Comparing Cardiac Output Differences in Patients With Fontan Physiology Between High and Low Tidal Volume Strategies:...

Area of Science:

• Pediatric Cardiology
• Critical Care Medicine
• Cardiovascular Physiology

Background:

• Patients with single ventricle congenital heart disease (CHD) palliated to Fontan physiology lack a native ventricle for pulmonary blood flow.
• Positive pressure mechanical ventilation can reduce cardiac output in these patients compared to negative pressure ventilation.
• Optimal tidal volume settings for mechanical ventilation in Fontan patients remain controversial.

Purpose of the Study:

• To determine if higher or lower tidal volumes are optimal for systemic cardiac output in pediatric Fontan patients.
• To compare systemic cardiac index (CI), pulmonary blood flow, and vascular resistances under different tidal volume strategies.

Main Methods:

• A crossover trial involving pediatric Fontan patients (<18 years) requiring mechanical ventilation during cardiac catheterization.
• Patients were randomized to initial high (10 mL/kg) or low (6 mL/kg) tidal volume ventilation strategies.
• Systemic CI, pulmonary blood flow, and vascular resistances were compared between ventilation strategies.

Main Results:

• Thirty patients completed the study. A higher cardiac index was observed in the low tidal volume strategy for more patients (42%) compared to the high tidal volume strategy (33%).
• No statistically significant difference in mean cardiac index was found between low (3.19 L/min/m² ) and high (2.96 L/min/m²) tidal volume strategies (p=0.062).
• The study was powered to detect a clinically significant difference of 0.7 L/min/m².

Conclusions:

• Direct comparison showed no significant difference in cardiac index between high and low tidal volume strategies in Fontan patients.
• Data suggest that lower tidal volume ventilation may be beneficial for maintaining cardiac index in some Fontan patients requiring positive pressure ventilation.