Noninvasive positive pressure ventilation (NPPV), after a short trial of standard therapy, could be effective for children with status asthmaticus.
Standard management of status asthmaticus
Corticosteroid is the mainstay of treatment. Oxygen, short acting β-agonist (SABA), and inhaled ipratropium bromide are used to treat hypoxemia and airflow obstruction. Adjunct therapies, including magnesium sulphate and helium-oxygen mixtures (heliox) may be used in exacerbations unresponsive to these initial treatments. However, in some patients maximal medical therapy is inadequate to relieve airway obstruction which may lead to fatigue and respiratory failure.
Tracheal intubation and mechanical ventilation
Absolute indications for tracheal intubation in asthma include cardio-respiratory arrest, severe hypoxemia, and rapid deterioration in the child’s mental state. Intubation should be avoided if at all possible, but it is sometimes necessary. When it is employed, controlled hypoventilation with permissive hypercapnia may reduce associated morbidity. Furthermore, we must be cognizant that tracheal intubation can aggravate bronchospasm; and positive pressure ventilation may increase the risk of barotrauma and circulatory depression.
Noninvasive positive pressure ventilation (NPPV) is increasingly being used in pediatric intensive care units (PICU) in the management of status asthmaticus - mainly in the setting of impending respiratory failure when the condition is refractory to medical management. However, if it is done early (after a few hours of standard medical management), it could decrease prolonged medical management, side effects of SABA, and length of stay. It also improves patient’s subjective sense of dyspnea and shortness of breath.
How it works
In patients with severe airway obstruction and expiratory flow limitation, dynamic hyperinflation may lead to the development of intrinsic-PEEP that imposes an inspiratory workload reducing the efficiency of the diaphragm. Application of a modest amount of external positive pressure may maintain small airway patency and offset auto-PEEP reducing inspiratory work of breathing without worsening hyperinflation.The use of inspiratory positive pressure “unloads” the diaphragm and accessory muscles, while still allowing active exhalation. NPPV might also improve delivery of bronchodilators to the more diseased, poorly ventilated areas of the lung. In addition, positive pressure has a direct bronchodilator effect and recruits smaller airways and collapsed alveoli, which improves ventilation perfusion mismatch.