Acute severe asthma with exhaustion and hypercapnia
A 34-year-old man with known asthma presents with a 6-hour history of worsening breathlessness. He is unable to speak in full sentences, is using accessory muscles, and has a respiratory rate of 34/min. Heart rate is 128/min, SpO₂ 89% on 15 L/min oxygen, and peak expiratory flow is 20% of predicted. Chest auscultation reveals a silent chest. He is drowsy but rousable. He has had two previous ICU admissions for asthma. He has received three back-to-back salbutamol nebulisers, ipratropium, intravenous hydrocortisone, and magnesium sulfate 2 g over 20 minutes. He remains exhausted. Blood gas on 15 L oxygen shows pH 7.28, PaCO₂ 6.8 kPa, PaO₂ 8.1 kPa. The department has NIV but no ECMO; an ICU bed is available.
1. Should this patient receive non-invasive ventilation? Justify your answer and state your next airway decision.
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NIV is not appropriate here. This patient has exhaustion, a silent chest, hypercapnia, and a history of ICU admissions-features of impending respiratory arrest. NIV in severe asthma can delay intubation, increase the risk of aspiration, and does not reliably improve dynamic hyperinflation. My next airway decision is a rapid sequence intubation with an experienced operator, using a plan for difficult airway and a strategy to avoid dynamic hyperinflation. I would pre-oxygenate, optimise haemodynamics, and call for ICU and anaesthetic support. The reasoning is that the risk of continuing NIV is cardiac arrest; the benefit of intubation is controlled ventilation and airway protection. I would not wait for further nebulisers or a trial of NIV.
2. Describe your rapid sequence intubation strategy, including drug choice, pre-oxygenation, and initial ventilator settings. Explain how you will avoid dynamic hyperinflation.
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For RSI I would use ketamine 1–1.5 mg/kg IV, which preserves respiratory drive and blood pressure, and rocuronium 1.2 mg/kg. I would pre-oxygenate with a tight-fitting mask for 3 minutes, use apnoeic oxygenation if available, and have suction and a difficult airway trolley ready. After intubation, initial settings should be volume-controlled or pressure-controlled ventilation with a tidal volume of 6–8 mL/kg predicted body weight, a low respiratory rate (8–10/min), a long expiratory time, and low PEEP. I would accept permissive hypercapnia and avoid high minute ventilation. The reasoning is to prevent dynamic hyperinflation, which causes hypotension and barotrauma. I would monitor for a rising peak pressure and allow full exhalation before the next breath.
3. Ten minutes after intubation, blood pressure falls to 70/40 mmHg and breath sounds are reduced on the right. What is your differential and immediate management?
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Hypotension with reduced right-sided breath sounds after intubation is a critical event. The differential includes tension pneumothorax, dynamic hyperinflation, oesophageal intubation, and drug-related hypotension. I would immediately disconnect the ventilator and allow the chest to exhale, check the tube position, and assess for tracheal deviation and percussion. If tension pneumothorax is suspected, I would perform needle decompression and then chest drain without waiting for imaging. I would also reduce the respiratory rate and tidal volume to treat dynamic hyperinflation, and give fluids or vasopressors. The reasoning is that both tension pneumothorax and dynamic hyperinflation can cause obstructive shock; disconnecting the circuit is a rapid diagnostic and therapeutic step.