Premium
Effect of laryngoplasty on respiratory noise reduction in horses with laryngeal hemiplegia
Author(s) -
BROWN J. A.,
DERKSEN F. J.,
STICK J. A.,
HARTMANN W. M.,
ROBINSON N. E.
Publication year - 2004
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.2746/0425164044868440
Subject(s) - medicine , airway , laryngoplasty , anesthesia , larynx , respiratory system , airway obstruction , surgery
Summary Reasons for performing study : Laryngoplasty is the technique of choice for treatment of laryngeal hemiplegia, with the aim of improving airway function and/or eliminating respiratory noise. However, there are no quantitative data in the literature describing the effect of laryngoplasty on upper airway noise or its relationship to upper airway mechanics in horses with laryngeal hemiplegia. Objectives : To determine whether laryngoplasty reduces respiratory noise in exercising horses with laryngeal hemiplegia; and to establish whether the degree of upper airway obstruction can be predicted by upper airway noise, or the degree of arytenoid abduction correlated with airway obstruction and noise production. Methods : Six Standardbred horses with normal upper airways during maximal exercise were used. Respiratory sounds and inspiratory transupper airway pressure (P ui ) were measured in all horses before and after induction of laryngeal hemiplegia and 30, 60 and 90 days after laryngoplasty. Inspiratory sound level (SL) and the sound intensity of the 3 inspiratory formants (F 1 , F 2 and F 3 , respectively) were measured using a computer‐based sound analysis programme. The degree of abduction was graded by endoscopic visualisation 1, 30, 60 and 90 days post operatively. Linear regression analysis was used to determine correlations between P ui , sound indices and grades of arytenoid abduction. Results : In laryngeal hemiplegia‐affected horses, P ui , inspiratory SL and the sound intensity of F 1 , F 2 and F 3 were significantly increased. At 30 days following laryngoplasty, the sound intensity of F 1 and P ui returned to baseline values. The sound intensities of F 2 , F 3 and SL were significantly improved from laryngeal hemiplegia values at 30 days post operatively, but did not return to baseline at any measurement period. Sound level, F 2 and F 3 were significantly correlated with P ui (P<0.05), but the correlations were weak (r 2 = 0.26, 0.35 and 0.40, respectively). Grade of abduction and F 2 were positively and significantly correlated (P<0.006, r 2 = 0.76). Grade of arytenoid abduction and P ui were not correlated (P = 0.12). Conclusions : Laryngoplasty reduced inspiratory noise in laryngeal hemiplegia‐affected horses by 30 days following surgery, but did not return it to baseline values. While upper airway noise and P ui were correlated, this relationship was insufficiently strong to predict P ui from noise in individual animals. The degree of arytenoid abduction was not correlated with P ui , but was positively correlated with noise production. Potential relevance : Laryngoplasty reduces upper airway noise in horses with laryngeal hemiplegia, but is not as effective as bilateral ventriculocordectomy in this regard, although respiratory noise reduction occurs more rapidly than with bilateral ventriculocordectomy. Residual noise during exercise cannot be used as a predictor of improvement in upper airway function in individual horses following laryngoplasty. The degree of arytenoid abduction obtained following surgery does not affect upper airway flow mechanics. Interestingly, we found that the greater the arytenoid abduction, the louder the respiratory noise.