Lung Volume loops:

Interpreting PFTs:
FVC – volume of air that can forcibly be blown out after full inspiration (L)
FEV1 – maximum volume of air that can forcibly blow out in the first second during the FVC (L)
FEV1/FVC – in healthy adults this should be >~75-80%

Restrictive Lung Disease: primarily due to decreased lung compliance (volume)

• Examples: ILD, sacroidosis, neuromuscular disease, pulmonary fibrosis, silicosis
• FEV1 and FVC are BOTH reduced proportionally and the FEV1/FVC value may be normal (or increased)
• Flow volume curve is narrowed because of diminished lung volumes, but the shape is generally the same as normal

Obstructive Lung Disease: primarily due to increased airway resistance (flow)

• Examples: ILD, sacroidosis, neuromuscular disease (AML), pulmonary fibrosis, silicosis
• FEV1 and FVC are BOTH reduced proportionally and the FEV1/FVC value may be normal (or increased)
• Flow volume curve is narrowed because of diminished lung volumes, but the shape is generally the same as normal

Top Right: Normal; Top Right: Asthma, Bottom Left: COPD, Bottom Right: Fixed Obstruction / Tracheal Stenosis

Asthma:

• Common chronic respiratory condition characterized by reversible airway obstruction and bronchial hyper-responsiveness

Epidemiology: affects ~8% of US population; allergic asthma is strongly associated with personal/family history of allergies.  Higher prevalence and severity in people of lower income, children, and black populations

Pathogenesis: airway inflammation; chronic inflammation may result in epithelial damage, smooth muscle hypertrophy, airway fibrosis, and remodeling in some

Risk Factors: genetics, exposures to allergens, tobacco smoke, viruses

Symptoms/Clinical Evaluation: classically present with episodes of coughing, chest tightness, SOB, and wheezing

• Consider other causes that may mimic asthma: COPD, vocal cord dysfunction, heart failure, bronchiectasis, ABPA, CF, mechanical obstruction, etc.
• Obtain spirometry to assess for severity of airway obstruction and reversibility (FEV1 > 12% and 200 mL)
• Chest radiographs are often normal

Asthma Syndromes:

• Allergic Asthma – most common form in adults; family history is often positive
• Cough-Variant Asthma – persistent/episodic cough without other symptoms
• Exercise-Induced Bronchospasm
• Occupational Asthma – related to workplace exposures (farmers, factory workers, hairdressers, etc.)
• Aspirin-Sensitive Asthma – triad of severe persistent asthma, aspirin sensitivity, and hyperplastic eosinophilic sinusitis with nasal polyposis

Step Up/Down Treatment: