Relationship between clinical signs and pulmonary function estimated by the single breath diagram for CO(2) (SBD-CO(2)) in horses with chronic obstructive pulmonary disease.

This research paper studies the connection between observed clinical signs in horses with chronic obstructive pulmonary disease (COPD) and lung function measured using single breath diagrams for carbon dioxide (SBD-CO2). The research found that specific abnormal clinical parameters indicated a measurable ventilation and perfusion imbalance, reflected in increases in dead space measurements and ratios related to tidal volume.

Methodology

• The study involved the examination of the pulmonary health of 66 horses using clinical examinations and additional simple diagnostic methods.
• The researchers used Single breath diagrams for Carbondioxide (SBD-CO2), and lung function indices derived from them, to estimate the pulmonary function of the horses.

Observations and Findings

• The researchers compared the observed clinical signs in different groups of horses to the results from lung function indices derived from SBD-CO2.
• In horses which were moderately to severely affected by Chronic Obstructive Pulmonary Disease (COPD), the researchers found a significant relationship between the respiratory frequency and the ratio of Bohr’s dead space (unventilated space) to tidal volume (VT).
• Additionally, they found a relation between the Physiological dead space/Tidal volume ratio and the ratio of the Alveolar dead space to the Alveolar tidal volume, but no significant connections were found between arterial oxygen tension and any lung function indices derived from SBD-CO2.
• The occurrence of cough, the viscosity of tracheo-bronchial mucus, and the amount of polynuclear neutrophils contained in tracheo-bronchial aspirates were significantly correlated with expiratory tidal volume (VT), the total volume of expired CO2, as well as the above-mentioned volume-to-dead-space ratios.
• These findings suggest that irregularities observed in these clinical parameters for horses are a sign of a measurable ventilation and perfusion (VA/Q) mismatch, which is indicated by increases in dead space, and the various dead space to tidal volume ratios.

Conclusion

• This research indicates that the study and observation of clinical parameters in horses, particularly those already affected by COPD, can provide measurable insight into ventilation and perfusion mismatches in said horses.