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). A practice patient is assessed with the Braden scale: sensory perception: slightly limited; moisture: constantly moist; activity: walks frequently; mobility: very limited; nutrition: very poor; friction and shear: no apparent problem. Find the Braden total B.
6–23
B =
2.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). Use the NEWS2 chart (SpO₂ scale 1) for these observations: respiration rate 18/min, SpO₂ 98% on room air, blood pressure 102/62 mmHg, pulse 82/min, alert, temperature 37.2 °C. Which clinical risk group does the patient fall into? Click it.
RR 18SpO₂ 98%airSBP 102HR 82AT 37.2 °C
1low
2low–medium
3medium
4high
3.Arterial blood gas interpretationMedium
A practice arterial blood gas shows pH 7.57, PaCO₂ 27 mmHg (3.6 kPa) and HCO₃⁻ 24 mmol/L. The primary disorder is respiratory alkalosis. How far is it compensated? Click your answer.
pH 7.57PaCO₂ 27 mmHg (3.6 kPa)HCO₃⁻ 24 mmol/L
1uncompensated
2partially compensated
3fully compensated
4.Arterial blood gas interpretationHard
A practice gas shows a metabolic acidosis: pH 7.20, PaCO₂ 21 mmHg (2.8 kPa), HCO₃⁻ 8 mmol/L. Compare the measured PaCO₂ with Winter’s formula. Click your interpretation.
pH 7.20PaCO₂ 21 mmHg (2.8 kPa)HCO₃⁻ 8 mmol/L
1appropriate compensation
2added respiratory acidosis
3added respiratory alkalosis
5.Nursing fundamentalsMedium
What is the most reliable way to check that a nasogastric tube is in the stomach before use?
AAsking the patient whether it feels right
BListening for a "whoosh" after injecting air
CPlacing the end of the tube in water to look for bubbles
DTesting aspirate pH, with a chest X-ray if needed
6.Nursing fundamentalsHard
An 82-year-old takes nine regular medicines and has had two falls this month. What is the most useful next step?
AAdvise the patient to stay in bed
BStop all the medicines straight away
CAsk for a full medication review
DAdd a sedative to help them rest
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A dose is charted at 1:15 PM. Which entry is the same time on the 24-hour clock? Click it.
1:15 PM
114:15
212:15
313:15
401:15
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). An order reads 1 mcg/kg/min for a patient who weighs 84 kg. Express the dose rate D in mg/h. Round to two decimal places.
1 mcg/kg/min84 kg
D = mg/h
3Solutions
1.Clinical assessment scores
Answer: B = 14
Braden scale: six subscales for pressure-injury risk. Sensory perception, moisture, activity, mobility and nutrition score 1 to 4, from the worst level (1) to no problem (4); friction and shear scores 1 to 3. The total runs from 6 to 23, and a lower total means a higher risk. Common bands: 19–23 not at risk, 15–18 mild risk, 13–14 moderate risk, 10–12 high risk and 9 or below very high risk.
Score each subscale
sensory perception: slightly limited → 3
moisture: constantly moist → 1
activity: walks frequently → 4
mobility: very limited → 2
nutrition: very poor → 1
friction and shear: no apparent problem → 3
Add
Braden total = 3 + 1 + 4 + 2 + 1 + 3 = 14
Answer
B = 14
2.Clinical assessment scores
Answer: low
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 98% → 0
on air → 0
SBP 102 mmHg → 1
HR 82/min → 0
alert (A) → 0
T 37.2 °C → 0
Total and red scores
NEWS2 = 0 + 0 + 0 + 1 + 0 + 0 + 0 = 1
No parameter scores 3.
Risk group
low
Answer
low
3.Arterial blood gas interpretation
Answer: uncompensated
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 7.57: alkalaemia (above 7.45)
PaCO₂ 27 mmHg: low (35–45)
HCO₃⁻ 24 mmol/L: normal (22–26)
Compensation
uncompensated
Answer
uncompensated
4.Arterial blood gas interpretation
Answer: appropriate compensation
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.
Expected PaCO₂
1.5·8 + 8 = 20 → 18–22 mmHg
Compare
measured: 21 mmHg → appropriate compensation
Answer
appropriate compensation
5.Nursing fundamentals
Answer: D · Testing aspirate pH, with a chest X-ray if needed
Why this is the answer
Aspirate pH supports gastric placement (5.5 or less in UK guidance; 5 or less is typical in US guidance). An X-ray is the most accurate confirmation, used for first placement in many US settings and whenever pH is unclear or no aspirate is obtained. The air insufflation test is unreliable.
Answer
D · Testing aspirate pH, with a chest X-ray if needed
6.Nursing fundamentals
Answer: C · Ask for a full medication review
Why this is the answer
Polypharmacy increases the risk of falls, side effects and interactions in older adults. A review by the prescriber or pharmacist can stop or adjust medicines safely.
Answer
C · Ask for a full medication review
7.Nursing math & unit conversions
Answer: 13:15
24-hour clock: from 1 PM onwards add 12 to the hour (3:45 PM = 15:45). Midnight to 12:59 AM is 00:00–00:59, and 12:00–12:59 PM stays 12:00–12:59. Going back, subtract 12 from hours 13–23 and add PM; hours 00 become 12 AM. Count time across midnight in two parts: up to 24:00 (00:00), then from 00:00 on.
Convert the hour
1 PM → 1 + 12 = 13
Answer
13:15
Answer
13:15
8.Nursing math & unit conversions
Answer: D = 5.04 mg/h
Dimensional analysis: write the given quantity, then multiply by conversion factors written as fractions (for example 60 min/1 h or 1 mg/1000 mcg) so that each unwanted unit appears once on top and once underneath and cancels. When only the wanted unit is left, calculate. Use the equivalents the question gives and round only the final answer.
Set up the chain
D = 1 mcg/kg/min × 84 kg × (60 min/1 h) × (1 mg/1000 mcg)