What are the suggested diagnostics and management for bronchial asthma during an acute exacerbation?

Diagnostic Evaluation for Acute Asthma Exacerbation

In acute asthma exacerbation, immediately assess severity using clinical symptoms, vital signs, and objective lung function measurement (PEF or FEV₁), then initiate treatment while monitoring response with serial measurements. 1

Immediate Clinical Assessment

Classify exacerbation severity upon presentation using the following parameters 1:

• Mild exacerbation: Dyspnea only with activity, PEF ≥70% predicted or personal best 1
• Moderate exacerbation: Dyspnea interferes with usual activity, PEF 40-69% predicted, inability to complete sentences comfortably 1
• Severe exacerbation: Dyspnea at rest interfering with conversation, PEF <40% predicted, respiratory rate >25/min, heart rate >110/min, use of accessory muscles 1
• Life-threatening features: PEF <25% predicted, silent chest, cyanosis, altered mental status, inability to speak, bradycardia, PaCO₂ ≥42 mmHg 1, 2

Essential Diagnostic Measurements

Objective Lung Function Testing

Peak expiratory flow (PEF) or FEV₁ is the primary determinant of severity and strongest predictor of hospitalization need 1:

• Measure PEF or FEV₁ immediately upon presentation before treatment 2
• Repeat measurements 15-30 minutes after initial bronchodilator treatment 1, 2
• Continue serial measurements at 1 hour and beyond—these are the strongest single predictor of hospitalization 1
• For children ≥5 years, lung function measures are useful but may not be obtainable during severe exacerbation 1

Pulse Oximetry

Continuous oxygen saturation monitoring is essential 1, 2:

• Measure immediately and monitor continuously until clear response to bronchodilator therapy 2
• Target SaO₂ >90% (>95% in pregnant patients or those with heart disease) 2
• For children, pulse oximetry <92-94% after 1 hour predicts need for hospitalization 1
• Hypoxemia cut-off varies from 90-92% between guidelines 1

Vital Signs Monitoring

Document the following parameters serially 1:

• Respiratory rate (>25/min indicates severe exacerbation) 1
• Heart rate (>110/min indicates severe exacerbation) 1
• Blood pressure 1
• Level of consciousness and ability to speak in sentences 1
• Use of accessory muscles 1

Additional Diagnostic Studies

Arterial Blood Gas (ABG)

Reserve ABG for specific clinical scenarios 1:

• Severe exacerbations with FEV₁ or PEF <40% after initial treatment 1
• Signs of impending respiratory failure (drowsiness, confusion, worsening fatigue) 1
• Suspected life-threatening exacerbation 1
• Normal or elevated PaCO₂ in a breathless asthmatic indicates life-threatening attack 1
• PaCO₂ ≥42 mmHg signals impending respiratory failure 2

Chest Radiography

Obtain chest X-ray when clinically indicated 1:

• Suspected pneumothorax, pneumonia, or pulmonary edema 2
• Severe exacerbation unresponsive to initial therapy 2
• Atypical presentation or concern for alternative diagnosis 1
• Not routinely necessary for straightforward exacerbations 1

Laboratory Testing

Blood work is not routinely required but consider 1:

• Complete blood count if infection suspected 1
• Serum electrolytes if using high-dose or continuous beta-agonists 1
• Blood eosinophil count may inform phenotype but not acutely necessary 3

Monitoring Response to Treatment

Serial reassessment determines disposition and ongoing management 1, 2:

• Reassess 15-30 minutes after initial bronchodilator dose 1, 2
• Repeat assessment after 3 doses of bronchodilator (60-90 minutes total) 2
• Response to treatment is a better predictor of hospitalization than initial severity 2
• Children with persistent symptoms after 1-2 hours of treatment have >84% chance of requiring hospitalization 1

Good Response Criteria (Discharge Consideration)

Patients may be discharged when 2:

• PEF ≥70% predicted or personal best 2
• Symptoms minimal or absent 2
• Oxygen saturation stable on room air 2
• Patient stable for 30-60 minutes after last bronchodilator dose 2

Poor Response Criteria (Hospitalization Indicated)

Admit patients with 1, 2:

• PEF <50% predicted after 1-2 hours of intensive treatment 2
• Persistent severe symptoms despite treatment 1
• Life-threatening features at any point 1
• Inability to maintain oxygen saturation on room air 2

Critical Pitfalls to Avoid

Do not underestimate severity 2:

• Severity is often underestimated by patients, families, and clinicians due to failure to obtain objective measurements 2
• Never rely solely on clinical assessment without objective lung function testing when feasible 1
• Absence of wheezing may indicate life-threatening "silent chest" rather than improvement 1

Avoid these diagnostic errors 1:

• Do not use peak flow meters for diagnosis—they are designed for monitoring, not diagnostic assessment 1
• Blood gas measurements are rarely helpful for initial management decisions in children 1
• Do not delay treatment to obtain diagnostic studies in severe exacerbations 1