Effect of instillation into lung of autologous blood on pulmonary function and tracheobronchial wash cytology

Training related risk factors for exercise induced pulmonary haemorrhage in British National Hunt racehorses

BACKGROUND

Exercise induced pulmonary haemorrhage (EIPH) is an important condition of horses performing high intensity exercise, with reported prevalence among racehorses of up to 95%, based on the detection of blood on tracheobronchoscopy. Previously identified risk factors include age, sex, season, race type, years spent in racing and lower airway inflammation.

OBJECTIVES

To estimate the prevalence of EIPH in British National Hunt racehorses as indicated by two outcome measures: presence of tracheal blood on tracheobronchoscopy, and presence of moderate-large (significant) proportions of haemosiderophages in tracheal wash (TW) fluid; and to identify training-related risk factors for these indicators of EIPH.

STUDY DESIGN

Prospective longitudinal study.

METHODS

Data from tracheobronchoscopy and TW cytology were analysed using univariable and multivariable mixed-effects logistic regression.

RESULTS

1184 observations, from 177 horses, were analysed. The prevalence of tracheal blood was 7.2% (95%CI: 5.8, 8.8) and significant haemosiderophages in TW fluid was 36% (95%CI: 33.3, 38.8). Increased time in training was significantly associated with increased odds of EIPH. For each additional year spent in training the odds of tracheal blood and presence of significant proportions haemosiderophages increased approximately 1.5-fold (OR = 1.5; 95%CI: 1.1-2.0; P = .005; and OR = 1.5; 95%CI: 1.3, 1.8; P < .001, respectively). Current inflammation was associated with previous haemorrhage, but not current haemorrhage.

MAIN LIMITATIONS

There are no standardised measures for quantification of TW cytological parameters for EIPH diagnosis. Few horses were examined following jumping. Recent racing dates were not included in analysis.

CONCLUSIONS

Increasing time in training was a risk factor for both indicators of EIPH. Current inflammation was associated with previous haemorrhage, but not current or future haemorrhage, suggesting that haemorrhage leads to inflammation but not that inflammation leads to haemorrhage. Overall, our findings are consistent with the capillary stress failure theory of EIPH. The development of standardised measures for TW cytological diagnosis of EIPH is warranted.

Respiratory diseases and their effects on respiratory function and exercise capacity

Given that aerobic metabolism is the predominant energy pathway for most sports, the respiratory system can be a rate-limiting factor in the exercise capacity of fit and healthy horses. Consequently, respiratory diseases, even in mild forms, are potentially deleterious to any athletic performance. The functional impairment associated with a respiratory condition depends on the degree of severity of the disease and the equestrian discipline involved. Respiratory abnormalities generally result in an increase in respiratory impedance and work of breathing and a reduced level of ventilation that can be detected objectively by deterioration in breathing mechanics and arterial blood gas tensions and/or lactataemia. The overall prevalence of airway diseases is comparatively high in equine athletes and may affect the upper airways, lower airways or both. Diseases of the airways have been associated with a wide variety of anatomical and/or inflammatory conditions. In some instances, the diagnosis is challenging because conditions can be subclinical in horses at rest and become clinically relevant only during exercise. In such cases, an exercise test may be warranted in the evaluation of the patient. The design of the exercise test is critical to inducing the clinical signs of the problem and establishing an accurate diagnosis. Additional diagnostic techniques, such as airway sampling, can be valuable in the diagnosis of subclinical lower airway problems that have the capacity to impair performance. As all these techniques become more widely used in practice, they should inevitably enhance veterinarians' diagnostic capabilities and improve their assessment of treatment effectiveness and the long-term management of equine athletes.

Association between exercise-induced pulmonary hemorrhage and performance in Thoroughbred racehorses

OBJECTIVE

To determine whether exercise-induced pulmonary hemorrhage (EIPH) was associated with racing performance inThoroughbred horses not medicated with furosemide and not using nasal dilator strips.

DESIGN

Observational cross-sectional study.

ANIMALS

744 two- to 10-year-old Thoroughbred horses racing in Melbourne, Australia.

PROCEDURE

Horses were enrolled prior to racing, and a tracheobronchoscopic examination was performed after 1 race. Examinations were recorded on videotape, and presence and severity (grade 0 to 4) of EIPH were subsequently determined by 3 observers blinded to the horses' identity. Race records were abstracted for each horse examined.

RESULTS

Overall, 52.1% of horses eligible for participation in the study were examined, and horses that were examined did not differ from horses that were not examined in regard to age, sex distribution, or proportion of horses that won or finished in the first 3 positions. Horses with EIPH grades < 1 were 4.0 times as likely to win, 1.8 times as likely to finish in the first 3 positions, and 3.03 times as likely to be in the 90th percentile or higher for race earnings as were horses with grades > 2. Horses with EIPH grades > 1 finished significantly farther behind the winner than did horses without EIPH. However, odds that horses with grade 1 EIPH would win or finish in the first 3 positions were not significantly different from odds for horses without EIPH.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that EIPH is associated with impaired performance in Thoroughbred racehorses not medicated with furosemide and not using nasal dilator strips.