The conducting airways of the lungs (bronchi and bronchioles) are to be distinguished from the portions of the lungs where gas exchange occurs (alveoli). The bronchi and bronchioles (excepting that portion of the bronchioles immediately adjacent to the alveoli) are tubes surrounded by smooth muscle. When this muscle constricts in response to neural impulses and chemical mediators, bronchospasm results and air flow, particularly expiratory air flow, is impeded. Wheezing is often produced.
Bronchospasm occurs in response to many triggers in susceptible individuals, including viral infections, pollens and other allergens, air pollutants, certain drugs, weather changes, emotions, and exercise.
Bronchiolitis is an infection of the smallest conducting airways (bronchioles), caused almost invariably by a virus. The infection results in inflammation, mucus production, swelling, and occasionally bronchospasm. The most common cause of bronchiolitis is a virus called respiratory syncytial virus (RSV), most commonly occurring in epidemics in late fall and winter each year. RSV affects almost all infants. Bronchiolitis can be a severe disease, but only about 1% of affected children require hospitalization. Premature infants and infants with underlying heart and lung disease are most at risk for severe, even life-threatening infections. Such infants may be candidates for a special injectable preventive therapy recently developed and approved for use. For all other patients supportive therapy (fluids and occasionally supplemental oxygen) will most often suffice to get them through the illness.
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KEYWORDS: bronchospasm, bronchiolitis, respiratory syncytial virus