From the Guidelines
For a patient with normal lung function test results, including a normal FEV1/FVC ratio, normal lung volumes, and normal diffusion capacity, the management plan should focus on health maintenance rather than treatment of lung disease. No specific respiratory medications are indicated since the pulmonary function tests show no evidence of obstructive or restrictive lung disease, as supported by the 2017 American Thoracic Society technical statement 1. The patient should be advised to maintain a healthy lifestyle including regular exercise, avoiding tobacco smoke and other respiratory irritants, and maintaining a healthy weight. Annual influenza vaccination is recommended, as well as pneumococcal vaccination according to age-appropriate guidelines. If the patient was referred for lung function testing due to respiratory symptoms despite these normal results, further investigation of alternative causes may be warranted, such as cardiac evaluation, upper airway assessment, or consideration of non-cardiopulmonary causes of dyspnea. Some key points to consider in the interpretation of lung function tests include:
- Using reference values based on healthy subjects with similar anthropometric and ethnic characteristics to the patient being tested, as recommended by the European Respiratory Journal in 2005 1
- Avoiding extrapolation beyond the size and age of investigated subjects when using reference equations
- Considering the use of race/ethnic-specific reference equations whenever possible
- Reporting only validated parameters, such as FVC, FEV1, and FEV1/FVC, and including clinical application in the report, as recommended by the American Thoracic Society in 2017 1 Normal lung function tests essentially rule out common pulmonary conditions like asthma, COPD, interstitial lung disease, and pulmonary vascular disease, though very early disease may sometimes be present despite normal testing. Regular follow-up with primary care is appropriate, with repeat pulmonary function testing only indicated if new respiratory symptoms develop or existing symptoms worsen.
From the Research
Patient Management Plan
Given the patient's normal lung function test results, including a normal FEV1/FVC ratio, normal lung volumes, and normal diffusion capacity, the management plan should focus on monitoring and potentially investigating other causes of symptoms if present.
- The patient's FEV1/FVC ratio of 88 post-bronchodilator is within the normal range, indicating no obstructive lung disease 2.
- The lack of acute response to bronchodilators suggests that the patient does not have reversible airflow obstruction, which is typically seen in asthma 3.
- Normal lung volumes (TLC: 91%) and normal diffusion capacity (DLCO: 92%) indicate that there is no significant restrictive lung disease or impairment in gas exchange 2.
- The normal oxygen saturation at rest (98% RA) further supports the absence of significant lung disease 2.
- The flow-volume loop showing no specific findings is consistent with normal lung function 2.
Further Investigation
If the patient presents with respiratory symptoms, further investigation may be warranted to rule out other conditions, such as:
- Exercise- or allergen-induced asthma, which may require bronchoprovocation tests (e.g., methacholine challenge, mannitol inhalation challenge, exercise testing) 2.
- Pre-chronic obstructive pulmonary disease (pre-COPD), which may be identified using lung function thresholds and respiratory symptoms 4.
- Conditions associated with a nonspecific pattern of pulmonary function tests, such as airway hyperresponsiveness or restricted expansion of the thorax or lung 5.
Monitoring
Regular monitoring of lung function and symptoms is essential to detect any changes or progression of disease. This may involve periodic spirometry and assessment of respiratory symptoms 2, 4.