Respiratory tract infections airway responsiveness

L C. Inflammation of the airway is a hallmark of asthma. The use of antiinflammatory drugs, such as inhaled corticosteroids, is critical to the long-term control of asthma. No credible data indicate either that asthma is psychosomatic or that it develops in response to vaccinations against childhood diseases. Asthma is a disease limited to the airways. It does not involve the lung parenchyma. Although upper respiratory tract infections can exacerbate asthma symptoms, asthma is not caused by infection, nor is it communicable. 

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 spe-... 

Recent studies have confirmed that the sensitivity of neuronal pathways activated by tussive mechanical stimuli of human airways is subject to plasticity. Subjects with upper respiratory tract infections were found to have reduced thresholds for mechanically evoked cough and in addition coughed more in response to mechanical stimuli than did healthy subjects (Lee and Eccles 2004). It has yet to be determined if mechanically evoked chough is similarly sensitized during chronic lung diseases. 

Airway resistance during inspiration is increased in patients with asthma, bronchitis, and upper respiratory tract infections. Expiratory resistance is elevated in patients with emphysema, since the causes of increased expiratory airway resistance are decreased driving pressures and the airway collapse. Airway resistance also may be used to determine the response of obstructed patients to bronchodilator medications. 

---