THis patient had a documented history of asthma for many years, with persistent worsening of dyspnoea and clear-coloured phlegm over the past 48 hours. She was commenced by her GP on oral steroids. Over the past 24 hours she has required her salbutamol inhaler every one to two hours and was tachypnoeic (respiratory rate of 32/min). She is conscious and wheezy, and on arrival in the emergency department her oxygen saturation (SpO²) is 94% on a 100% non-rebreather face mask. Her blood pressure is 150/90mmHg, heart rate is 130/min, and she is afebrile. 

On respiratory examination air entry was significantly reduced bilaterally; she was unable to perform a peak flow test due to severe dyspnoea, which is indicative of a very low peak expiratory flow rate (PEFR). Chest x-ray showed no focal consolidation or infiltrates. Arterial blood gases reveal a pH of 7.30, PCO² of 7.8kPa, PO² of 8.9kPa, HCO³ of 30mmol/L and SaO² of 92%.

How would you manage this patient?

The patient has features suggestive of acute severe asthma as characterised by tachypnoea and hypoxia. Blood gas analysis shows uncompensated acute respiratory acidosis with type 2 respiratory failure. Initial treatment involves 100% oxygen, aiming for a SpO² > 92%, nebulised beta-2 agonist (salbutamol) every 20 minutes or continuously, and intravenous corticosteroids. Steroids are of crucial importance in treatment of status asthmaticus. These agents can decrease mucous production, improve oxygenation, reduce beta-agonist or theophylline requirements, and activate properties that may prevent late bronchoconstrictive responses to allergens and bronchial provocation. 

Antibiotics are only recommended if there is evidence of infection, such as purulent phlegm or consolidation on the chest x-ray. The patient should be closely monitored to assess the ongoing response to treatment and identify signs of life-threatening asthma, so as to initiate mechanical ventilation in a timely manner. The role of non-invasive ventilatory support in patients with acute severe asthma remains unclear, but a trial of bi-level positive airway pressure therapy prior to invasive mechanical ventilation is reasonable in patients experiencing a severe, treatment-refractory exacerbation despite maximal bronchodilator therapy, if they do not already require immediate intubation.

After receiving initial treatment, the patient develops respiratory fatigue, is unable to complete a sentence and her chest examination becomes silent to auscultation. What is your immediate step?

The patient exhibits signs of a life-threatening asthmatic attack with progressive respiratory failure, which is unlikely to be reversed by further pharmacological therapy; intubation should therefore be performed expeditiously, before crisis ensues. It is a combination of the severity of bronchoconstriction and the exhaustion of the patient trying to overcome it that sets the stage for impending respiratory arrest. 

The clinical assessment that an asthma patient in respiratory distress requires intubation involves the patient’s appearance, vital signs including oxygen saturation, and a poor response to initial medical therapy. 

Most patients with a severe asthma exacerbation can be managed successfully with aggressive use of beta-agonists, anticholinergics, glucocorticoids and other medications, including magnesium sulphate. Infrequently, medical intervention with bronchodilators and oxygen is insufficient to reverse the immediate course of disease and endotracheal intubation is required. 

How is risk stratification carried out in patients with asthma? What preventive measure is recommended to avoid fatal and non-fatal asthma attacks?

The major risk factors for fatal asthma are:

• Previous history of mechanical ventilation
• Recent history of poorly controlled asthma
• Previous history of ICU admission.
• If a major risk factor is present assume the patient is at risk for a fatal asthma attack.

If only a minor risk factor is present, the patient is at possible high risk. Minor risk factors for fatal asthma are:

• Smoking exposure, poor compliance
• Multiple hospital admissions
• Oral glucocorticoid dependence.

Steps to prevent a fatal or non-fatal attack include: smoking cessation; allergen avoidance; education about early warning sign of deterioration; measure and maintain regular peak flow record; encourage medication compliance; annual influenza vaccination; optimise controller therapy; and regular review to assess asthma control.