Clinical classification

• Step 1 - Intermittent
• Intermittent symptoms occurring less than once a week
• Brief exacerbations
• Nocturnal symptoms occurring less than twice a month
• Asymptomatic with normal lung function between exacerbations
• No daily medication needed
• FEV₁ or PEF rate greater than 80%, with less than 20% variability
• Step 2 - Mild persistent
• Symptoms occurring more than once a week but less than once a day
• Exacerbations affect activity and sleep
• Nocturnal symptoms occurring more than twice a month
• Inhaled steroid (low dose), cromolyn (adult: 2-4 puffs tid/qid; child: 1-2 puffs tid/qid), or nedocromil (adult: 2-4 puffs bid/qid; child: 1-2 puffs bid/qid)
• FEV₁ or PEF rate greater than 80% predicted, with variability of 20-30%
• Step 3 - Moderate persistent
• Daily symptoms
• Exacerbations affect activity and sleep
• Nocturnal symptoms occurring more than once a week
• Anti-inflammatory, inhaled steroid (medium dose), or inhaled steroid (low-to-medium dose) and long-acting bronchodilator, especially for nighttime symptoms (either long-acting inhaled beta2-agonist [adult: 2 puffs q12h, child: 1-2 puffs q12h], sustained-release theophylline, or long-acting beta2-agonist tablets) (If needed, give inhaled steroids in a medium-to-high dose.)
• FEV₁ or PEF rate 60-80% of predicted, with variability greater than 30%
• Step 4 - Severe persistent
• Continuous symptoms
• Frequent exacerbations
• Frequent nocturnal asthma symptoms
• Physical activities limited by asthma symptoms
• Anti-inflammatory or inhaled steroid (high dose) and long-acting bronchodilator (either long-acting inhaled beta2-agonist [adult: 2 puffs q12h, child: 1-2 puffs q12h] and sustained-release theophylline or long-acting beta2-agonist tablets and steroid tablets or syrup long term) (Make repeated attempts to reduce systemic steroid and maintain control with high-dose inhaled steroid.)
• FEV₁ or PEF rate less than 60%, with variability greater than 30%

Physical

? General

o Evidence of respiratory distress manifests as increased respiratory rate, increased heart rate, diaphoresis, and use of accessory muscles of respiration.

o Marked weight loss or severe wasting may indicate severe emphysema.

? Pulsus paradoxus: This is an exaggerated fall in systolic blood pressure during inspiration and may occur during an acute asthma exacerbation.

? Depressed sensorium: This finding suggests a more severe asthma exacerbation with impending respiratory failure.

? Chest examination

o End-expiratory wheezing or a prolonged expiratory phase is found most commonly, although inspiratory wheezing can be heard.

o Diminished breath sounds and chest hyperinflation may be observed during acute exacerbations.

o The presence of inspiratory wheezing or stridor may prompt an evaluation for an upper airway obstruction such as vocal cord dysfunction, vocal cord paralysis, thyroid enlargement, or a soft tissue mass (eg, malignant tumor).

? Upper airway

o Look for evidence of erythematous or boggy turbinates or the presence of polyps from sinusitis, allergic rhinitis, or upper respiratory infection.

o Any type of nasal obstruction may result in worsening of asthma

? Skin: Observe for the presence of atopic dermatitis, eczema, or other manifestations of allergic skin conditions.

Diagnosis

Investigations

The diagnosis of asthma is made on the basis of a compatible clinical history combined with the demonstration of variable airflow obstruction.

Pulmonary function tests

Peak flow meters are inexpensive and widely available, and provide a simple and straightforward method of confirming the diagnosis. Ideally patients should be instructed to record peak flow readings after rising in the morning and before retiring in the evening. A diurnal variation in PEF (the lowest values typically being recorded in the morning) of more than 20% is considered diagnostic and the magnitude of variability provides some indication of disease severity. A trial of corticosteroids (e.g. 30 mg daily for 2 weeks) may be useful in documenting the improvement in PEF seen in patients with asthma.

The measurement of FEV1 and VC by spirometry allows the demonstration of airflow obstruction, and following the administration of a bronchodilator, confirms the diagnosis when a 15% (and 200 ml) improvement in FEV1 is noted. Spirometry is also particularly helpful in monitoring the severity of airflow obstruction in patients with impaired lung function.

Enhanced bronchoconstriction (AHR) to a variety of direct and indirect stimuli including exercise, cold air, dusts, smoke and chemicals such as histamine and methacholine, is an integral part of the definition of asthma, and may be helpful in patients presenting with normal lung function. For patients whose symptoms are prominently related to exercise, an exercise test may be followed by a drop in PEF or FEV1. AHR is sensitive but non-specific: it therefore has a high negative predictive value but positive results may be seen in other conditions such as COPD, bronchiectasis and CF. Challenge tests using adenosine are being developed and may prove more specific.

Date: 2016-06-13; view: 64