Tidal breathing flow-volume loops in horses with recurrent airway obstruction (heaves).

This study looks at how recurrent airway obstruction, also known as heaves, affects the breathing patterns of horses. By measuring the breath flow and volume of both healthy horses and those with heaves, researchers found that heaves alters the usual biphasic pattern of inhalation and exhalation in horses.

Study Overview and Methodology

• The research involved monitoring and analyzing the Tidal Breathing Flow-Volume (TBFV) loops in horses. TBFV loops are a way of graphically representing the flow and volume of breath a horse takes in (inspiration) and expels (expiration).
• Two groups of horses were studied: a control group of healthy horses and a group suffering from recurrent airway obstruction, more commonly known as heaves.
• The horses with heaves were studied both when the condition was in remission and as their airway obstruction increased. This was done by measuring changes in pleural pressure, pulmonary resistance, and dynamic compliance – elements that influence and reflect the level of airway obstruction.

Findings: Control Horses

• The TBFV loops of the control horses exhibited a biphasic pattern. This means their inspiratory and expiratory patterns had two phases each: peak inspiratory flow was detected early in the inspiration and peak expiratory flow was noticed early in expiration.

Findings: Horses with Heaves

• Interestingly, the volume of breath taken in by the horses (tidal volume) was not affected by heaves.
• However, horses with heaves had higher respiratory frequency at all stages of the condition, due to shorter inspiratory time, which resulted in an increased inspiratory flow rate.
• The TBFV loops of horses with heaves did not follow a biphasic pattern. Peak inspiratory flow came late in the inspiration process, and peak expiratory flow was observed early in expiration.
• As the severity of the airway obstruction increased, the peak expiratory flow also increased alongside the rise in pulmonary resistance. Consequently, during severe airway obstruction, TBFV loops had a distinct appearance, characterized by high peak expiratory flow early in expiration followed by a low flow rate.

Conclusion

• These findings depict the changes in breathing patterns in horses affected by heaves and contribute valuable insight for further study and treatment of this equine respiratory condition.