Effects of posture and accumulated airway secretions on tracheal mucociliary transport in the horse.

This research investigates how different head positions and the build-up of airway secretions affect the tracheal mucociliary clearance in horses. This study concludes that head-lowering speeds up the clearance, while head-elevation combined with accumulated secretions slows it down, which has significant implications for horse care practices.

Objectives and Methods

• The study aims to understand the effects of posture and airway secretions on tracheal mucociliary clearance in horses.
• The researchers used the method of intratracheal injection of a radiopharmaceutical substance (99mtechnetium-sulphur colloid) on the tracheal epithelium of horses to measure the rostrad transport, i.e., the process of clearing physiological debris along the trachea.
• Two different head positions were compared—normal standing position and the head-lowered position— to evaluate their impact on this transport process.
• Additionally, the effect of accumulated secretions, more specifically, purulent (pus-like) secretions in the horse’s airway, was studied.

Findings and Interpretations

• The results of the study indicated a significant acceleration in tracheal mucociliary clearance when the horses had their heads lowered, with the cranial (head-end) trachea being lower than the caudal (tail-end) one.
• Conversely, when horses were confined to an elevated head position for 24 hours, it led to the accumulation of purulent secretions in the lower respiratory tract.
• Subsequently, these secretions hosted an increased number of bacteria and led to decreased mucociliary clearance, compared to their previously measured rates when their airways contained only normal secretions.

Implications of the Study

• This research has serious implications for the management and care of horses.
• Horses are often prevented from lowering their heads in situations such as transportation and cross-tying. This study suggests that these practices might contribute to lower respiratory tract disease in horses due to the slowed mucociliary clearance.
• The evidence presents a clear case for re-evaluating and potentially adjusting these practices to allow horses to lower their heads more frequently, thus aiding their natural clearance method and reducing the risk of respiratory infections.