Effect of a syringe aspiration technique versus a mechanical suction technique and use of N-butylscopolammonium bromide on the quantity and quality of bronchoalveolar lavage fluid samples obtained from horses with the summer pasture endophenotype of equine asthma

Effect of Lavage Solution Type on Bronchoalveolar Lavage Fluid Cytology in Clinically Healthy Horses

Equine bronchoalveolar lavage (BAL) is usually performed with 250-500 mL of isotonic saline at pH 5.5. The acidic pH of saline may cause an increase in airway neutrophil count 48 h after BAL. Other isotonic solutions such as Ringer's solution, phosphate-buffered saline (PBS) or Plasma-Lyte 148® have a neutral pH of 7.4 and might be a better choice for BAL by not provoking inflammation and the influx of neutrophils into airways. BAL was performed in four healthy horses in four different lung lobes using four different solutions in a randomized crossover design. In each lobe, BAL was performed twice with a 48 h interval using 250 mL of solution. Automated total nucleated cell counts (TNCs) were recorded, and differential cell counts in lavage fluid were determined by two investigators blinded to treatments. The mean volume of BAL fluid retrieved was 51 ± 14%. The mean neutrophil percentage (%N) increased from 1.5 ± 0.9% to 14.7 ± 9.6% at 48 h (p < 0.001) but was not significantly affected by the solution used or the lung lobe sampled. In conclusion, in this study, the influx of neutrophils into airways after BAL was independent of the type of isotonic solution used and the lung lobe sampled. Saline remains an appropriate solution for BAL in horses.

Airway Diagnostics: Bronchoalveolar Lavage, Tracheal Wash, and Pleural Fluid

Indications for bronchoalveolar lavage, tracheal wash, and thoracocentesis for the diagnosis of respiratory diseases are discussed. Each technique is described in detail and illustrated by videos. Sample handling, preparation and evaluation are reviewed. The advantages and limitations of bronchoalveolar lavage and tracheal wash procedures as well as a critical comparison between the 2 techniques for equine asthma diagnosis are presented. Finally, validated cut-off values for equine asthma diagnosis are reviewed.