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Data Interpretation > Understanding ABGs > Flashcards

Understanding ABGs Flashcards

1
Q

Normal Ranges

A 
pH: 7.35 – 7.45
PaCO2: 4.7 – 6.0 kPa || 35.2 – 45 mmHg
PaO2: 11 – 13 kPa || 82.5 – 97.5 mmHg
HCO3–: 22 – 26 mEq/L
Base excess (BE): -2 to +2 mmol/L
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2
Q

PaO2 of Patient on O2 Therapy

A

PaO2 should be approximately 10kPa less than the % inspired concentration FiO2

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3
Q

Hypoxaemia

A

Hypoxaemia: <10kPa PaO2 on air

Severe hypoxaemia/resp failure: <8kPa on air

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4
Q

Type 1 Resp Failure

A

Hypoxaemia and normocapnia

Result of ventilation/perfusion (V/Q) mismatch

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5
Q

Examples of V/Q Mismatch

A

Reduced ventilation w normal perfusion (pulm oedema, bronchoconstriction)
Reduced perfusion w normal ventilation (PE)

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6
Q

Type 2 Resp Failure

A

Hypoxaemia and hypercapnia

Result of alveolar hypoventilation

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7
Q

Causes of hypoventilation

A

Incr airway resistance due to obstruction (COPD)
Reduced lung tissue/chest wall compliance (pneumonia, rib fracture, obesity)
Reduced strength of resp muscles (MNR)
Drugs acting on resp centre reducing overall ventilation (opiates)

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8
Q

Acidotic/Normal/Alkalotic

A

Acidotic: pH <7.35
Normal: pH 7.35 – 7.45
Alkalotic: pH >7.45

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9
Q

Respiratory or Metabolic Change

A

Changes in pH are caused by an imbalance in the CO2 (respiratory) or HCO3– (metabolic)

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10
Q

Compensation

A

The body can try and adjust other buffers (CO2/HCO3) to keep the pH within the normal range.

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11
Q

Compensation in Respiratory

A

Adjust HCO3

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12
Q

Compensation in Metabolic

A

Adjust CO2

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13
Q

HCO3

A

Base which helps mop up acids (H+ ions).
When HCO3– is raised –> pH is increased as there are less free H+ ions (alkalosis).
When HCO3– is low –> pH is decreased as there are more free H+ ions (acidosis).

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14
Q

Resp Acidosis

A

Decr pH
Incr CO2
Normal HCO3

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15
Q

Resp Alkalosis

A

Incr pH
Decr CO2
Normal HCO3

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16
Q

Resp acidosis w metabolic compensation

A

Decr/normal pH
Incr CO2
Incr HCO3

17
Q

Resp alkalosis w metabolic compensation

A

Incr/normal pH
Decr CO2
Decr HCO3

18
Q

Metabolic Acidosis

A

Decr pH
Decr HCO3
Normal CO2

19
Q

Metabolic Alkalosis

A

Incr pH
Incr HCO3
Normal CO2

20
Q

Metabolic acidosis w resp compensation

A

Decr pH
Decr HCO3
Decr CO2

21
Q

Metabolic alkalosis w resp compensation

A

Incr pH
Incr HCO3
Incr CO2

22
Q

Base excess

A

High BE: >+2mmol/L, primary metabolic alkalosis/comp resp acidosis
Low BE:

23
Q

Rate of Compensation

A

Resp compensation for metabolic disorder: quickly (by adjusting alveolar vent)
Metabolic compensation for resp disorder: few days (kidneys must adjust HCO3 production)

24
Q

Mixed Acidosis and Alkalosis

A

CO2 and HCO3 moving in opposite directions

Treatment is directed towards correcting each primary acid/base disturbance

25
Q

Causes of Resp Acidosis

A

Respiratory depression (e.g. opiates)
Guillain-Barre: paralysis leads to an inability to adequately ventilate
Asthma
COPD
Iatrogenic (incorrect mechanical ventilation settings)

26
Q

Causes of Resp Alkalosis

A

Anxiety (i.e. panic attack)
Pain: causing an increased respiratory rate.
Hypoxia: resulting in increased alveolar ventilation in an attempt to compensate.
Pulmonary embolism
Pneumothorax
Iatrogenic (e.g. excessive mechanical ventilation)

27
Q

Causes of Metabolic Acidosis

A

Increased acid production or acid ingestion.

Decreased acid excretion or rate of gastrointestinal and renal HCO3– loss.

28
Q

High Anion Gap Metabolic Acidosis

A

Diabetic ketoacidosis
Lactic acidosis
Aspirin overdose
Renal failure

29
Q

Normal Anion Gap Metabolic Acidosis

A

Gastrointestinal loss of HCO3– (e.g. diarrhoea, ileostomy, proximal colostomy)
Renal tubular disease
Addison’s disease

30
Q

Causes of Metabolic Alkalosis

A

Gastrointestinal loss of H+ ions (e.g. vomiting, diarrhoea)
Renal loss of H+ ions (e.g. loop and thiazide diuretics, heart failure, nephrotic syndrome, cirrhosis, Conn’s syndrome)
Iatrogenic (e.g. addition of excess alkali such as milk-alkali syndrome)

31
Q

Causes of Mixed Resp/Metabolic Acidosis

A

Cardiac arrest

Multi-organ failure

32
Q

Causes of Mixed Resp/Metabolic Alkalosis

A

Liver cirrhosis in addition to diuretic use
Hyperemesis gravidarum
Excessive ventilation in COPD

Data Interpretation (4 decks)

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