BRONCHIAL asthma, though highly treatable, causes over four thousand deaths annually in the United States. Measures currently available are so effective that control should rarely fail unless the patient delays too long in seeking help or if treatment is not vigorous enough.Functionally, the cardinal feature is airway obstruction, which may be so mild that only sensitive tests can demonstrate it, or so severe that marked respiratory effort is obvious with prolonged expiration, distant breath sounds, hypoxemia, cyanosis and sometimes carbon dioxide retention. The functional changes are strikingly reversible spontaneously or under treatment.Fatal asthma is characterized pathologically by plugging . . .