Asthma is one of the most common illnesses in pediatrics, with considerable variation in presentation. Patients can have an asthma attack with mild respiratory difficulties and not require more than an intermittent inhaled β-agonist. Alternatively, a severe asthmatic patient may require mechanical ventilation or even extracorporeal life support. Although an asthma attack that requires endotracheal intubation is rare, it is important to identify the risk factors for intubation. These include low socioeconomic status, active tobacco smoking or second-hand smoke exposure, parenteral history of allergy or asthma, prior intubation, intercurrent respiratory infection, prior asthma emergency room visit in past year, prior asthma hospitalization in past year, and steroid dependence.

Children require mechanical ventilation for asthma when they have profound hypoxemia, life-threatening respiratory muscle fatigue, or altered mental status. However, high airway pressures, barotrauma, and patient-ventilator dyssynchrony complicate mechanical ventilation in patients with asthma. Although potentially lifesaving, use of mechanical ventilation during an asthma exacerbation is associated with an increased risk of death from asthma. Therefore, the decision to intubate an asthmatic should not be made lightly. These patients are at high risk for cardiac dysfunction. A particularly difficult combination of factors merges to impact the asthmatic patient’s cardiac preload. Namely, dehydration, increased pulmonary vascular resistance due to bronchospasm, and the addition of positive pressure to the thoracic cavity will also decrease venous return to the heart and increase resistance to pulmonary blood flow. All of these factors combine to dramatically lower preload for the left ventricle.