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Thread: How do you gauge the severity of an asthma attack? - What does wheezing signify?

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    Default How do you gauge the severity of an asthma attack? - What does wheezing signify?

    Evaluating and Treating Asthma

    How do you gauge the severity of an asthma attack?

    What does wheezing signify?

    What are the red flags in an arterial blood gas analysis?


    Acute asthma management confers a significant burden on the health care system in the United States. Acute asthma annually accounts for two million emergency department visits, with a hospitalization rate of 20% to 30% and a relapse rate within two weeks of 10% to 20%.

    Millions of people suffer from chronic asthma, with prevalence rates in many countries estimated to be between 4% and 6%. Longitudinal cohort studies from New Zealand, Australia, and the United States have demonstrated that persistent asthma has its roots in early childhood. Such studies have demonstrated that wheezing that begins before age 5 and persists into adulthood results in an increased risk for impaired lung function. On the other hand, children who begin to wheeze after age 5 have a reduced risk of lung function abnormalities even if their wheezing persists into adulthood. Thus, it is becoming apparent that prevention of adult asthma often needs to begin during childhood.

    Risk factors for the development of asthma in childhood include a maternal history of asthma, exposure to tobacco smoke, and the development of allergic diatheses such as food allergy, eczema, and allergic rhinitis. In difficult cases, once asthma has developed, the patient also tends to display allergies to foods and to the outdoor mold Alternaria.
    UNCLEAR ETIOLOGY

    The etiology for the increasing incidence of asthma is unclear but likely involves multiple genetic, immunologic, and environmental influences. Exposure to endotoxins and natural infections in early childhood appear to protect against the development of atopic asthma, and avoidance of these infections through interventions such as mass immunization and antibiotic use is correlated with an increased incidence of atopy. This association has led to the theory popularly referred to as the "hygiene hypothesis," in which the failure to strengthen the developing immune system by exposing it to stimuli that interact with it leads to dysfunctional immune responses, such as allergy and asthma, in children.

    In addition, increasing exposure to environmental pollutants and tobacco smoke also is likely to influence the development of persistent airflow obstruction. Lastly, differences in genetic backgrounds, such as polymorphisms in the beta-adrenergic receptor and various cytokine genes, are likely to play an important role in the predisposition to asthma and its severity.

    Management of the patient with asthma requires an approach that has been well thought out and is accepted by those responsible for the delivery of care. For example, using a standardized protocol has been shown to improve asthma management in the emergency department. Such standardized protocols demand an understanding of the nature of the disorder, education of patients and care providers, and a commitment to their implementation
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    CLINICAL POINTS

    Certain clinical points are of paramount importance when taking a history from a patient experiencing an acute asthma exacerbation. Patients with a history of brittle asthma with quick declines in lung function, exemplified by multiple emergency department visits despite compliance with controller medications, a poor ability to sense dyspnea, a history of intubation, and the need for frequent systemic courses of steroids, will require more aggressive and prompt intervention.

    Studies done in both adult and pediatric patients have demonstrated that patients with lower socioeconomic status, a history of frequent emergency department visits, and more prescriptions, as well as more prescribers of asthma medications, are more likely to require hospitalization during an asthma exacerbation. Pediatric prospective cohort studies based in the emergency department found that risk factors for requiring beta-agonist therapy for 12 hours or longer following systemic corticosteroid administration included a history of ICU admission for asthma, an oxygen saturation of 92% or lower, and the need for hourly administration of albuterol.

    Historical clues regarding the etiology of an asthma exacerbation should be elicited. Most clinicians have heard the phrase "all that wheezes is not asthma," and it serves us well to keep this pearl in mind when evaluating a wheezing patient. In adults, the differential diagnosis for acute wheezing includes cardiac disease (such as heart failure), chronic obstructive pulmonary disease, emphysema, pneumonia (especially with Mycoplasma or Chlamydia), and localized obstruction due to a foreign body or tumor. Sometimes wheezing is caused by acute viral or bacterial bronchitis, but again, consider the history; recurrent episodes of wheezing "bronchitis" may in fact be asthma. Pulmonary embolus, aspirin-exacerbated respiratory disease, and anaphylaxis must also be considered.

    In children, the etiology for acute wheezing can be similar to that in adults but also includes cardiac disease such as congenital heart disease, as well as foreign body aspiration, gastroesophageal reflux disease, bronchiolitis (usually caused by respiratory syncytial virus or metapneumovirus), chronic lung disease in a child who was a premature infant, and vocal cord dysfunction.

    PHYSICAL EXAM FINDINGS

    Clues to the severity of an asthma exacerbation can be quickly gleaned on physical examination. An inability to speak in complete sentences, breathlessness, or labored and fast respirations, particularly with retractions and accessory muscle use, should alert the clinician to severe airflow obstruction. Auscultation may reveal diffuse wheezes or poor breath sounds, especially in the lung bases. Crackles may be heard over atelectatic areas.

    A quiet chest with little wheezing in a dyspneic patient is indicative of a severe airflow obstruction. Paradoxically, in this situation, beta-agonist therapy will often induce wheezing, reflecting improved air exchange. Cardiac causes for wheezing are suggested when the examination reveals cardiac gallops, heaves, and elevated jugulovenous distension as in heart failure. In children, tachycardia, tachypnea, and hepatosplenomegaly are cardinal signs of heart failure. Examination of the extremities may reveal edema in cardiac-related wheezing, cyanosis in extreme hypoxia or poor circulation, and clubbing in the patient with persistent hypoxia.

    If the patient routinely monitors his or her peak flow, a quick objective measurement of airway obstruction can be obtained and compared to the normal predicted value. In general, peak flows that are 60% to 80% of the predicted value demonstrate a mild to moderate airflow obstruction, while peak flows that are 60% to 50% or lower of the predicted value indicate a severe exacerbation of expiratory flow (see table below). Indeed, patients with peak flows below 50% of the predicted value following beta-agonist and steroid therapy are at increased risk of requiring subsequent hospitalization.
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    Last edited by trimurtulu; 01-05-2009 at 06:19 PM.

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