From the Guidelines
Intubation in asthma should be performed when there are signs of respiratory failure that cannot be managed with less invasive measures, specifically when the patient shows altered mental status, exhaustion, worsening hypoxemia despite supplemental oxygen, rising PaCO2, or severe acidosis. The decision to intubate should be based on the patient's clinical presentation and response to initial treatment. According to the National Asthma Education and Prevention Program Expert Panel Report 3 guidelines for the management of asthma exacerbations 1, intubation should be done semielectively and before respiratory arrest occurs. The Expert Panel recommends that intubation not be delayed once it is deemed necessary, as respiratory failure can progress rapidly and is difficult to reverse 1. Some key indicators for intubation include:
- Altered mental status
- Exhaustion
- Worsening hypoxemia despite supplemental oxygen
- Rising PaCO2 (especially >42 mmHg)
- Severe acidosis
- Deteriorating PEF, worsening or persisting hypoxia, respirations, confusion, or drowsiness 1 Before intubation, it is essential to maximize medical therapy with treatments such as continuous albuterol nebulization, IV magnesium sulfate, and systemic corticosteroids. When intubating, it is crucial to use a strategy that minimizes the risk of complications, such as permissive hypercapnia or controlled hypoventilation, to provide adequate oxygenation while minimizing airway pressures and the possibility of barotrauma 1. The goal of intubation and subsequent ventilation is to prevent complications like pneumothorax while maintaining oxygenation until bronchodilator therapy takes effect and inflammation subsides.
From the Research
Indications for Intubation in Asthma
- Cardiopulmonary arrest and severe hypoxemia in spite of O2 supplement and non-invasive ventilation (NIV) are absolute criteria for intubation and ventilation 2
- Deterioration in mental status and exhaustion are clinical findings that may lead to mechanical ventilation 2
- A continuously rising PaCO(2) or the development of a severe metabolic acidosis after 1 hour of NIV is a strong argument for invasive mechanical ventilation 2
- Evidence of cardiac failure with fall in pulse volume and dysrhythmias, pneumomediastinum or pneumothorax (which has to be drained before mechanical ventilation) are other criteria for intubation 2
Non-Invasive Ventilation (NIV) in Asthma
- NIV is associated with a reduced intubation rate, admission rate, and time to improvement in accessory muscle use in adults with acute asthma exacerbation 3
- NIV may be beneficial in reducing the need for intubation, although the overall quality of the evidence is low 3
Assessment of Acute Asthma
- Oxygen saturation as measured by pulse oximetry can be a reliable screening test for predicting those in respiratory failure, and an oxygen saturation of > 92% suggests that respiratory failure is unlikely 4
- Arterial blood gas estimation may not always be necessary in the assessment of patients presenting to hospital with acute severe asthma 4
Other Treatment Options
- Extracorporeal membrane oxygenation (ECMO) and inhaled anesthetic may have a role in the management of acute severe refractory asthma exacerbation, although more research is needed to fully understand their benefits and risks 5
- Nebulized magnesium does not significantly decrease the hospitalization rate for asthma within 24 hours in children with refractory acute asthma 6