What is the interpretation and management of abnormal pulmonary function test results showing significant variations in Forced Expiratory Volume (FEV1), Forced Vital Capacity (FVC), and other parameters?

Interpretation of Pulmonary Function Test Results

The pulmonary function test results show a mixed pattern with elements of both obstructive and restrictive ventilatory defects, requiring comprehensive evaluation and likely bronchodilator therapy to address the underlying respiratory condition. 1

Analysis of Key Parameters

• FEV1/FVC ratio of 68% indicates an obstructive ventilatory defect, as it falls below the threshold of 70% which defines airflow obstruction according to guidelines 1
• The FVC values show significant variability across measurements, with some values appearing normal and others reduced, suggesting possible inconsistent testing technique or variable airflow limitation 1
• MEF (mid-expiratory flow) values show marked variability, with some measurements significantly below predicted values, indicating small airway dysfunction 1
• The PEF (peak expiratory flow) measurements are inconsistent, with some values appearing normal and others reduced, which may indicate variable upper airway function or effort 1

Classification of Severity

• Based on the FEV1 values (which appear to be between 60-70% of predicted in some measurements), this represents moderate airflow obstruction according to the severity classification system 1
• The variable pattern with some normal FVC values but reduced FEV1/FVC ratio is consistent with early to moderate obstructive lung disease 1
• The concave appearance suggested by the flow measurements (particularly the reduced MEF values) is characteristic of small airways disease 1

Diagnostic Considerations

• Primary consideration should be given to:

  • Asthma - given the variability in measurements suggesting possible reversibility 1
  • Early COPD - particularly if there is a smoking history 1, 2
  • Small airways disease - indicated by the reduced mid-expiratory flows 1, 3

• Additional testing needed:

  • Bronchodilator reversibility testing to differentiate between asthma (typically reversible) and COPD (typically less reversible) 1, 2
  • Complete lung volumes by plethysmography to better assess for air trapping and hyperinflation 1
  • DLCO measurement to evaluate for emphysematous changes 1, 4

Management Recommendations

• Initiate bronchodilator therapy with short-acting beta-agonists to address the obstructive component 1
• Consider inhaled corticosteroids if there is significant bronchodilator reversibility suggesting asthma 1, 2
• Obtain complete clinical history focusing on:
  • Smoking history
  • Occupational exposures
  • Family history of lung disease
  • Pattern of symptoms (intermittent vs. persistent) 1, 4

Important Caveats and Pitfalls

• Inconsistent effort during testing can significantly affect results, particularly FVC and PEF measurements 1, 5
• Diurnal variation in airway resistance can affect test results, with values typically higher in the morning and lower at midday (up to 20% variation) 5
• Single measurements should not be over-interpreted; serial testing may be necessary to establish a clear pattern 1, 5
• The FEV1/FVC ratio should be interpreted using the lower limit of normal rather than fixed cutoffs, especially in older adults where fixed cutoffs may overdiagnose obstruction 1, 2
• Isolated abnormalities in mid-expiratory flows (MEF 25-75%) without other abnormalities have limited clinical significance 1, 3