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R M Christley

Publications and source records attributed to R M Christley.

24 records · Page 2Linked to original sources
PubMed2000

Issues associated with the application to veterinarians of a mailed questionnaire regarding lower respiratory-tract disease in racehorses.

This study evaluated a questionnaire investigating the attitudes and behaviours of veterinarians regarding the cause, diagnosis and treatment of lower respiratory-tract disease in racehorses. The questionnaire was sent to all non-student members (648) of the Australian Equine Veterinary Association: two mailings and a single telephone contact (each separated by four weeks). Subsequent phases were only administered to those who had not responded to earlier phases. In total, 467 (72.1%) of the 648 mailed questionnaires were returned. Of these, 354 were usable. The remaining 113 respondents gave various reasons for not completing the questionnaire; the most common (68%) was that horses were not a component of their practice. Those respondents working primarily with horses required fewer phases to return the questionnaire. Although deviating from previously described questionnaire designs, the described protocol provided a reasonable response rate.

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PubMed1999

Comparison of bacteriology and cytology of tracheal fluid samples collected by percutaneous transtracheal aspiration or via an endoscope using a plugged, guarded catheter.

Cytological and bacteriological results from tracheal fluid samples obtained endoscopically using a telescoping, plugged catheter (TPC) were compared with results from samples collected by percutaneous transtracheal aspiration (PTA). The TPC technique and PTA were performed in random order on 9 healthy Standardbred geldings. Three weeks later the procedures were performed on the same horses in the reverse order. The presence of oropharyngeal contamination was determined by quantitative bacteriology and quantification of squamous epithelial cells (SEC)/ml sample. The relative numbers of macrophages, haemosiderophages, giant cells, neutrophils, lymphocytes and eosinophils did not differ between techniques. The number of SEC/ml was greater in samples with more colony forming units/ml indicating that quantification of SEC provides evidence of the probable degree of oropharyngeal contamination. Fifteen out of the 18 TPC samples were free of contamination, indicating that the TPC can provide adequate samples for bacteriology. The results also indicate that tracheoscopy sometimes results in oropharyngeal contamination of the trachea, but that this does not affect the results of the TPC sample.

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PubMed1999

Blood gas changes during incremental and sprint exercise.

We investigated and compared arterial blood gas and ventilatory changes during rapid acceleration sprint and during incremental treadmill exercise. Seven clinically normal racehorses completed standardised incremental exercise tests and rapid acceleration tests at speeds calculated to elicit 115% VO2max. Arterial oxygen tension decreased (P < 0.001) between 15 s (mean +/- s.d. 103.8 +/- 14.3 mmHg) and 30 s (85.0 +/- 7.7 mmHg) after the onset of rapid acceleration exercise, but did not change significantly during the remainder of the sprint. This was accompanied by an increase in PaCO2 of 5.9 mmHg (P < 0.05). Despite reductions in SaO2 during exercise, CaO2 did not change due to increases in haemoglobin concentration. Heart rate increased rapidly (P < 0.001) during the first 15 s of exercise and thereafter remained constant. The mean maximum speed during the incremental test (11.4 +/- 0.5 m/s) was not significantly different to the speed calculated to elicit 115% VO2max during the sprint test (12.2 +/- 0.8 m/s). The mean peak HR and Hb during the sprint test were significantly less than during the incremental test. However, there were no significant differences in the maximum or minimum values achieved for other variables. We conclude that rapid acceleration exercise is accompanied by rapid changes in blood gas variables, reaching steady state within 45 s. Blood gas responses during the simpler incremental test describe maximal changes during high-intensity sprint exercise.

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PubMed1997

Cardiorespiratory responses to exercise in horses with different grades of idiopathic laryngeal hemiplegia.

The relationship between different grades of laryngeal function, as assessed by endoscopy at rest, and the measurements of indices of gas exchange and exercise capacity was assessed during a standardised treadmill exercise test in 149 horses. Horses with abnormalities other than idiopathic laryngeal hemiplegia (ILH) were excluded from the study and laryngeal function was graded according to an established system. There were no significant differences in age, weight, maximum oxygen uptake, maximum carbon dioxide production, maximum respiratory exchange ratio, maximum oxygen pulse and run time between the grades. Blood lactate concentration at 10 m/s was greater (P < 0.01) in horses with grade 5 laryngeal function than other grades. Minimum PaO2 (P < 0.001) and SaO2 (P < 0.01) were lower and maximum PaCO2 (P < 0.001), higher in horses with grades 4 and 5 laryngeal function than other grades. Horses with grade 4 function had a lower minimum CaO2 (P < 0.01) than horses with other grades. Minimum PAO2 decreased from grades 1 and 2 to grades 4 and 5 (P < 0.05). The minimum alveolar ventilation was lower (P < 0.05) in horses with grades 4 and 5 laryngeal function compared to other grades. The results of this study indicate that endoscopic assessment of laryngeal function at rest, using a simple grading system, provides an indication of dynamic changes in ventilation and the effects on blood gases during exercise. From the data, we suggest that horses that have some movement of the left arytenoid cartilage but are unable to achieve full abduction have similar ventilatory effects and blood gas responses during maximal exercise to those with complete paralysis. Some horses with grade 3 laryngeal function had blood gas results similar to those of horses with grades 4 and 5 laryngeal function, indicating that discrepancies may occur between the resting assessment and laryngeal function during strenuous exercise.

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PubMed1997

Effects of training on the development of exercise-induced arterial hypoxemia in horses.

OBJECTIVES: To compare the development of exercise-induced arterial hypoxemia in horses before and after training, and to determine whether increases in maximum oxygen uptake (VO2max) following training results in a greater degree of exercise-induced arterial hypoxemia. ANIMALS: 13 three- to five-year-old. Standardbred geldings without clinical signs of respiratory or cardiovascular disorders. PROCEDURE: Horses were rested for 4 months prior to commencing a 16-week training program. Arterial blood was collected from the transverse facial artery during standardized exercise tests performed before and after 8 and 16 weeks of training. Variables measured during exercise tests included arterial blood gas tensions and VO2max. Training and testing was performed on a treadmill set at a 10% slope. RESULTS: Minimum arterial partial pressures of oxygen (PaO2) during exercise decreased from 83.3 +/- 1.5 mm of Hg before training to 77.8 +/- 1.0 mm of Hg after 16 weeks of training. Maximum arterial oxygen content increased from 239.2 +/- 3.1 to 257.9 +/- 3.8 ml/L, which resulted from an increase in hemoglobin concentration. The VO2max increased by 19% following training. Minimum values of PaO2 and arterial oxygen saturation were significantly correlated with VO2max when data from each stage of training were pooled. Calculated values for minimum alveolar oxygen tension decreased after 8 weeks of training, and alveolar ventilation increased at the end of training. Alveolar-arterial oxygen tension of difference increased by 4 mm of Hg following training. CONCLUSIONS: In trained horses, an increase in VO2max is associated with a decrease in minimum PaO2, during intense exercise and is mostly attributable to an increase in the alveolar-arterial oxygen tension difference. Therefore, interpretation of blood gas data from exercising horses should take into consideration VO2max.

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