Acute severe asthma remains a major economic and health burden. The natural history of acute decompensations is one of resolution and only about 0.4% of patients succumb overall. Mortality in medical intensive care units is higher but is less than 3% of hospital admissions. "Near-fatal" episodes may be more frequent, but precise figures are lacking. However, about 30% of medical intensive care unit admissions require intubation and mechanical ventilation with mortality of 8%. Morbidity and mortality increase with socioeconomic deprivation and ethnicity. Seventy to 80% of patients in emergency departments clear within 2 hours with standardized care. The relapse rate varies between 7 and 15%, depending on how aggressively the patient is treated. The airway obstruction in the 20-30% of people resistant to adrenergic agonists in the emergency department slowly reverses over 36-48 hours but requires intense treatment to do so. Current therapeutic options for this group consist of ipratropium and corticosteroids in combination with beta2 selective drugs. Even so, such regimens are not optimal and better approaches are needed. The long-term prognosis after a near-fatal episode is poor and mortality may approach 10%.
Although wheezing is believed to be a cardinal manifestation of asthma, some patients with this disorder may not present with wheezing, but rather with either exertional dyspnea or cough. In 14 such patients with dyspnea, there was peripheral airway dysfunction with markedly elevated residual volumes, frequency dependence of dynamic compliance and depressed flow rates in the middle-vital-capacity range, whereas specific conductance and one-second forced expiratory volumes were normal. Circumstantial evidence suggests that mucosal edema or mucous secretions may have been responsible. In seven patients with cough, studies revealed a more severe obstructive pattern that appeared to be the result of increased large-airway resistance, and the patients' response to isoproterenol indicated that contraction of bronchial smooth muscle may have been principally responsible. Thus, intermittent episodes of cough or breathlessness may represent variant aspects of asthmatic attacks.
Cholinergic urticaria was elicited in seven subjects by experimental challenge that consisted of running on a treadmill in a plastic occlusive suit. A sensation of generalized warmth of the skin was followed by pruritus, erythema, urticaria, and transient respiratory-tract symptoms consisting of shortness of breath or wheezing or both. Statistically significant falls in one-second forced-expiratory volumes (FEV1), maximal midexpiratory flow rates (MMF), and specific conductance (SGaw) and a rise in residual volume were detected. The serum histamine concentration rose, with an augmentation of eosinophil and neutrophil chemotactic activities. Gel-filtration chromatography showed that the eosinophil chemotactic activity consisted of at least two principles. The chemotactic activities are similar in magnitude to those recognized in other skin disorders dependent on mast cells. These observations extend to the lungs the manifestations of a condition previously thought to be restricted to the skin.
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