Respiratory function is altered in a 16-year-old asthmatic.

(A) Altered surfactant production is found in sudden infant death syndrome. (B) Paradoxical breathing occurs when a negative intrathoracic pressure is transmitted to the abdomen by a weakened, poorly functioning diaphragm. (C) Asthma is characterized by spasm and constriction of the airways resulting in increased resistance to airflow. (D) If the pulmonary tree is obstructed for any reason, inspired air has difficulty overcoming the resistance and getting out. The rate of respiration increases in order to compensate, thus increasing air exchange.