From the Guidelines
Pulmonary function tests (PFTs) should be interpreted by analyzing key measurements including FEV1, FVC, and the FEV1/FVC ratio to determine the presence and type of respiratory impairment, with treatment options tailored to the specific underlying condition, severity of impairment, and patient factors 1. When interpreting PFTs, it is essential to consider the effects of race and ethnicity on pulmonary function testing interpretation, as highlighted in the 2023 American College of Chest Physicians (CHEST), American Association for Respiratory Care (AARC), American Thoracic Society (ATS), and Canadian Thoracic Society (CTS) evidence review and research statement 1.
Key Measurements
- FEV1 (forced expiratory volume in 1 second)
- FVC (forced vital capacity)
- FEV1/FVC ratio
Treatment Options
- Obstructive patterns: bronchodilators like albuterol (2 puffs every 4-6 hours as needed) and maintenance medications such as inhaled corticosteroids (fluticasone 100-500 mcg twice daily) or long-acting beta-agonists (salmeterol 50 mcg twice daily)
- Restrictive patterns: corticosteroids (prednisone 20-40 mg daily with taper) for inflammatory conditions, immunosuppressants for autoimmune disorders, or oxygen therapy (2-6 L/min) for hypoxemia
- Mixed patterns: combination therapy addressing both obstructive and restrictive components
Additional Considerations
- Bronchodilator reversibility testing to identify asthma and guide treatment intensity
- Diffusion capacity (DLCO) measurements to assess gas exchange efficiency and indicate conditions like emphysema or pulmonary fibrosis that may require more aggressive therapy
- Patient factors such as age, comorbidities, and medication tolerability should be taken into account when tailoring treatment options 1.
From the FDA Drug Label
The primary efficacy parameter, morning PEF, was collected daily for the first 12 weeks of the trial. Morning PEF improved significantly with fluticasone propionate and salmeterol inhalation powder 500 mcg/50 mcg compared with fluticasone propionate 500 mcg over the 12-week treatment period. Subjects receiving fluticasone propionate and salmeterol inhalation powder 250 mcg/50 mcg had significantly greater improvements in FEV1 (0.48 L, 23%) compared with fluticasone propionate 250 mcg (0.25 L, 13%), salmeterol (0.05 L, 4%), and placebo (decrease of 0. 11 L, decrease of 5%).
Pulmonary Function Tests (PFTs) Interpretation:
- PFTs are used to assess lung function, including FEV1 (Forced Expiratory Volume in 1 second) and PEF (Peak Expiratory Flow).
- Improvements in FEV1 and PEF are used to evaluate the efficacy of treatments, such as fluticasone propionate and salmeterol inhalation powder.
- A ≥15% improvement in FEV1 is considered clinically significant bronchodilatation.
- Morning PEF is a primary efficacy parameter used to evaluate treatment effects.
Treatment Options:
- Fluticasone propionate and salmeterol inhalation powder is a treatment option for asthma, which has been shown to improve lung function and quality of life.
- The treatment is available in different doses, including 100 mcg/50 mcg and 250 mcg/50 mcg.
- Treatment effects are evaluated based on improvements in FEV1, PEF, and quality of life measures, such as the Asthma Quality of Life Questionnaire (AQLQ) 2, 2.
From the Research
Pulmonary Function Tests (PFTs) Interpretation
Pulmonary function tests (PFTs) are used to assess lung function and diagnose various pulmonary diseases. The interpretation of PFTs involves analyzing the results of different tests, including static lung volumes, dynamic lung function (spirometry), and diffusion capacity 3.
Key Components of PFT Panels
The key components of PFT panels include:
- Static lung volumes: measure the amount of air in the lungs at different stages of breathing
- Dynamic lung function (spirometry): measures the rate of air flow in and out of the lungs
- Diffusion capacity: measures the ability of the lungs to transfer oxygen from the air into the blood
Patterns of PFT Results
PFT results can be classified into different patterns, including:
- Obstructive pattern: characterized by a decrease in air flow out of the lungs, often seen in diseases such as chronic obstructive pulmonary disease (COPD) 4
- Restrictive pattern: characterized by a decrease in lung volume, often seen in diseases such as interstitial lung disease
- Mixed pattern: characterized by a combination of obstructive and restrictive patterns
- Nonspecific pattern: characterized by abnormal PFT results that do not fit into a specific pattern, often seen in patients with mild lung disease or those with comorbid conditions 5
Treatment Options
The treatment options for patients with abnormal PFT results depend on the underlying disease and the severity of the lung function impairment. Treatment may include:
- Medications: such as bronchodilators for obstructive lung disease or corticosteroids for inflammatory lung disease
- Oxygen therapy: for patients with severe lung disease and low oxygen levels in the blood
- Pulmonary rehabilitation: a program of exercise, education, and support to help patients with chronic lung disease manage their symptoms and improve their quality of life
Common Pitfalls in PFT Interpretation
Common pitfalls in PFT interpretation include:
- Failure to consider the patient's clinical history and physical examination results when interpreting PFT results 4
- Failure to recognize the limitations of PFTs, such as the inability to distinguish between different causes of abnormal results
- Failure to use the correct reference equations for lung volumes and diffusing capacity of the lung for carbon monoxide (D(LCO)) 5
Complex Restrictive Pattern
A complex restrictive pattern is a type of PFT result characterized by a disproportionate reduction in FVC relative to TLC, often seen in patients with neuromuscular disease, obesity, or other conditions that affect lung emptying 6. This pattern can be challenging to interpret and requires careful consideration of the patient's clinical history and physical examination results.
Evaluating Post-Bronchodilator Vital Capacities
Evaluating post-bronchodilator vital capacities can help diagnose obstruction in PFTs, and using the largest measured vital capacity (VCmax) instead of FVC can change the interpretation of PFT results in some cases 7. This highlights the importance of carefully evaluating PFT results and considering multiple factors when interpreting the data.