Lung function testing in COPD: when everything is not so simple.

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Radiology

Background:

• Combined pulmonary fibrosis and emphysema (CPFE) is a distinct clinical entity primarily affecting male smokers.
• CPFE presents with unique alterations in lung mechanics and gas exchange compared to isolated pulmonary fibrosis or emphysema.
• Diagnosis can be challenging due to overlapping or atypical presentations.

Purpose of the Study:

• To report a case of CPFE in an elderly male former smoker presenting with progressive dyspnea.
• To illustrate the diagnostic challenges and limitations of standard lung function tests in CPFE.
• To emphasize the importance of integrated diagnostic approaches for symptomatic smokers.

Main Methods:

• Case report of an elderly male former heavy smoker with 1-year history of exertional dyspnea.
• Pulmonary function tests including spirometry, lung volumes, diffusing capacity for carbon monoxide (DLCO), and nitric oxide (DClNO).
• Arterial blood gas analysis and high-resolution computed tomography (HRCT) of the chest.

Main Results:

• Near-normal spirometry and lung volumes were observed.
• Marked reduction in diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DClNO).
• Reduced arterial partial pressure of oxygen with an increased alveolar-to-arterial difference.
• HRCT revealed upper lobe emphysema and lower lobe pulmonary fibrosis.

Conclusions:

• This case underscores the limitations of relying solely on spirometry and lung volumes for diagnosing symptomatic smokers with potential CPFE.
• Significant reductions in DLCO and DClNO, alongside gas exchange abnormalities, are critical indicators.
• Integrated assessment using imaging and detailed lung function testing is essential for accurate CPFE diagnosis.