The influence of body mass and thoracic dimensions on arterial oxygenation in anaesthetized horses and ponies.

The research article investigates how body mass and thoracic dimensions of horses and ponies affect their oxygen levels during anesthesia when positioned on their backs. The researchers found strong correlations between body-height and chest-circumference-to-body-mass ratios and the horses’ arterial oxygen tension 15 minutes into anesthesia.

Research Methodology

• This study was designed as a prospective clinical trial involving 36 client-owned horses and ponies aged between 1.5 to 20 years and having a mean body mass between 203 to 656 kg.
• Before the start of the experiment, the animals were deprived of food and water for 12 and 1 hours respectively.
• The researchers measured several parameters which included body mass, height, thoracic circumference, thoracic depth, thoracic width and thoracic diagonal length.
• Anesthesia was induced with a combination of Ketamine and Diazepam drugs, and maintained with a mixture of halothane, oxygen, and nitrous oxide.
• The horses and ponies were allowed to breathe spontaneously while positioned on their backs. Nitrous oxide was discontinued after 10 minutes.
• Blood samples were collected at 15, 30 and 60 minutes post-connection to the anesthetic circuit for analysis of gas tensions.
• The collected data was then analyzed using ANOVA (Analysis of Variance) and Pearson’s correlation coefficient.

Study Results and Conclusion

• The results showed that the ratios of height to body mass and thoracic circumference to body mass of the horses and ponies correlated strongly with their arterial oxygen tension 15 minutes post anesthesia.
• The study concluded that there is a strong positive correlation between these ratios and arterial oxygen tension after 15 minutes of anesthesia in halothane-anesthetized horses positioned on their backs.
• The researchers suggested that simple linear measurements such as height and thoracic circumference in comparison with body mass can be used to predict the ability of horses to oxygenate during anesthesia.