Key Clinical Questions
Which patients with asthma require hospital admission?
What are the evidence-based guidelines for treatment of asthma in hospitalized patients?
What is the optimal dosing of systemic corticosteroids in the treatment of an acute asthma exacerbation?
Which asthma patients require admission to the intensive care unit?
When are the indications for intubation in asthma exacerbation?
What conditions need to be met before discharging a patient from the hospital?
Asthma is a chronic respiratory disease associated with reversible airflow obstruction, bronchial hyperresponsiveness (BHR), and airway inflammation that can be triggered by various stimuli including viral upper respiratory infection, environmental allergens, and occupational exposures, and can lead to recurrent episodes of wheezing, cough, and dyspnea.
In the United States in 2009, the prevalence of asthma was 8.2% affecting 24.6 million people (17.5 million adults and 7.1 million children). Thus, asthma stands as one of the leading chronic diseases in the United States.
The prevalence of current asthma is higher in children (9.6%) compared to adults (7.7%), and in females (9.3%) compared to males (7.0%). There is considerable variation in asthma prevalence estimates across racial and ethnic groups, with African Americans having higher prevalence than Caucasians and Hispanics. However, within Hispanics, there is marked variation among different ethnic groups; for example, Puerto Ricans have the highest asthma prevalence in the U.S. population in contrast to Mexican Americans, who have the lowest prevalence rates. The reasons why there are large differences in asthma prevalence rates across races and ethnicities are poorly understood and are likely explained by multiple factors including genetic susceptibility, health care access, environmental exposures, and nutritional factors.
History and physical examination of the asthmatic patient reveal recurrent respiratory symptoms characterized by wheezing, cough, and chest tightness. Trigger exposures may exacerbate respiratory symptoms and may include exposure to airway irritants (smoke, strong fumes, air pollution, etc), aeroallergens, respiratory infections, and cold air. Psychological stress and physical exercise are also known to trigger respiratory symptoms in the absence of any other concomitant exposures; however, in many instances trigger factors are not identified.
Respiratory symptoms may have a nocturnal predominance and are frequently more severe in the morning after waking up, when airflows are usually lower. The frequency and severity of respiratory symptoms is highly variable and may stem from sporadic to constant and from barely noticeable to life threatening.
Although asthma is generally regarded as a single disease entity, it is likely a syndrome composed of a heterogeneous group of pathophysiologic mechanisms (different triggers, risk factors, patterns of inflammation, and response to treatment) that cause airway obstruction and common respiratory symptoms. Persistent adult asthma phenotypes have been broadly divided into the following categories: clinical or physiologic phenotypes (severity defined, exacerbation prone, treatment resistant, and adult versus child onset); phenotypes related ...