Workup for a 60-Year-Old Male with Asthma and Shortness of Breath
Immediate Assessment of Severity
Begin by rapidly assessing severity using objective criteria: respiratory rate >25 breaths/min, heart rate >110 beats/min, inability to complete sentences, and peak expiratory flow (PEF) <50% of predicted or personal best indicate acute severe asthma requiring immediate intervention. 1
Key Clinical Parameters to Assess:
- Speech pattern: Can the patient complete full sentences in one breath? Inability indicates severe attack 1, 2
- Respiratory rate: >25 breaths/min suggests acute severe asthma 1
- Heart rate: >110 beats/min indicates severity 1
- Peak expiratory flow: <50% predicted/best = severe; <33% = life-threatening 1, 3
- Oxygen saturation: Maintain SpO2 >92% 1, 3
Essential Diagnostic Workup
Immediate Bedside Tests:
- Peak flow measurement before and 15-30 minutes after bronchodilator administration 1, 3
- Pulse oximetry to assess oxygenation status 1, 3
- Blood pressure measurement 1
Laboratory Investigations:
- Arterial blood gas if life-threatening features present (PEF <33%, silent chest, cyanosis, confusion, exhaustion) or if SpO2 <92% on room air 1, 3
- Look specifically for: PaCO2 >45 mmHg (hypercapnia indicating life-threatening attack), pH <7.35 (respiratory acidosis), PaO2 <60 mmHg (severe hypoxemia) 3
- Chest X-ray to exclude pneumothorax, pneumonia, or cardiac causes 1
- ECG in a 60-year-old to rule out cardiac ischemia as alternative/concurrent diagnosis 1
Pulmonary Function Testing (When Stable):
- Spirometry with bronchodilator response to confirm reversible airflow obstruction when patient is not in acute distress 1, 4
- Exhaled nitric oxide (FeNO) if diagnosis uncertain: >50 ppb suggests eosinophilic inflammation and likely steroid responsiveness 1
Critical Decision Points Based on Severity
If Acute Severe Asthma (PEF <50%, RR >25, HR >110, cannot complete sentences):
- Immediate arterial blood gas to assess for hypercapnia and respiratory acidosis 3
- Repeat PEF 15-30 minutes after initial bronchodilator treatment 1, 3
- Continuous pulse oximetry monitoring 3
- Consider hospital admission if PEF remains <50% after initial treatment 1
If Life-Threatening Features (PEF <33%, silent chest, hypercapnia, confusion, exhaustion):
- Immediate ICU consultation with physician prepared to intubate 3
- Arterial blood gas within 2 hours if initial PaCO2 normal/raised or PaO2 <60 mmHg 3
- Do not delay treatment for diagnostic tests 3
Differential Diagnosis Workup
In a 60-year-old with known asthma and new/worsening dyspnea, consider alternative or concurrent diagnoses 1:
Cardiac Evaluation:
- ECG and cardiac biomarkers (troponin) to exclude acute coronary syndrome, especially given age and that beta-agonists may precipitate angina 1
- BNP/NT-proBNP if heart failure suspected 1
Other Respiratory Causes:
- Chest X-ray to exclude pneumonia, pneumothorax, pulmonary edema 1
- Consider COPD overlap if patient has smoking history (though not mentioned here) 1
If FeNO Low (<25 ppb) Despite Symptoms:
Consider non-eosinophilic causes 1:
- Vocal cord dysfunction
- Anxiety-hyperventilation
- Cardiac disease
- Gastroesophageal reflux disease
- Rhinosinusitis
Common Pitfalls to Avoid
- Never withhold oxygen due to concerns about CO2 retention—hypercapnia is not aggravated by oxygen therapy in asthma 3
- Do not rely solely on pulse oximetry in patients with darker skin pigmentation, as it may overestimate oxygen saturation 1
- Avoid sedatives in acute asthma—they are absolutely contraindicated 3
- Do not assume all wheezing is asthma in a 60-year-old; cardiac disease and COPD must be excluded 1, 5
- Blood gases are critical if any life-threatening features present—clinical assessment alone may miss impending respiratory failure 3