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Effect of Equal Ratio Ventilation on Respiratory Mechanics and Oxygenation During Volume-Controlled Ventilation in
Ha Yeon Kim1, Sung Yeon Ham2, Eun Jung Kim3
1Department of Anesthesiology and Pain Medicine, Ajou University School of Medicine, Suwon, Korea.
Insights
A 1:1 inspiratory to expiratory (I:E) ratio improved lung compliance and reduced peak airway pressure in pediatric surgery patients. This ratio did not significantly enhance oxygenation compared to a 1:2 I:E ratio.
Area of Science:
- Pediatric Anesthesiology
- Respiratory Physiology
- Mechanical Ventilation
Background:
- Pediatric patients have compliant chest walls and underdeveloped alveoli, increasing lung collapse risk.
- Prolonged inspiratory to expiratory (I:E) ratio ventilation is crucial for optimizing gas exchange and respiratory mechanics during pediatric surgery.
- The optimal I:E ratio for pediatric surgical patients remains undetermined.
Purpose of the Study:
- To compare the effects of 1:1 versus 1:2 I:E ratios on dynamic compliance, oxygenation, and peak airway pressure in pediatric surgical patients.
- To test the hypothesis that a 1:1 I:E ratio improves dynamic compliance and oxygenation while affecting peak airway pressure compared to a 1:2 ratio.
Main Methods:
- Forty-eight pediatric patients (≤6 years) undergoing surgery were randomized to 1:1 or 1:2 I:E ratio ventilation.
- Airway pressure, respiratory system compliance, and arterial blood gases were measured at multiple time points.
- Data were collected immediately after induction, at 30 and 60 minutes, immediately after surgery, and upon arrival at the post-anesthesia care unit.
Main Results:
- The 1:1 I:E ratio group showed significantly higher dynamic and static lung compliance at 30 minutes post-induction (p=0.044 and 0.045).
- Peak and plateau airway pressures were significantly lower in the 1:1 group compared to the 1:2 group at 30 minutes (p=0.044 and 0.048).
- No significant difference in partial pressure of oxygen was observed between the groups.
Conclusions:
- A 1:1 I:E ratio enhances dynamic lung compliance and reduces peak airway pressure in pediatric surgical patients compared to a 1:2 ratio.
- The 1:1 I:E ratio was implemented without observed complications.
- Current evidence does not support using a 1:1 I:E ratio solely for the purpose of improving oxygenation in this population.
Purpose:
Children have few small alveoli, which reduce lung compliance; in contrast, their cartilaginous rib cage makes their chest wall highly compliant. This combination promotes lung collapse. Prolonged inspiratory to expiratory (I:E) ratio ventilation is used to optimize gas exchange and respiratory mechanics in surgery. However, the optimal ratio is unclear in children. We hypothesized that, compared to a 1:2 I:E ratio, a 1:1 I:E ratio would improve dynamic compliance and oxygenation, and affect the peak airway pressure in pediatric patients undergoing surgery.
Materials And Methods:
Forty-eight patients aged ≤6 years who were scheduled to undergo surgery under general anesthesia with an arterial line were randomly allocated to receive 1:1 (group 1:1) or 1:2 (group 1:2) I:E ratio ventilation. Airway pressure, respiratory system compliance, and arterial blood gas analyses were compared between groups immediately after induction (T0), 30 min after induction (T1), 60 min after induction (T2), immediately after surgery (T3), and on arrival at the post-anesthesia care unit (T4).
Results:
Peak and plateau airway pressures were significantly lower in group 1:1 than in group 1:2 at T1 (p=0.044 and 0.048, respectively). The dynamic and static compliances were significantly higher in group 1:1 than in group 1:2 at T1 (p=0.044 and 0.045, respectively). However, the partial pressure of oxygen did not significantly differ between groups.
Conclusion:
Compared to a 1:2 I:E ratio, a 1:1 I:E ratio improved dynamic compliance and lowered the peak airway pressure without complications in pediatric patients. Nevertheless, our results do not support its use solely for improving oxygenation.
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