Characteristics of respiratory function during swimming exercise in thoroughbreds.

The research article studies the breathing patterns of thoroughbred horses during swimming exercise. The researchers focused on the rate of breathing, changes in intratracheal pressures, the duration of inhaling and exhaling, the horse’s heart rates, and changes in blood composition.

Study Methodology

• The researchers observed the respiratory function of five normal, healthy thoroughbred horses during swimming.
• The swimming exercise had two parts. It started with a preliminary warming-up phase, followed by six circuits of swimming around a 50-meter-circumference pool.

Measurements and Observations

• The research team investigated multiple factors such as respiratory rates, intratracheal pressures, inspiratory time (TI), expiratory time (TE), complete respiratory cycle (T), horse’s heart rates, concentration of lactate in the blood, hematocrit levels, and blood gases.
• The respiratory rates during the swimming exercise were found to be maintained approximately at 25 breaths per minute.
• Notably, blood gas values underwent significant changes over the swimming duration.

Findings on Intratracheal Pressures

• One significant outcome was the observation of changes in the horses’ intratracheal pressures during expiration and inspiration. The pressures noticeably increased with the duration of the exercise compared to the phase immediately after the warming-up stage.

Role of Inspiratory and Expiratory Time

• The research identified that the duty ratio, which is the ratio of the inspiratory time (TI) to the total respiratory cycle (T), averaged 0.33. This indicated that horses spent about double the time exhaling compared to inhaling during swimming.
• The extended exhaling duration was considered instrumental in preventing a sudden collapse of the horse’s airways due to water pressure. It also served to thwart a drastic reduction in air space volume, maintaining the horse’s buoyancy while swimming.