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.
falls 25, diagnosis 15, aid 15/30, IV 20, gait 10/20, mental status 15
NEWS2 risk
0–4 low; single 3 low–medium; 5–6 medium; ≥ 7 high
Mean arterial pressure
MAP = (SBP + 2·DBP)/3 = DBP + PP/3
Pulse pressure and shock index
PP = SBP − DBP, SI = HR/SBP
Body mass index
BMI = kg/m² = 703·lb/in²
Method
Find the score sheet that the question uses and its range (GCS 3–15, APGAR 0–10, Braden 6–23, Morse 0–125).
Score every item separately, matching the description to its level.
Add the item scores and check that the total lies inside the range.
Apply the cut-offs: for NEWS2 also look for any single parameter scoring 3.
For derived values use MAP = (SBP + 2·DBP)/3, PP = SBP − DBP, SI = HR/SBP and BMI = kg/m².
Med-surg: cardiovascular & respiratory
Method
Name the problem: pump failure, blocked artery, rhythm, clot, airway narrowing, infection or a device problem.
Check the danger signs first: hypoxia, hypotension, chest pain, new confusion, a cold pulseless limb.
Match the oxygen to the patient: 94–98% for most, 88–92% for those at risk of CO₂ retention.
Link each drug to its test and its risk: warfarin and INR, heparin and aPTT and platelets, diuretics and potassium.
Choose the safe first action, then escalate and reassess.
2Practice problems
1.Oxygen therapy & respiratory calculationsMedium
Practice exercise (made-up values, not clinical guidance). A patient has Hb 130 g/L, SaO₂ 96% and PaO₂ 83 mmHg (11.1 kPa). Find the arterial oxygen content CaO₂ = 1.34 × Hb (g/dL) × SaO₂ + 0.003 × PaO₂ (mmHg) in mL O₂/dL.
Hb 130 g/LSaO₂ 96%PaO₂ 83 mmHg (11.1 kPa)
CaO₂ = mL/dL
2.Oxygen therapy & respiratory calculationsHard
Practice exercise (made-up values, not clinical guidance). A transfer will take 75 minutes. The size E cylinder (factor 0.28 L/psi) reads 1400 psi. Keeping a safe residual of 200 psi, what is the highest whole-number flow Q in L/min that lasts the whole transfer?
75 min1400 psif = 0.28 L/psi200 psi
Q = L/min
3.Arterial blood gas interpretationMedium
A practice arterial blood gas shows pH 7.38, PaCO₂ 66 mmHg (8.8 kPa) and HCO₃⁻ 38 mmol/L. The primary disorder is respiratory acidosis. How far is it compensated? Click your answer.
pH 7.38PaCO₂ 66 mmHg (8.8 kPa)HCO₃⁻ 38 mmol/L
1uncompensated
2partially compensated
3fully compensated
4.Arterial blood gas interpretationHard
Practice values: Na⁺ 142, Cl⁻ 111 and HCO₃⁻ 8 mmol/L. Calculate the delta ratio (AG − 12)/(24 − HCO₃⁻), using AG = Na⁺ − (Cl⁻ + HCO₃⁻). Give two decimals.
Na⁺ 142 mmol/LCl⁻ 111 mmol/LHCO₃⁻ 8 mmol/L
delta ratio =
5.Clinical assessment scoresMedium
Practice exercise (made-up values, not clinical guidance). A practice patient is assessed with the Morse fall scale: history of falling in the last 3 months: yes; secondary diagnosis: no; ambulatory aid: none, bed rest or nurse assists; IV therapy or saline lock: yes; gait: normal, bed rest or wheelchair; mental status: knows own limits. Find the Morse total MFS.
0–125
MFS =
6.Clinical assessment scoresHard
Practice exercise (made-up values, not clinical guidance). At 5 minutes after birth, a practice newborn has a pink body with blue hands and feet, a heart rate of 90/min, no response to stimulation, limp limbs with no muscle tone and slow, irregular breathing with a weak cry. Score the APGAR and click how the score is interpreted.
1reassuring
2moderately abnormal
3low
7.Med-surg: cardiovascular & respiratoryMedium
After thrombolysis for a myocardial infarction, which complication is the nurse most concerned to detect?
AA high blood glucose caused by the thrombolytic drug itself
BConstipation from bed rest
CBleeding, including a sudden change in neurological status
DA skin rash appearing at the sites of the ECG electrodes
8.Med-surg: cardiovascular & respiratoryHard
As the defibrillator charges, a nurse sees a colleague still holding the patient's bed rail. What should the nurse do?
ACall clearly for everyone to stand clear and check before the shock
BDeliver the shock now, as the bed rail is not part of the patient
CAsk the colleague to hold the patient's hand instead
DTurn off the defibrillator and start a new cycle of CPR
3Solutions
1.Oxygen therapy & respiratory calculations
Answer: CaO₂ = 16.97 mL/dL
Oxygen content and delivery: CaO₂ = 1.34 × Hb (g/dL) × SaO₂ + 0.003 × PaO₂ (mmHg), in mL O₂ per dL of blood, with SaO₂ as a fraction. Almost all oxygen is bound to haemoglobin; the dissolved part is small. Delivery DO₂ = CaO₂ × cardiac output (L/min) × 10 (mL/min), because 1 L = 10 dL; a normal resting adult value is about 1000 mL/min.
Hb in g/dL
130 g/L = 13 g/dL
Bound oxygen
1.34·13·0.96 = 16.72 mL/dL
Dissolved oxygen
0.003·83 = 0.249 mL/dL
Oxygen content
CaO₂ = 16.72 + 0.249 = 16.97 mL/dL
Answer
CaO₂ = 16.97 mL/dL
2.Oxygen therapy & respiratory calculations
Answer: Q = 4 L/min
Cylinder duration: usable litres = (gauge pressure − safe residual) × cylinder factor, with the safe residual usually 200 psi. Cylinder factors in L/psi: D 0.16, E 0.28, H (and K) 3.14. Duration (min) = usable litres/flow (L/min). Round a duration down, never up, so the cylinder is changed in time. In bar-based systems, the gas volume is the water capacity (L) × the pressure (bar).
Usable litres
(1400 − 200)·0.28 = 336 L
Highest flow
336/75 = 4.48 L/min → Q = 4 L/min
Answer
Q = 4 L/min
3.Arterial blood gas interpretation
Answer: fully 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 7.38: within 7.35–7.45
PaCO₂ 66 mmHg: high (35–45)
HCO₃⁻ 38 mmol/L: high (22–26)
Compensation
fully compensated
Answer
fully compensated
4.Arterial blood gas interpretation
Answer: delta ratio = 0.6875
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 = 142 − (111 + 8) = 23
Delta ratio
(23 − 12)/(24 − 8) = 11/16 = 0.6875
Answer
delta ratio = 0.6875
Below 1: an added normal anion gap acidosis.
5.Clinical assessment scores
Answer: MFS = 45
Morse fall scale: six items. History of falling: no 0, yes 25. Secondary diagnosis: no 0, yes 15. Ambulatory aid: none, bed rest or nurse assistance 0; crutches, cane or walker 15; holding on to furniture 30. IV therapy or saline lock: no 0, yes 20. Gait: normal, bed rest or wheelchair 0; weak 10; impaired 20. Mental status: knows own limits 0; overestimates or forgets limits 15. The total runs from 0 to 125. Risk cut-offs differ between hospitals; a common set is 0–24 low, 25–44 moderate and 45 or more high.
Score each item
history of falling in the last 3 months: yes → 25
secondary diagnosis: no → 0
ambulatory aid: none, bed rest or nurse assists → 0
IV therapy or saline lock: yes → 20
gait: normal, bed rest or wheelchair → 0
mental status: knows own limits → 0
Add
Morse total = 25 + 0 + 0 + 20 + 0 + 0 = 45
Answer
MFS = 45
6.Clinical assessment scores
Answer: low
APGAR score: five signs, each scored 0, 1 or 2, checked at 1 and 5 minutes after birth. Appearance (colour): blue or pale 0, pink body with blue extremities 1, pink all over 2. Pulse: absent 0, below 100/min 1, 100/min or more 2. Grimace (reflex irritability): none 0, grimace 1, cry, cough or sneeze 2. Activity (tone): limp 0, some flexion 1, active movement 2. Respiration: absent 0, slow or irregular with a weak cry 1, good with a strong cry 2. A total of 7–10 is reassuring, 4–6 moderately abnormal and 0–3 low.
Score each sign
Appearance: a pink body with blue hands and feet → 1
Pulse: 90/min → 1
Grimace: no response to stimulation → 0
Activity: limp limbs with no muscle tone → 0
Respiration: slow, irregular breathing with a weak cry → 1
Add
APGAR = 1 + 1 + 0 + 0 + 1 = 3
Interpretation
3 → low
Answer
low
Below 7 at 5 minutes, the score is usually repeated every 5 minutes up to 20 minutes.
7.Med-surg: cardiovascular & respiratory
Answer: C · Bleeding, including a sudden change in neurological status
Why this is the answer
The main risk of thrombolysis is bleeding, from puncture sites, gums or the gut, and most seriously intracranial haemorrhage. The nurse monitors puncture sites, vital signs and neurological status and minimises invasive procedures. Reperfusion arrhythmias are also common.
Answer
C · Bleeding, including a sudden change in neurological status
8.Med-surg: cardiovascular & respiratory
Answer: A · Call clearly for everyone to stand clear and check before the shock
Why this is the answer
Before every shock, the operator states a clear warning, checks that nobody is touching the patient or bed and that oxygen is moved away from the chest. Compressions continue during charging in many protocols, then everyone stands clear for the shock. Touching the bed can conduct current to staff.
Answer
A · Call clearly for everyone to stand clear and check before the shock