Effect of increased inspired CO2 on respiratory dead space in ponies.

This research study investigates the effect of increased inspired carbon dioxide (CO2) on the respiratory dead space (VD) of various groups of ponies, including normal, carotid body-denervated (CBD), hilar nerve-denervated (HND), and a combined group of CBD and HND ponies. The results suggest that increased inspired CO2 enlarges the VD and influences the ponies’ breathing pattern.

Study Objectives

• The study aimed to investigate the influence of increased inspired CO2 on the respiratory dead space (VD) of normal and different groups of nerve-denervated ponies.
• The study groups included normal ponies and ponies with specific types of nerve denervation: carotid body-denervated (CBD), hilar nerve-denervated (HND), and a combination of CBD and HND.
• The researchers used the Fowler technique to measure VD while the ponies breathed room air and inspired CO2 at 3% and 6% concentrations.

Findings

• The researchers found variations in the tidal volume (VT) and VD among the different groups of ponies during normal room air breathing. They observed that the HND ponies had greater VT and VD than the normal and CBD ponies.
• Importantly, for all groups, with an increase in inspired CO2, there were significant increases observed in VD, VT, and breathing frequency (f). Correspondingly, the ratio of VD/VT decreased.
• During an increase in CO2, the VT and VD were higher in the HND ponies than all other groups. The greatest decrease in VD/VT was observed in the mixed group (CBD+HND), and the breathing frequency was lower in the HND and combined group than in the normal and CBD ponies.
• Moreover, when inspired CO2 was increased from 0 to 6%, a greater decrease in VD/VT and a smaller increase in arterial PCO2 were noted after CBD than before CBD.

Conclusion

• In summary, the study indicates that increases in inspired CO2 affect the respiratory dead space and the breathing pattern in ponies. The specific impact varies depending on whether the ponies are normal, or have had certain types of nerve denervation.
• The findings provide valuable insights into the physiological response to increased CO2 inspiration and could potentially contribute to practices in veterinary science and animal care.