Cardiovascular and pulmonary effects of recumbency in two conscious ponies.

This study analyzed the impact of lying down versus standing on two trained ponies’ cardiovascular and pulmonary systems. Measurements were taken in both positions, which included respiratory dead-space, tidal volume, respiratory rate, blood gases, cardiac output, heart rate, and arterial and pulmonary arterial blood pressures. They found that the ponies did not want to remain lying down for more than around 20 minutes. The recumbent position led to a reduced tidal volume, but the respiratory rate increase kept the minute volume comparable to that of a standing pony.

Research Objective

• The purpose of this study was to evaluate the impact of recumbency (or lying down) on the cardiovascular and pulmonary functions of two trained ponies.

Methods

• The researchers gathered data on various physiological parameters of the ponies in both standing and recumbent positions. Parameters measured include respiratory dead-space, tidal volume, respiratory rate, blood gases, cardiac output, heart rate, and arterial and pulmonary arterial blood pressures.
• The scientists also evaluated the ponies’ willingness to stay in the recumbent position, noting that they seemed reluctant to remain down for an extended period.

Findings

• The study discovered that the ponies’ tidal volume (the volume of air displaced between normal inhalation and exhalation) was reduced when they laid down, but their respiratory rates increased.
• This increase in respiratory rate during recumbency helped to maintain the minute volume (the amount of air moved in and out of the lungs per minute) consistent with that of a standing pony.
• The lying position did not notably affect the arterial carbon dioxide tension, but there was a slight decrease in the mean arterial oxygen tension for both ponies. This was due to a small increase in the mixing of venous and arterial blood (pulmonary venous admixture) in the lungs.
• This research revealed that the level of this venous admixture in conscious ponies in a recumbent position was significantly less than what’s been previously observed in anaesthetized subjects. This indicates that anesthetized ponies could experience much greater changes in blood oxygenation due to changes in body position.