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 22/min, SpO₂ 98% on room air, blood pressure 136/82 mmHg, pulse 88/min, alert, temperature 35.2 °C. What is the NEWS2 total score?
RR 22SpO₂ 98%airSBP 136HR 88AT 35.2 °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 14/min, SpO₂ 88% on room air, blood pressure 102/62 mmHg, pulse 70/min, alert, temperature 37.5 °C. Which clinical risk group does the patient fall into? Click it.
RR 14SpO₂ 88%airSBP 102HR 70AT 37.5 °C
1low
2low–medium
3medium
4high
3.Arterial blood gas interpretationMedium
A practice gas shows PaCO₂ 76 mmHg (10.1 kPa). Use the rule that in acute respiratory acidosis HCO₃⁻ rises by 1 mmol/L for every 10 mmHg that PaCO₂ is above 40, starting from HCO₃⁻ 24 mmol/L, to find the expected HCO₃⁻.
At sea level, a practice gas taken on 24% oxygen shows PaO₂ 63 mmHg (8.4 kPa) and PaCO₂ 34 mmHg (4.5 kPa). Use PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8 to find the A–a gradient.
How does pursed-lip breathing help a patient with COPD?
AIt keeps the airways open longer and slows the breathing
BIt makes the patient breathe faster to take in more air
CIt increases the amount of carbon dioxide in the blood
DIt replaces the need for inhaled medicines
6.Nursing fundamentalsHard
Eight hours after surgery a patient has not passed urine and has lower abdominal discomfort with a swelling above the pubic bone. What should the nurse do?
AEncourage the patient to drink two litres of water quickly
BGive a laxative to relieve the swelling
CRecord it and check again the next morning
DCheck the bladder volume with a scanner and report the findings
7.Nursing math & unit conversionsMedium
Practice exercise (made-up values, not clinical guidance). A patient is 164 cm tall. Using 1 in = 2.54 cm, find the height h in inches. Round to one decimal place.
164 cm1 in = 2.54 cm
h = in
8.Nursing math & unit conversionsHard
Practice exercise (made-up values, not clinical guidance). An infusion delivers 40 mcg/min. Express this dose rate D in mg/h.
40 mcg/min1 h = 60 min1 mg = 1000 mcg
D = mg/h
3Solutions
1.Clinical assessment scores
Answer: NEWS2 = 3
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 22/min → 2
SpO₂ 98% → 0
on air → 0
SBP 136 mmHg → 0
HR 88/min → 0
alert (A) → 0
T 35.2 °C → 1
Add
NEWS2 = 2 + 0 + 0 + 0 + 0 + 0 + 1 = 3
Answer
NEWS2 = 3
2.Clinical assessment scores
Answer: low–medium
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 14/min → 0
SpO₂ 88% → 3
on air → 0
SBP 102 mmHg → 1
HR 70/min → 0
alert (A) → 0
T 37.5 °C → 0
Total and red scores
NEWS2 = 0 + 3 + 0 + 1 + 0 + 0 + 0 = 4
At least one parameter scores 3.
Risk group
low–medium
Answer
low–medium
A single score of 3 needs an urgent review even when the total is low.
3.Arterial blood gas interpretation
Answer: HCO₃⁻ = 27.6 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.
Change in PaCO₂
|76 − 40| = 36 mmHg → 3.6 × 10 mmHg
Expected HCO₃⁻
HCO₃⁻ = 24 + 1·3.6 = 27.6 mmol/L
Answer
HCO₃⁻ = 27.6 mmol/L
4.Arterial blood gas interpretation
Answer: A–a gradient = 65.62 mmHg
Derived values: calculated serum osmolality is 2·Na⁺ + glucose + urea with all values in mmol/L (2·Na⁺ + glucose/18 + BUN/2.8 with glucose and BUN in mg/dL); normal is about 275–295 mOsm/kg. The P/F ratio is PaO₂ divided by FiO₂ as a fraction. The alveolar oxygen pressure is PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8 mmHg at sea level, and the A–a gradient is PAO₂ − PaO₂.
Answer: A · It keeps the airways open longer and slows the breathing
Why this is the answer
Breathing out slowly through pursed lips creates back-pressure that keeps small airways open, helping to empty trapped air and reducing breathlessness.
Answer
A · It keeps the airways open longer and slows the breathing
6.Nursing fundamentals
Answer: D · Check the bladder volume with a scanner and report the findings
Why this is the answer
These signs suggest postoperative urinary retention. A bladder scan confirms the volume, and the doctor is told so it can be relieved, often by catheterisation.
Answer
D · Check the bladder volume with a scanner and report the findings
7.Nursing math & unit conversions
Answer: h = 64.6 in
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.
Centimetres to inches
h = 164/2.54 = 64.57 ≈ 64.6 in
Answer
h = 64.6 in
8.Nursing math & unit conversions
Answer: D = 2.4 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.