What should I order for an elderly female with inspiratory and expiratory wheezing and low‑normal SpO₂, no cardiac or pulmonary disease?

Diagnostic Workup for Elderly Female with Wheezing and Low-Normal SpO₂

Order spirometry with bronchodilator response and a chest X-ray immediately to objectively establish the diagnosis and exclude life-threatening conditions like malignancy, heart failure, or pneumonia. 1, 2

Immediate Essential Testing

Spirometry with Bronchodilator Challenge

• Spirometry is mandatory to objectively confirm or exclude obstructive airways disease and differentiate between asthma and COPD 1, 3
• Measure FEV1, FVC, and FEV1/FVC ratio before and after bronchodilator administration 1
• >12% and >200mL improvement in FEV1 post-bronchodilator supports asthma 1
• FEV1 <80% predicted with FEV1/FVC <0.7 and minimal reversibility suggests COPD 4, 1

Chest Radiograph

• Obtain chest X-ray urgently to exclude mass, nodule, infiltrate, heart failure, emphysema, pneumothorax, or pleural effusion 1, 2
• This is critical even without smoking history, as bronchogenic carcinoma can occur in non-smokers with mean diagnosis age of 64 years 2
• Any abnormalities on chest X-ray necessitate urgent specialist referral 1

Additional Critical Investigations

Arterial Blood Gas Analysis

• Measure arterial blood gases to distinguish simple hypoxemia from hypercapnic respiratory failure 2
• Document the inspired oxygen concentration when obtaining the sample 2
• This helps determine appropriate oxygen therapy targets and identifies patients at risk for CO2 retention 2

Cardiac and Infectious Workup

• Consider BNP or NT-pro-BNP to evaluate for left ventricular failure, particularly in patients >65 years with orthopnea or cardiovascular risk factors (BNP <40 pg/mL or NT-pro-BNP <150 pg/mL makes heart failure unlikely) 2
• Check CRP if pneumonia is suspected (CRP >100 mg/L makes pneumonia likely; <20 mg/L with symptoms >24 hours makes it highly unlikely) 2
• Consider D-dimer if pulmonary embolism is in the differential, especially with recent immobilization or malignancy history 2

Critical Diagnostic Pitfalls

Avoid Premature Diagnostic Labels

• Do not use the term "reactive airway disease" as it lacks diagnostic precision and clinical utility in older adults 1
• Wheezing is nonspecific and can result from cardiac failure, malignancy, vocal cord dysfunction, or other non-pulmonary causes 2, 5, 6

Red Flags Requiring Urgent Evaluation

• Hemoptysis, weight loss, night sweats, persistent cough >2 months, or brown sputum mandate immediate evaluation for malignancy 1
• New-onset wheezing in patients >40 years with tobacco exposure requires advanced imaging (CT chest) to evaluate for malignancy 3
• Displaced apex beat, orthopnea, or history of MI/hypertension/atrial fibrillation should prompt cardiac evaluation 2

Oxygen Therapy While Awaiting Results

• Target SpO₂ 94-98% initially using nasal cannulae at 2-6 L/min or simple face mask at 5-10 L/min 2
• If COPD is suspected based on clinical features, consider lower target of 88-92% pending blood gas results 2
• Adjust to 94-98% if PCO2 is normal and recheck blood gases after 30-60 minutes 2

Empiric Treatment Considerations

• A trial of short-acting beta agonists (salbutamol 5 mg or terbutaline 10 mg nebulized) can be initiated while awaiting formal evaluation 4, 3
• However, do not initiate long-term bronchodilator therapy without objective confirmation of reversible airflow obstruction 1
• If severe features are present (respiratory rate >25/min, heart rate >110/min, inability to complete sentences), add systemic corticosteroids (prednisolone 30-60 mg) immediately 4