Endotracheal tube placement during computed tomography of brachycephalic dogs alters upper airway dimensional measurements

Computed tomography (CT) is used to document upper airway lesions in dogs with brachycephalic obstructive airway syndrome. The presence of an endotracheal tube during CT scanning is often required for general anesthesia. We hypothesized that the endotracheal tube placement would change the soft tissue dimensions of the upper airway. The aims of this prospective, method comparison study were to evaluate the reliability of the previously reported upper airway CT measurements with endotracheal tube placement, and to propose measurements that are minimally affected by the endotracheal tube. Twenty brachycephalic dogs were included in this study. Each dog underwent head/neck CT with an endotracheal tube, followed by a second scan without the endotracheal tube. Ten measurements of the soft palate, nasopharynx, and trachea were performed. Tracheal dimension was significantly larger with the endotracheal tube compared to without, whereas the soft palate cross‐sectional area was significantly smaller with the endotracheal tube than without the endotracheal tube. The influence of the endotracheal tube on the caudal nasopharynx cross‐sectional (transverse‐sectional) area varied with a mean proportional absolute difference of 35%. Rostral soft palate thickness, tracheal perimeter, and cross‐sectional area of the rostral nasopharynx were the measurements least affected by the endotracheal tube (intraclass correlation coefficient = 0.964, 0.967, and 0.951, respectively). Therefore, we proposed that these three measurements may be most useful for future brachycephalic obstructive airway syndrome studies that require CT scanning of intubated animals. However, with endotracheal tube placement, measurements of soft palate length, caudal nasopharyngeal cross‐sectional area, and trachea height and width may not be reliable.     

Effect of Prosthesis Number and Position on Rima Glottidis Area in Equine Laryngeal Specimens

Objective— To assess the effect of 1 or 2 laryngeal prosthetic sutures on rima glottidis areas in equine laryngeal specimens. Study Design— Experimental, randomized design. Animals— Cadaveric equine larynges (n=16). Methods— Larynges were collected from 10 horses; 2 sutures each were preplaced in the right and left sides of each larynx. A dorsal suture (DS) was placed through the caudal rim of the dorsal midline of the cricoid cartilage, under the cricopharyngeus muscle and through the proximal and rostral aspect of the muscular process. A lateral suture (LS) was placed 1.5 cm lateral to the DS and through the muscular process more distal and caudal to the 1st suture. Larynges were positioned in a customized stand and the rima glottidis photographed after each suture (LS or DS) or suture combination (CS) was tied in random sequence. An additional 6 larynxes were used to determine whether the tension applied to the sutures was repeatable. Sutures were preplaced in both the right and left side of each larynx as described above and each suture and CS was tied and released 3 times in each larynx. Photographs were taken of the rima glottidis after each suture or CS was tied generating 3 replicates for each suture configuration on each side of the 6 larynges. Results— Mean rima glottidis area was not different between DS and LS when tied alone (P=.85); however, mean area after CS (DS+LS) was greater than DS (P<.001) and LS (P<.001) alone. The coefficient of variation for the 6 suture patterns were low (1–7%) and the intraclass correlation coefficient estimates were very high (0.997–0.998) demonstrating excellent repeatability between replicates for each of the 3 suture configurations. Conclusion— Our results suggest that laryngoplasty using 2 prostheses; 1 placed dorsally in the cricoid and through the rostral and proximal muscular process and 1 placed 1.5 cm lateral to the 1st and more caudal and distal in the muscular process results in a greater cross sectional area of the rima glottidis than either suture used alone. Clinical Relevance— Seemingly prosthetic sutures contribute independently to each other in determining the contour of the rima glottidis. Use of 2 prosthetic sutures improves crosssectional area of the rima glottidis compared with each suture alone and may improve surgical outcome in laryngoplasty.     

Implications of different degrees of arytenoid cartilage abduction on equine upper airway characteristics

Reason for performing study: The necessary degree of arytenoid cartilage abduction (ACA) to restore airway patency at maximal exercise has not been determined. Objectives: Use computational fluid dynamics modelling to measure the effects of different degrees of ACA on upper airway characteristics of horses during exercise. Hypothesis: Maximal ACA by laryngoplasty is necessary to restore normal peak airflow and pressure in Thoroughbred racehorses with laryngeal hemiplegia. Methods: The upper airway was modeled with the left arytenoid in 3 different positions: maximal abduction; 88% cross‐sectional area of the rima glottis; and 75% cross‐sectional area of the rima glottis. The right arytenoid cartilage was maximally abducted. Two models were assumed: Model 1: no compensation of airway pressures; and Model 2: airway pressure compensation occurs to maintain peak airflow. The cross‐sectional pressure and velocity distributions for turbulent flow were studied at peak flow and at different positions along the airway. Results: Model 1: In the absence of a change in driving pressure, 12 and 25% reductions in cross‐sectional area of the larynx resulted in 4.11 and 5.65% reductions in peak airflow and 3.68 and 5.64% in tidal volume, respectively, with mild changes in wall pressure. Model 2: To maintain peak flow, a 6.27% increase in driving tracheal pressure was required to compensate for a cross‐sectional reduction of 12% and a 13.63% increase in driving tracheal pressure was needed for a cross‐sectional area reduction of 25%. This increase in negative driving pressure resulted in regions with low intraluminal and wall pressures, depending on the degree of airway diameter reduction. Conclusion: Assuming no increase in driving pressure, the decrease in left ACA reduced airflow and tidal volume. With increasing driving pressure, a decrease in left ACA changed the wall pressure profile, subjecting the submaximally abducted arytenoid cartilage and adjacent areas to airway collapse. Clinical relevance: The surgical target of ACA resulting in 88% of maximal cross‐sectional area seems to be appropriate.     

Quantification of nasal airflow resistance in English bulldogs using computed tomography and computational fluid dynamics

Stenotic nares, edematous intranasal turbinates, mucosal swelling, and an elongated, thickened soft palate are common sources of airflow resistance for dogs with brachycephalic airway syndrome. Surgery has focused on enlarging the nasal apertures and reducing tissue of the soft palate. However, objective measures of surgical efficacy are lacking. Twenty‐one English bulldogs without previous surgery were recruited for this prospective, pilot study. Computed tomography was performed using conscious sedation and without endotracheal intubation using a 128 multidetector computed tomography scanner. Raw multidetector computed tomography data were rendered to create a three‐dimensional surface mesh model by automatic segmentation of the air‐filled nasal passage from the nares to the caudal soft palate. Three‐dimensional surface models were used to construct computational fluid dynamics models of nasal airflow resistance from the nares to the caudal aspect of the soft palate. The computational fluid dynamics models were used to simulate airflow in each dog and airway resistance varied widely with a median 36.46 (Pa/mm)/(l/s) and an interquartile range of 19.84 to 90.74 (Pa/mm)/(/s). In 19/21 dogs, the rostral third of the nasal passage exhibited a larger airflow resistance than the caudal and middle regions of the nasal passage. In addition, computational fluid dynamics data indicated that overall measures of airflow resistance may significantly underestimate the maximum local resistance. We conclude that computational fluid dynamics models derived from nasal multidetector computed tomography can quantify airway resistance in brachycephalic dogs. This methodology represents a novel approach to noninvasively quantify airflow resistance and may have utility for objectively studying effects of surgical interventions in canine brachycephalic airway syndrome.     

Medium term endoscopic assessment of the surgical outcome following laryngeal saccule resection in brachycephalic dogs

Laryngeal saccule eversion has been widely reported as an important component of brachycephalic airway obstructive syndrome (BAOS). The authors hypothesised that saccules affected by acute histological changes in patients showing marked improvement following palate and nares surgery might spontaneously return to normal; moreover, spontaneous resolution of the eversion in patients with fibrotic saccules and/or without clinical improvement following BAOS surgery might be impossible and, on the contrary, the persistence of turbulent airflow and associated ongoing inflammation might lead to aberrant tissue proliferation after resection. In order to demonstrate our hypotheses, the authors decided to perform a unilateral sacculectomy and to postpone and assess the need for the execution of the contralateral saccule resection according to the findings of a second-look laryngoscopy. Ten dogs were enrolled. None of the saccules left in situ underwent spontaneous resolution of the eversion. In one dog, after sacculectomy, proliferation of a soft tissue lesion endoscopically similar to a newly formed saccule occurred. The results of the present study suggest that spontaneous resolution of saccule eversion is uncommon, even after the correction of the primary abnormalities (palate, nares). Resection of the saccules can relieve ventral rima glottidis obstruction; however, secondary intention healing might occasionally result in the recurrence of the obstruction.     

Disorders of the larynx.

The upper respiratory tract is a frequent cause of exercise intolerance in horses, particularly in racing horses. There are a myriad of laryngeal abnormalities that may restrict airflow at the rima glottidis. Careful endoscopic examination is a crucial part of the examination of any racing horse suffering from poor performance. There has recently been interest in spectrum analysis of respiratory sounds. It has been determined that laryngeal hemiplegia and dorsal displacement of the soft palate have unique sound patterns. Therefore, spectrum analysis of respiratory sounds may prove to be useful in the diagnosis of laryngeal disorders in horses. Accurate diagnosis and appropriate surgical intervention are necessary to provide the horse the best chance of returning to its full athletic potential.     

Upper airway dysfunction associated with collapse of the apex of the corniculate process of the left arytenoid cartilage during exercise in 15 horses

OBJECTIVE: To report dynamic collapse of the apex of the left corniculate process under the right corniculate process into the airway at the dorsal apposition of the paired arytenoid cartilages during exercise as a cause of upper airway dysfunction in horses. DESIGN: Retrospective study. ANIMALS: Fifteen horses with a history of poor performance and/or upper respiratory tract noise during exercise. METHODS: Video recordings of all horses referred for upper airway evaluation using high-speed treadmill videoendoscopy (HSTV) between January 1998 and December 2003 were reviewed. Records of horses that developed dynamic collapse of the apex of the left corniculate process into the airway were included. Clinical history, age, gender, breed, and use of the horse were retrieved. RESULTS: Of 309 horses referred for examination for poor performance and/or upper respiratory tract noise during exercise, 15 (4.9%) had collapse of the apex of the left corniculate process under the right and into the airway at the dorsal apposition between the paired arytenoid cartilages during HSTV. There were 3 females and 13 males, aged from 2 to 5 years. Five horses had previous surgery for left recurrent laryngeal neuropathy (RLN): 2 had nerve muscle pedicle graft and 3 had laryngeal prosthesis. During HSTV, all 15 horses had progressive collapse of the apex of the left corniculate process under the right at the dorsal apposition of the 2 arytenoid cartilages, and into the dorsal aspect of the rima glottidis. Review of video recordings revealed that collapse of the apex of the corniculate process was followed by progressive collapse of the left aryepiglottic fold and left vocal fold. The ventral aspect of the left corniculate cartilage maintained abduction in all horses. Two horses also had progressive collapse of the right vocal fold, 1 had rostral displacement of the palatopharyngeal arch, and another had dorsal displacement of the soft palate. CONCLUSIONS: Dynamic collapse of the apex of the left corniculate process of the arytenoid cartilage under the right is an uncommon cause of upper airway dysfunction in horses and the pathogenesis is unclear. We speculate that the left arytenoideus transversus muscle is unable to support the dorsal apposition between the arytenoid cartilages. This loss of support allows the elastic cartilage of the left corniculate process to collapse under the right and into the airway, as inspiratory pressure increases during exercise. This condition may be associated with an unusually advanced neuropathy of the adductor components of the left recurrent laryngeal nerve and may be an unusual manifestation of RLN; however, this is speculative and further investigation is required to determine its cause. CLINICAL RELEVANCE: Dynamic collapse of the apex of the left corniculate process and into the airway at the dorsal apposition between the paired arytenoid cartilages can only be diagnosed during HSTV. It is an uncommon cause of upper airway dysfunction but may affect the athletic potential of racing Thoroughbreds and Standardbreds.     

The effect of two modifications of unilateral arytenoid lateralization on rima glottidis area in dogs

OBJECTIVES: To evaluate the clinical outcome and percentage increase in rima glottidis area achieved using a combined technique of cricoarytenoid and thyroarytenoid cartilage lateralization compared with cricoarytenoid cartilage lateralization alone in live anesthetized dogs clinically affected with bilateral laryngeal paralysis. STUDY DESIGN: Randomized prospective clinical study. ANIMALS: Twenty dogs with bilateral laryngeal paralysis. Methods-Bilateral laryngeal paralysis was diagnosed by direct laryngoscopy. Each dog was allocated randomly to 1 of 2 surgical groups: CAL (cricoarytenoid lateralization) and CTAL (cricoarytenoid and thyroarytenoid lateralization). Photographs were taken of each larynx before and after surgery, the images were digitized, and the preoperative and postoperative areas of each rima glottidis were measured. The percentage increase in rima glottidis area produced by each of the arytenoid lateralization procedures was compared. Follow-up was obtained by telephone survey of owners and referring veterinarians. RESULTS: There was no significant difference in mean (+/- SD) percentage increase in rima glottidis area for the CAL group (241.5 +/- 42.9%) or the CTAL group (236.4 +/- 44.5%). Clinical follow-up (median, 18 months postoperatively) indicated 60% of the dogs were still alive and only 1 dog had died as a result of complications related to surgery. CONCLUSIONS: CTAL for the treatment of canine laryngeal paralysis does not significantly increase rima glottidis area compared with CAL alone. The mean percentage increase in rima glottidis area obtained with both procedures was comparable to previously reported mean increases with CAL in live anesthetized dogs. Both procedures resulted in good long-term clinical outcome. CLINICAL RELEVANCE: CTAL is as effective as CAL in providing an increased rima glottidis for the treatment of bilateral laryngeal paralysis in dogs.     

Cross-sectional area of the aditus laryngis and rima glottidis before and after transection of the left recurrent laryngeal nerve in the horse

The ventral-to-dorsal height of the rima glottidis was measured from lateral pharyngeal radiographs after correction for magnification. The rima glottidis height was used to enlarge accurately endoscopic photographs of 5 horses taken before and after transection of the left recurrent laryngeal nerve. Areas of the rima glottidis and aditus laryngis were measured, using a computerized digitizer. Mean area of the aditus laryngis was 1,908 mm2 before neurectomy and 1,346 mm2 after neurectomy (P = 0.025). Mean area of the rima glottidis was 1,198 mm2 before neurectomy and 805 mm2 after neurectomy (P = 0.025). Mean width of the rima glottidis was 31 mm before neurectomy and 20 mm after neurectomy (P = 0.001). Significant differences were not found between the pre- and postneurectomy heights of the rima glottidis.     

Sternothyroideus myotomy, staphylectomy, and oral caudal soft palate photothermoplasty for treatment of dorsal displacement of the soft palate in 102 thoroughbred racehorses

Objective— To compare racing performance before and after sternothyroideus myotomy, staphylectomy, and oral caudal soft palate photothermoplasty in Thoroughbred racehorses with intermittent dorsal displacement of the soft palate (DDSP).
Study Design— Retrospective study.
Animals— Thoroughbred racehorses (n=102) with DDSP.
Methods— Retrieved data included signalment, primary complaint, and upper respiratory tract endoscopic finding. Lifetime race records were compared for earnings per start before and after surgery, days to 1st start, and races won postoperatively.
Results— Comparing mean earnings per start for 3 races before ($2792) and after ($3806) surgery, racing performance improved significantly after surgery in 63% (46/73) of horses that competed in at least 1 race before and after surgery ( P =.02). Mean and median days to 1st start after surgery were 109 and 69 days, respectively. Of horses that raced postoperatively 65% (60/92) won at least 1 race, and 77% (71/92) raced in >5 races after surgery.
Conclusions— Sternothyroideus myotomy, staphylectomy, and oral caudal soft palate photothermoplasty significantly improved racing performance in experienced Thoroughbred racehorses with performance limiting DDSP, and overall had a similar outcome to other reported surgical techniques for treatment of DDSP.
Clinical Relevance— Sternothyroideus myotomy, staphylectomy, and oral caudal soft palate photothermoplasty should be considered as a surgical approach to correction of DDSP in Thoroughbred racehorses; however, it is possible that staphylectomy may not be necessary to achieve a desirable outcome.     

Chronic chondritis of the arytenoid cartilages in a pony mare

The upper respiratory tract of a pony mare with marked exercise intolerance and respiratory stridor was examined with a flexible fibreoptoscope. Both arytenoids were adducted and distorted. A diagnosis of bilateral chondritis of the arytenoids was made and confirmed at autopsy after surgery to enlarge the rima glottidis was unsuccessful. Other space occupying lesions of the rima glottidis are discussed and theories on the aetiology are postulated.     

Persistent dorsal displacement of the soft palate attributable to a frenulum of the epiglottis in a racing Thoroughbred

CASE DESCRIPTION: A 7-year-old sexually intact male Thoroughbred racehorse was evaluated because of exercise intolerance, respiratory tract noise, and coughing when eating. CLINICAL FINDINGS: A persistent dorsal displacement of the soft palate was identified during endoscopic examination of the upper portions of the respiratory tract. Radiography of the pharyngeal and laryngeal regions revealed a hypoplastic epiglottis that was ventral to, and not in contact with, the soft palate. The horse was anesthetized, and an oral endoscopic examination revealed a subepiglottic frenulum that had resulted in the dorsal displacement of the soft palate. TREATMENT AND OUTCOME: The frenulum was transected transendoscopically by use of a diode laser. Twenty-four hours following surgery, repeat endoscopic and radiographic examinations revealed that the epiglottis had returned to its correct anatomic position in relation to the soft palate. Four weeks after surgery, endoscopy of the upper portions of the airway revealed recurrence of the dorsal displacement of the soft palate. CLINICAL RELEVANCE: A subepiglottic frenulum should be considered as a cause of persistent dorsal displacement of the soft palate in horses. An endoscopic examination of the oropharyngeal region should be performed in horses prior to undertaking any surgical interventions to treat persistent dorsal displacement of the soft palate.     

A Comparison of the Effects of Unilateral Thyroarytenoid Lateralization Versus Cricoarytenoid Laryngoplasty on the Area of the Rima Glottidis and Clinical Outcome in Dogs with Laryngeal Paralysis

OBJECTIVE: To compare the clinical effects of unilateral thyroarytenoid lateralization versus unilateral cricoarytenoid laryngoplasty for the treatment of canine laryngeal paralysis. Study Design-A prospective, clinical trial. ANIMALS: Twenty client-owned dogs admitted to Glasgow University Veterinary Hospital (GUVH) between 1997 and 1999 with a diagnosis of laryngeal paralysis. METHODS: A thorough evaluation of each dog was undertaken that included history, physical and neurologic examinations, complete blood count, serum biochemistry profile, serum thyroxine (T4) level, and thyroid-stimulating hormone (TSH) assay. The exercise tolerance of each dog was investigated by assessing respiratory rate and arterial blood gas analysis at rest and after 5 minutes of mild exercise. Animals were included in the study on the basis of a definitive diagnosis of laryngeal paralysis made by endoscopic observation of the larynx in the lightly anesthetized patient. The animals were randomly assigned to 1 of 2 treatment groups: unilateral thyroarytenoid lateralization or unilateral cricoarytenoid laryngoplasty, with all procedures being performed by the same surgeon. Video images of the rima glottidis were recorded pre- and postoperatively using video endoscopy. Video images were digitized and the area of the rima glottidis measured using image-analysis software. An increase in the area of the rima glottidis was expressed as a percentage of the preoperative area. All animals were reassessed 6 weeks' postoperatively, and exercise tolerance tests were repeated. RESULTS: The mean increase in the area of the rima glottidis postoperatively when compared with the preoperative area was 140% for those animals undergoing unilateral thyroarytenoid lateralization (range, 120%-158%) and 207% for those animals undergoing unilateral cricoarytenoid laryngoplasty (range, 183%-228%). This difference was statistically significant (P < .0001). At the 6-week postoperative examination, there was no significant difference in improvement between the 2 groups when compared on either a clinical basis or exercise tolerance tests. The mean surgical time in the 2 groups was 25 minutes for thyroarytenoid lateralization and 43 minutes for cricoarytenoid laryngoplasty. This was a statistically significant difference (P = .002). CONCLUSION: Although increase in area of the rima glottidis was significantly greater after unilateral cricoarytenoid laryngoplasty compared with unilateral thyroarytenoid lateralization, no difference in clinical outcome could be detected. However, the cricoarytenoid laryngoplasty procedure required significantly more surgical time. CLINICAL RELEVANCE: Both unilateral cricoarytenoid laryngoplasty and unilateral thyroarytenoid lateralization are successful methods for the treatment of laryngeal paralysis; however, thyroarytenoid lateralization requires less surgical time to perform.     

Can an external device prevent dorsal displacement of the soft palate during strenuous exercise?

REASONS FOR PERFORMING STUDY: Dorsal displacement of the soft palate (DDSP) is a common condition in racehorses for which various surgical treatments are often performed. In light of recent findings that suggested the position of the larynx may influence the occurrence of DDSP, we investigated whether a noninvasive mean of affecting the position of the larynx could be effective in the management of DDSP. HYPOTHESIS: An external device (laryngohyoid support; LHS) positioning the larynx in a more rostral and dorsal location and preventing caudal displacement of the basihyoid bone would be effective in preventing DDSP during strenuous exercise. METHODS: Ten horses were exercised on a high-speed treadmill under 4 different treatment conditions: control (n = 10); control with external device (n = 10); after bilateral resection of thyrohyoid (TH) muscles (n = 7); and after bilateral resection of TH muscles with external device (n = 7). Two trials were performed randomly for each of the 4 conditions. In Trial 1, videoendoscopic images of the upper airway, pharyngeal and tracheal static pressures, and arterial blood gases were collected. In Trial 2, airflow measurement combined with mask and tracheal static pressure was obtained, and upper airway impedance calculated. The trials allowed calculation of airway impedance and respiratory frequency, and assessment of ventilation using arterial PO2 and PCO2. RESULTS: Under control conditions, none of the 10 horses developed DDSP. There was no statistically significant effect from the LHS on airway impedance or respiratory frequency, nor on arterial PO2 and PCO2. Seven of the 10 horses developed DDSP during exercise after resection of the TH muscles. None of these 7 horses continued to experience DDSP during exercise with the external device. In the latter group and condition, the LHS significantly improved inspiratory and expiratory flow and impedance. CONCLUSIONS: The LHS helped prevent experimentally induced DDSP at exercise, probably by statically positioning the larynx in a more rostral and dorsal position. POTENTIAL RELEVANCE: Field studies are required to investigate whether the LHS can successfully prevent DDSP in horses with naturally occurring disease.     

Dynamic obstructions of the equine upper respiratory tract. Part 1: observations during high-speed treadmill endoscopy of 600 Thoroughbred racehorses

REASONS FOR PERFORMING STUDY AND OBJECTIVE: To review the prevalence of single and complex forms of dynamic airway obstructions within a large group of Thoroughbred horses in training referred for investigation of poor performance. METHODS: Video-endoscopic recordings of the upper respiratory tract made during a standardised treadmill exercise test of 600 Thoroughbred racehorses were reviewed and analysed in real time and slow motion to identify dynamic collapse by the tissues bordering onto the pharyngeal and laryngeal airways. RESULTS: Dynamic collapse within the nasopharynx or larynx was confirmed in 471 of the 600 horses. Dorsal displacement of the soft palate (DDSP; 50%) and palatal instability (33%) were the disorders most frequently identified. It was concluded that deglutition is not a significant event in the triggering of DDSP. Complex forms of dynamic collapse were present in 30% of the horses with upper respiratory tract obstructions. A significant influence of age on the prevalence of DDSP and dynamic laryngeal collapse was identified. There was an increased risk of DDSP in younger horses, and of laryngeal collapse in older horses. No association with gender or format of racing was identified. CONCLUSIONS AND POTENTIAL RELEVANCE: Palatal instability and DDSP comprised the most frequently encountered forms of dynamic collapse within the upper respiratory tract of the Thoroughbred racehorses in this study and are probably expressions of the same nasopharyngeal malfunction. Complex obstructions, i.e. where more than one structure collapses into the airway, occur frequently and therefore treatments that address solitary disorders may often be unsuccessful. Younger horses were found to be at greater risk of sustaining DDSP while older horses seemed more at risk to vocal cord collapse but not to collapse of the arytenoid cartilage itself.     

Stabling is associated with airway inflammation in young Arabian horses

We examined the effect of stabling on upper and lower airway inflammation in 14 yearling Arabian horses that had been at pasture since birth. Horses were divided into 2 groups of 7. One group was stabled for 3 months and the other remained at pasture. The groups were then switched over for another 3 months. The nasopharynx, guttural pouches and trachea were examined endoscopically and bronchoalveolar lavage performed every month. An upper airway inflammation score was devised based on the magnitude of pharyngeal lymphoid hyperplasia and guttural pouch inflammation. During stabling this score remained constant, whereas it decreased during the 3 months at pasture. Stabling was also associated with a higher number and percentage of neutrophils in bronchoalveolar lavage fluid and with a smaller percentage of lymphocytes. There was no correlation between upper airway inflammation score and bronchoalveolar lavage cytology. During a nasal occlusion test, dorsal displacement of the soft palate occurred more times in stabled than in pastured horses, but this was heavily biased by the results from one animal. We conclude that stabling is associated with inflammation of both the upper and lower airway of young horses.     

Dynamic computed tomography evaluation of the nasopharynx in normal Beagle dogs

Pharyngeal collapsibility has been used as diagnostic criteria in dogs, whereas the normal range and quantitative method have not been studied. Dynamic and static computed tomography (CT) was performed in 23 normal Beagle dogs to quantify the nasopharyngeal collapsibility at different locations. Using dynamic CT, maximum and minimum nasopharyngeal cross-sectional areas (CSAs) were measured at the level of the cranial end of the soft palate, pterygoid hamulus, foramen lacerum, bony labyrinth, and caudal end of the soft palate. The ratio of all maximum and minimum CSA to nasopharyngeal CSA at the level of the caudal hard palate (rCSAmax and rCSAmin) and the nasopharyngeal collapsibility were calculated. The differences of rCSAmax, rCSAmin, and nasopharyngeal collapsibility were analyzed at various locations. The nasopharyngeal collapsibility at the level of foramen lacerum, bony labyrinth, and caudal end of soft palate were higher than the others. At the level of the caudal end of the soft palate, rCSAmin was lower than that of the foramen lacerum and bony labyrinth, whereas rCSAmax at foramen lacerum was higher than that of the caudal end of the soft palate. These results indicated that the nasopharynx at the level of foramen lacerum and caudal end of the soft palate were considered notable locations for evaluating collapsibility. Dynamic CT could show the nasopharyngeal dynamic profile and will be an adequate modality for evaluating nasopharynx. Our results will be helpful for further comparative studies in dogs with and without nasopharyngeal collapse.