An 8-year-old girl is brought to the emergency department due to worsening shortness of breath and chest tightness for the past 2 hours. On physical examination, the patient speaks in short sentences. Lung auscultation reveals diffuse wheezing. During the evaluation, the patient is instructed to take a deep breath and blow as hard as possible into the mouthpiece of a hand-held device. The measured airflow rate is significantly lower than expected. Treatment with an inhaled medication is begun. A repeat evaluation several minutes later shows an increase in the airflow rate. The administered medication most likely affected which of the following to produce the observed finding in this patient?

Question

An 8-year-old girl is brought to the emergency department due to worsening shortness of breath and chest tightness for the past 2 hours.  On physical examination, the patient speaks in short sentences.  Lung auscultation reveals diffuse wheezing.  During the evaluation, the patient is instructed to take a deep breath and blow as hard as possible into the mouthpiece of a hand-held device.  The measured airflow rate is significantly lower than expected.  Treatment with an inhaled medication is begun.  A repeat evaluation several minutes later shows an increase in the airflow rate.  The administered medication most likely affected which of the following to produce the observed finding in this patient?

Quizplus · Accepted Answer

This patient's acute-onset shortness of breath and chest tightness are consistent with the airway spasm and bronchoconstriction that occurs in asthma. She received a bronchodilator to reduce airway resistance and increase airway flow. In asthma, bronchodilation is typically accomplished with a beta-2 receptor agonist (eg, albuterol); these drugs work by stimulating beta-2 adrenergic receptors on bronchial smooth muscle cells, leading to an increase in cyclic AMP and consequent smooth muscle relaxation (decrease in smooth muscle tone). (Choices A and B) Corticosteroids, both inhaled (eg, budesonide, fluticasone) and systemic (eg, prednisone), modify gene transcription to reduce the airway inflammatory response in patients with asthma. Corticosteroids are also used to stimulate alveolar surfactant production and reduce the risk of neonatal respiratory distress syndrome in premature infants. (Choice D) Inhaled antibiotics (eg, tobramycin) are used to reduce lower-airway bacterial load in patients with cystic fibrosis. (Choice E) Several medications, including endothelin receptor antagonists (eg, bosentan), phosphodiesterase inhibitors (eg, sildenafil), and prostacyclin analogs, are used to lower pulmonary vascular resistance in patients with pulmonary arterial hypertension. Educational objective: Bronchodilators induce bronchial smooth muscle relaxation to relieve airway spasm and bronchoconstriction in patients with asthma. Bronchodilation is most commonly accomplished with beta-2 receptor agonists (eg, albuterol), which function by increasing cyclic AMP levels in bronchial smooth muscle.

An 8-Year-Old Girl Is Brought to the Emergency Department Due