Normal Results

Definition: All measured parameters are within the normal range and FEV1/FVC ratio is > 0.70

Possible Intervention: Review patient in 12 months following repeat spirometry

Obstructive Pattern

Definition: FEV1/FVC ratio is ≤ 0.70

• Mild > 70%
• Moderate 60 – 69%
• Moderately severe 50 – 59%
• Severe 35 – 49%
• Very severe ≤ 34%

Severity based on post-FEV1 percent predicted (as per ATS/ERS guidelines)

COPD or chronic asthma should be considered given the correct clinical context.

Possible Interventions:

1. Consider bronchodilator therapy
2. Review patient in 3 months following repeat flow volume loop
3. If no improvement and/or symptoms persist – consider referral to Respiratory Physician and/or full lung function testing

Restrictive Pattern

Definition: FEV1/FVC ratio is within normal range (or elevated) with FVC < LLN

• Mild 70% – LLN
• Moderate 60 – 69%
• Moderately severe 50 – 59%
• Severe ≤ 49%

Severity based on FVC percent predicted (adapted from ATS/ERS guidelines)

An interstitial or extra-thoracic pathology should be considered given the correct clinical context. Full lung function testing recommended.

Possible Interventions:

1. Consider further investigation such as chest imaging (CXR or CT chest)
2. Review patient in 3-6 months following repeat spirometry
3. If no improvement and/or symptoms persist – consider referral to Respiratory Physician and/or full lung function testing to confirm restrictive abnormality

IF FEV1 & FVC – NORMAL RANGE BUT 

• FEF 25-75 ≤ LLN OR 
• FEF 50 ≤ LLN

Report:FEV1 and FVC within normal range, but with a non-specific small airway abnormality.

Possible Interventions:

1. Consider bronchodilator therapy if symptomatic and/or respiratory risk factors present
2. Consider investigation for asthma e.g. mannitol challenge test
3. Review patient in 6-12 months following repeat spirometry
4. If no improvement and/or symptoms persist – consider referral to Respiratory Physician and/or full lung function testing

BRONCHODILATOR RESPONSE FOLLOWING SALBUTAMOL (10 MINUTES BETWEEN PRE– AND POST–MEASUREMENTS)

Definition: If FEV1 and/or FVC increase ≥ 12% and ≥ 200ml following bronchodilator

(as per ATS/ERS guidelines, GOLD and COPD-X)

Report: Significant response following bronchodilator, suggestive of asthma.

Possible Interventions:

1. Prescribe inhaled therapy
2. Review patient in 3 months following repeat spirometry
3. If no improvement and/or symptoms persist – consider referral to Respiratory Physician

If these thresholds are not met: Report: No significant response following bronchodilator.

Abbreviations

• FEV1 Forced Expiratory Volume in 1 second FVC Forced Vital Capacity
• LLN Lower Limit of Normal
• FEF Forced Expiratory Flow (between 25 and 75% of vital capacity or at 50% vital capacity) ERS European Respiratory Society
• ATS American Thoracic Society
• GOLD Global Initiative for Chronic Obstructive Lung Disease

References

1. Pellegrino, R. et al. Interpretative strategies for lung function tests. Eur Respir J 2005; 26: 948–968
2. Decramer, M. et al. Global Initiative for Chronic Obstructive Lung Disease 2015
3. Abramson M, et al. COPD-X Concise Guide for Primary Care. Brisbane. Lung Foundation Australia. 2014