.35 = acidaemia
  • >7.45 = alkalaemia
  • 7.35-7.45
    • Normak
    • mixed acid-base abnormality
18
Q

What is step 3 in looking at arterial blood gases

A

Determine the primary problem

19
Q

What is supected if pH and pCO2 are changing in the opposite direction?

A

respiratory problem

20
Q

What is suspected in pCO2 and pH are changing in the same direction?

A

metabolic problem

21
Q

What is step 4 when looking at arterial blood gases?

A

Is compensation occuring?

22
Q

What is compensation?

A

altering of function of the respiratory or renal system in an attempt to correct an acid-base imbalance

23
Q

What happens to pH and HCO3- if compensation is possibly occuring?

A

they move in the same direction (proportional)

If both values move in opposite durections more than 1 pathology must be present

24
Q

How do the kidneys compensate for chronic respiratory acidosis?

A

retaining bicarbonate

takes a few days to reach maximum

25
Q

Causes of hyperventilation

A
  • acute severe asthma
  • pulmonary embolism
  • pulmonary oedema
  • anxiety attack
26
Q

What can cause an abnormal level of central respiratory drive?

A
  • hypoxia
  • stimulation lung mechanoreceptors/chemoreceptors
  • direct stimulation of respiratory centre
  • psychogenic

MD3001 - Respiratory Clinical (7 decks)

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