Reduced hemoglobin-corrected diffusing capacity in pulmonary arterial hypertension with preserved pulmonary function...

Area of Science:

• Pulmonary Hypertension Research
• Respiratory Physiology
• Cardiopulmonary Medicine

Background:

• Pulmonary arterial hypertension (PAH) is known to reduce diffusing capacity and transfer coefficient of the lung for carbon monoxide (D_LCO and K_CO).
• The isolated impact of PAH on these parameters and their clinical significance remain incompletely understood.
• This study aimed to clarify the exclusive effect of PAH on D_LCO and K_CO and their associations with other clinical indicators.

Purpose of the Study:

• To determine the specific impact of pulmonary arterial hypertension on D_LCO and K_CO.
• To investigate the relationship between these lung function parameters and established clinical markers of PAH severity.
• To explore the underlying mechanisms, including ventilation-perfusion mismatch and vascular pathology.

Main Methods:

• Retrospective analysis of 50 patients with pulmonary arterial hypertension.
• Inclusion criteria: normal pulmonary function tests and normal lung parenchyma on CT scan.
• Calculation of hemoglobin-corrected D_LCO (D_LCO-Hbc) and K_CO (K_CO-Hbc); correlation with clinical parameters; exploratory autopsy analysis.

Main Results:

• Median %D_LCO-Hbc was 62% and %K_CO-Hbc was 70% in PAH patients.
• D_LCO-Hbc correlated with functional class, 6-minute walk distance, alveolar-arterial oxygen difference, cardiac output, and mortality.
• Both parameters correlated with ventilation-perfusion mismatch indices.

Conclusions:

• Reduced D_LCO-Hbc and K_CO-Hbc (60-70%) are present in PAH patients even with preserved lung function and morphology.
• These reductions are linked to clinical severity and survival outcomes.
• Heterogeneous pulmonary vasculopathy and resulting ventilation-perfusion mismatch likely contribute to these findings.