A quantitative study on the trachea of the dog

This study was carried out to record the detailed morphometric structure of the trachea in dogs using 15 female and four male healthy adult mongrel dogs. The diameter and thickness of each tracheal ring were measured, the number of tracheal rings varying from 36 to 45. All data were subjected to statistical analysis which was carried out on individual sections of the trachea, i.e. the cranial cervical, middle cervical, thoracic inlet and the intrathoracic tracheal regions, which consisted of 12, 12, nine and 12 tracheal rings, respectively. Fusion of the tracheal rings was especially obvious in the cranial cervical and thoracic inlet regions as a result of neck movements. The diameter and thickness of the tracheal rings are smallest at the thoracic inlet level because the direction of the trachea changes at this point where the thoracic inlet is relatively small and surrounded by bone. The ratios of inner transverse to inner vertical and outer transverse to outer vertical diameters were almost the same, between 1.14 and 1.25 in all regions, which indicated that the trachea is near-circular in shape in the dog. At the thoracic inlet level cross-sectional lumen areas are 7 and 6% smaller than those in the middle cervical and intrathoracic regions, respectively. The thinnest cartilage was seen at the thoracic inlet level where there is a risk of tracheal collapse.     

Computed tomographic and radiographic bronchial collapse may be a normal characteristic of forced expiration in dogs

Tracheobronchomalacia has been diagnosed using radiography or bronchoscopy to confirm bronchial changes in luminal diameter during the respiratory cycle. However, studies in healthy humans suggest that some degree of bronchial collapse may be observed during the normal respiratory cycle. In this analytical study, the luminal diameter of the bronchus to each of the six pulmonary lobes and the mean percentage of expiratory collapse from end inspiratory, end expiratory, and two forced expiratory phases (10 and 15 ml/kg) were determined via computed tomography (CT) and radiography in 22 healthy Beagle dogs. The bronchial collapsibility was significantly greater during the forced expiration than the end expiration (P < 0.001); the same results were observed in dorsal and sagittal CT images and radiographs (P < 0.001). Median collapsibility values associated with 15 ml/kg forced expiratory collapse determined via cross‐sectional CT images were measured as 16.6–45.5% and differed according to the pulmonary lobe. Median collapsibilities on radiography with 15 ml/kg forced expiration were 57.8% and 62.1% in the right cranial lobe and right caudal lobe, respectively. In conclusion, bronchial diameter may change during the respiratory cycle, and some degree of reduction in bronchial diameter may be an incidental finding in healthy dogs. More rigorous criteria are needed with regards to bronchial collapsibility during normal respiration for the diagnosis of bronchomalacia in order to avoid false‐positive diagnoses.     

CT and radiographic evaluation of bronchial collapsibility at forced expiration in asymptomatic brachycephalic dogs

Bronchial collapse due to bronchomalacia is an important cause of chronic coughing in dogs. Radiographic and CT evidence of bronchial collapse has previously been reported in healthy Beagle dogs under forced expiration. However, published studies in brachycephalic dog breeds that are prone to bronchial collapse are currently lacking. In the present prospective analytical experimental study, CT and radiography were used to measure the bronchial diameter and collapsibility of each pulmonary bronchus during end‐expiratory, 5 mL/kg forced‐expiratory, and 10 mL/kg forced‐expiratory phases in 17 asymptomatic brachycephalic dogs and six healthy Beagle dogs. Bronchial collapsibility was significantly greater during forced expiration, than that at the end of expiration in both groups (P < .001). Bronchial collapsibility measurements of the left lung lobes and the right cranial, middle, and accessory lobes were significantly higher in asymptomatic brachycephalic dogs than those in healthy Beagle dogs, during all expiratory phases (P < .05). The higher bronchial collapsibility of brachycephalic dogs was also supported using CT multiplanar reconstruction images and radiography. In conclusion, radiographic and CT measures of bronchial collapsibility in asymptomatic brachycephalic dogs are higher than measures in healthy Beagle dogs. Therefore, measures of bronchial collapse in brachycephalic dogs should not be evaluated using the same baseline measures as those used for healthy Beagle dogs.     

COMPUTED TOMOGRAPHIC,RADIOGRAPHIC, AND ENDOSCOPIC TRACHEAL DIMENSIONS IN ENGLISH BULLDOGS WITH GRADE 1 CLINICAL SIGNS OF BRACHYCEPHALIC AIRWAY SYNDROME

Tracheal hypoplasia is commonly seen in English Bulldogs affected with brachycephalic airway syndrome. Previously published diagnostic criteria for tracheal hypoplasia in this breed have been a radiographic tracheal diameter:tracheal inlet ratio (TD:TI) < 0.12 or a tracheal diameter:third rib diameter ratio (TD:3R) < 2.0. Computed tomography has become increasingly used for airway evaluation, however published information is lacking regarding CT tracheal dimensions in English Bulldogs. Objectives of this prospective cross‐sectional study were to describe radiographic and CT tracheal dimensions in a sample of clinically normal English Bulldogs and compare these values with tracheoscopy scores. Computed tomography (n = 40), radiography (n = 38), and tracheoscopy (n = 40) studies were performed during a single general anesthesia session for each included dog. Tracheal measurements were recorded at three locations: cervical, thoracic inlet, and thorax. Tracheal diameters were narrowest at the thoracic inlet with all techniques. Computed tomographic measurements averaged 19% greater than radiographic measurements. All included dogs had radiographic tracheal measurements greater than the previously published criteria for tracheal hypoplasia. Mean CT TD:TI was 0.26 (± 0.03, 0.20–0.33), and mean CT TT:3R was 2.27 (± 0.24, 1.71–2.74). Radiographic TD:TI and CT TD:TI were significantly correlated (P = 0.00); however radiographic TT:3R and CT TT:3R were not significantly correlated (P = 0.25). Tracheoscopy identified hypoplastic changes in all dogs and tracheoscopy scores were not correlated with CT or radiography diameter measurements. In conclusion, findings indicated that some CT and radiographic tracheal diameter measurements were comparable in English Bulldogs however diameters for both imaging techniques were not comparable with tracheoscopy scores.     

Radiographic and computed tomographic appearance of tracheal collapse with axial rotation in four dogs

Tracheal collapse with axial rotation was diagnosed in four dogs. Radiographs showed increased tracheal dorsoventral height at the caudal cervical and thoracic inlet with and apparent intraluminal soft tissue opacity, mimicking an intraluminal tracheal foreign body. Computed tomography confirmed dorsoventral tracheal collapse with axial rotation in all dogs. Short‐term outcome with medical treatment of all dogs was excellent.     

Radiographic measurements of the trachea in domestic shorthair and Persian cats

Tracheal diameter can be assessed from a thoracic radiograph, with assessment of tracheal diameter in dogs based on ratios between tracheal diameter and a skeletal measurement. Reference intervals are not, however, available for the cat. Tracheal narrowing may cause significant clinical problems, although tracheal hypoplasia in dogs may be clinically silent, and is rarely reported in cats (both mesati- and brachycephalic). The tracheal diameter and trachea:thoracic inlet and trachea:rib ratios were calculated for populations of domestic shorthair (DSH) (n?=?68) and Persian (n?=?40) cats. This gave reference intervals for radiographic tracheal measurements in these breeds. It is proposed that the tracheal diameter in a normal DSH cat should be 18% of the diameter of the thoracic inlet, and compared to 20% in Persian cats.     

Agreement Among Radiographs,Fluoroscopy and Bronchoscopy in Documentation of Airway Collapse in Dogs

Background

Airway collapse is a common finding in dogs with chronic cough, yet the diagnosis can be difficult to confirm without specialty equipment.

Hypothesis

Bronchoscopic documentation of tracheobronchial collapse will show better agreement with fluoroscopic imaging than with standard radiography.

Animals

Forty‐two dogs prospectively evaluated for chronic cough.

Methods

In this prospective study, three‐view thoracic radiographs were obtained followed by fluoroscopy during tidal respiration and fluoroscopy during induction of cough. Digital images were assessed for the presence or absence of collapse at the trachea and each lobar bronchus. Bronchoscopy was performed under general anesthesia for identification of tracheobronchial collapse at each lung segment. Agreement of imaging tests with bronchoscopy was evaluated along with sensitivity and specificity of imaging modalities as compared to bronchoscopy.

Results

Airway collapse was identified in 41/42 dogs via 1 or more testing modalities. Percent agreement between pairs of tests varied between 49 and 87% with poor–moderate agreement at most bronchial sites. Sensitivity for the detection of bronchoscopically identified collapse was highest for radiography at the trachea, left lobar bronchi, and the right middle bronchus, although specificity was relatively low. Detection of airway collapse was increased when fluoroscopy was performed after induction of cough compared to during tidal respiration.

Conclusions

Radiography and fluoroscopy are complementary imaging techniques useful in the documentation of bronchial collapse in dogs. Confirming the presence or absence of tracheal or bronchial collapse can require multiple imaging modalities as well as bronchoscopy.     

A RETROSPECTIVE STUDY OF THE RELATIONSHIP BETWEEN TRACHEAL COLLAPSE AND BRONCHIECTASIS IN DOGS

Tracheal collapse is common in middle age toy and miniature breed dogs. Cartilaginous defects have been identified histologically and are considered a form of chondromalacia. In addition to tracheal cartilaginous changes, concurrent lower airway histologic changes indicative of inflammation have been noted in dogs with tracheal collapse and these changes may lead t o concurrent bronchiectasis. The purpose of this study was to investigate the prevalence of bronchiectasis in dogs with a previous radiographic diagnosis of tracheal collapse. The thoracic radiographs of 60 dogs with tracheal collapse were evaluated for evidence of concurrent bronchiectasis. Eighteen of 60 (30%) dogs had evidence of bronchiectasis, and all were cylindrical in morphology. The signalment of affected dogs was similar to that previously reported. The occurrence of bronchiectasis in this group of dogs with tracheal collapse (18 dogs) was six times higher (P < 0.05) than the expected prevalence within a random sample population (three dogs). The results of this study provide evidence of a link between tracheal collapse and bronchiectasis. A finding of bronchiectasis with tracheal collapse should encourage further evaluation for chronic lower airway disease in these patients.     

Tidal breathing flow-volume loop analysis for clinical assessment of airway obstruction in conscious dogs

Using a mask, pneumotachograph, and X-Y recorder, tidal breathing flow-volume loops (TBFVL) were evaluated in 33 healthy dogs and in 18 dogs with acquired obstructive respiratory tract disease. The loops were evaluated for qualitative shape, tidal volume (VT), respiratory rate, peak and midtidal inspiratory flow (PIF and IF50, respectively), peak and midtidal expiratory flow (PEF and EF50, respectively), inspiratory and expiratory flow at end expiratory volume plus 25% VT (IF25 and EF25, respectively), inspiratory time, and expiratory time. Indices of loop shape were developed by division of flow measurements (eg, PEF/PIF and IF50/IF25). Twenty healthy dogs had the same TBFVL (type 1). Typically, PEF occurred at the beginning of expiration, and PIF occurred toward the end of inspiration. Three other TBFVL types were identified in the remaining dogs. Mean coefficients of variation for TBFVL indices ranged from 7% to 18%. Dogs with a fixed-type upper airway obstruction (pharyngeal or laryngeal mass, n = 7) had TBFVL abnormalities, indicating inspiratory and expiratory phase flattening. Concavity or late expiratory phase flattening was detected in TBFVL from dogs with chronic bronchitis/tracheal collapse (n = 11). The TBFVL were easily evaluated in conscious dogs and were useful in the functional assessment of airway obstruction.     

Surgical management of atypical lateral tracheal collapse in a dog

A FOUR-year-old spayed miniature poodle was presented for evaluation because of a chronic cough which had been present from eight weeks of age. The condition had gradually worsened until exercise intolerance, inappetence and abdominal breathing occurred. The dog was thin and weighed only 1.5 kg. Auscultation revealed tachycardia, a normal respiratory rate and wheezing noises - more prominent on inspiration and localised to the cervical portion of the trachea. There was marked inspiratory and expiratory effort. Tracheal sensitivity was moderate and palpation induced a dry hacking cough. Radiography demonstrated mild thickening of the bronchial wall and pulmonary hyperinflation. Expiratory/inspiratory radiographs failed to demonstrate dynamic tracheal collapse. On fluroscopy, substantial changes in tracheal calibre were not apparent. Bronchoscopy was performed and the tracheal lumen was normal up to 12.5 cm from the incisors. At this point, there was lateral tracheal collapse to about 30 per cent. There was dynamic collapse with respiratory effort. The bronchoscope could be passed beyond the narrowing (consisting of five tracheal rings) to a trachea of normal size. No pathogens were found on tracheal lavage. Surgery was undertaken through a midline, ventral approach. Six specially made tracheal ring prostheses were individually inserted around the trachea and inside the recurrent laryngeal nerve. Each prosthesis was sutured in four places to the tracheal ring, to give external support. The dog improved clinically and 11 months after surgery, bronchoscopy was again performed. The trachea was narrowed to approximately 60 per cent but there was no dynamic collapse of the airway. Twenty-seven months after surgery the dog continued to lead a healthy active life.     

Fracture of an endoluminal nitinol stent used in the treatment of tracheal collapse in a dog

A 5-year-old castrated male Pomeranian was evaluated because of severe dyspnea and coughing, and a diagnosis of complete, static collapse of the trachea at the thoracic inlet was made. After failure to improve with medical management alone, an endoluminal tracheal stent was placed, which resulted in resolution of signs. Ten weeks after stent placement, the dog underwent tracheal resection and anastomosis because the stent had fractured at the level of the thoracic inlet. One year after surgery, the dog was doing well and required treatment with hydrocodone infrequently. Compared with other surgical treatment options, placement of an endoluminal tracheal stent is a relatively noninvasive intervention that can provide effective relief from the clinical signs associated with tracheal collapse in dogs. Implantation of endoluminal tracheal stents may be associated with complications; therefore, the procedure may best be regarded as a salvage procedure for dogs with end-stage disease that are refractory to appropriate medical management, have extensive collapse of the intrathoracic portion of the trachea, or are poor candidates for surgery.     

Radiography, computed tomography and virtual bronchoscopy in four dogs and two cats with lung lobe torsion

This report describes the imaging features of radiography, computed tomography and virtual bronchoscopy in dogs and cats with lung lobe torsions. The medical records, thoracic radiographs and computed tomography images of four dogs and two cats with confirmed lung lobe torsions were retrospectively reviewed. Computed tomography with virtual bronchoscopy showed bronchial narrowing, collapse or occlusion in all six animals, while this was only appreciated on one radiographic examination. A tapering terminating angle of the air-filled bronchus proximal or distal to the collapsed region was seen only on computed tomography and virtual bronchoscopy in all six animals. The vesicular emphysema pattern typical of lung lobe torsion was seen on three computed tomographies but only on one radiographic examination. The lung lobe torsion-specific findings of vesicular emphysema and a proximally narrowed or occluded bronchus were more easily recognised on computed tomography and virtual bronchoscopy than with radiographs. Computed tomography slices acquired through the bronchus and lung lobe of interest in a cat or dog with possible lung lobe torsion can be reformatted into virtual bronchoscopic images that can be utilised along with computed tomography to help make a more definitive preoperative diagnosis.     

Does the computed tomographic appearance of the lung differ between young and old dogs?

In computed tomographic (CT) images of humans, decreased lung attenuation, bronchial dilation, and/or thickening, air trapping, cysts, and thickened interlobular septa have been associated with increasing age. To determine if there are differences in the CT appearance of the lungs of young and old dogs that could affect interpretation of diagnostic studies, pulmonary CT images of dogs with conditions unrelated to the thorax were reviewed retrospectively in a case–control study. Computed tomography studies of 42 young dogs (range 0.3–4.8 years) and 47 old dogs (range 9–15.1 years) were jumbled and reviewed by an observer blinded to dog age. Computed tomography was performed under sedation in 62 (70%) dogs and under general anesthesia in 27 (30%). Heterotopic bone was more prevalent (62% vs. 14%) in old dogs. Lung collapse was significantly associated with old age, greater body weight, and anesthesia. There were no significant differences in median lung attenuation or occurrence of ground glass pattern, cysts, bronchial thickening, bronchial dilation, or degree of tracheal calcification. No examples of reticular pattern, emphysema, pleural thickening, or septal thickening were observed in any dog. Despite previous studies describing age‐related changes in the radiographic appearance of the lungs of old dogs, it appears that there are minimal observable differences in CT images. Old dogs are more likely to have visible foci of heterotopic bone and may be more prone to lung lobe collapse than young dogs, but neither of these differences should contribute to misdiagnosis of pulmonary disease.     

Atypical lateral tracheal collapse in a Yorkshire terrier

A 10-month-old, neutered female Yorkshire terrier was presented with a 6-month history of inspiratory dyspnoea, coughing and exercise intolerance. Tracheoscopy revealed marked lateral-to-lateral fixed collapse of the cervical trachea and mild collapse of the thoracic trachea. Surgical exploration revealed a marked reduction in lateral tracheal width and multiple malformed tracheal rings. Placement of extraluminal ring prostheses around the cervical trachea resulted in widening of the tracheal diameter and an immediate improvement in clinical signs. 6 years postoperatively the patient was reported to have an excellent quality of life with complete resolution of clinical signs.     

Ultrasonographic evaluation of tracheal collapse in dogs

Tracheal ultrasonography was performed to measure the width of the tracheal ring shadow and to assess the clinical relevance of these measurements for identifying tracheal collapse. The first tracheal ring width (FTRW) and thoracic inlet tracheal ring width (TITRW) were measured on both expiration and inspiration. The mean of the FTRW width (129 dogs) was greater in expiration (10.97 ± 1.02 mm, p = 0.001) than that in inspiration (9.86 ± 1.03 mm). For 51 normal dogs, the mean of the TITRW width was greater in expiration (9.05 ± 1.52 mm, p = 0.001) than in inspiration (8.02 ± 1.43 mm). For 78 tracheal collapse dogs, the mean of the TITRW width was greater in expiration (15.89 ± 1.01 mm, p = 0.001) than in inspiration (14.85 ± 1.17 mm). The TITRW/FTRW ratio of the normal dogs was higher (p = 0.001) in expiration (0.81 ± 0.09) than that in inspiration (0.79 ± 0.10). When compared between the normal and tracheal collapse dogs, the TITRW/FTRW ratio was also increased (p = 0.001) both in expiration (1.54 ± 0.09) and inspiration (1.47 ± 0.08), respectively. Based on these results, the cutoff level of the TITRW/FTRW ratio was statistically analyzed according to the receiver operating characteristic curve and it could be set at 1.16 in expiration and at 1.13 in inspiration. We have demonstrated that tracheal ultrasonography is a useful technique for the evaluation of tracheal collapse and it can be a supportive tool together with the radiographic findings for making the correct diagnosis.     

COMPARISON OF COMPUTED TOMOGRAPHY, TANGENTIAL VIEW RADIOGRAPHY, AND CONVENTIONAL RADIOGRAPHY IN EVALUATION OF CANINE PELVIC TRAUMA

Thirteen dogs with fractures requiring surgical repair were evaluated by standard two-view (i.e., lateral and ventrodorsal) radiography, tangential view (ventro 20 degrees cranial-dorsocaudal [inlet] and ventro 20 degrees caudal-dorsocranial [outlet]) radiography, and computed tomography (CT). Radiographic and CT examinations were reviewed independently by the three authors, and specific anatomic sites were graded for the presence or possibility of lesions. The results of radiographic interpretations were compared to CT scan interpretations. Eighty-one percent of skeletal lesions detected by CT scans were diagnosed definitively radiographically. Differences between the interpretation of CT and radiographic examinations included abnormalities associated with soft-tissue structures (P < 0.0001), the sacroiliac joints (P = 0.02), and the acetabula (P = 0.04). Interpretation of the lateral/ventrodorsal and inlet/outlet radiographic series were not statistically different, although inlet views may be complimentary to the standard radiographic examination. Its use deserves further study. Reader variation was less on evaluation of CT examinations than radiographic examinations. CT multiplaner reformations and three-dimensional reconstructions were useful for surgical planning in seven dogs. CT scanning is superior to survey radiography in assessing skeletal and soft-tissue injuries in dogs with pelvic trauma, although all clinically significant surgical lesions were described accurately radiographically. Based on this small series, the routine CT examination of dogs with pelvic trauma may not be justifiable for diagnosis but may be advantageous for surgical planning, especially if acetabular fractures are suspected on radiographs.     

Clinical findings and diagnostic value of post-traumatic thoracic radiographs in dogs and cats with blunt trauma

Objective: To characterize the clinical findings in dogs and cats that sustained blunt trauma and to compare clinical respiratory examination results with post‐traumatic thoracic radiography findings. Design: Retrospective clinical study. Setting: University small animal teaching hospital. Animals, interventions and measurements: Case records of 63 dogs and 96 cats presenting with a history of blunt trauma and thoracic radiographs between September 2001 and May 2003 were examined. Clinical signs of respiratory distress (respiratory rate (RR), pulmonary auscultation) and outcome were compared with radiographic signs of blunt trauma. Results: Forty‐nine percent of dogs and 63.5% of cats had radiographic signs attributed to thoracic trauma. Twenty‐two percent of dogs and 28% of cats had normal radiographs. Abnormal auscultation results were significantly associated with radiographic signs of thoracic trauma, radiography score and presence and degree of contusions. Seventy‐two percent of animals with no other injuries showed signs of thoracic trauma on chest radiographs. No correlation was found between the radiographic findings and outcome, whereas the trauma score at presentation was significantly associated with outcome and with signs of chest trauma but not with the radiography score. Conclusion: Thoracic trauma is encountered in many blunt trauma patients. The RR of animals with blunt trauma is not useful in predicting thoracic injury, whereas abnormal chest auscultation results are indicative of chest abnormalities. Thorough chest auscultation is, therefore, mandatory in all trauma animals and might help in the assessment of necessity of chest radiographs.     

Cervical lung lobe herniation in dogs identified by fluoroscopy

This study aimed to determine the frequency of cervical lung lobe herniation (CLLH) in dogs evaluated fluoroscopically and to identify associated characteristics. Reports of diagnostic procedures and patient summaries from 2008 to 2010 were reviewed retrospectively. Signalment, body weight, duration of cough, presence of heart murmur and airway collapse, and radiographic findings were compared between dogs with and without CLLH. Of the 121 dogs that were examined, CLLH occurred in 85 (70%). The extra-thoracic trachea kinked during herniation in 33 (39%) dogs with CLLH. Collapse of the intra-thoracic trachea (assessed fluoroscopically or bronchoscopically) and collapse of major bronchi (assessed fluoroscopically) were strongly associated with CLLH. Although redundant dorsal tracheal membrane on radiographs was associated with CLLH, extra-thoracic tracheal collapse, assessed fluoroscopically or bronchoscopically, was not. No other associations were found. Cervical lung lobe herniation was present in most dogs evaluated during cough and was associated with intra-thoracic large airway collapse, but not duration of cough.     

Evaluation of the Palmaz Stent in the Trachea and Mainstem Bronchi of Normal Dogs

Objective — This study evaluates the efficacy of the Palmaz balloon expandable intraluminal stent in the trachea and mainstem bronchi of normal dogs. Study Design — Effects of the stent were evaluated by physical examination, thoracic radiography, respiratory tract fluoroscopy and endoscopy, tracheal diameter measurement, postmortem examination, and airway histomorphometry. Animals or Sample Population — Ten normal beagle dogs. Methods — Stent size was estimated from thoracic radiographs in awake dogs. Group I dogs (n = 4) had two stents placed: one in the thoracic trachea (TT) plus a randomly chosen mainstem bronchus (MB). Group II dogs (n = 3) had stents placed in the MB (one stent), TT (one stent), and mid- or proximal cervical trachea (CT) (one or two stents). Three dogs were used as sham-operated controls (group III). Temperature, pulse, respiration, and cough were measured twice daily. Dogs were evaluated at 21 and 49 to 56 days after stent placement, euthanatized, and tissues were collected for histomorphometric analysis of stent integration and epithelial pathology. Results — Mean tracheal diameters of awake (10.5 ±1.7 mm) and anesthetized dogs before stent implantation (13.9 ± 2.0 mm) were significantly different (P <.01). Complications associated with stent placement included acute pulmonary edema (n = 2), stent migration (n = 7), stent collapse (n = 4 CT, 2 TT, and 1 MB), and positive tracheal culture (n = 10). Group II dogs coughed more at rest, exercise, and with tracheal palpation than dogs in other groups (P <.01). Group I dogs coughed more at rest than group III dogs (P <.01). Stent integration ranged from 0 to 91.3%. Squamous metaplasia and epithelial ulceration associated with stents ranged from 0 to 57.5% and 0 to 32.7%, respectively. Conclusions — Determination of stent size should be based on measurements taken on anesthetized dogs because use of inappropriately sized stents may promote stent migration, squamous metaplasia, and/or ulceration. Epithelialization over stent struts may occur if the stent is closely associated with tracheal epithelium. Clinical Relevance — Palmaz stents do not appear to be appropriate for placement in the CT of dogs; however, with technical modifications, application in the TT and MB may be feasible.     

Tidal Breathing Flow‐Volume Loop Analysis for the Diagnosis and Staging of Tracheal Collapse in Dogs

Background: Tracheoscopy is generally used for the diagnosis of tracheal collapse (TC) in dogs; yet, it is costly, requires anesthesia, and can irritate the airway. The tidal breathing flow‐volume loop (TBFVL) is a safe, quick, and noninvasive pulmonary function test currently used in humans. Hypothesis: TBFVL will differentiate dogs with TC from healthy controls and contribute to disease grading. Animals: Twenty‐eight dogs with naturally occurring TC and 10 healthy controls. Methods: Cross‐sectional, prospective clinical study: The 38 dogs were assigned to one of 4 groups based on tracheoscopy results: group A (n = 10, healthy controls), group B (n = 10, grade I TC), group C (n = 10, grade II TC), and group D (n = 8, grade III TC). The TBFVL measurement was performed on all dogs and loops were assessed for their shape. Forty‐four TBFVL parameters were calculated. Results: Two types of TBFVL shapes were identified: Type I, representative of the 10 healthy controls, and Type II, representative of the 28 dogs with TC. Statistical analysis showed the dogs could be differentiated into healthy or affected by TC by 3 indices, TE/TI (expiratory time divided by inspiratory time), TI/TTOT (inspiratory time divided by total respiratory time), and EF75/IF75 (expiratory flow at end tidal volume plus 75% end tidal volume divided by inspiratory flow at end tidal volume plus 75% end tidal volume). The TC could also be graded as mild‐moderate (grades I and II) or severe (grade III), showing a diagnostic value of 97.4%. Conclusion and Clinical Importance: TBFVL is accurate, quick, noninvasive, and safe and can contribute to the diagnosis of TC in dogs.