Advertisement

Effect of topical anesthesia of the laryngeal mucosa on upper airway mechanics in exercising horses

Susan J. HolcombeDepartment of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48624.

Search for other papers by Susan J. Holcombe in
Current site
Google Scholar
PubMed
Close
 VMD, PhD
,
Frederik J. DerksenDepartment of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48624.

Search for other papers by Frederik J. Derksen in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
Cathy BerneyDepartment of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48624.

Search for other papers by Cathy Berney in
Current site
Google Scholar
PubMed
Close
 BS
,
Adrianne C. BeckerDepartment of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48624.

Search for other papers by Adrianne C. Becker in
Current site
Google Scholar
PubMed
Close
 BS
, and
Natalie T. HornerDepartment of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48624.

Search for other papers by Natalie T. Horner in
Current site
Google Scholar
PubMed
Close
 BS

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)

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)