Case study: The importance of Complex Pulmonary Function Test versus Spirometry alone

29 Oct Case study: The importance of Complex Pulmonary Function Test versus Spirometry alone

An 84-year-old never-smoker (PHx passive smoke exposure) presented with mild shortness of breath.

• Mild SOB, increasing last 3/12
• No reported cough or wheeze
• No reported upper airway dysfunction (Rhinitis/Sinusitis)
• No SABA/SAMA/LABA/LAMA/ICS usage
• Rheumatoid Arthritis with long-term Methotrexate use.

Lung Function Test Results as follows:   

Test Findings:

• Spirometry indicates normal FEV1/FVC ratio due to both parameters being equally reduced.
• Many interpretation algorithms may interpret this spirometry as purely obstructive in nature. Furthermore, post-BD spirometry indicated positive acute response to bronchodilator, consistent with reversible small airways disease.
• However, further testing indicates the patient had a reduction in Total Lung Volume (TLC), Residual Volume (RV), and Alveolar Volume (VA).
• A reduction in uncorrected gas diffusion (DLCOuncor) was due to reduction in TLC, however KCO corrected for VA.

Learning points:

• The lung volume and gas diffusion results give context to the spirometry result.
• These findings confirm the patient has a mixed ventilatory response, consistent with both obstructive and restrictive ventilatory impairment
• The obstructive component is consistent with asthma whilst the restrictive impairment may be associated with long-term methotrexate use.