Pre-hospital medical devices: DipIMC practice questions
PHEM curriculum unit 3.3 · Theme 3: Using Pre-hospital Equipment
The DipIMC is blueprinted against phase 1 of the UK Pre-hospital Emergency Medicine (PHEM) curriculum. This page covers unit 3.3, Operate all types of commonly used pre-hospital emergency medical device.
Below are 3 free practice questions from the DipIMC.Ninja bank, in the Part A single best answer format. Every answer names the textbook page, guideline or statute it was written from, so you can check it rather than take it on trust. The bank holds 44 questions on this unit.
Question 1 · Medical & Resuscitation · Moderate
During a road transfer of an intubated, ventilated trauma patient the end-tidal carbon dioxide falls steadily over four minutes from 4.6 kPa to 2.1 kPa. The waveform keeps its normal square shape, the ventilator settings are unchanged and no alarm has sounded. The blood pressure has also drifted down. What does this pattern most likely indicate?
AOesophageal intubation
BWorsening bronchospasm
CA tracheal tube cuff leak
DA falling cardiac output
EInadvertent hyperventilation
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Answer: D
A falling cardiac output
Quantitative waveform capnography reports on respiratory rate, airway and tube obstruction, ventilator disconnection, muscle relaxation, cellular function and cardiac output; the ABC's gallery of abnormal traces includes a pattern for reducing cardiac output. With ventilation unchanged, a gradual fall in end-tidal carbon dioxide with a preserved waveform and a drifting blood pressure points to falling pulmonary blood flow — a falling cardiac output. RCUK 2025 makes the same link: a decrease in end-tidal carbon dioxide (ETCO2) may indicate cardiac arrest or a very low cardiac output state. Oesophageal intubation would have shown from the start, not four minutes into a transfer with a confirmed tube. Bronchospasm changes the shape of the trace, producing a ramp-shaped upslope rather than a preserved square wave. A cuff leak and hyperventilation both appear in the gallery as their own patterns, and the ventilator settings have not been touched. End-tidal carbon dioxide reads lower than arterial — by about 0.7 kPa in health, more in shock and lung disease — which is why paired measurements are taken before an inter-hospital transfer.
Where this comes from
ABC of Prehospital Emergency Medicine
Ch. 11 Prehospital Monitoring · Capnography · p. 59“muscle relaxation, cellular function and cardiac output”
An adult in out-of-hospital cardiac arrest has had 25 minutes of high-quality cardiopulmonary resuscitation (CPR). A tracheal tube is in place, its position confirmed, and ventilation is adequate. The rhythm is asystole and the end-tidal carbon dioxide has read 0.9 kPa throughout. A team member suggests stopping on the basis of the capnography value. What is the correct use of this reading?
AA value below 1.3 kPa after 20 minutes is an accepted criterion for stopping
BA low value alone must not be used to decide whether to stop resuscitation
CA low value justifies stopping once a second reading has confirmed it
DThe value indicates tube displacement and should prompt re-intubation
EThe value confirms pulmonary embolism and should prompt thrombolysis
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Answer: B
A low value alone must not be used to decide whether to stop resuscitation
Resuscitation Council UK Guidelines 2025 state: do not use a low end-tidal carbon dioxide (ETCO2) value alone to decide if a resuscitation attempt should be stopped. Waveform capnography during CPR is used to confirm tracheal tube placement and to monitor the quality of CPR, and a pragmatic physiology-guided target is an ETCO2 of at least 3.3 kPa (25 mmHg). Confirming a low value a second time does not change what it means. The tube has been confirmed and a waveform persists, so displacement does not explain the number. The special circumstances guideline says that low ETCO2 values (below 1.7 kPa) with confirmed intubation, appropriate minute volume and high-quality compressions may support a diagnosis of pulmonary embolism, although it is a non-specific sign, so it does not confirm one. ABC of Prehospital Emergency Medicine describes quantitative capnography as arguably the single most useful monitor in pre-hospital care, to be used on all intubated patients. The decision to stop is a clinical judgement on the whole picture.
ABC of Prehospital Emergency Medicinep. 59Ch. 11 Prehospital Monitoring · Capnography“It should be used on all intubated and ideally non-intubated patients.”
A patient with severe facial burns cannot be intubated or oxygenated by any other means, and a needle cricothyroidotomy has been performed with a 14-gauge cannula, oxygen at 15 litres per minute and a Y-connector. Twenty minutes later the oxygen saturation is acceptable but the patient is increasingly hypercapnic. What is the explanation and the correct next step?
AKinked cannula obstructing flow; site a second needle cricothyroidotomy
BInadequate oxygen flow; increase the insufflation to 25 litres per minute
CExpected after burns; continue jet insufflation and transfer as planned
DHypoventilation via the cannula; ventilate through it with a bag-valve
ENo carbon dioxide clearance; convert to a surgical cricothyroidotomy
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Answer: E
No carbon dioxide clearance; convert to a surgical cricothyroidotomy
Needle cricothyroidotomy with jet insufflation oxygenates but leaves minimal opportunity for elimination of carbon dioxide, so progressive hypercapnia limits its effectiveness and survivability to about 20 minutes. It does not allow ventilation, merely insufflation of oxygen: it is a temporising measure, and a definitive airway requires surgical cricothyroidotomy, which, where the skills exist, has a much higher success rate and is the intervention of choice. A second cannula repeats the same physiology, a higher flow creates no expiratory route, and a bag-valve device cannot turn a needle into a ventilating airway. Hypercapnia here is a failure of the technique, not an expected feature of burns. For the surgical airway, the Oxford Handbook says the kit's tube should have a minimum lumen of 6 mm, and the burns consensus recommends a large-bore, uncut tube so that bronchoscopy remains possible and the tube is not lost as the face swells.
Where this comes from
Oxford Handbook of Pre-Hospital Care
Ch. 5 Airway, analgesia and anaesthesia · Needle cricothyroidotomy and jet insufflation · p. 353“progressive hypercapnia limits the effectiveness and survivability of this procedure to approximately 20 minutes”
Ch. 5 Airway, analgesia and anaesthesia · Needle cricothyroidotomy: temporising only · p. 353“a definitive airway requires surgical cricothyroidotomy”
Ch. 1 An approach to pre-hospital care · Notes on equipment: cricothyroidotomy kit · p. 17“does not allow ventilation, merely insufflation of oxygen”
Ch. 1 An approach to pre-hospital care · Notes on equipment: cricothyroidotomy kit · pp. 16–17“the tube should have a minimum lumen of 6mm”