Assessment of computed tomography derived cricoid cartilage and tracheal dimensions to evaluate degree of cricoid narrowing in brachycephalic dogs

The aims of this observational, analytical, retrospective study were to (i) obtain computed tomographic (CT) cricoid dimensions (height, width, and transverse‐sectional area), (ii) compare the cricoid dimensions between brachycephalic and mesaticephalic breeds, and (iii) compare cricoid cartilage dimensions between dogs without and affected with brachycephalic airway syndrome. The study is important to help to further evaluate and understand the anatomical components of brachycephalic airway syndrome. Measurements were performed in 147 brachycephalic and 59 mesaticephalic dogs. The cricoid cartilage was found to be significantly more oval in Pugs and French Bulldogs compared to mesaticephalic breeds. The cricoid cartilage transverse‐sectional area was smallest for the Pug and, after adjusting for weight, significantly smaller for Pugs (P < 0.001), Boston Terriers (P = 0.001), and French Bulldogs (P < 0.001) compared to Jack Russell Terriers. The tracheal transverse‐sectional area at C4 of English Bulldogs was significantly smaller than for Jack Russell Terriers (P = 0.005) and Labradors (P < 0.001). The cricoid cartilage transverse‐sectional area:weight ratio was significantly lower in brachycephalic breeds compared to mesaticephalic breeds (P < 0.001). The cricoid cartilage:trachea at C4 transverse‐sectional area for brachycephalic dogs was significantly larger than for mesaticephalic dogs (<0.001), demonstrating that the trachea was the narrowest part of the airway. No significant differences were found for cricoid dimensions between dogs affected with and without brachycephalic airway syndrome. However, large individual variation was found among the brachycephalic breeds and further studies investigating the relationship between cricoid cartilage size, laryngeal collapse, concurrent tracheal hypoplasia, and/or severity of brachycephalic airway syndrome are warranted.     

Intrathoracic tracheal rupture

This paper reports five new cases of intrathoracic tracheal rupture in cats, and summarizes these cases in conjunction with 11 cases from the literature. Most cats had no obvious respiratory signs at the time of injury, and in half of them the tracheal rupture was the only injury. The interval from trauma to onset of dyspnoea ranged from 1 to 28 days (median 12.5 days). Radiographic findings include loss of continuity of the trachea, often with a gas-filled diverticulum present between separated tracheal rings. With careful attention to surgical technique and anaesthetic management the prognosis for these cats is excellent. All eight of the cats reported in the last 14 years having surgical correction survived and returned to normal. The surgical anatomy, approach and tracheal anastomosis technique is described and recommendations for anaesthetic management are made.     

Canine tracheal collapse

Tracheal collapse occurs most commonly in middle‐aged, small breed dogs. Clinical signs are usually proportional to the degree of collapse, ranging from mild airway irritation and paroxysmal coughing to respiratory distress and dyspnoea. Diagnosis is made by documenting dynamic airway collapse with radiographs, bronchoscopy or fluoroscopy. Most dogs respond well to medical management and treatment of any concurrent comorbidities. Surgical intervention may need to be considered in dogs that do not respond or have respiratory compromise. A variety of surgical techniques have been reported although extraluminal ring prostheses or intraluminal stenting are the most commonly used. Both techniques have numerous potential complications and require specialised training and experience but are associated with good short‐ and long‐term outcomes.     

Intraluminal tracheal stenting for treatment of tracheal narrowing in three cats

OBJECTIVE: To describe the use of intraluminal tracheal stenting in 3 cats with either benign or malignant tracheal obstruction. STUDY DESIGN: Retrospective clinical study. ANIMALS: Three client-owned cats. METHODS: Medical records were reviewed and information regarding signalment, clinical signs, physical examination findings, diagnostic tests performed, treatment, outcome and follow-up were retrieved. Intraluminal tracheal stent placement was performed as previously described in the literature. RESULTS: Three cats received intraluminal tracheal stents for the treatment of tracheal obstruction due to 3 different underlying causes: stricture secondary to traumatic endotracheal intubation, stricture secondary to a previous tracheotomy, and neoplasia. Self-expanding metallic stents of varying sizes were placed, and all cats recovered uneventfully from the procedures. The cat with tracheal neoplasia was euthanized because of pulmonary metastatic disease 6 weeks post-stent placement. The two cats with tracheal obstructions secondary to benign strictures are currently 39 months and 32 weeks post-stent placement, respectively. No complications were noted during the post-stent period in any of the 3 cats. CONCLUSIONS: Intraluminal tracheal stenting was easily, safely, and rapidly performed without complications and resulted in immediate improvement in clinical signs in all three cases. None of the cats in this study developed significant stent-associated complications during the study period. CLINICAL RELEVANCE: Intraluminal tracheal stenting has the potential to be a viable option for the treatment of tracheal obstruction in cats and perhaps for similar disease processes in other veterinary patients.     

Morphological study of tracheal shape in donkeys with and without tracheal obstruction

Reason for performing study: There is limited information on the gross tracheal morphology of donkeys with or without tracheal abnormalities. Objectives: To: 1) examine the morphology of tracheas of donkeys with and without clinical and/or post mortem evidence of tracheal obstruction; 2) record the cross‐sectional dimensions and shapes of tracheal rings at fixed sites; and 3) document prevalence, sites and characteristics of detected tracheal abnormalities. Methods: The tracheas of 75, predominantly aged (median age 30 years, range 7–48 years) donkeys that died or were subjected to euthanasia on humane grounds were examined. Five had severe dyspnoea due to tracheal obstruction (with intercurrent lung disease in 3), while 7 had post mortem evidence of severe tracheal airway obstruction. Every 5th tracheal ring was dissected free and the inner and outer vertical and transverse dimensions and cross sectional areas were measured. Each dissected ring was photographed and the shape of the trachea was classified as normal or, in one of 6 abnormal grades, according to the type and degree of structural abnormality present. Results: The tracheas had a mean of 43 (range 34–50) tracheal rings that tended to be more oval in shape in the distal cervical region. Only 31.2% of rings examined had a circular to oval shape. Dorso‐ventral flattening was present in 0.9% of tracheal rings, dorsal ligament separation in 24.4%, slight cartilage deformity in 26.0%, moderate cartilage deformity in 10.4%, marked cartilage deformity in 1.9% and miscellaneous other abnormalities in 4.9% of tracheal rings. The 12 donkeys with ante or post mortem evidence of tracheal obstruction had significantly increased tracheal abnormality grade in comparison to the remaining donkeys. Conclusions and potential relevance: Structural tracheal abnormalities are present in most old donkeys, but generally do not cause clinical problems in these sedentary animals unless intercurrent pulmonary disease is present.     

A simple,inexpensive method for estimating linear tree dimensions

A simple, inexpensive method for estimating linear tree dimensions is described and tested. The method is based on a visual overlap of two images, namely, the tree to be estimated and a group of length scales incorporated on a colour slide. Additional advantages of the proposed method include accuracy, application by one person only and both vertical and horizontal estimating capabilities.     

Experimental rabies in skunks: oral, nasal, tracheal and intestinal exposure.

Striped skunks (Mephitis mephitis) were exposed to challenge virus standard rabies virus by feeding infected mouse brain in suspension or as intact brain free choice, by forced feeding of suspension, and by intranasal, intratracheal and intraintestinal instillation of suspension. All of five skunks exposed intranasally, two of five exposed intratracheally and two of ten exposed by forced feeding developed rabies. None of the skunks exposed to challenge virus standard virus, by other methods, became rabid. Most of the survivors, when challenged intramuscularly with street rabies virus at six months, developed rabies. The results indicate that the skunk is much more susceptible to challenge virus standard rabies virus given intranasally than by the other methods used. When disease occurs following oral administration, infection may be associated with prolonged contact with buccal mucosa or accidental contact with nasal mucosa. Survivors had little or no protection when challenged intramuscularly with street rabies virus.     

Effect of tracheal mucus and tracheal cytology on racing performance in Thoroughbred racehorses

REASON FOR PERFORMING STUDY: Accumulations of mucus within the trachea are often found during endoscopic examinations of the airways of poorly performing racehorses, but the clinical importance of this finding is unknown. OBJECTIVES: To determine the effect of tracheal mucus, pharyngeal lymphoid hyperplasia (PLH) and cytological indices of tracheal aspirate on racing performance in Thoroughbred horses assessed by race place and whether the horse was raced. METHODS: Endoscopic examination of the nasopharynx, larynx and trachea was performed, and a tracheal aspirate obtained monthly at Thistledown racetrack from April to December, 2002 and 2003. Horses received a score of 0-4 for the degree of PLH and 0-4 for the amount of mucus visible in the trachea. The tracheal aspirate was assessed for turbidity, and total and differential cell counts. Generalised estimating equations models were used as repeated measures models for each risk factor and the level of association assessed through the risk factor's P value in the model. RESULTS: Moderate to severe tracheal mucus (2-4) was a risk factor for poor racing performance. There was no association between degree of PLH, cell counts or turbidity of tracheal wash fluid and racing performance. However, horses that raced had higher total neutrophil counts in tracheal wash aspirates than horses that did not race. CONCLUSIONS: Grades 2-4 tracheal mucus should be considered a potential cause of poor racing performance in Thoroughbred horses. CLINICAL RELEVANCE: Because moderate to severe tracheal mucus accumulation, and not increased tracheal neutrophils, was a risk factor for poor racing performance, functionally significant airway inflammation may best be confirmed by the presence of mucus rather than increased number of neutrophils in the trachea.     

Structural considerations in tracheal disease

Examinations were made of three sections of trachea obtained from eight dogs. The sections examined were at the regions of the second ring caudal to the larynx, the thoracic inlet, and the origin of the brachiocephalic trunk. Measurements were made of the lateral and ventrodorsal diameters, the lumen area of the trachea, the width and thickness of the tracheal cartilages, and the thickness of the trachealis muscle. Cell counts-per-square-micrometer of the cartilage and trachealis muscle were made. The results of these measurements were subjected to statistical analyses by means of one-way and two-way analyses of variance. The tracheal diameters, cartialge thickness, muscle thickness, and tracheal lumen area had significantly different measurements among the areas compared with both statistical methods. Ventrodorsal tracheal diameter and lumen area were not found to have significantly different measurements between the levels of the thoracic inlet and the brachiocephalic trunk. The cell counts did not have significantly different values among the areas considered when body weight was not a factor, but the values were significant when weight was a factor.     

Pelvic dimensions, bodyweight and parturition in rare breeds of sheep

External pelvic measurements were made in 837 adult ewes of 21 different breeds, the majority of which were rare breeds. The pelvic measurements were the intertuber coxal diameter, the distance between the lateral tuber ischii and medial tuber ischii and the rump length. There was a considerable breed variation with the Soay ewes having the smallest and the Suffolk the largest pelvic dimensions. However when the relationship between pelvic size and ewe's bodyweight was compared, the ratio of the medial tuber ischii:bodyweight and sum of four pelvic dimensions:bodyweight of the Soay was over twice that of the Suffolk ewes. When the size of the pelvis was related to the lamb's birth weight the Soay's was relatively larger. Dystocia caused by feto-maternal disproportion occurred in 19 ewes, all with singletons. In 16 cases involving four different breeds the birth weights of the lambs were significantly larger than those lambs which were born normally.     

Yolk sac, body dimensions and hatchling quality of ducklings, chicks and poults

1. One-day-old chicks of Pekin duck, turkey, layer fowl and broiler fowl were examined for bacteria in the yolk sac and yolk fluid. 2. Whole hatchling, yolk-free hatchling and yolk sac weights were recorded for all species along with crown-rump length and beak-tip to toe-tip length. 3. Bacteriology revealed positive results for the whole yolk sacs of 43 to 64% of the birds in the sample of ducklings, poults and layer chicks. Broiler chicks had a 6.6% incidence of bacteria isolated from the whole yolk sac. By contrast, there were very few positive results from swabs of yolk fluid for any of the bird types. 4. The presence of bacteria in the yolk sac of hatchlings suggests that there is colonisation, rather than infection, of the yolk sac membrane during the hatching period or the first few hours post-hatching. Isolation of bacteria from the yolk sacs of young chicks might no longer be considered as solely indicative of yolk sac infection but further research is required to confirm this result. 5. Contrary to what is being suggested in commercial practice relationships between linear dimensions and hatchling weight suggest that measurement of chick length is at best a very crude measure of chick quality.     

Management of apposing,full‐thickness tracheal perforations in two horses

Two horses, one 15‐year‐old Arabian gelding and one 10‐year‐old Quarter Horse gelding, presented with a history of marked subcutaneous emphysema. The first case exhibited no external wound, although there was a depression noted on the ventral neck. The second case had a laceration on the ventral aspect of the neck over the trachea. Endoscopic examination revealed both horses to have concurrent dorsal and ventral perforations of the trachea. The horses were managed by placing a short, cuffed, J‐shaped tracheostomy tube in the ventral perforation, while the dorsal perforation healed. The dorsal perforation in the first horse was allowed to heal by second intention, whereas sutures were placed in the dorsal perforation in the second case to reduce the healing time. Both horses were maintained on oral antimicrobial and nonsteroidal anti‐inflammatory medications throughout treatment. The dorsal perforation healed after 13 days in the first horse, and 22 days in the second horse. The ventral perforation healed in both horses by second intention following tracheostomy removal, giving a cosmetically acceptable result. In addition to facilitating tracheal healing, the tracheostomy tubes prevented the progression of subcutaneous emphysema, and promoted its resolution.     

Primary tracheal collapse in a cat

A 7-year-old, neutered male, domestic shorthair cat was presented for severe inspiratory dyspnea of 2 to 3 days' duration. Radiography and tracheobronchoscopy confirmed the diagnosis of primary extrathoracic tracheal collapse. The cat was treated with oxygen, dexamethasone, and terbutaline, but no improvement was seen. Surgical correction was performed using nine prosthetic tracheal ring implants. Clinical signs improved after surgery, and the cat continued to do well 11 months after surgery, despite development of unilateral laryngeal paralysis.     

Vertical dimensions of suspended horses

Reasons for study: The dimensions of anaesthetised hobbled horses during suspension and transfer onto the operating table are unknown. These data are required for the cost‐effective construction of equine surgical facilities. Objectives: To measure the distance from the toe to dependent back margin (Bsusp ) and poll (Psusp ) of anaesthetised suspended horses and correlate them with readily obtained measures from standing animals. Methods: Digital photographs of suspended horses were taken in the anaesthesia induction box at a fixed position that allowed trigonometric determination of Bsusp and Psusp . These values were linked with body mass, height at the withers (Wstand ), the length of the crest from the poll to the withers (crest) and of the back (back) from the withers to the crop, by deriving an equine morphological index (EMI) using principal component analysis. The EMI and other linear variables were then subjected to single variable regression analysis. Results: EMI was 0.531mass_(kg)+ 0.528Wstand _(cm)+ 0.469crest_(cm)+ 0.468back_(cm). Bsusp was most accurately estimated using the expression Bsusp = 118.71 + 0.128EMI while Psusp was most strongly associated with Wstand , i.e. Psusp = 46.9 + 1.01Wstand _(cm). Conclusions: The height of suspended horses at the most ventral margin of the back and the poll can be estimated from measures taken from the standing animal. Potential relevance: The data will allow the more informed planning and construction of equine surgical facilities in which mechanical hoists are used.     

Surgical reconstruction for collapsed tracheal rings

A surgical procedure is described for repair of tracheal narrowing due to collapse of the dorsal soft structures of the trachea. Indications for the procedure are described and precautionary measures are outlined. Résumé. On décrit un procédé chirurgique pour la réparation de rétrécissement trachéal dǔ au collapsus des structures molles dorsales de la trachée. Des indications pour le procédé sont décrites et on indique des mesures de précaution. Zusammenfassung. Ein chirurgisches Verfahren zur Ausbesserung von Luftrǒhrenverengung, zuzuschreiben dem Kollaps der dorsalen weichen Struktur der Trachea, wurde beschrieben. Hinweise fur das verfahren waren beschrieben und Vorsichtsmassnahmen kurz umrissen.