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Stertor and Stridor

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Abstract

The flow of air from the upper to lower respiratory tracts is relatively quiet in the normal patient at rest. However, abnormal sounds may result from obstructive upper airway disease. These sounds are audible without a stethoscope. Their presence and, in particular, their persistence, suggests that a diagnostic work‐up for the patient is indicated. Stertor and stridor are two abnormal sounds that result from upper airway partial or complete obstruction. These sounds are not distinguished based upon where they originate in the respiratory cycle: either can be inspiratory or expiratory. Rather, stertor and stridor are distinct because of their pitch. The low‐pitched sound that is associated with stertor suggests that flaccid tissue is vibrating throughout the respiratory cycle. This occurs routinely in brachycephalic patients that have elongated soft palates: although their skulls are foreshortened, the reduction in soft tissue structures is not proportional. This additional tissue bulges into the airway lumen, creating resistance to airflow. This forces the patient to increase respiratory effort to take in sufficient air. An elongated soft palate is just one structural abnormality that is associated with brachycephalic airway syndrome. Affected patients may also experience the additive effects of having stenotic nares, with or without everted laryngeal saccules. As compared to stertor, which sounds like a snore, stridor is a high‐pitched sound that results from rigid tissue vibrations. It is typically associated with laryngeal or tracheal disease. Laryngeal paralysis and tracheal collapse are two common presentations in companion animal practice.

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This focused resource covers all medical conditions that affect cats. Using a unique problem-based approach, it provides essential information for assessing presenting symptoms, reaching a differential diagnosis, and selecting the appropriate course of treatment for feline patients. A consistent format makes it easy to find information related to key signs and possible causative factors (graded to indicate how common each is), diagnosis, differential diagnosis (including tests where appropriate), treatment, prognosis, and prevention (where applicable) for each clinical condition. Unique problem-based approach discusses how to make a problem-based diagnosis. Concise, logical format makes this resource ideal for quick reference in the clinical setting. Covers every condition likely to be encountered in cats worldwide. Features a strong international contributor list of feline experts from North America, UK, Europe, and Australia A comprehensive drug formulary lists all drug treatments available for cats. A separate chapter on drugs in cats lists the problems veterinarians might encounter due to differences in feline metabolism.
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This retrospective study reports the presence and incidence of nasal turbinates in the nasopharynx (nasopharyngeal turbinates) in a population of brachycephalic dogs and cats exhibiting signs of upper respiratory disease. Medical records were reviewed for 53 brachycephalic dogs and 10 brachycephalic cats undergoing upper airway endoscopy. Nasopharyngeal turbinates were identified in 21% of brachycephalic animals, including 21% of dogs and 20% of cats. Pugs accounted for 32% of all dogs in the study population and 82% of dogs with nasopharyngeal turbinates. The presence of nasopharyngeal turbinates may play a role in upper airway obstruction in the brachycephalic airway syndrome.
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A multi-institutional retrospective study of 103 dogs in which hypoplasia of the trachea was diagnosed was conducted. Bulldogs (55%) and Boston Terriers (15%) were most commonly affected. Age at diagnosis ranged from 2 days to 12 years, with a median of 5 months. Hypoplasia of the trachea was diagnosed more frequently in males (66%) than females (34%). Congenital anomalies in dogs with hypoplasia of the trachea included elongated soft palate (n = 44), stenotic nares (n = 23), cardiac defects (n = 12), and megaesophagus (n = 10). Ratios between tracheal lumen diameter and depth of the thoracic inlet or width of the third rib did not correlate with dyspnea. Of 42 dogs reexamined greater than 6 months after diagnosis, 25 (60%) were clinically normal. The remaining 17 were dyspneic and 15 (88%) had concurrent respiratory or cardiovascular disease that could account for their clinical signs. Hypoplasia of the trachea appears to be tolerated well in the absence of concurrent respiratory or cardiovascular disease.
Article
The range of clinical syndromes and the pathophysiology of respiratory disorders in brachycephalic animals are presented. The problem of deciding which patients require surgical management is reviewed in the light of recent studies and the author's clinical experience. Newer information from related disorders in humans suggests that serious problems can be subclinical and difficult to diagnose. The index of suspicion and guidelines for providing surgical relief to veterinary patients may need to undergo revision.
Article
The understanding of the mechanisms of dog and cat airway disease is in its infancy, because the clinical tools necessary to measure airway function in patients have not been readily available. The advent of lung function computers that can rapidly analyze flow-volume loops and calculate Cdyn and RL will make it easier to evaluate airway function in disease and to detect the effects of the newer specific receptor blockers. In the not-too-distant future, measurements of lung function will be used to prove the efficacy of new therapeutic agents for canine and feline airway disease and to guide the clinician in the use of these agents.
Article
This is a complex condition, recognized primarily in brachycephalic breeds, that results in varying degrees of upper airway obstruction. The signs consist of respiratory distress, stridor, reduced exercise tolerance, and in more severe cases, cyanosis and collapse. The inherent anatomy of the brachycephalic skull contributes to the development of these signs. Such anatomic features include: a shortened and distorted nasopharynx, stenotic nares, an elongated soft palate, and everted laryngeal saccules. The increased negative pressure created in the pharyngolaryngeal region, as a result of these obstructing structures, ultimately results in distortion and collapse of the arytenoid cartilages of the larynx.
Article
This article presents an overview of the clinical features of upper airway obstructive disorders. It includes more detailed discussions of certain common conditions such as brachycephalic airway syndrome, laryngeal paralysis, and upper airway obstruction due to trauma, foreign bodies, extraluminal masses, and tumours of the larynx and trachea.
Article
Tracheas from 15 toy breed dogs with normal tracheas and 6 dogs with collapsed tracheas were examined histologically and histochemically. Tracheal cartilage was analyzed for chondroitin sulfate by means of alcian blue (CEC method) and for calcium with alizarin red S. Cartilage arcs from dogs with collapsed tracheas had areas that were apparently hypocellular, and some had other areas that appeared like fibrocartilage or fibrous tissue. Histochemically, collapsed tracheal cartilage had less chondroitin sulfate and calcium than did normal tracheal cartilage. Cartilage arcs from the collapsed tracheas were not uniformly affected to the same degree, and parts of a given tracheal arc appeared normal, whereas other parts had an abnormal histologic appearance.
Article
In dogs which are panting due to a heat load, most of the respired air enters through the nose and leaves through the mouth. Different patterns of flow are, however, possible. The unidirectional flow over the evaporative (nasal) surfaces is an important mechanism for regulating the amount of heat dissipated in panting.
Article
Tracheas were removed from 8 average-sized (13 to 19 kg) dogs, 12 toy breed dogs, and 6 toy breed dogs with collapsed trachea. The tracheal arcs were counted whenever possible and measurements of the inner ventrodorsal and lateral diameters, lumen areas, cartilage and muscle thicknesses, and numbers of chondrocytes and muscle cells/0.1 mm2 were obtained from 3 regions. The regions were the 3rd ring caudal to the larynx, the region at the thoracic inlet, and the 2nd ring cranial to the carina. The 3 tracheal regions were compared with one another for all the variables in the 3 dog groups. All groups exhibited similar significant regional variations for tracheal diameters, lumen areas, and cartilage and muscle thicknesses. There were no significant differences between regions for chondrocyte and muscle cell counts. In the comparison of average dogs and normal toy breed dogs, the former had larger ventrodorsal tracheal diameters, lumen areas, and cartilage and muscle thicknesses. The measurements from the toy breed dogs with collapsed tracheas were smaller than those from the normal toy breed dogs. There were no significant differences in chondrocyte and muscle cell counts between average dogs and normal toy breed dogs.
Article
Use of a CO2 laser to resect the soft palate in 6 dogs with elongated soft palate is described. The technique was rapid and uncomplicated; hemostasis was not a problem. Breathing was noticeably improved in all dogs immediately after surgery. Use of the CO2 laser represents a new option for surgical treatment of elongated soft palate in dogs.
Article
To determine factors associated with long-term outcome in dogs with tracheal collapse treated with extraluminal polypropylene C-shaped stents. Retrospective case series. 90 dogs. Medical records of dogs with surgically treated tracheal collapse were reviewed. Follow-up was obtained either by recheck at the veterinary teaching hospital only (n = 10) or by telephone interviews with referring veterinarians and owners (n = 35), referring veterinarians alone (n = 23), or owners alone (n = 16). The chi 2 test was used to determine which factors were associated with long-term outcome. 11 breeds were represented. Yorkshire Terriers, Poodles, and Pomeranians were most common. Median age at the time of surgery was 6.8 years. Median weight was 2.9 kg. Severity of collapse ranged from grade II to grade IV. Dogs < 6 years old had more severe collapse than did dogs > or = 6 years old. Dogs > or = years old had more postoperative complications and a poorer longterm outcome than did dogs < 6 years old. 17 dogs required permanent tracheostomy, 10 within 24 hours after surgery. Surgical placement of extraluminal polypropylene C-shaped stents was an effective method of attenuating clinical signs of tracheal collapse. Dogs < 6 years old had more severe tracheal collapse but did better after surgery than did dogs > or = 6 years old.