[Acute severe asthma: emergency diagnostic and therapeutic measures].
There is growing evidence that the prevalence and the severity of bronchial asthma are rising in the industrialized countries despite a marked increase in the sale of antiasthmatic drugs. Non-diagnosis and undertreatment of patients with asthma may be causative factors. Identification of acute severe asthma by the physician and early hospitalization of patients at risk are important factors in lowering morbidity and mortality. Indicators of severe asthma on initial assessment are a history of poor long-term control (previous hospital admissions, regular use of inhaled beta agonists, maintenance oral corticosteroid treatment, prolonged current attack and low or greatly varying peak flow values) and clinical examination with spirometry as the most objective tool. A peak expiratory flow (PEF) of < 30% pred. (< 100-120 l/min) and a forced expiratory volume in the first second (FEV1) of < 25% pred. (< 0.7-1.01) indicate severe asthma. The physical signs and symptoms correlate well with the spirometric values but show too much variability to be used alone. A PaCO2 value of > or = 45 mm Hg (6 kPa) is very specific for severe asthma. Patients whose asthma is considered severe on initial assessment must be referred to a hospital. In the emergency ward the documented response to treatment, i.e. the speed of recovery, is the most important parameter for discharge or admission to hospital. Only patients who improve within a few hours, who remain clinically stable and who have a PEF > 75% pred. or an FEV1 > 50% pred. should be discharged.