1. A 65 years old woman presenting to the Emergency room with acute breathlessness. She is a known diabetic and hypertensive on medications. On examination her BP is 230/140 mmHg. Her Chest X-Ray shows bilateral fluffy pulmonary infiltrates.
2. A 45 years old asthmatic presents to the Emergency Room with acute exacerbation of his asthma. He is given repeated respiratory therapy with albuterol, ipratropium and steroids, but there is very poor response.
3. A 40 years old man who is a chronic smoker presents to the Emergency room with history of choking over his dinner while he was trying to eat a large piece of bare meat. He is acutely tachypneic and dyspneic. His face is bloated and cyanotic.
4. A 67 years old woman who is a known patient of carcinoma of the larynx presents with acute onset breathlessness. Her voice had progressively become hoarse over the past 3 days. On laryngoscopic examination her larynx is almost completely blocked by a mass of cancerous tissue.

Answer: The correct answer is (b). The first case scenario describes a flash pulmonary edema in a hypertensive patient. She needs control of her blood pressures initially. If the treatment is resistant she may need bilevel positive airway ventilation in the near future. The third scenario is of choking over a foreign body namely food. This requires Heimlich manoeuvre to dislodge the food particle. The last and final scenario describes a total obstructive laryngeal carcinoma. This needs an emergency tracheostomy and bilevel positive airway ventilation will not help. Acute exacerbation of asthma, which is resistant to routine treatment, is a classical indication for bilevel positive airway ventilation.