Phase Difference between End-Tidal CO₂ and Ventilation in Heart Failure with Oscillatory Breathing

Area of Science:

• Cardiology
• Pulmonology
• Exercise Physiology

Background:

• Oscillatory breathing (OB) during cardiopulmonary exercise testing (CPX) is common in heart failure patients.
• OB involves cyclic changes in ventilation (VE), oxygen uptake (VO2), carbon dioxide output (VCO2), and end-tidal gases (PETCO2, PETO2).
• Understanding OB's relationship with cardiopulmonary function is crucial for patient assessment.

Purpose of the Study:

• To investigate the correlation between the phase difference of respiratory gas variables during CPX and cardiopulmonary function.
• To assess if phase differences in oscillatory breathing patterns reflect disease severity.

Main Methods:

• Retrospective analysis of 1,740 cardiovascular disease patients undergoing CPX.
• Selection of 42 patients exhibiting clear oscillatory breathing patterns.
• Analysis of phase differences between ventilation (VE) and end-tidal partial pressure of carbon dioxide (PETCO2) alongside other respiratory variables.

Main Results:

• A significant positive correlation was found between the phase difference of PETCO2 and VE, and the VE-VCO2 slope (r=0.414, p=0.006).
• The phase difference also correlated significantly with resting and peak PETCO2 levels (r=-0.453, p=0.003 and r=-0.424, p=0.005, respectively).
• Oscillations in PETCO2 and PETO2 preceded changes in VO2, VCO2, and VE.

Conclusions:

• The phase difference between PETCO2 and VE during CPX is associated with heart failure severity.
• Oscillatory breathing in cardiovascular patients may be linked to impaired arterial PCO2 regulation.