What is the appropriate management for a patient with an asthma exacerbation?

Identification and Assessment of Asthma Exacerbation

Asthma exacerbations are acute or subacute episodes of progressively worsening shortness of breath, cough, wheezing, and chest tightness that require immediate recognition through symptom assessment, vital signs, and objective lung function measurement, with severity classification (mild, moderate, severe, or life-threatening) determining the treatment pathway. 1

Key Clinical Features to Identify

Cardinal Symptoms

• Breathlessness, coughing, wheezing, and chest tightness are the hallmark symptoms that distinguish an exacerbation from poor chronic asthma control 1
• The critical distinction is that exacerbations represent acute worsening rather than the diurnal variability characteristic of poorly controlled chronic asthma 1, 2

Physical Examination Findings

• Agitation, increased respiratory rate, increased pulse rate are early warning signs 1
• Use of accessory muscles of respiration indicates significant airway obstruction 1
• Inability to speak in complete sentences (or even phrases in severe cases) signals dangerous airway compromise 1
• Decreased breath sounds may paradoxically indicate severe obstruction rather than improvement 3

Objective Severity Assessment

Primary Determinant: Lung Function

• Percent predicted FEV₁ or peak expiratory flow (PEF) is the primary determinant of exacerbation severity and should be measured immediately 1
• Severity categories based on lung function:
  • Mild: PEF or FEV₁ ≥70% predicted 1
  • Moderate: PEF or FEV₁ 40-69% predicted 1, 4
  • Severe: PEF or FEV₁ <40% predicted 1
  • Life-threatening: Unable to perform lung function testing, altered mental status, or silent chest 1

Vital Signs and Oxygen Saturation

• Pulse oximetry should be performed immediately with oxygen saturation <90% indicating severe exacerbation 1, 5
• Respiratory rate >25 breaths/min and heart rate >110 beats/min suggest severe exacerbation in adults 6
• Pulsus paradoxus >25 mmHg indicates severe airway obstruction 3

Critical Pitfall: Normal PaCO₂ in Severe Exacerbation

• A rising PaCO₂ (even into the "normal" range of 35-45 mmHg) in the setting of tachypnea and distress indicates impending respiratory failure because patients should be hyperventilating and hypocapnic 7
• This represents respiratory muscle fatigue and exhaustion requiring immediate escalation of care 7

Risk Stratification for Asthma-Related Death

High-Risk Historical Features (Require Heightened Vigilance)

• Previous severe exacerbation requiring intubation or ICU admission 1
• Two or more hospitalizations for asthma in the past year 1
• Three or more ED visits for asthma in the past year 1
• Hospitalization or ED visit for asthma in the past month 1
• Using >2 canisters of short-acting beta-agonist per month 1
• Difficulty perceiving asthma symptoms or severity (a particularly dangerous trait) 1

Social and Comorbidity Risk Factors

• Low socioeconomic status, illicit drug use, major psychosocial problems 1
• Cardiovascular disease, other chronic lung disease, chronic psychiatric disease 1

Initial Assessment Algorithm

Step 1: Immediate Triage (Within Minutes)

• Assess airway, breathing, circulation and determine if patient can speak in sentences 1
• Measure oxygen saturation via pulse oximetry 1, 5
• Obtain PEF or FEV₁ if patient is able to perform maneuver 1

Step 2: Brief Focused History

• Time of onset and potential triggers (viral infection, allergen exposure, medication nonadherence) 1, 3
• Current medications and recent use of oral corticosteroids 1, 3
• Severity compared to previous exacerbations 1
• Response to any home treatment already administered 1

Step 3: Severity Classification and Treatment Initiation

• Treatment should be instituted immediately upon determination of moderate, severe, or life-threatening exacerbation without waiting for complete assessment 1
• Serial measurement of lung function provides objective measure of treatment response and is more predictive of hospitalization need than initial severity 1, 5

Special Populations Requiring Extra Vigilance

Infants

• Infants are at greater risk during exacerbations and require lower thresholds for escalation of care 1

Pregnant Patients

• Maintain oxygen saturation >95% in pregnant patients (compared to >90% in non-pregnant adults) to ensure adequate fetal oxygenation 5

Common Assessment Pitfalls to Avoid

• Physicians' subjective assessments of airway obstruction are often inaccurate - always obtain objective measurements 3
• Wheezing may be absent in severe exacerbations due to severely reduced airflow ("silent chest") 3
• Normal or rising PaCO₂ in a tachypneic patient indicates severe exacerbation, not improvement 7
• Pulse oximetry >90% does not exclude CO₂ retention or severe obstruction 3