skip to main content

ACIP — SCE Respiratory MCQ

Instant feedback + full explanation. One question, done properly.

HardACIPSCE Respiratory

A 59-year-old woman is admitted with lower-limb cellulitis. Over the next 12 hours she becomes increasingly somnolent and develops worsening hypoxaemia. She has a BMI of 52 kg/m², longstanding orthopnoea, loud snoring, witnessed apnoeas and morning headaches. She takes no opioids or sedatives. Previous spirometry showed an FEV1/FVC ratio of 0.81. She is rousable to voice, cooperative and protecting her airway. Respiratory rate is 22 breaths/min and SpO₂ is 84% breathing air. There is elevated jugular venous pressure and marked bilateral peripheral oedema. Chest radiography shows low-volume lungs with bibasal atelectatic change but no focal consolidation. Arterial blood gas analysis breathing air shows pH 7.37, PaCO₂ 9.2 kPa, PaO₂ 6.8 kPa and bicarbonate 39 mmol/L. Renal function and serum potassium are normal. Which immediate management plan is most appropriate?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Start bilevel non-invasive ventilation in HDU/ICU, target SpO₂ 88–92%, and give intravenous loop diuretic therapy

Explanation lettering: B = shown as A · C = shown as B · D = shown as C · A = shown as D

This is acute-on-chronic ventilatory failure due to obesity hypoventilation syndrome: severe obesity, sleep-disordered breathing symptoms, daytime hypercapnia and markedly raised bicarbonate are accompanied by acute somnolence and hypoxaemia. The near-normal pH reflects renal compensation and does not make ventilatory support unnecessary. BTS/ICS guidance specifically permits NIV in hospitalised obese hypercapnic patients without acidosis when somnolence, sleep-disordered breathing or right heart failure is present. NICE recommends NIV as first-line treatment for OHS with acute ventilatory failure. NIV should be delivered in HDU/ICU because OHS carries an increased risk of NIV failure, sudden deterioration and difficult intubation. Oxygen should be titrated to 88–92% in acute hypercapnic respiratory failure. The raised JVP and oedema indicate fluid overload, which commonly aggravates ventilatory failure in OHS and warrants active diuresis. A is inappropriate because CPAP treats upper-airway obstruction but does not provide the pressure support needed to correct acute hypoventilation. C risks worsening hypercapnia through excessive oxygen administration. D is premature because she remains cooperative and protects her airway; these features support a closely monitored NIV trial rather than immediate intubation. E incorrectly treats pH below 7.35 as an obligatory threshold: the somnolence, severe hypercapnia and right-heart failure constitute the relevant exception.

Reference: BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults (March 2016; correction June 2017) — https://www.brit-thoracic.org.uk/document-library/guidelines/niv/btsics-guideline-for-the-ventilatory-management-of-acute-hypercapnic-respiratory-failure-in-adults NICE NG202: Obesity hypoventilation syndrome (20 August 2021; links updated March 2025) — https://www.nice.org.uk/guidance/ng202/chapter/2-obesity-hypoventilation-syndrome