Effect of prior lavage on bronchoalveolar lavage fluid cell population of lavaged and unlavaged lung segments in horses.

This study examined whether bronchoalveolar lavage (BAL), a procedure to examine the airways of horses, caused inflammation in the lungs. The procedure was performed on different groups of horses, with changes in the lungs measured over time. Some increase in specific cells (neutrophils) was observed, suggesting a localized response in the lungs that persisted for at least 48 hours post-procedure, but overall the procedure appeared to be safe.

Procedure

• BAL was carried out on 16 horses in different groupings and combinations to test for any potential inflammatory response triggered by the procedure.
• In the first group, BAL was performed in both lungs of 7 horses twice, with a gap of 48 hours. In the second group, BAL was performed in one lung of 5 horses and repeated 48 hours later in the same lung and in the equivalent area in the opposite lung. As for the last group, 4 horses had BAL performed in one lung and then 48 hours later, this was repeated in an area close to the first BAL site, and in the equivalent spot in the opposite lung.

Findings

• The study observed that although the total cell counts in the BAL samples remained largely unchanged, there was an increase in neutrophils, a type of white cell, in the second lavage (wash-out) samples. This increase was both in absolute terms and as a proportion of total cells.
• A statistically significant increase in absolute cell count and neutrophil quantity was measured in the second sample from the lung that was lavaged twice.
• No significant differences were observed in the total or differential cell counts of the BAL fluid at any time, except for a rise in neutrophil percentage in the second contralateral lung sample.

Conclusion

• The elevated neutrophil counts observed were within the normal range for healthy horses, suggesting that BAL may stimulate an influx of neutrophils into the lungs that persists for at least 48 hours. This neutrophil influx appears to represent a localized, rather than systemic inflammatory response.
• The study further confirms that BAL is a safe procedure that provides cell samples that correlate well with pathological lesions in horses’ lungs.
• However, further research is required to examine the localized pulmonary neutrophil influx since the implications and long-term effects of this phenomenon are still not fully understood.