Read the pH: below 7.35 is acidosis, above 7.45 alkalosis.
Find the value that explains it: PaCO₂ moving opposite to the pH is respiratory, HCO₃⁻ moving with the pH is metabolic.
Look at the other value: normal means uncompensated, abnormal in the compensating direction means partial compensation, and a normal pH with both abnormal means full compensation.
In a metabolic acidosis, compare PaCO₂ with Winter’s formula, 1.5·HCO₃⁻ + 8 ± 2, and calculate the anion gap Na⁺ − (Cl⁻ + HCO₃⁻).
Check a high anion gap with the delta ratio and, when albumin is low, with the corrected gap.
Nursing math & unit conversions
Metric steps
1 kg = 1000 g, 1 g = 1000 mg, 1 mg = 1000 mcg, 1 L = 1000 mL
Weight and length
1 kg = 2.2 lb, 1 lb = 16 oz, 1 in = 2.54 cm, 1 ft = 12 in
Household measures
1 tsp = 5 mL, 1 tbsp = 15 mL, 1 fl oz = 30 mL, 1 cup = 8 fl oz = 240 mL
Write the given quantity with its unit and the unit you want.
Pick the equivalent: 1000 between kg, g, mg and mcg or L and mL; 1 kg = 2.2 lb; 1 tsp = 5 mL, 1 tbsp = 15 mL, 1 fl oz = 30 mL, 1 cup = 240 mL.
Write it as a fraction so that the unwanted unit cancels; for a rate, use one fraction per unit that changes.
Check the direction: a smaller unit gives a bigger number.
Round only the final answer, to the precision the question names.
2Practice problems
1.Clinical assessment scoresMedium
Practice exercise (made-up values, not clinical guidance). Use the NEWS2 chart (SpO₂ scale 1) for these observations: respiration rate 18/min, SpO₂ 86% on supplemental oxygen, blood pressure 102/62 mmHg, pulse 88/min, alert, temperature 35.5 °C. What is the NEWS2 total score?
RR 18SpO₂ 86%O₂SBP 102HR 88AT 35.5 °C
NEWS2 =
2.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). Use the NEWS2 chart (SpO₂ scale 1) for these observations: respiration rate 23/min, SpO₂ 99% on room air, blood pressure 96/58 mmHg, pulse 140/min, alert, temperature 36.7 °C. Which clinical risk group does the patient fall into? Click it.
RR 23SpO₂ 99%airSBP 96HR 140AT 36.7 °C
1low
2low–medium
3medium
4high
3.Arterial blood gas interpretationMedium
A practice arterial blood gas shows pH 7.22, PaCO₂ 78 mmHg (10.4 kPa) and HCO₃⁻ 31 mmol/L. The primary disorder is respiratory acidosis. How far is it compensated? Click your answer.
pH 7.22PaCO₂ 78 mmHg (10.4 kPa)HCO₃⁻ 31 mmol/L
1uncompensated
2partially compensated
3fully compensated
4.Arterial blood gas interpretationHard
Practice values: Na⁺ 140, Cl⁻ 106, HCO₃⁻ 16 mmol/L and albumin 37 g/L. Find the albumin-corrected anion gap AGc = AG + 0.25·(40 − albumin).
How should a patient walk with a standard (non-wheeled) walking frame?
AStep forward first, then pull the frame after
BLean forward on the frame and slide the feet
CPush the frame along the floor while walking quickly
DLift the frame forward, then step into it
6.Nursing fundamentalsHard
Aspirate from a newly placed nasogastric tube has a pH of 7. What should the nurse do?
AStart the feed, as a pH of 7 confirms that the tube is in the stomach
BNot use the tube and follow policy, which may mean a chest X-ray
CPush air down the tube and listen over the stomach
DFlush the tube with water and start the feed
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A drip-rate calculation gives 106.124 gtt/min. The rule in this exercise is that drip rates are rounded to the nearest whole drop. What value x do you record?
106.124 gtt/min
x = gtt/min
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). During a shift a patient takes 1½ tsp of cough syrup, 3 cups of tea, 1 tbsp of liquid supplement, 6 fl oz of juice. Using the equivalents given, find the total oral intake V in mL.
1 tsp = 5 mL1 cup = 8 fl oz = 240 mL1 tbsp = 15 mL1 fl oz = 30 mL
V = mL
3Solutions
1.Clinical assessment scores
Answer: NEWS2 = 7
NEWS2 (National Early Warning Score 2, Royal College of Physicians 2017): score each of the seven parameters with the chart (respiration rate, SpO₂ on scale 1, air or supplemental oxygen, systolic blood pressure, pulse, consciousness on the ACVPU scale and temperature) and add the scores. Clinical risk: 0–4 low; a score of 3 in any single parameter low–medium; 5–6 medium; 7 or more high. A total of 5 or more needs an urgent response.
Score each parameter
RR 18/min → 0
SpO₂ 86% → 3
on oxygen → 2
SBP 102 mmHg → 1
HR 88/min → 0
alert (A) → 0
T 35.5 °C → 1
Add
NEWS2 = 0 + 3 + 2 + 1 + 0 + 0 + 1 = 7
Answer
NEWS2 = 7
2.Clinical assessment scores
Answer: high
NEWS2 (National Early Warning Score 2, Royal College of Physicians 2017): score each of the seven parameters with the chart (respiration rate, SpO₂ on scale 1, air or supplemental oxygen, systolic blood pressure, pulse, consciousness on the ACVPU scale and temperature) and add the scores. Clinical risk: 0–4 low; a score of 3 in any single parameter low–medium; 5–6 medium; 7 or more high. A total of 5 or more needs an urgent response.
Score each parameter
RR 23/min → 2
SpO₂ 99% → 0
on air → 0
SBP 96 mmHg → 2
HR 140/min → 3
alert (A) → 0
T 36.7 °C → 0
Total and red scores
NEWS2 = 2 + 0 + 0 + 2 + 3 + 0 + 0 = 7
At least one parameter scores 3.
Risk group
high
Answer
high
A total of 5 or more calls for an urgent clinical response.
3.Arterial blood gas interpretation
Answer: partially compensated
Reading a blood gas (ROME): first the pH: below 7.35 is acidaemia, above 7.45 alkalaemia. Then find the value that explains it. PaCO₂ (normal 35–45 mmHg, 4.7–6.0 kPa) is the respiratory part and moves Opposite to the pH in a respiratory disorder; HCO₃⁻ (normal 22–26 mmol/L) is the metabolic part and moves in the same direction as the pH (Respiratory Opposite, Metabolic Equal). The other value shows the compensation: normal means uncompensated; abnormal in the direction that pulls the pH back while the pH is still abnormal means partially compensated; a normal pH with both values abnormal means fully compensated. Ranges differ slightly between laboratories; these are practice values.
ROME, value by value
pH 7.22: acidaemia (below 7.35)
PaCO₂ 78 mmHg: high (35–45)
HCO₃⁻ 31 mmol/L: high (22–26)
Compensation
partially compensated
Answer
partially compensated
4.Arterial blood gas interpretation
Answer: AGc = 18.75 mmol/L
Expected compensation: in metabolic acidosis Winter’s formula predicts PaCO₂ = 1.5·HCO₃⁻ + 8 ± 2 mmHg; a measured value above that range points to an additional respiratory acidosis, below it to an additional respiratory alkalosis. The anion gap AG = Na⁺ − (Cl⁻ + HCO₃⁻), normally about 8–12 mmol/L, separates high-gap from normal-gap metabolic acidosis; low albumin hides a high gap (add 2.5 per g/dL that albumin is below 4.0). The delta ratio (AG − 12)/(24 − HCO₃⁻) between about 0.8 and 2 fits a pure high-gap acidosis (some texts use 1 instead of 0.8), below that an added normal-gap acidosis, and above 2 an added metabolic alkalosis.
Anion gap
AG = 140 − (106 + 16) = 18
Correction for albumin
18 + 0.25·(40 − 37) = 18.75 mmol/L
Answer
AGc = 18.75 mmol/L
Above about 12 after correction: a high anion gap.
5.Nursing fundamentals
Answer: D · Lift the frame forward, then step into it
Why this is the answer
The frame is lifted a short step forward with all four feet placed down, then the patient steps into it, usually leading with the weaker leg.
Answer
D · Lift the frame forward, then step into it
6.Nursing fundamentals
Answer: B · Not use the tube and follow policy, which may mean a chest X-ray
Why this is the answer
A low pH supports gastric placement (1–5.5 in UK guidance; 5 or below is typical in US guidance). A pH of 7 does not rule out the lungs, so nothing is put down the tube until position is confirmed, usually by X-ray. The "whoosh" air test is unreliable.
Answer
B · Not use the tube and follow policy, which may mean a chest X-ray
7.Nursing math & unit conversions
Answer: x = 106 gtt/min
Rounding: look at the digit just after the place you round to: 5 or more rounds up, 4 or less leaves the digit as it is. Round only the final answer, never the steps. Typical exam rules: volumes of 1 mL or more to the nearest tenth, volumes below 1 mL to the nearest hundredth, drip rates to whole drops and weights to one decimal place; always follow the rule the question states.
Digit in the ones place
106.124 → 6
Only the next digit decides
106.124 → 1
1 is 4 or less, so 6 stays.
The digits after it (24) are ignored: round once, never step by step.
Round
x = 106 gtt/min
Answer
x = 106 gtt/min
8.Nursing math & unit conversions
Answer: V = 922.5 mL
Household measures and weight: nursing exams use rounded equivalents: 1 teaspoon (tsp) = 5 mL, 1 tablespoon (tbsp) = 15 mL = 3 tsp, 1 fluid ounce (fl oz) = 30 mL = 2 tbsp, and 1 cup = 8 fl oz = 240 mL. For weight, 1 kg = 2.2 lb and 1 lb = 16 oz; for length, 1 inch = 2.54 cm. Set the conversion up so that the unit you do not want cancels out.