[Pulmonary function testing of dyspnea complaint by the pulmonologist].

Area of Science:

• Respiratory Medicine
• Pulmonary Physiology
• Diagnostic Medicine

Background:

• Dyspnea, or shortness of breath, stems from an imbalance between the body's demand for ventilation and the respiratory system's capacity to meet that demand.
• Standard pulmonary function tests like spirometry primarily assess ventilatory capacity, often overlooking ventilatory demand, a key factor in conditions like pulmonary vascular diseases.

Purpose of the Study:

• To explore the complex mechanisms underlying dyspnea and evaluate the diagnostic utility of various investigations.
• To highlight the limitations of resting pulmonary function tests in fully explaining dyspnea.
• To emphasize the role of cardiopulmonary exercise testing in uncovering exercise-induced or unexplained dyspnea.

Main Methods:

• Review of existing literature on the pathophysiology of dyspnea.
• Analysis of the diagnostic performance of spirometry, lung volumes, DLCO, and cardiopulmonary exercise testing (CPET).
• Discussion of the relationship between ventilatory demand, ventilatory capacity, and the subjective experience of dyspnea.

Main Results:

• DLCO (Diffusing capacity of the lungs for carbon monoxide) measurement shows the strongest statistical correlation with dyspnea compared to spirometry and static lung volumes.
• Resting investigations explain less than 50% of the variance in dyspnea, indicating its complex, multifactorial nature.
• Cardiopulmonary exercise testing provides valuable insights into pathophysiological mechanisms and can unmask causes of unexplained dyspnea, though its etiological diagnostic value remains challenging.

Conclusions:

• Dyspnea is a complex symptom resulting from an imbalance between ventilatory demand and capacity, not fully captured by standard resting tests.
• DLCO measurement offers a better correlation with dyspnea than spirometry alone.
• Cardiopulmonary exercise testing is essential for a comprehensive evaluation of dyspnea, particularly for exercise-related or unexplained symptoms.