Comparison of various types of inert gas components on efficacy of an alveolar recruitment maneuver in dorsally recumbent anesthetized horses.

The research involves a study on the impact of different inert gases, nitrogen and helium, on the effectiveness of a lung maneuver intended to improve respiratory mechanics and oxygen exchange in anesthetized horses.

Research Methodology

• The study was conducted on six healthy adult horses which were anesthetized twice as part of a randomized crossover study. Being a crossover study, each horse received both treatments (Nitrogen and Helium) at different times, allowing for direct comparison of the treatments’ effects within the same animal.
• The horses were placed in dorsal recumbency, a common position for anesthetized horses, with inhalation anesthetic isoflurane and were ventilated with 30% oxygen combined with either 70% nitrogen (Treatment N) or 70% helium (Treatment H).
• After 60 minutes, an alveolar recruitment maneuver (ARM) was performed, a technique used to open up the collapsed parts of the lungs. The optimal positive end-expiratory pressure (PEEP), a pressure level that improves oxygenation, was identified and maintained for the next 120 minutes.
• Arterial blood pressures, heart rate, peak inspiratory pressure, dynamic compliance (C), and the partial pressure of oxygen in the arterial blood (PaO) were all measured throughout the experiment. The impact on these variables were then compared with their baseline values and between the treatments using Analysis of Variance (ANOVA).

Results

• The ARM caused significant rises in PaO and dynamic compliance (indicative of improved lung mechanics), and decreases in the alveolar-arterial oxygen gradient (indicative of improved oxygen exchange) in all horses.
• Following the ARM and during the next 120 minutes, the mean values of PaO and C were significantly lower for the group ventilated with nitrogen (Treatment N) in comparison to the group ventilated with helium (Treatment H).
• The optimal positive end-expiratory pressure was consistently 15 cm H2O for nitrogen treated horses (Treatment N), while it varied between 10 cm H2O and 15 cm H2O for helium treated horses (Treatment H).

Conclusions

• The results of the study suggest that using helium as the inert gas in this particular alveolar recruitment maneuver may yield better results in terms of improved PaO and dynamic compliance as compared to using nitrogen. It is suggested that an ARM in anesthetized horses might be more effective in improving these parameters when the animals breathe in a helium-oxygen mix, rather than a nitrogen-oxygen mix.