FACTORS CONTRIBUTING TO ASTHMA SEVERITY
VIRAL INFECTIONS
Viral infections are primarily responsible for exacerbations of
asthma. Viral upper respiratory tract infections are a major precipitant of acute asthma in children, being involved in up to 20% to 40% of acute episodes.Infants are particularly susceptible to airways obstruction and wheezing with viral infections because of their small airways. The most common cause of exacerbations in both children and adults is the common rhinovirus.Other viruses isolated include respiratory syncytial virus (RSV), parainfluenza virus, coronavirus, and influenza viruses.
The inflammatory response to viral infection is thought to be associated directly with the increasing BHR. Certain viruses (RSV and parainfluenza virus) are capable of inducing specific IgE antibodies, and rhinovirus can activate eosinophils directly in asthmatics. The increase in asthma symptoms and BHR that occurs may last for days or weeks following resolution of the symptoms of the viral infection. The NAEPP recommends annual influenza vaccinations for patients with asthma.
Viral infections are primarily responsible for exacerbations of
asthma. Viral upper respiratory tract infections are a major precipitant of acute asthma in children, being involved in up to 20% to 40% of acute episodes.Infants are particularly susceptible to airways obstruction and wheezing with viral infections because of their small airways. The most common cause of exacerbations in both children and adults is the common rhinovirus.Other viruses isolated include respiratory syncytial virus (RSV), parainfluenza virus, coronavirus, and influenza viruses.
The inflammatory response to viral infection is thought to be associated directly with the increasing BHR. Certain viruses (RSV and parainfluenza virus) are capable of inducing specific IgE antibodies, and rhinovirus can activate eosinophils directly in asthmatics. The increase in asthma symptoms and BHR that occurs may last for days or weeks following resolution of the symptoms of the viral infection. The NAEPP recommends annual influenza vaccinations for patients with asthma.
ENVIRONMENTAL AND OCCUPATIONAL FACTORS
Agents and events and the mechanisms that are known to trigger asthma are listed in Table The general mechanisms are unknown but presumably are the result of epithelial damage and inflammation
in the airway mucosa. Ozone and sulfur dioxide, common components of air pollution, have been used to induceBHRin animals. Exposure to 0.2 ppm ozone for 2 to 3 hours can induce bronchoconstriction and increase BHR in asthmatics. Sulfur dioxide in the ambient atmosphere is highly irritating. It presumably induces bronchoconstriction through mast cell or irritant-receptor involvement. Asthma produced by repeated prolonged exposure to industrial inhalants is a significant health problem. It has been estimated that occupational asthma accounts for 2% of all asthmatic persons. Persons with occupational asthma have the typical symptoms of asthma with cough, dyspnea, and wheeze. Typically, the symptoms are related to work and improve on weekends and during vacations.In some instances, symptoms may persist even after termination of exposure.
Agents and events and the mechanisms that are known to trigger asthma are listed in Table The general mechanisms are unknown but presumably are the result of epithelial damage and inflammation
in the airway mucosa. Ozone and sulfur dioxide, common components of air pollution, have been used to induceBHRin animals. Exposure to 0.2 ppm ozone for 2 to 3 hours can induce bronchoconstriction and increase BHR in asthmatics. Sulfur dioxide in the ambient atmosphere is highly irritating. It presumably induces bronchoconstriction through mast cell or irritant-receptor involvement. Asthma produced by repeated prolonged exposure to industrial inhalants is a significant health problem. It has been estimated that occupational asthma accounts for 2% of all asthmatic persons. Persons with occupational asthma have the typical symptoms of asthma with cough, dyspnea, and wheeze. Typically, the symptoms are related to work and improve on weekends and during vacations.In some instances, symptoms may persist even after termination of exposure.
PSYCHOLOGICAL FACTORS
Emotions and stress rarely can precipitate attacks of asthma but more commonly worsen an attack in progress.2 Bronchoconstriction from psychological factors appears to be mediated primarily through excess parasympathetic input. Atropine has been shown to block experimental psychogenic bronchoconstriction. It is most important to emphasize to patients and to parents of asthmatic children that asthma is not an emotional disease; however, calming influences and relaxation techniques may benefit the patient who becomes severely emotionally distraught during an asthma attack.
Emotions and stress rarely can precipitate attacks of asthma but more commonly worsen an attack in progress.2 Bronchoconstriction from psychological factors appears to be mediated primarily through excess parasympathetic input. Atropine has been shown to block experimental psychogenic bronchoconstriction. It is most important to emphasize to patients and to parents of asthmatic children that asthma is not an emotional disease; however, calming influences and relaxation techniques may benefit the patient who becomes severely emotionally distraught during an asthma attack.
SINUSITIS AND RHINITIS
Disorders of the upper respiratory tract, particularly sinusitis and rhinitis, have been linked with asthma formany years. Asmany as40% to 50% of asthmatics have abnormal sinus radiographs. However, chronic sinusitis may just represent a nonbacterial coexisting condition with allergic asthmatics because the histologic changes in the paranasal sinuses are similar to those seen in the lung and nose. Some studies have shown that asthma symptoms improve with treatment of sinusitis. The mechanism by which sinusitis aggravates asthma is unknown. The treatment of allergic rhinitis with inhaled corticosteroids and cromolyn but not antihistamines will reduce BHR in asthmatic patients. It has been postulated that transport of mucus chemotactic factors and inflammatory mediators from nasal passages duringallergic rhinitis into the lung may accentuate BHR.
GASTROESOPHAGEAL REFLUXDisorders of the upper respiratory tract, particularly sinusitis and rhinitis, have been linked with asthma formany years. Asmany as40% to 50% of asthmatics have abnormal sinus radiographs. However, chronic sinusitis may just represent a nonbacterial coexisting condition with allergic asthmatics because the histologic changes in the paranasal sinuses are similar to those seen in the lung and nose. Some studies have shown that asthma symptoms improve with treatment of sinusitis. The mechanism by which sinusitis aggravates asthma is unknown. The treatment of allergic rhinitis with inhaled corticosteroids and cromolyn but not antihistamines will reduce BHR in asthmatic patients. It has been postulated that transport of mucus chemotactic factors and inflammatory mediators from nasal passages duringallergic rhinitis into the lung may accentuate BHR.
Gastroesophageal reflux has been associated with asthma for many years. Nocturnal asthma may be associated with nighttime reflux. Reflux of acidic gastric contents into the esophagus is thought to initiate a vagally mediated reflex bronchoconstriction. Also of concern is that most medications that decrease airways smooth muscle tone have a relaxant effect on gastroesophageal sphincter tone as well. The therapeutic approach most commonly taken for patients with gastroesophageal reflux and asthma is to initiate standard antireflux therapy and observe the asthma symptoms.
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