Measuring end expiratory lung volume after cardiac surgery

Area of Science:

• Critical Care Medicine
• Respiratory Physiology
• Surgical Outcomes

Background:

• End expiratory volume (EELV) is a key respiratory parameter.
• Post-cardiac surgery patients often experience altered lung volumes.
• The clinical utility of EELV measurement in this population requires investigation.

Purpose of the Study:

• To evaluate the clinical interest and utility of measuring end expiratory volume (EELV) after cardiac surgery.
• To assess the relationship between EELV and other physiological parameters.

Main Methods:

• EELV was measured using nitrogen washout technique at hourly intervals for three hours post-stabilization.
• EELV was compared to predicted functional residual capacity (FRC).
• Relationships with respiratory system compliance, PaO2/FiO2 ratio, and BMI were analyzed. Recruitment maneuvers (RM) were performed in half the patients.

Main Results:

• Measured EELV was 52% of predicted values and remained stable.
• EELV showed strong correlations with PaO2/FiO2 ratio (r2=0.40) and respiratory compliance (r2=0.525).
• EELV was inversely correlated with BMI (r2=0.165), and RM did not significantly alter EELV.

Conclusions:

• End expiratory volume is substantially reduced following cardiac surgery.
• EELV measurement is a novel tool providing valuable information during mechanical ventilation.
• Recruitment maneuvers, including sighs, do not impact EELV in this context.