Search Results

You are looking at 11 - 20 of 28 items for

  • Author or Editor: Frederik J. Derksen x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract

Objective—To determine the effect of a tongue-tie on upper airway mechanics in exercising horses.

Animals—5 Standardbreds.

Procedure—Peak inspiratory and expiratory tracheal and pharyngeal pressures and airflow were measured while horses exercised on a treadmill with and without a tongue-tie. Respiratory rate was also measured. Horses ran at speeds that corresponded to 50 (HR50), 75, 90 (HR90), and 100% of maximal heart rate. The tongue-tie was applied by pulling the tongue forward out of the mouth as far as possible and tying it at the level of the base of the frenulum to the mandible with an elastic gauze bandage. Peak inspiratory and expiratory tracheal, pharyngeal, and translaryngeal resistance, minute ventilation, and tidal volume were calculated. Data were analyzed by use of 2-way repeated-measures ANOVA. For post hoc comparison of significant data, the Student-Newman- Keuls test was used.

Results—We were unable to detect significant differences between groups for peak inspiratory or expiratory tracheal or pharyngeal resistance, peak pressure, peak expiratory flow, tidal volume, respiratory rate, or minute ventilation. Horses that ran with a tongue-tie had significantly higher peak inspiratory flows, compared with horses that ran without a tongue-tie. In the post hoc comparison, this effect was significant at 4 m/s, HR50, and HR90.

Conclusion and Clinical Relevance—Application of a tongue-tie did not alter upper respiratory mechanics in exercising horses and may be beneficial in exercising horses with certain types of obstructive dysfunction of the upper airways. However, application of a tongue-tie does not improve upper airway mechanics in clinically normal horses. (Am J Vet Res 2001; 62:775-778)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of a commercially available nasal strip on airway mechanics in exercising horses.

Animals—6 horses (5 Standardbreds and 1 Thoroughbred).

Procedure—Horses exercised on a treadmill at speeds corresponding to 100 and 120% of maximal heart rate with and without application of a commercially available nasal strip. Concurrently, tracheal pressures, airflow, and heart rate were measured. Peak inspiratory and expiratory tracheal pressures, airflow, respiratory frequency, and tidal volume were recorded. Inspiratory and expiratory airway resistances were calculated by dividing peak pressures by peak flows. Endoscopic examination of the narrowest point of the nasal cavity (ie, nasal valve) was performed in 1 resting horse before, during, and after application of a nasal strip.

Results—During exercise on a treadmill, peak tracheal inspiratory pressure and inspiratory airway resistance were significantly less when nasal strips were applied to horses exercising at speeds corresponding to 100 and 120% of maximal heart rate. Application of the nasal strip pulled the dorsal conchal fold laterally, expanding the dorsal meatus.

Conclusions and Clinical Relevance—The commercially available nasal strip tented the skin over the nasal valve and dilated that section of the nasal passage, resulting in decreased airway resistance during inspiration. The nasal strip probably decreases the amount of work required for respiratory muscles in horses during intense exercise and may reduce the energy required for breathing in these horses. (Am J Vet Res 2002;63:1101–1105)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of desensitization of the laryngeal mucosal mechanoreceptors on upper airway mechanics in exercising horses.

Animals—6 Standardbreds.

Procedure—In study 1, videoendoscopic examinations were performed while horses ran on a treadmill with and without topical anesthesia of the laryngeal mucosa. In study 2, peak tracheal and nasopharyngeal pressures and airflows were obtained from horses during incremental treadmill exercise tests, with and without topical anesthesia of the laryngeal mucosa. A nasal occlusion test was performed on each horse while standing during an endoscopic examination for both trials.

Results—In study 1, horses had nasopharyngeal collapse while running on the treadmill when the laryngeal mucosa was anesthetized. In study 2, inspiratory upper airway and nasopharyngeal impedance were significantly higher, and peak tracheal inspiratory pressure, respiratory frequency, and minute ventilation were significantly lower in horses when the laryngeal mucosa was anesthetized, compared with values obtained when horses exercised without topical anesthesia. Peak inspiratory and expiratory airflows were lower in horses when the laryngeal mucosa was anesthetized, although differences did not quite reach significance (P = 0.06 and 0.09, respectively). During a nasal occlusion test, horses had episodes of nasopharyngeal collapse and dorsal displacement of the soft palate when the laryngeal mucosa was anesthetized. Upper airway function was normal in these horses without laryngeal mucosal anesthesia.

Conclusions and Clinical Relevance—Receptors within the laryngeal mucosa may be important in maintaining upper airway patency in exercising horses. (Am J Vet Res 2001;62:1706–1710)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To record respiratory sounds in exercising horses and determine whether spectrum analysis could be use to identify sounds specific for laryngeal hemiplegia (LH) and dorsal displacement of the soft palate (DDSP).

Animals—5 Standardbred horses.

Procedure—Respiratory sounds were recorded and pharyngeal pressure and stride frequency were measured while horses exercised at speeds corresponding to maximum heart rate, before and after induction of LH and DDSP.

Results—When airway function was normal, expiratory sounds predominated and lasted throughout exhalation. After induction of LH, expiratory sounds were unaffected; however, all horses produced inspiratory sounds characterized by 3 frequency bands centered at approximately 0.3, 1.6, and 3.8 kHz. After induction of DDSP, inspiratory sounds were unaffected, but a broad-frequency expiratory sound, characterized by rapid periodicity (rattling) was heard throughout expiration. This sound was not consistently detected in all horses.

Conclusions and Clinical Relevance—The technique used to record respiratory sounds was well tolerated by the horses, easy, and inexpensive. Spectrum analysis of respiratory sounds from exercising horses after experimental induction of LH or DDSP revealed unique sound patterns. If other conditions causing airway obstruction are also associated with unique sound patterns, spectrum analysis of respiratory sounds may prove to be useful in the diagnosis of airway abnormalities in horses. (Am J Vet Res 2001;62:659–664)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine the dose of aerosolized albuterol sulfate required to cause bronchodilation in horses with recurrent airway obstruction (RAO) and duration of this effect.

Animals

19 horses with RAO (10 in experiment 1; 9 in experiment 2).

Procedure

Horses were moved from pasture to stables, and airway obstruction was induced. Pulmonary function was measured in 10 horses before and 5, 10, and 30 minutes after administration of vehicle or 120, 240, 360, or 720 µg of the drug. Nine horses received vehicle or 360 or 720 µg of albuterol, and pulmonary function was measured at baseline and 5 minutes and 1, 2, 3, 4, 5, 6, and 7 hours later. Horses were evaluated for adverse drug effects.

Results

360 µg of albuterol was required to cause significant bronchodilatation; 720 µg did not enhance bronchodilatation or increase duration of action. Depending on which pulmonary function parameter was evaluated, bronchodilatation achieved by use of albuterol lasted between 30 minutes and 1 hour. Because there was a significant vehicle effect, the combined effect of vehicle and drug lasted up to 3 hours. Adverse effects were not observed.

Conclusions

Aerosolized albuterol, 360 or 720 µg, is a safe and effective bronchodilator in horses with RAO. Onset of action is rapid (5 minutes), and effects last from 30 minutes to 3 hours.

Clinical Relevance

Aerosolized albuterol is useful for treatment of bronchospasm in horses with RAO. (Am J Vet Res 1999;60:689–693)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To compare tracheal and pharyngeal inspiratory and expiratory pressures achieved during 60 seconds of nasal occlusion in standing horses with pressures achieved in horses during intense exercise.

Animals

5 Standardbreds.

Procedure

Tracheal and pharyngeal inspiratory and expiratory pressures were obtained from 5 horses during 60 seconds of nasal occlusion and compared with tracheal and pharyngeal pressures achieved during incremental treadmill exercise tests in which horses ran at 50, 75, and 100% of the speed that resulted in maximal heart rate ( HRmax)

Results

Significant difference was not detected between peak tracheal inspiratory pressure during nasal occlusion and peak tracheal inspiratory pressure at HRmax. Peak pharyngeal inspiratory pressure was sig nificantly more negative, and peak tracheal and peak pharyngeal expiratory pressures were sig nificantly more positive during 60 seconds of nasal occlusion than those observed in horses running at HRmax.

Conclusion

During upper airway endoscopy in standing horses, 60-second nasal occlusion induced tracheal and pharyngeal inspiratory pressures that equaled or exceeded pressures achieved during high-intensity exercise.

Clinical Relevance

Nasal occlusion is useful to simulate upper airway pressures achieved during high-intensity exercise. (Am J Vet Res 1996;57:1258–1260)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the safety and efficacy of thoracoscopically guided pulmonary wedge resection in horses.

Animals—10 horses (5 control horses and 5 horses affected with recurrent airway obstruction [ie, heaves]).

Procedure—Each horse underwent a thoracoscopically guided pulmonary wedge resection. Before, during, and after surgery, heart rate, respiratory rate, arterial blood gases, and systemic and pulmonary arterial pressures were measured. Physical examination, CBC, and thoracic radiography and ultrasonography were performed 24 hours before and 2 and 48 hours after surgery. Pulmonary specimens were assessed by histologic examination. A second thoracoscopic procedure 14 days later was used to evaluate the resection site.

Results—The technique provided excellent specimens for histologic evaluation of the lung. Heart and respiratory rates decreased significantly after horses were administered sedatives. A significant transient decrease in PaO2 was detected immediately after pulmonary wedge resection, but we did not detect significant effects on arterial pH, Paco2, or mean arterial and pulmonary arterial pressures. All horses except 1 were clinically normal after thoracoscopic surgery; that horse developed hemothorax attributable to iatrogenic injury to the diaphragm. The second thoracoscopy revealed minimal inflammation, and there were no adhesions.

Conclusion and Clinical Relevance—Thoracoscopically guided pulmonary wedge resection provides a minimally invasive method for use in obtaining specimens of lung tissues from healthy horses and those with lung disease. This technique may be useful for the diagnosis of diseases of the lungs and thoracic cavity. (Am J Vet Res 2002;63:1232–1240)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare endoscopic findings of the upper portion of the respiratory tract in Thoroughbred yearlings with their subsequent race records to determine whether subjective assessment of airway function may be used as a predictor of future racing performance.

Design—Retrospective study.

Animals—427 Thoroughbred yearlings.

Procedures—Endoscopic examination findings were obtained from the medical records and the videoendoscopic repository of the Keeneland 1996 September yearling sales. Racing records were requested for the yearlings through the end of their 4-year-old racing season (1997–2000). Twenty-nine measures of racing performance were correlated with endoscopic findings. Subjective arytenoid cartilage movement grades were determined, using a 4-point grading scale (grade 1 = symmetrical synchronous abduction of the arytenoid cartilages; grade 4 = no substantial movement of the left arytenoid cartilage).

Results—Of the 427 Thoroughbred yearlings included in this study, 364 established race records, and 63 did not. Opinions regarding suitability for purchase, meeting conditions of the sale, and the presence of epiglottic abnormalities had no significant association with racing performance. Arytenoid cartilage movement grades were significantly associated with many of the dependent variables. However, palatine abnormalities were not predictive of inferior racing performance.

Conclusions and Clinical Relevance—Thoroughbred yearlings with grade-1 and -2 arytenoid cartilage movements had significantly better racing performance as adults, compared with yearlings with grade- 3 arytenoid cartilage movements. In contrast, epiglottic and palatine abnormalities were not predictive of inferior racing performance. Therefore, evaluation of laryngeal function, but not epiglottic or palatine abnormalities, using the 4-point grading system, should be the major factor in developing recommendations for prospective buyers. (J Am Vet Med Assoc 2001;219: xxx–xxx)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To evaluate the efficacy of prosthetic laryngoplasty with and without bilateral ventriculocordectomy for treatment of experimentally induced left laryngeal hemiplegia (LLH).

Animals

15 adult Standardbreds.

Procedure

Horses were allotted to 3 equal groups. Sham operation (group 1), prosthetic laryngoplasty (group 2), or prosthetic laryngoplasty with bilateral ventriculocordectomy (group 3) was performed after induction of LLH. Upper airway function testing was performed prior to left recurrent laryngeal neurectomy (LRLN), 14 days after LRLN, and 60 and 180 days after surgical treatment. Measurements were obtained at rest and at treadmill speeds corresponding to 75 and 100% of maximal heart rate. Videoendoscopy was performed at rest and during exercise in all horses prior to LRLN and 60 and 180 days after surgical treatment. Upper airway endoscopy was performed immediately after LRLN to document induction of grade-IV LLH. Also, horses in group 3 were endoscopically examined at 7, 14, 21, 28, and 120 days after surgical treatment to evaluate healing of the ventriculocordectomy sites.

Results

When horses were at rest, significant differences were not apparent between groups at any period or between periods for any measured variable. LRLN induced airway obstruction in all horses during exercise. In sham-operated horses, this obstruction was unaffected by time. In contrast, 60 and 180 days after surgical treatment, inspiratory flow limitations induced by LRLN were reversed in horses of groups 2 and 3. There were no significant differences between the 2 treatment groups. Endoscopy revealed the left arytenoid cartilage abducted beyond the intermediate position, but not touching the pharyngeal wall in all horses with a laryngeal prosthesis. After surgical treatment, 4 group-2 horses had filling of both ventricles with air during exercise. There was moderate to marked swelling of the ventriculocordectomy sites immediately after surgery, and this swelling resolved by 7 days after surgery. The ventriculocordectomy sites looked best at 14 and 180 days.

Conclusions

60 and 180 days after prosthetic laryngoplasty, upper airway function returned to pre-LRLN values in horses with experimentally induced LLH exercising at 100% of maximal heart rate. Combining ventriculocordectomy with prosthetic laryngoplasty does not further improve upper airway function in these horses. (Am J Vet Res 1996;57:1668–1673)

Free access
in American Journal of Veterinary Research

SUMMARY

Once-daily administration of aminoglycosides may be a safe and effective therapeutic regimen, on the basis of the microbiologic and pharmacokinetic characteristics of these antibiotics. This study was designed to determine serum and tissue concentrations following IV administration of gentamicin, at dosages of 6.6 mg/kg of body weight, every 24 hours, and 2.2 mg/kg, every 8 hours, for 10 days in adult horses. Nephrotoxicosis from these dosage regimens also was compared, and microbiologic effects, including postantibiotic effects, were determined with various concentrations of gentamicin against an equine clinical isolate of Pseudomonas aeruginosa. Treatment at the 6.6-mg/kg dosage resulted in maximal serum concentrations (77.93 ± 19.90 μg/ml, mean ± sem) and area under the concentration-vs-time curves (83.79 ± 14.97 μg.h/ml) that were significantly (P < 0.05) greater than those following treatment at the 2.2-mg/kg dosage (5.05 ± 0.50 μg/ml and 6.03 ± 0.66 μg.h/ml, respectively). Nephrotoxicosis was not induced with either dosage regimen, and postantibiotic effects were prolonged with a higher gentamicin concentration. This study provided evidence to support the use of once-daily gentamicin treatment in adult horses.

Free access
in American Journal of Veterinary Research