Arterial blood gas interpretation worksheet with answers

Free printable Arterial blood gas interpretation worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

A practice blood gas shows PaO₂ 99 mmHg (13.2 kPa) while the inspired oxygen is 35%. Calculate the ratio P/F = PaO₂/FiO₂ in mmHg.

PaO₂ 99 mmHg (13.2 kPa)FiO₂ 35%
P/F = mmHg
2.Easy
pH7.357.457.26PaCO₂mmHg354555HCO₃⁻mmol/L222624respiratorymetabolicacidosisalkalosis

A practice arterial blood gas shows pH 7.26, PaCO₂ 55 mmHg (7.3 kPa) and HCO₃⁻ 24 mmol/L. Which primary disorder is it? Click the cell in the grid.

pH 7.26PaCO₂ 55 mmHg (7.3 kPa)HCO₃⁻ 24 mmol/L
  1. 1respiratory acidosis
  2. 2metabolic acidosis
  3. 3respiratory alkalosis
  4. 4metabolic alkalosis
3.Medium

A practice gas shows PaCO₂ 67 mmHg (8.9 kPa). Use the rule that in chronic respiratory acidosis HCO₃⁻ rises by 3.5 mmol/L for every 10 mmHg that PaCO₂ is above 40, starting from HCO₃⁻ 24 mmol/L, to find the expected HCO₃⁻.

PaCO₂ 67 mmHg (8.9 kPa)baseline: 40 mmHg, 24 mmol/L
HCO₃⁻ = mmol/L
4.Medium

Practice values: Na⁺ 151 mmol/L, glucose 13.3 mmol/L and urea 19.1 mmol/L. Calculate the serum osmolality Osm = 2·Na⁺ + glucose + urea to the nearest whole number.

Na⁺ 151 mmol/Lglucose 13.3 mmol/Lurea 19.1 mmol/L
Osm = mOsm/kg
5.Hard

At sea level, a practice gas taken on 24% oxygen shows PaO₂ 67 mmHg (8.9 kPa) and PaCO₂ 49 mmHg (6.5 kPa). Use PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8 to find the A–a gradient.

FiO₂ 24%PaO₂ 67 mmHg (8.9 kPa)PaCO₂ 49 mmHg (6.5 kPa)
A–a gradient = mmHg
6.Hard
pH7.357.457.26PaCO₂mmHg354572HCO₃⁻mmol/L222631acutechronicacute on chronic

A practice gas shows a respiratory acidosis: pH 7.26, PaCO₂ 72 mmHg (9.6 kPa), HCO₃⁻ 31 mmol/L. Use the rules ‘HCO₃⁻ rises 1 mmol/L per 10 mmHg (acute) or 3.5 mmol/L per 10 mmHg (chronic)’ to classify it. Click your answer.

pH 7.26PaCO₂ 72 mmHg (9.6 kPa)HCO₃⁻ 31 mmol/L
  1. 1acute
  2. 2chronic
  3. 3acute on chronic

Answer key

  1. 1. P/F = 282.9 mmHg
  2. 2. respiratory acidosis
  3. 3. HCO₃⁻ = 33.45 mmol/L
  4. 4. Osm = 334 mOsm/kg
  5. 5. A–a gradient = 42.87 mmHg
  6. 6. acute on chronic

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